Pontiac 400 heads

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Geoff2
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Re: Pontiac 400 heads

Post by Geoff2 »

Stan,
Pontiac had the advantageous 14* valve angle v 23* for Chev. Plus large 2.11" intake valves & the later ports had improved flow.
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Re: Pontiac 400 heads

Post by Walter R. Malik »

Geoff2 wrote: Mon Aug 02, 2021 4:16 am Stan,
Pontiac had the advantageous 14* valve angle v 23* for Chev. Plus large 2.11" intake valves & the later ports had improved flow.
With a low port, that valve angle is not much of an advantage.
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Re: Pontiac 400 heads

Post by mag2555 »

When your running a factory Cam of no more then .406” lift like in the average 4 bbl high comp 350 hp 445 ft lb 400 motor, then yes the 14 degree inclination which allowed a 7% bigger intake valve then the old 21 degree angle and also made for a nice reduction in the curvature of the exh ports , then yes it a plus!

The factory engineer’s concern was always tilted towards maxing out port velocity for superior throttle response in terms of the D port heads .
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Re: Pontiac 400 heads

Post by rebelrouser »

There was a lot of interest in this post so I thought I would post an update. The owner did not want to buy new valves so we stayed with the 30 degree seats. opened the throats up a little, good valve job, tried to make short turn as good as possible, polished the push rod pinch a little. it made on average a 7% improvement on my flow bench, on the intake side however hardly any improvement over .400 lift, all the improvement was lower valve opening only. Again the guy did not want to pay for a full porting job. Cam was 214 @.050 .443 intake and 224 @.050 .467 exhaust with a 112 centerline installed at 108. since the lift was just a little over where the heads stopped flowing good, I just left it. flat top pistons around 10 to 1 compression, edelbrock torker manifold, 1 3/4 long tube headers. Engine made 448 ft. lbs @ 4,000 rpm and 384 HP @ 5000 rpm. I started the pull at 2,000 rpm and is was making 412 ft lbs and held 403 ft lbs @ 5,000 rpm a really long flat torque curve.
The owner brought me a FAST throttle body injection system, and I think it might have made a little more HP if I could have gotten it a little richer. I tried to lie to it a couple different ways and just never did get 12.5 AFR, 12.75 was as rich as I could get it. Not sure if the learning feature has something to do with it? I asked the computer for as rich as 12.3 and lied to it and said it was 30 cubic inches bigger than it really was. But 12.75 was all it would provide. AFR was good at idle and at the start of the pull, but about 3,000 rpm it went to 12.75 and stayed there.
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Re: Pontiac 400 heads

Post by mag2555 »

I hope you mean the intake used on the dyno run was a Torquer II that takes a square bore carb, and not the Torquer I which is set up for a Q jet?

The Torquer I will drop off torque even on a 455 cid motor until 4000 rpm!
Edelbrock did not do the street 455 any favors when they put out that T1 intake back in the 70s, that’s been proven many many times over !

Anyway even if it was the later Torquer Intake the performer will make better power with heads that flow like that and with that Cam, especially with a power band that will be well nosed over by 5400 rpm.
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Re: Pontiac 400 heads

Post by Geoff2 »

The Torker intake. Pete McCarthy, author of two Pontiac books & founder of Pontiac Enthusiast magazine said it best: one the thing the Torker intake does NOT have is torque.

A Perf or factory dual plane would be best for that combo.
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Re: Pontiac 400 heads

Post by mag2555 »

Reguardless of the Intake used I did want to compliment that wide torque curve that build has!
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Re: Pontiac 400 heads

Post by tjs44 »

2X on a factory or IMO a RPM Performer.Not enough cam for a single plane.Tom
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