'67 GTO tuning question - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 05-09-2006, 04:34 AM Thread Starter
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'67 GTO tuning question

Hi there,
I am new to this forum. I got me a '67 GTO 400 ci 325 hp recently and I would like to tune it now. Performer RPM intake is already there. What would you recommend now? Is there an ideal combination of parts, carburetor / head / drive chain / camshaft ... if I want to bring bghp to around 500? Should I stay with Edelbrock or mix it with other producers?
Any advice would be greatly appreciated!
Thanks
Jak
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post #2 of 10 (permalink) Old 05-10-2006, 06:28 PM
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My opinion;

Keep the Edelbrock, find a set of #670 heads (port and polish), change the cam (236/244 degrees at .050 duration .489/.500 lift) bore the cylinders (.030,) TRW flat top pistons, hooker headers, rochester q-jet carb.

Good luck!

Randy


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post #3 of 10 (permalink) Old 05-11-2006, 09:10 AM Thread Starter
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Thanx for the advice! Didn't think that I have to bore the cylinders.
J.
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post #4 of 10 (permalink) Old 05-11-2006, 10:08 AM
 
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500 horse out of a 400 is a very ambitious project, and you're not getting there with stock heads unless you're going to be doing some serious rework of the flow characteristics. Recommend you do a little research on articles published by Ken Crocie, Hand, and Butler to see what you're up against... I've been building Pontiac engines for 30 years, and I've never had a street-able normally aspirated 400 hit 500 horse yet...
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post #5 of 10 (permalink) Old 05-11-2006, 02:20 PM
 
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Quote:
Originally Posted by lars
500 horse out of a 400 is a very ambitious project, and you're not getting there with stock heads unless you're going to be doing some serious rework of the flow characteristics. Recommend you do a little research on articles published by Ken Crocie, Hand, and Butler to see what you're up against... I've been building Pontiac engines for 30 years, and I've never had a street-able normally aspirated 400 hit 500 horse yet...

I'll second that! I used to own a automobile machine shop, and a lot of people talk horsepower, but the dyno is the only way to really make it happen!
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post #6 of 10 (permalink) Old 05-11-2006, 02:53 PM Thread Starter
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Thank you for your opinions!
But what do you think is the max possible with standard techniques, I mean no rocket-science-stuff, you know.

J.
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post #7 of 10 (permalink) Old 05-12-2006, 11:16 AM
 
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If you're looking for a streetable engine using conventional, affordable hop-up techniques and a well-built set of stock casting heads, you can get it into the 400-horse range (1 horse per cubic inch is a pretty good performance standard).
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post #8 of 10 (permalink) Old 05-13-2006, 02:05 AM
 
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Most Pontiac heads seem to exhibit better intake flow than exhaust flow. So you'll want to make sure the exhaust system is properly set up for the performance level you are trying to achieve. That means a good set of headers, an x pipe crossover (Bassani makes a good one) and at least 2 1/2 inch tubing all the way back. Remember that torque is what really makes the vehicle accelerate, so have the heads properly done, get a hydraulic roller (I'd like to see it no bigger than 230/240) and a set of the Comp Cams beehive springs and you'll have a good balance of performance and driveability. You have not mentioned the tranny. If it is a TH400, you're going to want at least 3.42's and a decent converter in there as well. If it is a 4 speed, we need a whole other discussion of how it ought to be geared based on which gear box you want to run. I'd also like to see an MSD 6AL and then we need to get Crane Cams to make a Pontiac version of their electronic distributor. You set the timing curve with dip switches on the distributor and it has a MAP sensor rather than an advance canister.
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post #9 of 10 (permalink) Old 05-13-2006, 02:44 PM Thread Starter
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I guess the exhaust is alright. X-Pipe and 3'' tubing are on, and also an electronic ignition.
Tranny is a Hurst 4-Speed.
I tried to dyno the car the other day at the local Porsche-dealer (writing from Germany). At about 270 hp, 4400 rpm and an impressive 445 Nm (325 ft-lbs) the wheels lost their grip. In the end there were four Porsche-technicians sitting in the car to exert the necessary pressure - but it wouldn't work. Very funny sight that.
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post #10 of 10 (permalink) Old 05-17-2006, 03:03 PM
 
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I had a 69 - 400. MAx rpms in a goat the were 5000. buidl your engine around that. I used a dual plane offenhauser manifold. It keeps you fuel velocity up until you punch or open the big carb up. Next headers are a must, polish and port your heads ( use a specialist)or get some made for the Judge which are tunnel port, you'llknow them when you see them they are round. I did a three angle cut on my valves to ensure quick seating. With 400 cubes lots of gas in ( 780 min ) and exhaust out gets quick revs. Lower end torque cams are better check their troque curves. 4:11 OLds gears were available for the street higher for the strip like 4:56. You'll top end before the end but that's what you want. Traction - Air bags inside the springs help stop wheel hop. Oh use a high voltage system and a good plug. With many of the above mods I did mid 13's in 60 series streeet tires.
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