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 Pontiac 400 engine
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Bob
Tribal Scout

USA
2 Posts

Posted - 23 Feb 2018 :  6:31:55 PM  Show Profile  Reply with Quote
I need your help guys. Building a 400 pontiac engine . Seems to me they all have low compression 7.1 with 6x8 or 6x4 heads how do you guys make any power with a motor like this. 400s are rated between 350 to 200 hp with basically the same parts. It's hard to beat the stock intake so all you have left is a cam change and headers. Thanks , Bob

David keefer

tjs44
Cochise

USA
484 Posts

Posted - 23 Feb 2018 :  8:11:19 PM  Show Profile  Reply with Quote
many put stroker cranks in to get more CI which also increases the CR.Some find smaller chamber heads to help raise it also.Where there is a will and a wallet there is a way.Tom
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cortcomp
Coyote

USA
5417 Posts

Posted - 23 Feb 2018 :  8:40:55 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
They were only low compression after about 70? Before that, had small chamber heads. So only difference between 350HP really was a cam and head change.
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Phil
The Great White Buffalo

USA
7266 Posts

Posted - 23 Feb 2018 :  9:38:12 PM  Show Profile  Reply with Quote
You can get a decent street/pump friendly CR on a 400 with certain low compression (eg: 46, 6X-4) heads if they are milled a bit, block zero decked, correct pistons used etc.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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Lee
Sitting Bull

168 Posts

Posted - 23 Feb 2018 :  10:51:53 PM  Show Profile  Visit Lee's Homepage  Reply with Quote
A few years ago, I helped a guy with a 6X/400 that had 8.3:1 compression ratio. I had Dave Bischopp at SD Performance do his CNC port job on the heads, we used R/A 2.5" outlet exhaust manifolds, Performer intake, q-jet, and a hydraulic roller cam I had custom ground. It put 312hp to the wheels on my DynoJet chassis dyno, so probably right at 400 at the flywheel. Runs great on 87 octane, too.

Note the torque. This is a street engine. TQ is ALWAYS going to be greater than HP below 5,252RPM. If you are building a motor that that will rarely/never go past 5,200rpm (i.e., nearly every true street engine), then you should focus more on torque than HP.




CURRENT: '73 T/A clone, starting to get less boring!...
67 Firebird (sold) 11.27 @ 119.6 Feb. '05 issue HPP
69 Falcon wagon, 10.51 @ 130mph Feb. '10 issue PHR (sold)
72 Cutlass Convertible, first car, owned since '82, now with a 6.0 LS, mild, putting just under 400 hp/tq to the wheels.
www.LNLPD.com

Edited by - Lee on 24 Feb 2018 09:49:17 AM
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Bob
Tribal Scout

USA
2 Posts

Posted - 24 Feb 2018 :  9:18:34 PM  Show Profile  Reply with Quote
OK guys thanks , now how about a camshaft for this. It's a 400 .060 oversized bore with 6x4 heads. Looks like 8 8.5 compression have a holley street dominator but guess I will go with the stock cast iron unit as people tell me they are hard to beat. I will do headers and maybe a 750 afb carb. It's going in a 1980 T/A. With 373 gears probably an auto with a shift kit. What cam should I be using. Just looking for good street performance . THANKS

David keefer
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beertracker
Cochise

363 Posts

Posted - 25 Feb 2018 :  4:58:10 PM  Show Profile  Reply with Quote
With your CR take a look at this cam. http://lunatipower.com/Product.aspx?id=1775
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Corncob2061
Sitting Bull

USA
107 Posts

Posted - 27 Feb 2018 :  2:37:16 PM  Show Profile  Reply with Quote
With 3.73 gearing I would suggest the lunati 268/276 or comp xe268,. The xe274 would be ok but would drive worse and not gain much hp, which Is the direction I tend to go:)
Jay
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Corncob2061
Sitting Bull

USA
107 Posts

Posted - 28 Feb 2018 :  2:03:19 PM  Show Profile  Reply with Quote
Beer trackers suggestion would be great too, you could run highway gears
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Steve C.
Chief PONTIAC

1813 Posts

Posted - 28 Feb 2018 :  3:43:30 PM  Show Profile  Reply with Quote
Lee designs his own cams. And his results are very good !


.
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Lee
Sitting Bull

168 Posts

Posted - 28 Feb 2018 :  8:07:04 PM  Show Profile  Visit Lee's Homepage  Reply with Quote
quote:
Originally posted by Steve C.

Lee designs his own cams. And his results are very good !

.



Thank you Steve!

CURRENT: '73 T/A clone, starting to get less boring!...
67 Firebird (sold) 11.27 @ 119.6 Feb. '05 issue HPP
69 Falcon wagon, 10.51 @ 130mph Feb. '10 issue PHR (sold)
72 Cutlass Convertible, first car, owned since '82, now with a 6.0 LS, mild, putting just under 400 hp/tq to the wheels.
www.LNLPD.com
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beertracker
Cochise

363 Posts

Posted - 01 Mar 2018 :  6:31:45 PM  Show Profile  Reply with Quote
Here are the specs on the Voodoo 268\276; http://www.lunatipower.com/Product.aspx?id=1776
Give Lunati a call they are good about helping.
bt
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