462 Dyno - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 02-18-2017, 03:09 PM Thread Starter
 
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462 Dyno

My goals were between 420-480 hp and around 500 torque.

I wanted the engine to remain stock looking but get as much driver performance as possible.

The engine has a Butler rotating assembly with eagle forged crank and dished pistons. 9.5:1 comp. SD performance rebuilt the 62 Pontiac heads with port work, stump puller roller cam, and Pontiac intake manifold ported. Q Jet carb was rebuilt by SMI. Ram air exhaust manifolds and pertronix hei distributor. Brads machine shop assembled the engine and performed the dyno.

SD performance, Butler, SMI induction, Brads machine shop were all very professional and extremely helpful for this build. Last but not least my friend Greg that had a huge impact on this successful outcome.

Dyno results:

Torque peak - 549

Horsepower - 469

Extremely pleased with the results. Should be a blast this summer on the streets. 3.23 gears rear end.
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post #2 of 10 (permalink) Old 02-18-2017, 03:46 PM
 
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"... Should be a blast this summer on the streets..."


Yeah, you can make all the tire smoke you wanna make.

If you have a 3-speed auto trans, make sure it has a heavy duty int sprag--at least a 34 element for a TH400 & a 36 element for a TH350. Otherwise, if your street tires get a decent bite, your engine will break the outer sprag race of the TH350, and the sprag itself, in the TH400, on the 1-2 shift.

I know, because I broke 2 TH350 outer races, & 2 TH400 16 element sprags, with less power than you have. This was at the track, with slicks. So, if your street tires spin, you may not ever break a trans. But, if they get a bite, you MIGHT break a trans.
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post #3 of 10 (permalink) Old 02-18-2017, 04:04 PM Thread Starter
 
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Thanks for the heads up bigD. My th400 was rebuilt about a year ago and hasn't been ran yet. I'll contact the rebuilder and ask him about that.
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post #4 of 10 (permalink) Old 02-18-2017, 05:00 PM
 
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Nice honest numbers for an iron headed engine. Ton of torque which is the way to build the Pontiac engine. Should be a real killer on the street. Make sure you follow up with your opinion once you get it on the road, would like to hear your impression on the power you'll have.
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post #5 of 10 (permalink) Old 02-18-2017, 05:15 PM Thread Starter
 
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Looking forward to driving, but I know putting all these pieces together will likely create some headaches with all the minor details.

I'll post with the final outcome and drivability. Thanks Jim.
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post #6 of 10 (permalink) Old 02-19-2017, 05:02 PM Thread Starter
 
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Hey bigD just to follow up the HD 34 sprag was installed in the th400. Appreciate the heads up. :+1:
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post #7 of 10 (permalink) Old 07-21-2017, 11:31 PM Thread Starter
 
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2 years later and she's alive!! Trailered the car to the exhaust shop yesterday and drove her home this evening.

Man!!! What a blast to drive! Smooth power, nice shifting (mild shift kit), no rubber laid on the first date though.

The motor did not like vacuum advance and seems to run way better without it. In fact, Butler informed me of this early on.
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post #8 of 10 (permalink) Old 07-22-2017, 07:39 AM
 
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Quote:
Originally Posted by Wendt69 View Post
2 years later and she's alive!! Trailered the car to the exhaust shop yesterday and drove her home this evening.

Man!!! What a blast to drive! Smooth power, nice shifting (mild shift kit), no rubber laid on the first date though.

The motor did not like vacuum advance and seems to run way better without it. In fact, Butler informed me of this early on.

Excellent! Thanks for the update and its nice to hear a positive story where everything worked out. Should be a blast to drive once you get some miles on it and it is broken in. That kind of HP can be addictive and soon you'll be exercising it against redlights, stop signs, LS powered machines, hot rods, Fords, imports, and police chargers. Did I say police? Oh wait, that would be me. Never mind that one. LOL
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post #9 of 10 (permalink) Old 12-29-2017, 07:01 AM
 
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Why did they recommend no advance?

1964 Convertible GTO
2004 PBM M6 GTO
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post #10 of 10 (permalink) Old 12-31-2017, 01:15 PM
 
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Originally Posted by bustac View Post
Why did they recommend no advance?
The vacuum advance was not used.

This is over simplification, but gives you an idea of how this works.

If you do use vacuum advance you have two choices - manifold vacuum or a ported vacuum source on the carb which will do the same thing once the throttle is opened. The maximum vacuum advance will be the same in both cases, its just based on the vacuum source and how it is brought in. If you had your initial timing set at 12 degrees at the crank and had manifold source, the advance might be 24 at idle. If you had 12 degrees at the crank and used a ported source, the vacuum would be 12 degrees at idle until you cracked open the carb (not wide open), it would then become 24 degrees, so you now would get the same vacuum advance as you would with manifold vacuum. (You car may run best using manifold vacuum versus ported. Ported vacuum and retarded timing was also one of those things used to keep engine emission gasses in check. The use of vacuum advance also improves gas mileage during part throttle/cruising type driving)

However, when you open the carb wide open, vacuum drops and in both these cases, the advance would drop to the crank setting of 12 degrees until manifold vacuum recovers and builds back up. (I am not covering the function of the mechanical advance and its role in all this)

The vacuum advance can be eliminated and the engine's initial timing can be set to what would be the 12 degrees at the crank plus the vacuum advance of 12 degrees for a total of 24 degrees initial at the crank - which is what was done on Wendt69's engine. With the vacuum advance eliminated and set at 24 degrees at the crank, the remaining advance is brought in and tailored by the distributor's mechanical weights. The optimum total advance for Wendt69's engine combination, as tuned on the dyno, showed the most power/torque to be at 36 degrees. So the timing curve and total advance was adjusted by the rate at which the weights pulled in the total advance (using different weight springs) and the maximum number of degrees which in this case was 12 degrees more (24 initial plus 12 mechanical) for a total of 36 degrees and as I recall it was all in around 3,000 or 3,500 RPM's.

Normally aspirated drag cars do not use vacuum advance as the engines are wide open all the way down the track providing no vacuum signal to be used and you will always see the old factory dual point type distributors without vacuum advance as they were purpose made for high-performance/racing cars. They also use high octane racing gas so the engine will not detonate/ping at the higher initial crank timing.

So very basic explanation. Actual timing using the initial crank timing, mechanical timing, and the vacuum advance to custom tailor the engine's timing curve has been cover more thoroughly in other posts. Each engine can be different in how all these settings are used to maximize the engine's HP/Torque and running condition and what each change can effect.
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