421 SBC - something holding it back at the track !

[67RS502]

look at the old version in the 1st post.
small head and less power then yours... do you see a pattern?
http://www.speedtalk.com/forum/viewtopi ... d5e3608be2
you've got to let them breath, choke will just loose power everywhere... where it counts.

[6.50camaro]

I total understand that the combination is what it is . 95% street driven and you don't want to or need to make major changes. It made 580 hp @ 6000 rpm on the dyno ,are you happy with that or were you looking for more?
Wallace racing calculators says 580 hp in a 3617 lbs car should do 1.49 60' 10.72 @ 125 1/4 mile , so using the numbers you gave are .02 off on the 60' .2 off on the et and a little less than 2.5 mph slow . Pretty close for the first time out . You don't need a bigger carb at 100% VE you are only using 793 CFM@6500rpm.( I am presently running a 6.50@104+ 1/8 mile index class car with a 422 and a old school holley 750 DP) You don't need more gear, 3.73's with the 25.9 tall 275/50 drag radials is about the same as having 4.30 gears w/ a 28.5 tall tire.
IMHO your exhaust is the hold back . Not that there is a lot of restriction but the tuned length of the system in whole is to long . It would really be to your advantage if you could make some runs without the whole system but with 12 to 18" collector extensions . I would try to work some kind of cut out into the system between the collectors and the X pipe trying to keep to the 12 to 18' length to the end of the cutout. .Any extra torque from the X pipe is not where you can use it with a 5000 stall convertor .
Watching the video I notice the car pulling to the left as you sit in the car. Add more preload about 1 flat at a time on the cal trac bar on that side till it leaves straight . On the one run it looks like it was puffing smoke on shifts ? Nice ride, a almost 600 hp classic street car running in the 10's is still the best ride .
Just my thoughts Good Luck with tuning. Dan

[Keith Morganstein]

Watching the video I notice the car pulling to the left as you sit in the car. Add more preload about 1 flat at a time on the cal trac bar on that side till it leaves straight .

Is the car also “dog tracking”? A common issue with those cars.

[steve cowan]

you've got a variety of responses.
your mph is showing loss of power, even with different gears and stalls it should mph better.
Since my 420 ( and my car) is similar to your set up, heres the issues I see with your setup:
1. Heads... those heads are just too small, pinch is around 2.1", you need around 2.4-2.5" csa, have them ported! this will be worth a ton of power.
2. Cam is on the small side, which will limit power and rpm, my HR cam is a few degrees bigger, but don't believe all the nonsense of HR cams no power no rpm bs, I shift at 7200-7300, with matching valvetrain hr cams will make good power.
3. its going to want 1 7/8" headers, but 1 3/4" isn't hurting it that bad, about 20hp.
4. make sure your fuel and exhaust system is up to the job.

Dan,
you make some good points of interest,is it fair to say if you have a bigger MCSA being the pinch or the valve throat area and you run a bigger camshaft that all you will do is push peak up higher in the rpm range ? all things been equal as in intake and exhaust ports been optimized for the MCSA.
with the compression it has,the smaller head and cam the engine will make good torque and running 11.7 static and pump fuel must be on the edge depending where the builder wanted to put EVO maybe to bleed off some cylinder pressure,
i am a fan of over reving the engine past peak but i doubt that would help in this instance because as you stated about choke point and cam but we have seen a bit of stuff over achieve with small camshaft duration in the past and valve timing is probably more important that total numbers we take for granted.anyway would be interested on your opinion on the subject.

[6.50camaro]

Steve,
Not sure if your looking for a response from me (Dan) or 67RS502 that you quoted . Please clarify more brain cells must have retired. Dan

[67RS502]

Must be you, as I don't know anything about cams, I can guesstimate some for engines I'm familiar with, but I really leave that to the experts.

[steve cowan]

Steve,
Not sure if your looking for a response from me (Dan) or 67RS502 that you quoted . Please clarify more brain cells must have retired. Dan

Dan,
sorry my mistake, i quoted towards 67RS502 post

Must be you, as I don't know anything about cams, I can guesstimate some for engines I'm familiar with, but I really leave that to the experts.

67RS502,
my post was talking about making the cylinder head bigger at the MCSA which can mean power can peak at a higher rpm if all else is equal as in cam,induction,etc

[6.50camaro]

steve ,
I will attempt to answer you with my non-expert opinion on these matters . First when you say MCSA are you referring to minimum cross section because I have also seen MCSA used as Mean Cross Section Area or Average Cross Section Area .
I think we have seen that peak torque on a "street" motor is set more by the Avg.CSA of the intake tract including the manifold runner . Peak torque occurs at the rpm when maximum filling of the cylinder takes place as allowed by air speed velocity (csa) and the duration-lift window . So yes larger CSA more duration an engine of any given size will have peak torque at higher rpm. That makes the difference between a Cam that is "drive" able or not
My thoughts are that moving the EO to bleed of pressure is cutting off the wrong end of the stick. Move the IC later less dynamic CR more Ram effect from the High velocity air column . No wasting of power generated by early opening the exhaust valve. Speaking of that Crane Cams hyd. rollers are bad at this . any thing more than 248* @.050 and the ex valve opens before 90* BBDC if degreed in with their valve events . Bleeding pressure off at the end of the cycle doesn't help prevent detonation just reduces power leading to the engine having to work harder and hotter leading to more detonation.
SBC-68-FIREBIRD was that cam custom ground ? I see no listing for those specs in my Master catalog although it is 8 or 9 years old .
My thoughts for what it matters . Dan

[MadBill]

A common prevailing theory holds that an 'early' EVO helps power above the peak because the reduced pumping losses during the shorter blowdown period have more effect than trying to wring more torque from the falling cylinder pressure*, enough to outweigh the torque loss lower in the power band. *At these high revs, with falling V.E., far less at EVO than at say peak torque.

[6.50camaro]

A common prevailing theory holds that an 'early' EVO helps power above the peak because the reduced pumping losses during the shorter blowdown period have more effect than trying to wring more torque from the falling cylinder pressure*, enough to outweigh the torque loss lower in the power band. *At these high revs, with falling V.E., far less at EVO than at say peak torque.

I would agree with you on a motor that spends most of its time a few hundred rpm's either side of peak hp or is expected to rev and not fall on its face up to 1000 rpm's or more above peak hp. In this case I was referring to a the example Steve gave, smaller than optimum head and cam with high-ish static CR. As I said, far from an expert just sharing my thoughts and experiences. Dan

[steve cowan]

A common prevailing theory holds that an 'early' EVO helps power above the peak because the reduced pumping losses during the shorter blowdown period have more effect than trying to wring more torque from the falling cylinder pressure*, enough to outweigh the torque loss lower in the power band. *At these high revs, with falling V.E., far less at EVO than at say peak torque.

Bill,
As per usual your posts are concise and are precious in there value,always leaving me for more but i always suspect the little guy always scratching his chin is telling me you are throwing breadcrumbs and i need to research a bit deeper to fully comprehend.
Bill am i getting warmer????......

[MadBill]

It would be amazing Steve to have even a minute fraction of the arcane knowledge re cylinder pressure possessed by one of our members whose sharing is severely limited by NDAs, but alas, although I share them freely, crumbs are all I have in my pockets...

[steve cowan]

steve ,
I will attempt to answer you with my non-expert opinion on these matters . First when you say MCSA are you referring to minimum cross section because I have also seen MCSA used as Mean Cross Section Area or Average Cross Section Area .
I think we have seen that peak torque on a "street" motor is set more by the Avg.CSA of the intake tract including the manifold runner . Peak torque occurs at the rpm when maximum filling of the cylinder takes place as allowed by air speed velocity (csa) and the duration-lift window . So yes larger CSA more duration an engine of any given size will have peak torque at higher rpm. That makes the difference between a Cam that is "drive" able or not
My thoughts are that moving the EO to bleed of pressure is cutting off the wrong end of the stick. Move the IC later less dynamic CR more Ram effect from the High velocity air column . No wasting of power generated by early opening the exhaust valve. Speaking of that Crane Cams hyd. rollers are bad at this . any thing more than 248* @.050 and the ex valve opens before 90* BBDC if degreed in with their valve events . Bleeding pressure off at the end of the cycle doesn't help prevent detonation just reduces power leading to the engine having to work harder and hotter leading to more detonation.
SBC-68-FIREBIRD was that cam custom ground ? I see no listing for those specs in my Master catalog although it is 8 or 9 years old .
My thoughts for what it matters . Dan

Dan,
thanks for your reply,
i feel we have got off topic a bit but your first post is very good and i believe Scott (OP) is looking for answers as you said,i am sure he knows more head,cam,rpm,rear gear etc etc would change the car totally,the engine made 580 hp on the dyno with bigger pipes,Scott says from the get go the pipes in there design are probably a crutch,change the pipes?? why not but its at a cost and the return might not be there,plenty of people pay for new pipes and it dont make a brass razoo of difference but you dont know until until you try,You have to remember down here in Australia where the water spins the other way we get jammed in the preverbial on cost of go fast parts...........
anyway i want to talk about the AFR 210 competition head if thats ok
MCSA at the pinch 2.11'' a bit small probably,but the head flows a claimed 322cfm @ 0.650'' lift and i dont know the velocity profile past the pinch and over the short turn but i would think if they go turbulent earlier they would not pick up flow,i under stand with a modified super victor intake thats had plenum work and work around the short length runners down to a port match at the flange,what are we saying 3.2-3.3'' at the plenum down to 2.4-2.6'' at the runner exit??
i calculated 421ci @ 6000 rpm is aprox 2.2-2.3'' at the pinch,have these heads been modified at the pinch ?? i dont know ask Scott but he might not know either.
I would like Rafel (67RS502) if he could explain what he means by open the pinch up to 2.6'' and let her breathe,i can understand if the thought is to try and keep AVG CSA through the complete intake tract,just grinding the pinch bigger is not the answer because if it was everyone would just do that and pat it on the head and call it good.
i am not here to criticize or question anyone's ideas i am here to learn

[steve cowan]

It would be amazing Steve to have even a minute fraction of the arcane knowledge re cylinder pressure possessed by one of our members whose sharing is severely limited by NDAs, but alas, although I share them freely, crumbs are all I have in my pockets...

Bill,
they are good breadcrumbs and i thank you for sharing them,i have read from pages 713 down to 394 here on speedtalk over the last few months,you have been in the mix alot and i see you pick your battles where need be,damn good information available to anybody willing to dig,just wish i could retain all the good info

[SBC-68-FIREBIRD]

Hey Boys,

Some answers to the above questions posts -

No, the car does not dog track.

The heads are the 1103 Comp port heads & other than valve springs they are untouched.

It is a genuine street car, it gets cruised around most weekends & I dont mean to get milk & back home, it drives everywhere & anywhere. When going to the track the only changes I make are to fit the Calvert front & rear shocks & put the Convo's on but after going to the track I often get lazy & dont change shocks for 6-12 months.
You are correct Dan, having a street car that runs 10's is pretty cool to me

You are very right Steve, we do get reamed a new ass down here. Just to change up to bigger pipes which is a real easy thing to try but theres nothing easy about it in the $ department.
A custom set of headers only is about $2500.
A set of 1 7/8" Hooker Super Comps are roughly $600 for you guys but by the time the $ gets converted to Aussie dollars, add freight then GST on top of the whole lot they are about $1150 here.

The cam is a custom grind done by Crane that was ground to suit everything - engine, trans, gears, weight etc etc.