#41  
Old 11-24-2022, 01:39 PM
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If we are going to throw out HP numbers how about MPH and weight to go with them. That kind of helps even out if a stingy or a happy dyno. and numbers can be changed by a different correction factor easily also.

My IA runs closer to the uncorrected numbers(132.5mph 3595 lbs) which is less than the 695 corrected. probably because most track days are warm and humid like the dyno day was! The 455 in my TA at 3750 ran 124 mph and only dynoed 525 corrected! Wallace calculator and Moroso slide 550 hp.Different dynos.

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  #42  
Old 11-24-2022, 02:09 PM
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Originally Posted by Skip Fix View Post
If we are going to throw out HP numbers how about MPH and weight to go with them. That kind of helps even out if a stingy or a happy dyno. and numbers can be changed by a different correction factor easily also.

My IA runs closer to the uncorrected numbers(132.5mph 3595 lbs) which is less than the 695 corrected. probably because most track days are warm and humid like the dyno day was! The 455 in my TA at 3750 ran 124 mph and only dynoed 525 corrected! Wallace calculator and Moroso slide 550 hp.Different dynos.
Issue with dyno and track comparison for street cars is there are accessories and full exhaust that kill power at the track. Easier to look at race cars vs dyno numbers.

  #43  
Old 11-24-2022, 04:11 PM
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Originally Posted by yellow1098 View Post
So my engine is finally done here is the combo……..
70 4 bolt main block, 461 , compression 10.2, 340 Cfm eheads,, port matched northwind intake, camshaft: 248 intake 254 exhaust 620 gross lift 112 lobe separation.

I am also running a Holley terminator x with a 1300 cfm throttle body

The engine was Dynoed with only a 750cfm carb as they didn’t have the setup to run efi on the Dyno and it made 551 hp and 555 torque at 6500 rpm

When I bought my combo from butler the parts combo was put together with the goal of 650hp so I was about 100hp shy of that

My questions is how close will I get to that with my 1300 cfm throttle body compared to the obviously to small 750 carb?

The goal with the Dyno was only to break the engine in properly before I put it in the car which I accomplished and everything ran great! I just wanted to get your thoughts on how much HP and torque I lost with the engine being under carbed compared to what my goal is.

Thanks as always
Watch this video, give you a good idea on what you could pick up with Throttle body. Forget it’s a Chevy tho…LOL

https://youtu.be/iry0QhiuulM

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  #44  
Old 11-24-2022, 07:48 PM
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Originally Posted by slowbird View Post
Issue with dyno and track comparison for street cars is there are accessories and full exhaust that kill power at the track. Easier to look at race cars vs dyno numbers.
My TA had no accessories on the engine dyno yet track numbers show more HP! PS, PB, full exhaust, transmission and rear end. So kind of opposite there. And it ran the same without any exhaust at all on it as with full X 3".

I understand what you are saying and why maybe the IA is less based on mph running an exhaust. But dynos like flow benches can be all over the place on the same engine, especially when you start using correction factors.


I still think knowing taking some off for accessories and some for a full exhaust would get us closer to comparing using mph. ET yes more traction/60ft bottom end issues(chasing that on the IA Camaro).

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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
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  #45  
Old 11-24-2022, 11:45 PM
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Quote:
Originally Posted by Skip Fix View Post
If we are going to throw out HP numbers how about MPH and weight to go with them. That kind of helps even out if a stingy or a happy dyno. and numbers can be changed by a different correction factor easily also.

My IA runs closer to the uncorrected numbers(132.5mph 3595 lbs) which is less than the 695 corrected. probably because most track days are warm and humid like the dyno day was! The 455 in my TA at 3750 ran 124 mph and only dynoed 525 corrected! Wallace calculator and Moroso slide 550 hp.Different dynos.
No doubt you need to know your exact race weight at the very least when trying to convert et/ mph to hp

Body style and wind conditions will play large factors as well….a low slung car with low frontal area and a tail wind will obviously mph higher …

Not an exact science by any stretch!

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  #46  
Old Yesterday, 12:16 AM
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Quote:
Originally Posted by Gach View Post
Watch this video, give you a good idea on what you could pick up with Throttle body. Forget it’s a Chevy tho…LOL

https://youtu.be/iry0QhiuulM

That video is great! I’m hoping for some results like that with my efi….especially with the carb that was used being so small

  #47  
Old Yesterday, 01:21 AM
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I think you will. Being crab was only 750. How much who knows. But hey down road you can always make a cam change, that will definitely get you there.

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  #48  
Old Yesterday, 05:21 AM
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Pontiacs take more carb for a horsepower number than a comparable Chevy does. Its always been that way.
Has something to do with our long strokes for a given cid and crappy heads.
Still better than a puke Chevy.

  #49  
Old Yesterday, 09:37 AM
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If your going to compare track numbers you're in the same boat with dynos. You still need correction factors. Cars out here at elevation and desert heat won't run as quick as someone in Florida or Maine.
In fact all my stuff ran quicker in Ohio than it does here in Arizona.
Figure in DA and it starts making sense.

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  #50  
Old Yesterday, 09:43 AM
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Originally Posted by Dragncar View Post
Pontiacs take more carb for a horsepower number than a comparable Chevy does. Its always been that way.
Has something to do with our long strokes for a given cid and crappy heads.
Still better than a puke Chevy.
Yeah Pontiacs never have been big HP makers anyway when talking about using conventional heads. So they always make great torque curves and that's what carries them down track. BBC has a far superior head much easier to make HP with that doesn't need a monstrous cam to get there, but they don't have the torque curve a Pontiac does.

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  #51  
Old Yesterday, 10:07 AM
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+2

A big block Chevy build can get there with a much smaller cam for sure. Less stroke/piston speed, not nearly the mass of spinning and reciprocating parts, smaller bearing diameter, better bore to stroke ratio, and you can drop a tennis ball thru the intake ports on most of the heads they are using to get the big numbers we see on dyno runs, etc.

As far as the 750cfm carb being used here. About 20 years ago I did a carb CFM test back to back on they dyno an repeated the testing at the track. The carbs tested were 750cfm, 825cfm, and 850cfm. On a 500hp engine the 750cfm carb cost 13hp with no other changes. The 827cfm carb and 849cfm carb were near mirror images of each other on the dyno.

At the track remarkably the entire spead of ET was less than .05 seconds between all the carbs tested. The 825cfm actually ran the highest MPH for all runs made that day by .30 mph. The quickest ET was using the 850cfm carb. I wasn't really all that surprised because on the dyno ALL the carbs were dead nuts even to 4500rpm's and they shift points were 5500rpms. The engine simply spent very little time in the RPM range where the larger carbs were using more power plus at the 500hp mark the engine didn't act like it needed much more than 800cfm.

So there is no doubt you are giving up some power at high RPM with the smaller carburetor but it's not going to be anywhere near 100hp.......IMHO........

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  #52  
Old Yesterday, 10:15 AM
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Originally Posted by Cliff R View Post
+2

A big block Chevy build can get there with a much smaller cam for sure. Less stroke/piston speed, not nearly the mass of spinning and reciprocating parts, smaller bearing diameter, better bore to stroke ratio, and you can drop a tennis ball thru the intake ports on most of the heads they are using to get the big numbers we see on dyno runs, etc.

...
Yes, as comparison, my 454 with a conventional AFR head uses a much smaller camshaft than the OP (242 @ .050) and makes 608hp, and did that with a dual plane intake no less. You just aren't going to get there with a 455 Pontiac using a conventional head and that size cam. Either the cam is going to need to be much more radical or you need a bigger head.

Torque curves however are a different story. My 454 only makes 589 where as a similar sized Pontiac will generally make well over 600 and be nice and flat. But that's to be expected when building a 455 Pontiac that has SBC sized intake ports.

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  #53  
Old Yesterday, 10:18 AM
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Originally Posted by mchell View Post
No doubt you need to know your exact race weight at the very least when trying to convert et/ mph to hp

Body style and wind conditions will play large factors as well….a low slung car with low frontal area and a tail wind will obviously mph higher …

Not an exact science by any stretch!
I agree but believing dyno numbers between different shops is often way off, like different flow benches.

My now retired machinist had on old dial dyno, engines "ran the numbers". A shop down the road with a Superflow the same identical combination engine would always be 50HP more. He eventually took over that shop(owner died in a racing crash) and it took him quite a while to calibrate that dyno correctly to read correctly.

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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #54  
Old Yesterday, 11:09 AM
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Originally Posted by ta man View Post
I'm at 127.5 mph with Dave's 310cfm heads and his 235/245 cam at 3700 lbs what ever that works out to? 590?

That's dam good. I wonder if the Road paver at 246/252 would have you gaining anything.?

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  #55  
Old Yesterday, 11:18 AM
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Originally Posted by chuckies76ta View Post
That's dam good. I wonder if the Road paver at 246/252 would have you gaining anything.?
Most likely in a year or 2 I will be swapping to something similar, I've asked Dave Bisschop if he comes up with something that will work with my current combo to let me know.
My engine is capable of more rpm for sure.

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  #56  
Old Yesterday, 11:21 AM
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What RPM are you going through the traps at now? I forgot what your rear gearing is and 60 ft times.

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