Post by Administrator on Dec 15, 2006 19:04:52 GMT -5
TAFF2
Super Stock 400 motors
What HP numbers are these 400 motors putting out,and at what RPM? As I understand it ,this class has to use stock ,unported iron heads(yeah,I know they get acid ported), what are the intake manifolds of choice,are roller cams allowed,is compression limited,what other tricks are used(if they can be disclosed!). I take it that thin rings,high ring land pistons and gasporting are the norm,and probably cut down cranks.Thanks.
Skip Fix
I'm not sure when but maybe 10 years ago they let the SS guys port heads.They have open intake choices but must run a factory carb.Roller cams OK. Alot more suspension mods.
The Stock guys can't port and they have to use factory intakes, flat tappet cams also. Pretty stock suspension.
NHRASuperStock455SD
Stock has unported heads, but usually are ported, then covered up. Super Stock you can port with limits, but you cannot exceed the published(supposedly stock) OEM volumes. All kinds of tricks give you additional volumes.
www.nhra.com/tech_specs/rods/index.html
www.nhra.com/tech_specs/runners/index.html
Any manifold even sheet metal, any piston/ring/ land location in Super Stock, no gas porting allowed. Any cam allowed.
Heads are reserved to OEM castings with published volumes.
SS 400 6X motors are making 550-600HP
SS 400 16 motors 590-610
SS 400 RA-IV 620-650HP
Cranks are not allowed to be cut down. Yes people cheat, but face a year suspension and flogging on all the internet sites.
Lynn
NHRASuperStock455SD
SS car still for sale. Soon available turn key. (if it is too fast, probably wont sell it.)
forums.performanceyears.com/f...26#post2748926
taff2
Thanks guys.
Lynn, what rpm are the SS 400 16 motors making their HP at? Although there's no Stock or SuperStock class over here,I'm interested in seeing how far I can push my old iron headed(#16) 400 motor.
issach428
If its possible to modify stock parts and have different intake and cam choices, why arent there more stock parts guys pushing 600hp?? with lightly ported iron heads etc.??
72firebird 3800# 462 eheads e nitrous cam, continental converter 3.73. Pump gas 11.60's 120 on street tires/ race gas with a controlled 175hp n20 10.28 at 132mph with a 1.61 60ft. on drag radials spinning bad.
screamingchief
Quote:
If its possible to modify stock parts and have different intake and cam choices, why arent there more stock parts guys pushing 600hp?? with lightly ported iron heads etc.??
Why???
Lots of details I'm sure.
But I'm pretty sure part of the reason is because ALOT of them are afraid to put real cams in their "little ol' 400" motors!
JMO...
They listen to folks who say things like,"that cam will never work in that little motor,it's way too big!",,,"there's not enough head flow" or "it'll need to rev to 8000 RPM's to work,and the bottom end will be soft"...
But if you launch at 4000+ RPM's,the torque below that is hardly an issue of concern in a race situation.
The "little" motors need healthy doses of cam and/or compression,with plenty of convertor and gear for maximum affect!
Most are'nt in a hurry to use that sort of combo with their pontiacs,they go for the low RPM torque packages.
Especially if it's a "street/strip" combo...
My 406/670 "A" motor will be running a custom crower 256/260 solid on a 108 LSA.
The "B" motor will have a comp 290b6 solid which is 255/266 on a 106 LSA.
Most folks would tell you outright those cams are way too big for a "little" 400,but you gotta look at the rest of the combination in question,look at things like it's compression ratio,convertor,gears,intake,carb,exhaust etc.etc.,then it starts making more sense.
My racecar will be running something like a 3800-4200 convertor,with a th400 trans,and 4.10 gears with 28" tires to make those cams work with the rest of the combo.
Now granted I wont be making the max HP out of those combos till the iron heads get to their final state of prep (260-270 ish cfm @ 28"h2o),but I'll work with those combos till that happens.
I'm wanting to see what those changes bring to the table,so I'll be establishing a baseline with more or less "stock" heads,and working them from there to see the gains those mods yeild.
Ask guys like OMT and Steve C. what cams they ran with their high HP 400 combos,or better yet maybe Lynn will give a rough idea what he uses (though I would'nt expect him to be too precise on that info. ),I'm sure they're not no "baby" cams,that's for sure!
I know a lot of the stockers 350's & 400's use really big "juice" cams,specs are close to my solid cam specs often,yet they're hydraulics,Dave R. races stock eliminator,he had some of his old cams listed,pretty long duration lobes with stock lifts,not the norm,but they get the job done,tricks the motor into thinking it has more head up there than it actually has,then tighten up the LSA to narrow the power band some where it can be best utilized by the cars convertor and gearing.
Bret.
NHRASuperStock455SD
Quote:
Originally Posted by taff2
Thanks guys.
Lynn, what rpm are the SS 400 16 motors making their HP at? Although there's no Stock or SuperStock class over here,I'm interested in seeing how far I can push my old iron headed(#16) 400 motor.
Nice to see a guy in the UK doing some cast iron engines!
An average motor will go 6200 peak HP and 4700 peak torque with a cam about 106 L/S. Probably about 282/282 @ 0.050. (sorry dont know metric numbers without doing conversions). This would be with 1.65 studded crocker systems like Crane, and average valve train....lets say 280 lbs on the seat and about 700-800 open, Proflow valves, and about .700 lift at the valve. Heads will flow about 250cfm.
A killer engine will have much better heads and flow about 285 with good flow and not bad flow. The ports will have good CSA minimum about 2.000 square inches. Small ports with high velocity flow do NOT WORK! (Too much cylinder head choke.) Our old heads flowed 240 cfm, but if they had good CSA they made very good power. Small heads with big flow are stones.
This bigger motor will have peak HP around 6700 and torque around 5200 larger tubed headers.
The better motor will also have valve spring upwards of 400lbs on the seat with 1100lbs open. Good rocker shaft system (T&D)
Use a ported Victor and dont even think about it. Bringing the flow dividers under the carb to promote equalization is way more important than trying to achieve shorter intake runners. We haver tried it both ways and and always lose power by making the runner shorter. The Victor manifold dropped peak HP and torque by 300RPM. At every point it was more power, but one can't help to wonder about gaining that 300RPM back. (A Victor with about 3 inches shorter runner and same CSA is what I think would be perfect).
The 400 motor with 16 heads is not as competitive as it has too much HP in SS compared to other combos. However, it will make very good power and is a very competitive SS engine.
Lynn
NHRASuperStock455SD
Bret,
You hit the nail dead square. The cheezy Chevrolet 350's with Q-jets are making 660HP. We can run with them. They make that because it is a smaller cubic inch size for the cylinder heads 1.94 intakes that allow that engine to come in about 7800 RPM with a killer valve train and port job.
The Pontiac 350 is a killer engine, and would love someone to do a 1969 350 for SS. Truman Fields has expressed interest. Same heads smaller motor means more HP, yes less torque, but who cares? Race cars dont run off of peak torque. Gear the piss out of it, and forget the torque with a smaller motor.
The average cam these days in a Pontiac is about 0.740 lift, 106 to 108 L/S and 282/282 or bigger @.050. Bret, even your cam is way small compared to a SS car. Before ported heads they had even more duration like 288/288@0.50 With this kind of cam you also need the valve train to go with it. If you dont, then valve bounce will kill you ever seeing the RPM and HP capability that the killer Pontiacs have to offer you.
Just watch the BSFC that is going nice and smooth, then jumps radically from 0.48 to 0.55, then 0.58, and the HP going into the crapper. That is valve train in most cases. Everytime we make an improvement in the valve train, we get HP.
Lynn
Old Man Taylor
The cam in my 400 is a solid roller, 271/278 at 0.050" on a 106 LSA. Gross lift is 0.626, net is 0.600".
omt.my67.net/
screamingchief
Quote:
Bret, even your cam is way small compared to a SS car.
Yeah,,,I know,,,that's what I find so funny myself,have still had people who claim to know what they're talking about try and tell me (and others like me) that those solid cams I mentioned are too big for a 400 and I just gotta laugh to myself and wonder how the hell they think these "small engine" race cars are supposed to do what they can do.
I totally agree both of mine are pretty mild 400 combos,I'm shooting for some 12-ohs to high elevens on the motor,from there I'll rely on "bottled atmosphere" for the low 11-high 10 second time slips when the urge hits.
Mine are likely closer to 450-500 or so hp N/A,definately nowhere near a SS combo,at least not till the nitrous is brought into the picture.
Pretty much just a "bracket" package,not an "all out" deal.
I kinda based my combo off the premise that it's kinda like an "outlaw" stock class car,just with a dose of nitrous and no super tight engine/body rules to follow,seeing as how it has a lift-off glass FE and such.
Roll bar only,so nothing faster than 10 ohs for this current car that's for sure,got another car I'm gonna build for that "really fast" stuff.
Right now for me it's more about the journey,not the destination,maybe when I have a bit better finances I'll get a chance to step the whole program up a notch or two.
I have always liked the small cube/high RPM stuff myself,part of the reason I took up the "screamingchief" moniker!
I like to stay open to all options.
Just right now all this 400 based stuff is soooo affordable,and money has been soooo tight,,,just been real lucky picking up decent 400 gear real well priced lately,so for me I cant afford to turn it down,the "A" motor is virtually good to go now,and I got a bunch of stuff for 2 more 400 based motors now for what most folks would spend building just one 455 based combo,hard to turn these deals down when I know d**n well I can get them to do what I want them to do and keep me racing for a good long while,that should help me out a bunch while I get the "faster" car together hopefully.
Bret.
azbirds
This is also good info
www.petemccarthy.com/
455-4+1
Lynn, Great thread and info
Are the Stock motors limited to lift
The class we currently run in the sprint boat has a 0.500" lift limit with a flat tappet. We are running ported #16's with no restrictions.
Who makes the best lobes for a Pontiac with limited lift and still decent duration without going to one of the "launcher" series with titanium valves etc
We are currently running 253 deg @ 050 (0.505" net lift) with 107 sep installed at 102 intake and 113 ex CL (flat tappet)
I limited my choice of lobes by running 1.65 rockers I already had but think a 1.5 may allow more choices
Looks like I could be around 20-30 degrees short on duration as as the 6200/4700 peaks look spot on for what we are doing
Working on going faster (and now staying dry at the same time !!)
NHRASuperStock455SD
Quote:
Originally Posted by 455-4+1
Lynn, Great thread and info
Are the Stock motors limited to lift
The class we currently run in the sprint boat has a 0.500" lift limit with a flat tappet. We are running ported #16's with no restrictions.
Who makes the best lobes for a Pontiac with limited lift and still decent duration without going to one of the "launcher" series with titanium valves etc
Stocker engine can run any overlap, any duration, but have a limit of the stock lift measured at the valve and stock valve angle, stock valve seat angle(can use 3 angle valve jobs). They also require that you have a hydraulic lifter, but the rules are such that they are getting away with murder. Picking apart the rules are part of the game I guess. Schubech lifters are common.
My recommendation? If you can run titanium Pro Flows, DO IT! Valve bounce is a big issue that limits Pontiac motors. Of course it is exacerbated by valve close speed. Most Pontiac guys put bigger rockers, get nothing or slow the car down, and forget it...take them off. Really what they did was increase valve bounce or screwed up geometry. Do it light first, then start beefing it. There is big power in most Pontiacs by systematically addressing valve train issues.
Quote:
Originally Posted by 455-4+1
We are currently running 253 deg @ 050 (0.505" net lift) with 107 sep installed at 102 intake and 113 ex CL (flat tappet)
I limited my choice of lobes by running 1.65 rockers I already had but think a 1.5 may allow more choices
Looks like I could be around 20-30 degrees short on duration as as the 6200/4700 peaks look spot on for what we are doing
Boats are different than drag cars. I am not an expert, but my boat buddy says they go for torque. (kind of sounds like the average Pontiac guy) My Baja does not RPM quickly, it does it very slow, so I guess this is partly true. The rest is that it is a BBC and probably isnt so good down low.
In drag cars, you do the rocker ratio first, and the cam SECOND! Dont get rid of those 1.65's is my recommendation. It gives you 10% more lift across the entire lobe.
Lynn
taff2
This is the info I like to see! My little 400 has run consistent 10.50s with a solid flat tappet of 245/253 at 0.050" straight up on a 106 lda and 1.65 roller rockers,peaking at about 6100rpm and crossing the top end at 6400rpm ,using an old Torker 1 and tiny 1 5/8" headers. I have changed to 2" headers this year and was planning a cam change and convertor change from my tight 10" Art Carr,and going up to an 850 Holley from my 800, looks like I'll be changing the intake too. Thanks guys for the info,Taff.
Skip Fix
Comp has a number of lift limited lobes. They and Lunati both had some "stocker" lobes of lots of duration and limited lift.
I have a Comp RAIV one that has 274/274 @ 0.050 and stock lift for 1.65 rockers.
taff2
Talking of the 350 motors,I was looking at two of my blocks side by side,a '75 350 and a '75 400.The 350 block is thicker in all the right places compared to the 400, thicker pan rails,thicker mains webbing,blind mains bolt holes,even the mains caps are thicker around the dowel holes. If I can pick up a sonic tester and the bore walls turn out ok I'll bore it to 4.00" for SBC pistons and 3/4 fill it,should make a nice 383 screamer.
455-4+1
Quote:
Originally Posted by NHRASuperStock455SD
My recommendation? If you can run titanium Pro Flows, DO IT! Valve bounce is a big issue that limits Pontiac motors. Of course it is exacerbated by valve close speed. Most Pontiac guys put bigger rockers, get nothing or slow the car down, and forget it...take them off. Really what they did was increase valve bounce or screwed up geometry. Do it light first, then start beefing it. There is big power in most Pontiacs by systematically addressing valve train issues. Lynn
Hmmmm. May have just learnt a valuble lesson.
My 2.11"x5.065" long 30 degree intakes weigh 128
My 1.77"x5.065" long 45 degree exhausts (slight tulip) weigh 120g??
Thought there would have been more difference between the two ?
In saying this I understand the importance of the intake closing in relation to power output and the effect that "bounce" can have on this
For comparision an ugly stock TRW Chevy exhaust (1.600"x 4.725" long) was a mere 96 grams in comparison (no back cut just 45 deg seat). I imagine a race series valve could cut this down considerably !!. A comparison For a Stainless vs Ti valve I have seen was 101g vs 67g for the equivalent valve size/length.
Even comparing stock to stock a 400 Pontiac could have a valve mass over 25% greater than a 400 Chevy due to head size, design and length.
A shorter (lighter) valve with offset locks or retainers to gain installed height could help slightly ??
We are in the proccess of increasing our seat pressure in increments to see if we can gain rpm this way to begin with (crude fix for heavy intake valve)
Anyone like to chime in on what they would consider a maximum seat/over the nose pressure that would be reliable on an endurance (60 second) flat tappet with crower solids (no face oil feed), heavy valves and a usable rpm limit of 6500 (max rpm for jet unit) (0.500" max lift)
Quote:
Originally Posted by NHRASuperStock455SD
Boats are different than drag cars. I am not an expert, but my boat buddy says they go for torque. (kind of sounds like the average Pontiac guy) My Baja does not RPM quickly, it does it very slow, so I guess this is partly true. The rest is that it is a BBC and probably isnt so good down low.Lynn
Our sprint boats seem to be the opposite. They rpm very quicky until held at a "stalemate" rpm by the combination of impellor pitch and nozzle size. I was alerted to a possible valve/ spring problem by changing impellors and nozzles and seeing no rpm change at the top end. Engine would accelerate and hit the wall at the same point every time. No miss or anything just a flatten off at 5900 rpm. Hmmmmmmm
Working on going faster (and now staying dry at the same time !!)
NHRASuperStock455SD
Quote:
Originally Posted by 455-4+1
Hmmmm. May have just learnt a valuble lesson.
My 2.11"x5.065" long 30 degree intakes weigh 128
My 1.77"x5.065" long 45 degree exhausts (slight tulip) weigh 120g??
Thought there would have been more difference between the two ?
In saying this I understand the importance of the intake closing in relation to power output and the effect that "bounce" can have on this
For comparision an ugly stock TRW Chevy exhaust (1.600"x 4.725" long) was a mere 96 grams in comparison (no back cut just 45 deg seat). I imagine a race series valve could cut this down considerably !!. A comparison For a Stainless vs Ti valve I have seen was 101g vs 67g for the equivalent valve size/length.
Even comparing stock to stock a 400 Pontiac could have a valve mass over 25% greater than a 400 Chevy due to head size, design and length.
Remember that 5 grams in a valve is a bunch! 25 grams is the difference between night and day. I have seen engines like yours valve bounce with titanium valves. I sincerely believe that valve bounce hurts on an engine during acceleration much worse. So, you dont see it on the dyno as glaringly when doing a 300RPM/SEC acceleration test. However on the track(in your case in the water), first gear asks the engine to accelerate upwards of 1200RPMs/SEC. You wont see that on the dyno. That is where a SBC kicks your butt!
Quote:
Originally Posted by 455-4+1
A shorter (lighter) valve with offset locks or retainers to gain installed height could help slightly ??
You are walking down the slippery slope of many Pontiac guys. Remember that the taller you make that installed height, the more things flex, and the short the rocker fulrum length becomes. If you are using a stud mounted rocker, it will find its natural "stand height" based on the length push rod used. Most people ignor this and screw up their rocker geometry. If you are using a shaft system, this is where the hard work begins. A killer expensive motor, I recommend T & D because they will custom make the rockers for your application. Jesel will only sell you what they have in stock.
I just went through the entire valve train. It was no easy task, but we ended up with a 9.700 push rod length. We went with 7/16-0.180 wall to handle the monster springs. This required extensive special modifications to the stands, pushrods, rocker ratios and push rod tubes through the head.
Quote:
Originally Posted by 455-4+1
We are in the proccess of increasing our seat pressure in increments to see if we can gain rpm this way to begin with (crude fix for heavy intake valve)
Sometimes you have no choice as in SS guys. We are required to run Stainless valves. So we run 430lbs on the seat, about 1250 open. If I fall below about 360lbs on the seat, we see a loss in ET as the car starts nosing over in first and second at higher RPMs. (And we used to laugh at the SBC guys shimming their springs in the pits all the time )
Quote:
Originally Posted by 455-4+1
Anyone like to chime in on what they would consider a maximum seat/over the nose pressure that would be reliable on an endurance (60 second) flat tappet with crower solids (no face oil feed), heavy valves and a usable rpm limit of 6500 (max rpm for jet unit) (0.500" max lift)
As much as you can. Remember it isnt just pressure. Springs deform the more and faster you hit them. Try the engine with 1.5 rockers. If it runs better or the same, then this could be the problem.
Quote:
Originally Posted by 455-4+1
Our sprint boats seem to be the opposite. They rpm very quicky until held at a "stalemate" rpm by the combination of impellor pitch and nozzle size. I was alerted to a possible valve/ spring problem by changing impellors and nozzles and seeing no rpm change at the top end. Engine would accelerate and hit the wall at the same point every time. No miss or anything just a flatten off at 5900 rpm. Hmmmmmmm
Definitely Valve bounce. I have a whole drawer full of dynos where our Pontiac engines all quit at 6200RPM. We saw the HP fall off the edge of the kitchen counter there every time, independant of cubic inches, head flow, compression. We always thought it was rotating weight.
Until, one day we put SS valves in our Tunnel Port motor to put in a bracket car. Where did it stop pulling at on the dyno? 6300 RPM. This engine with titanium valves shifted at 9000RPM in the modified car. NO FREAKIN WAY!
We then went to a dyno session or our 400-6X motor with 6 sets of springs. Bumped the pressure from 280 to 350, got 200RPM up to 6400 peak.(we high fived). Then put on the NEXTEC spring and got another 200(another high 5). We then put the PRO Stock springs on and the 6X-400 pulled all the way to 7200, and never quit!
We stood there with our jaws open in utter amazement.
Lynn
455-4+1
Cheers for that Lynn
Valve weight and valvetrain mass in general is an area I have probably neglected in the past. (and present by the looks of it)
I hadnt really thought it neccesary with our "limited" RPM range but now see that this could actually be limiting it !!!
Started thinking about it when I picked up an insainly long 2.40" Ti intake out of a Big Cheif chevy head and just about threw it because it was so light. (compared to my perceived weight from its apperarance)
This engine (around 500 cid) would turn 9000rpm without breaking a sweat with close to an inch lift. I thought this and Winston cup type engines were the only ones that would benefit from Ti intakes.
Now starting to think differently
Working on going faster (and now staying dry at the same time !!)
ponchoshop
You the man Lynn.
Not many people here realize how much $$$$ you've spent in research-n-developement.
Mike Wachter "Region Warrior"
J Brady
Lynn if you were going to build a Pontiac for Stock eliminator, what combination would you look at? We are thinking about racing Stock along with S/C next year.
NHRASuperStock455SD
stock combos
Quote:
Originally Posted by J Brady
Lynn if you were going to build a Pontiac for Stock eliminator, what combination would you look at? We are thinking about racing Stock along with S/C next year.
Thanks guys for the kind words.
I love that Catalina, what year is that about a '60? Maybe we ought to look at that?
Depends on how much you want to spend. I am doing a 69 TA w a RA-IV. Only if NHRA appproves the Edelbrock heads as a replacement. Why? Because it runs in A, B, and C stock where all the cars that have their bogus cylinder head replacements. They all cheat. So I am not going to run stock heads against aftermarket replacements like GM Performance, and Dove against a 37 year old casting.
I think the best combo is the 1974 400 4X Firebird, 1978 400 6X Firebird, Anything with the D-port 1972 455 Engine, or the early 350 Venturas. There are several 350 Firebirds in the late 70's. One of the best combos is the regular 400 200HP in around 1978. They have the combustion chamber listed at 89.06ccs instead of 98cc's like it is suppose to be, but the HP rating on it is still low. Don Himes runs it and goes way under the index in a 78 Grand Prix.
If you want to run an earlier high compression engine, and it hasnt had the HP reduced, we can probably get it done.
That 389 with the Carter 4 barrell is such a good engine around 1960 to 64. It was around 240HP. The 64 is the best motor as it is listed with a zero deck and has huge compression.
I helped do a 67 400 Firebird stocker. It went 11.00's on its first few runs in E/SA. Those 670 heads are a favorite of mine.
The absolute best combo is that V-8 Turbo 80-81 TA or the V-6, but it will be tough to keep it consistent for the eliminator part of the show.
Lynn
Super Stock 400 motors
What HP numbers are these 400 motors putting out,and at what RPM? As I understand it ,this class has to use stock ,unported iron heads(yeah,I know they get acid ported), what are the intake manifolds of choice,are roller cams allowed,is compression limited,what other tricks are used(if they can be disclosed!). I take it that thin rings,high ring land pistons and gasporting are the norm,and probably cut down cranks.Thanks.
Skip Fix
I'm not sure when but maybe 10 years ago they let the SS guys port heads.They have open intake choices but must run a factory carb.Roller cams OK. Alot more suspension mods.
The Stock guys can't port and they have to use factory intakes, flat tappet cams also. Pretty stock suspension.
NHRASuperStock455SD
Stock has unported heads, but usually are ported, then covered up. Super Stock you can port with limits, but you cannot exceed the published(supposedly stock) OEM volumes. All kinds of tricks give you additional volumes.
www.nhra.com/tech_specs/rods/index.html
www.nhra.com/tech_specs/runners/index.html
Any manifold even sheet metal, any piston/ring/ land location in Super Stock, no gas porting allowed. Any cam allowed.
Heads are reserved to OEM castings with published volumes.
SS 400 6X motors are making 550-600HP
SS 400 16 motors 590-610
SS 400 RA-IV 620-650HP
Cranks are not allowed to be cut down. Yes people cheat, but face a year suspension and flogging on all the internet sites.
Lynn
NHRASuperStock455SD
SS car still for sale. Soon available turn key. (if it is too fast, probably wont sell it.)
forums.performanceyears.com/f...26#post2748926
taff2
Thanks guys.
Lynn, what rpm are the SS 400 16 motors making their HP at? Although there's no Stock or SuperStock class over here,I'm interested in seeing how far I can push my old iron headed(#16) 400 motor.
issach428
If its possible to modify stock parts and have different intake and cam choices, why arent there more stock parts guys pushing 600hp?? with lightly ported iron heads etc.??
72firebird 3800# 462 eheads e nitrous cam, continental converter 3.73. Pump gas 11.60's 120 on street tires/ race gas with a controlled 175hp n20 10.28 at 132mph with a 1.61 60ft. on drag radials spinning bad.
screamingchief
Quote:
If its possible to modify stock parts and have different intake and cam choices, why arent there more stock parts guys pushing 600hp?? with lightly ported iron heads etc.??
Why???
Lots of details I'm sure.
But I'm pretty sure part of the reason is because ALOT of them are afraid to put real cams in their "little ol' 400" motors!
JMO...
They listen to folks who say things like,"that cam will never work in that little motor,it's way too big!",,,"there's not enough head flow" or "it'll need to rev to 8000 RPM's to work,and the bottom end will be soft"...
But if you launch at 4000+ RPM's,the torque below that is hardly an issue of concern in a race situation.
The "little" motors need healthy doses of cam and/or compression,with plenty of convertor and gear for maximum affect!
Most are'nt in a hurry to use that sort of combo with their pontiacs,they go for the low RPM torque packages.
Especially if it's a "street/strip" combo...
My 406/670 "A" motor will be running a custom crower 256/260 solid on a 108 LSA.
The "B" motor will have a comp 290b6 solid which is 255/266 on a 106 LSA.
Most folks would tell you outright those cams are way too big for a "little" 400,but you gotta look at the rest of the combination in question,look at things like it's compression ratio,convertor,gears,intake,carb,exhaust etc.etc.,then it starts making more sense.
My racecar will be running something like a 3800-4200 convertor,with a th400 trans,and 4.10 gears with 28" tires to make those cams work with the rest of the combo.
Now granted I wont be making the max HP out of those combos till the iron heads get to their final state of prep (260-270 ish cfm @ 28"h2o),but I'll work with those combos till that happens.
I'm wanting to see what those changes bring to the table,so I'll be establishing a baseline with more or less "stock" heads,and working them from there to see the gains those mods yeild.
Ask guys like OMT and Steve C. what cams they ran with their high HP 400 combos,or better yet maybe Lynn will give a rough idea what he uses (though I would'nt expect him to be too precise on that info. ),I'm sure they're not no "baby" cams,that's for sure!
I know a lot of the stockers 350's & 400's use really big "juice" cams,specs are close to my solid cam specs often,yet they're hydraulics,Dave R. races stock eliminator,he had some of his old cams listed,pretty long duration lobes with stock lifts,not the norm,but they get the job done,tricks the motor into thinking it has more head up there than it actually has,then tighten up the LSA to narrow the power band some where it can be best utilized by the cars convertor and gearing.
Bret.
NHRASuperStock455SD
Quote:
Originally Posted by taff2
Thanks guys.
Lynn, what rpm are the SS 400 16 motors making their HP at? Although there's no Stock or SuperStock class over here,I'm interested in seeing how far I can push my old iron headed(#16) 400 motor.
Nice to see a guy in the UK doing some cast iron engines!
An average motor will go 6200 peak HP and 4700 peak torque with a cam about 106 L/S. Probably about 282/282 @ 0.050. (sorry dont know metric numbers without doing conversions). This would be with 1.65 studded crocker systems like Crane, and average valve train....lets say 280 lbs on the seat and about 700-800 open, Proflow valves, and about .700 lift at the valve. Heads will flow about 250cfm.
A killer engine will have much better heads and flow about 285 with good flow and not bad flow. The ports will have good CSA minimum about 2.000 square inches. Small ports with high velocity flow do NOT WORK! (Too much cylinder head choke.) Our old heads flowed 240 cfm, but if they had good CSA they made very good power. Small heads with big flow are stones.
This bigger motor will have peak HP around 6700 and torque around 5200 larger tubed headers.
The better motor will also have valve spring upwards of 400lbs on the seat with 1100lbs open. Good rocker shaft system (T&D)
Use a ported Victor and dont even think about it. Bringing the flow dividers under the carb to promote equalization is way more important than trying to achieve shorter intake runners. We haver tried it both ways and and always lose power by making the runner shorter. The Victor manifold dropped peak HP and torque by 300RPM. At every point it was more power, but one can't help to wonder about gaining that 300RPM back. (A Victor with about 3 inches shorter runner and same CSA is what I think would be perfect).
The 400 motor with 16 heads is not as competitive as it has too much HP in SS compared to other combos. However, it will make very good power and is a very competitive SS engine.
Lynn
NHRASuperStock455SD
Bret,
You hit the nail dead square. The cheezy Chevrolet 350's with Q-jets are making 660HP. We can run with them. They make that because it is a smaller cubic inch size for the cylinder heads 1.94 intakes that allow that engine to come in about 7800 RPM with a killer valve train and port job.
The Pontiac 350 is a killer engine, and would love someone to do a 1969 350 for SS. Truman Fields has expressed interest. Same heads smaller motor means more HP, yes less torque, but who cares? Race cars dont run off of peak torque. Gear the piss out of it, and forget the torque with a smaller motor.
The average cam these days in a Pontiac is about 0.740 lift, 106 to 108 L/S and 282/282 or bigger @.050. Bret, even your cam is way small compared to a SS car. Before ported heads they had even more duration like 288/288@0.50 With this kind of cam you also need the valve train to go with it. If you dont, then valve bounce will kill you ever seeing the RPM and HP capability that the killer Pontiacs have to offer you.
Just watch the BSFC that is going nice and smooth, then jumps radically from 0.48 to 0.55, then 0.58, and the HP going into the crapper. That is valve train in most cases. Everytime we make an improvement in the valve train, we get HP.
Lynn
Old Man Taylor
The cam in my 400 is a solid roller, 271/278 at 0.050" on a 106 LSA. Gross lift is 0.626, net is 0.600".
omt.my67.net/
screamingchief
Quote:
Bret, even your cam is way small compared to a SS car.
Yeah,,,I know,,,that's what I find so funny myself,have still had people who claim to know what they're talking about try and tell me (and others like me) that those solid cams I mentioned are too big for a 400 and I just gotta laugh to myself and wonder how the hell they think these "small engine" race cars are supposed to do what they can do.
I totally agree both of mine are pretty mild 400 combos,I'm shooting for some 12-ohs to high elevens on the motor,from there I'll rely on "bottled atmosphere" for the low 11-high 10 second time slips when the urge hits.
Mine are likely closer to 450-500 or so hp N/A,definately nowhere near a SS combo,at least not till the nitrous is brought into the picture.
Pretty much just a "bracket" package,not an "all out" deal.
I kinda based my combo off the premise that it's kinda like an "outlaw" stock class car,just with a dose of nitrous and no super tight engine/body rules to follow,seeing as how it has a lift-off glass FE and such.
Roll bar only,so nothing faster than 10 ohs for this current car that's for sure,got another car I'm gonna build for that "really fast" stuff.
Right now for me it's more about the journey,not the destination,maybe when I have a bit better finances I'll get a chance to step the whole program up a notch or two.
I have always liked the small cube/high RPM stuff myself,part of the reason I took up the "screamingchief" moniker!
I like to stay open to all options.
Just right now all this 400 based stuff is soooo affordable,and money has been soooo tight,,,just been real lucky picking up decent 400 gear real well priced lately,so for me I cant afford to turn it down,the "A" motor is virtually good to go now,and I got a bunch of stuff for 2 more 400 based motors now for what most folks would spend building just one 455 based combo,hard to turn these deals down when I know d**n well I can get them to do what I want them to do and keep me racing for a good long while,that should help me out a bunch while I get the "faster" car together hopefully.
Bret.
azbirds
This is also good info
www.petemccarthy.com/
455-4+1
Lynn, Great thread and info
Are the Stock motors limited to lift
The class we currently run in the sprint boat has a 0.500" lift limit with a flat tappet. We are running ported #16's with no restrictions.
Who makes the best lobes for a Pontiac with limited lift and still decent duration without going to one of the "launcher" series with titanium valves etc
We are currently running 253 deg @ 050 (0.505" net lift) with 107 sep installed at 102 intake and 113 ex CL (flat tappet)
I limited my choice of lobes by running 1.65 rockers I already had but think a 1.5 may allow more choices
Looks like I could be around 20-30 degrees short on duration as as the 6200/4700 peaks look spot on for what we are doing
Working on going faster (and now staying dry at the same time !!)
NHRASuperStock455SD
Quote:
Originally Posted by 455-4+1
Lynn, Great thread and info
Are the Stock motors limited to lift
The class we currently run in the sprint boat has a 0.500" lift limit with a flat tappet. We are running ported #16's with no restrictions.
Who makes the best lobes for a Pontiac with limited lift and still decent duration without going to one of the "launcher" series with titanium valves etc
Stocker engine can run any overlap, any duration, but have a limit of the stock lift measured at the valve and stock valve angle, stock valve seat angle(can use 3 angle valve jobs). They also require that you have a hydraulic lifter, but the rules are such that they are getting away with murder. Picking apart the rules are part of the game I guess. Schubech lifters are common.
My recommendation? If you can run titanium Pro Flows, DO IT! Valve bounce is a big issue that limits Pontiac motors. Of course it is exacerbated by valve close speed. Most Pontiac guys put bigger rockers, get nothing or slow the car down, and forget it...take them off. Really what they did was increase valve bounce or screwed up geometry. Do it light first, then start beefing it. There is big power in most Pontiacs by systematically addressing valve train issues.
Quote:
Originally Posted by 455-4+1
We are currently running 253 deg @ 050 (0.505" net lift) with 107 sep installed at 102 intake and 113 ex CL (flat tappet)
I limited my choice of lobes by running 1.65 rockers I already had but think a 1.5 may allow more choices
Looks like I could be around 20-30 degrees short on duration as as the 6200/4700 peaks look spot on for what we are doing
Boats are different than drag cars. I am not an expert, but my boat buddy says they go for torque. (kind of sounds like the average Pontiac guy) My Baja does not RPM quickly, it does it very slow, so I guess this is partly true. The rest is that it is a BBC and probably isnt so good down low.
In drag cars, you do the rocker ratio first, and the cam SECOND! Dont get rid of those 1.65's is my recommendation. It gives you 10% more lift across the entire lobe.
Lynn
taff2
This is the info I like to see! My little 400 has run consistent 10.50s with a solid flat tappet of 245/253 at 0.050" straight up on a 106 lda and 1.65 roller rockers,peaking at about 6100rpm and crossing the top end at 6400rpm ,using an old Torker 1 and tiny 1 5/8" headers. I have changed to 2" headers this year and was planning a cam change and convertor change from my tight 10" Art Carr,and going up to an 850 Holley from my 800, looks like I'll be changing the intake too. Thanks guys for the info,Taff.
Skip Fix
Comp has a number of lift limited lobes. They and Lunati both had some "stocker" lobes of lots of duration and limited lift.
I have a Comp RAIV one that has 274/274 @ 0.050 and stock lift for 1.65 rockers.
taff2
Talking of the 350 motors,I was looking at two of my blocks side by side,a '75 350 and a '75 400.The 350 block is thicker in all the right places compared to the 400, thicker pan rails,thicker mains webbing,blind mains bolt holes,even the mains caps are thicker around the dowel holes. If I can pick up a sonic tester and the bore walls turn out ok I'll bore it to 4.00" for SBC pistons and 3/4 fill it,should make a nice 383 screamer.
455-4+1
Quote:
Originally Posted by NHRASuperStock455SD
My recommendation? If you can run titanium Pro Flows, DO IT! Valve bounce is a big issue that limits Pontiac motors. Of course it is exacerbated by valve close speed. Most Pontiac guys put bigger rockers, get nothing or slow the car down, and forget it...take them off. Really what they did was increase valve bounce or screwed up geometry. Do it light first, then start beefing it. There is big power in most Pontiacs by systematically addressing valve train issues. Lynn
Hmmmm. May have just learnt a valuble lesson.
My 2.11"x5.065" long 30 degree intakes weigh 128
My 1.77"x5.065" long 45 degree exhausts (slight tulip) weigh 120g
??Thought there would have been more difference between the two ?
In saying this I understand the importance of the intake closing in relation to power output and the effect that "bounce" can have on this
For comparision an ugly stock TRW Chevy exhaust (1.600"x 4.725" long) was a mere 96 grams in comparison (no back cut just 45 deg seat). I imagine a race series valve could cut this down considerably !!. A comparison For a Stainless vs Ti valve I have seen was 101g vs 67g for the equivalent valve size/length.
Even comparing stock to stock a 400 Pontiac could have a valve mass over 25% greater than a 400 Chevy due to head size, design and length.
A shorter (lighter) valve with offset locks or retainers to gain installed height could help slightly ??
We are in the proccess of increasing our seat pressure in increments to see if we can gain rpm this way to begin with (crude fix for heavy intake valve)
Anyone like to chime in on what they would consider a maximum seat/over the nose pressure that would be reliable on an endurance (60 second) flat tappet with crower solids (no face oil feed), heavy valves and a usable rpm limit of 6500 (max rpm for jet unit)
(0.500" max lift)Quote:
Originally Posted by NHRASuperStock455SD
Boats are different than drag cars. I am not an expert, but my boat buddy says they go for torque. (kind of sounds like the average Pontiac guy) My Baja does not RPM quickly, it does it very slow, so I guess this is partly true. The rest is that it is a BBC and probably isnt so good down low.Lynn
Our sprint boats seem to be the opposite. They rpm very quicky until held at a "stalemate" rpm by the combination of impellor pitch and nozzle size. I was alerted to a possible valve/ spring problem by changing impellors and nozzles and seeing no rpm change at the top end. Engine would accelerate and hit the wall at the same point every time. No miss or anything just a flatten off at 5900 rpm. Hmmmmmmm
Working on going faster (and now staying dry at the same time !!)
NHRASuperStock455SD
Quote:
Originally Posted by 455-4+1
Hmmmm. May have just learnt a valuble lesson.
My 2.11"x5.065" long 30 degree intakes weigh 128
My 1.77"x5.065" long 45 degree exhausts (slight tulip) weigh 120g
??Thought there would have been more difference between the two ?
In saying this I understand the importance of the intake closing in relation to power output and the effect that "bounce" can have on this
For comparision an ugly stock TRW Chevy exhaust (1.600"x 4.725" long) was a mere 96 grams in comparison (no back cut just 45 deg seat). I imagine a race series valve could cut this down considerably !!. A comparison For a Stainless vs Ti valve I have seen was 101g vs 67g for the equivalent valve size/length.
Even comparing stock to stock a 400 Pontiac could have a valve mass over 25% greater than a 400 Chevy due to head size, design and length.
Remember that 5 grams in a valve is a bunch! 25 grams is the difference between night and day. I have seen engines like yours valve bounce with titanium valves. I sincerely believe that valve bounce hurts on an engine during acceleration much worse. So, you dont see it on the dyno as glaringly when doing a 300RPM/SEC acceleration test. However on the track(in your case in the water), first gear asks the engine to accelerate upwards of 1200RPMs/SEC. You wont see that on the dyno. That is where a SBC kicks your butt!
Quote:
Originally Posted by 455-4+1
A shorter (lighter) valve with offset locks or retainers to gain installed height could help slightly ??
You are walking down the slippery slope of many Pontiac guys. Remember that the taller you make that installed height, the more things flex, and the short the rocker fulrum length becomes. If you are using a stud mounted rocker, it will find its natural "stand height" based on the length push rod used. Most people ignor this and screw up their rocker geometry. If you are using a shaft system, this is where the hard work begins. A killer expensive motor, I recommend T & D because they will custom make the rockers for your application. Jesel will only sell you what they have in stock.
I just went through the entire valve train. It was no easy task, but we ended up with a 9.700 push rod length. We went with 7/16-0.180 wall to handle the monster springs. This required extensive special modifications to the stands, pushrods, rocker ratios and push rod tubes through the head.
Quote:
Originally Posted by 455-4+1
We are in the proccess of increasing our seat pressure in increments to see if we can gain rpm this way to begin with (crude fix for heavy intake valve)
Sometimes you have no choice as in SS guys. We are required to run Stainless valves. So we run 430lbs on the seat, about 1250 open. If I fall below about 360lbs on the seat, we see a loss in ET as the car starts nosing over in first and second at higher RPMs. (And we used to laugh at the SBC guys shimming their springs in the pits all the time )
Quote:
Originally Posted by 455-4+1
Anyone like to chime in on what they would consider a maximum seat/over the nose pressure that would be reliable on an endurance (60 second) flat tappet with crower solids (no face oil feed), heavy valves and a usable rpm limit of 6500 (max rpm for jet unit)
(0.500" max lift) As much as you can. Remember it isnt just pressure. Springs deform the more and faster you hit them. Try the engine with 1.5 rockers. If it runs better or the same, then this could be the problem.
Quote:
Originally Posted by 455-4+1
Our sprint boats seem to be the opposite. They rpm very quicky until held at a "stalemate" rpm by the combination of impellor pitch and nozzle size. I was alerted to a possible valve/ spring problem by changing impellors and nozzles and seeing no rpm change at the top end. Engine would accelerate and hit the wall at the same point every time. No miss or anything just a flatten off at 5900 rpm. Hmmmmmmm
Definitely Valve bounce. I have a whole drawer full of dynos where our Pontiac engines all quit at 6200RPM. We saw the HP fall off the edge of the kitchen counter there every time, independant of cubic inches, head flow, compression. We always thought it was rotating weight.
Until, one day we put SS valves in our Tunnel Port motor to put in a bracket car. Where did it stop pulling at on the dyno? 6300 RPM. This engine with titanium valves shifted at 9000RPM in the modified car. NO FREAKIN WAY!
We then went to a dyno session or our 400-6X motor with 6 sets of springs. Bumped the pressure from 280 to 350, got 200RPM up to 6400 peak.(we high fived). Then put on the NEXTEC spring and got another 200(another high 5). We then put the PRO Stock springs on and the 6X-400 pulled all the way to 7200, and never quit!
We stood there with our jaws open in utter amazement.
Lynn
455-4+1
Cheers for that Lynn
Valve weight and valvetrain mass in general is an area I have probably neglected in the past. (and present by the looks of it)
I hadnt really thought it neccesary with our "limited" RPM range but now see that this could actually be limiting it !!!
Started thinking about it when I picked up an insainly long 2.40" Ti intake out of a Big Cheif chevy head and just about threw it because it was so light. (compared to my perceived weight from its apperarance)
This engine (around 500 cid) would turn 9000rpm without breaking a sweat with close to an inch lift. I thought this and Winston cup type engines were the only ones that would benefit from Ti intakes.
Now starting to think differently
Working on going faster (and now staying dry at the same time !!)
ponchoshop
You the man Lynn.
Not many people here realize how much $$$$ you've spent in research-n-developement.
Mike Wachter "Region Warrior"
J Brady
Lynn if you were going to build a Pontiac for Stock eliminator, what combination would you look at? We are thinking about racing Stock along with S/C next year.
NHRASuperStock455SD
stock combos
Quote:
Originally Posted by J Brady
Lynn if you were going to build a Pontiac for Stock eliminator, what combination would you look at? We are thinking about racing Stock along with S/C next year.
Thanks guys for the kind words.
I love that Catalina, what year is that about a '60? Maybe we ought to look at that?
Depends on how much you want to spend. I am doing a 69 TA w a RA-IV. Only if NHRA appproves the Edelbrock heads as a replacement. Why? Because it runs in A, B, and C stock where all the cars that have their bogus cylinder head replacements. They all cheat. So I am not going to run stock heads against aftermarket replacements like GM Performance, and Dove against a 37 year old casting.
I think the best combo is the 1974 400 4X Firebird, 1978 400 6X Firebird, Anything with the D-port 1972 455 Engine, or the early 350 Venturas. There are several 350 Firebirds in the late 70's. One of the best combos is the regular 400 200HP in around 1978. They have the combustion chamber listed at 89.06ccs instead of 98cc's like it is suppose to be, but the HP rating on it is still low. Don Himes runs it and goes way under the index in a 78 Grand Prix.
If you want to run an earlier high compression engine, and it hasnt had the HP reduced, we can probably get it done.
That 389 with the Carter 4 barrell is such a good engine around 1960 to 64. It was around 240HP. The 64 is the best motor as it is listed with a zero deck and has huge compression.
I helped do a 67 400 Firebird stocker. It went 11.00's on its first few runs in E/SA. Those 670 heads are a favorite of mine.
The absolute best combo is that V-8 Turbo 80-81 TA or the V-6, but it will be tough to keep it consistent for the eliminator part of the show.
Lynn
