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 Pontiac 400 combo hp/tq expectations
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Brody
Tribal Scout

USA
4 Posts

Posted - 27 May 2016 :  01:38:00 AM  Show Profile  Reply with Quote
Here we go with another combo. What hp/tq and max rpm can I expect with this combo?
In a 66 LeMans I've got.

73' Pontiac 400 block 60 over
stock crank
stock rods
Sealed Power forged pistons
Comp Cam # 51- 423-9 hydraulic roller
(276/282) (224/230@.50)
Roller rockers
9.5/1 compression
Edlebrock performer heads
87cc chamber 215cc intake 175cc exhaust. 211/166 intake/exhaust valve diameter.
Edlebrock performer RPM intake
Sean Murphy Induction stage 2 800 cfm quadrajet
DUI HEI distributer 22 at 3000 rpm
Art Carr 200 4r trans with a TCI 2200-2400 stall converter, non lock up
3:55 gears

tjs44
Cochise

USA
412 Posts

Posted - 27 May 2016 :  09:27:22 AM  Show Profile  Reply with Quote
First of all 5200 redline with stock rods.JMO
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Brody
Tribal Scout

USA
4 Posts

Posted - 27 May 2016 :  2:01:05 PM  Show Profile  Reply with Quote
Yes I know stock rods limit rpm but I think I can go higher than 5200. Seems like most guys with similar builds make peak power mid to higher 5000's. And the more radical builds with forged crack and high performance rods rev and make peak power higher still. I'm not going to treat this thing like a high revving beast though. I just haven't seen anybody with this exact combo so I'm guessing a lot on what I got. I want to put this car on a dyno and if I make power nothing more @ 5500 that's probably a good thing. Not sure I would need to rev higher anyway with my top end combo. Again it's all guessing at this point.
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Tub
Sitting Bull

172 Posts

Posted - 27 May 2016 :  4:55:54 PM  Show Profile  Reply with Quote
We ran the cast rods to 6000, in 2 different Stocker 400's--no failures. Also ran 'em to 5500, in several 455 bracket engines--no failures.

But, that was in the 70's & '80's. The rods were a lot newer then. Don't know if 40 year old rods are weaker than 5-15 year old rods, or not. I've heard of guys turning ridiculous rpm's, with cast rods, which I would never attempt. Then, you hear of some cast rods that fail for no apparent reason.

I assume that some rods have small fractures that can't be seen without quality checking procedures. So, I assume that if you decide to use cast rods, they should be checked for cracks, by a competent machine shop, then resized, with ARP bolts.

Lots of guys nowadays choose to go with the RPM 5140 forged rods. They're $288, today. I think they are a different weight than the cast rods, so would need to be balanced accordingly.

http://www.racingpartsmaximum.com/sae5140stockrod-2.html

Some choose the H-beams, for $400.

http://www.racingpartsmaximum.com/sae4340steelhbeam-2.html



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Brody
Tribal Scout

USA
4 Posts

Posted - 27 May 2016 :  5:20:44 PM  Show Profile  Reply with Quote
If I knew then what I know now I would of went with aftermarket rods but the motor is built and purring in my ride. Guess I'll just drive with a safety factor in mind. After some pulls on the dyno I'll know where I'm at and hopefully around 5500 is my sweet spot anyway. Any idea what I could expect for hp/tq with my combo?
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Tub
Sitting Bull

172 Posts

Posted - 27 May 2016 :  5:41:33 PM  Show Profile  Reply with Quote
quote:
Originally posted by Brody

...Any idea what I could expect for hp/tq with my combo?



That would be strictly a guess.

If I had alum heads and a roller cam, I'd want at least 400hp. But, with only 3.75 stroke, I'd expect less than 500ft lbs of torque.
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Brody
Tribal Scout

USA
4 Posts

Posted - 28 May 2016 :  12:05:50 AM  Show Profile  Reply with Quote
That sounds reasonable. Thanks for the info
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Lee
Sitting Bull

101 Posts

Posted - 11 Oct 2016 :  09:01:18 AM  Show Profile  Visit Lee's Homepage  Reply with Quote
This chassis dyno graph is from a 400 with ported 6X heads (SD Performance), 8.3:1, R/A exhaust manifolds, Performer intake, and a nice Q-jet. The cam is an HR that I designed - a tad more intake duration, more exhaust, a bit more lift, and a much wider LSA.

With headers and a higher CR, you should make more torque. That cam will cause power to fall off more quickly, so it may or may not make a bit more HP.

If you have quality rod bolts and they were installed to the proper the proper stretch amount, the should be fine. I ran low-11's turning nearly 6000rpm in my old '67 Firebird with stock rods. I sold that car over 10 years ago, and last I heard it was STILL running fine.


CURRENT: '73 T/A clone, boring at the moment...
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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