Quote:
Originally Posted by NYGTO
That's more A/FX than C/S :--)
I have this handy book to help keep the theme.
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If you try to recreate the car using the 1965 rules for stock class cars, you will be limited as to what can be done to the heads as they must remain essentially stock. The chambers need to be CC'd to 65 cc's so they are all the same. You can port match them. 3-angle valve job. Good head prep/rebuild.
Here is a suggested list of improvements.
The Carter carb should have stock .0935" primary jet and .078" secondary jets. Open the secondary jets up to .086" for an increase in HP.
The ignition system is where HP can be found.
Use a good low resistance spark plug wire.
Use AC44 spark plugs gapped to .032" (or Champion J-10 plugs)
Dial in the distributor advance curve. These numbers are distributor degrees as used by a distributor machine. X2 would be degrees at the crank/balancer.
Stock - 6 degrees initial
.5 - 2.5 degrees @ 450 RPM
7 - 9 degrees @ 1,000 RPM
8 - 10 degrees @ 1450 RPM
10 - 12 degrees @ 2300 RPM
Modified - 14 degrees initial
1 degree @ 250 RPM
5 degrees @ 550 RPM
9 degrees @ 900 RPM
Vacuum advance 8" - 10" starts the advance
14" - 16.5" @ 10 degrees for full advance
10 degrees @ 1200 RPM
You can run forged pistons but must be same as stock type - 10.75 compression. So go with a light forged piston with light piston pin all to save weight and rev higher/faster.
Use aftermarket forged rods - the lighter the better.
Balance the assembly.
Next is the "Bobcat" treatment.
Thin .020" head gaskets.
Blocked exhaust crossover intake gaskets.
Poly locks to make the non-adjustable valve train adjustable and "zero-lash" the hydraulic lifters for higher RPM's and usable power. Be aware that your heads will have press-in 3/8" bottle neck studs and adding a larger lift cam could pull the studs out or break them. The best route will be the addition of 7/16" screw-in studs added to your stock heads for more radical cams.
NHRA did allow for headers in the stock class. But you can use stock log manifolds if you want to go that route. Have them polished inside to remove all rough castings, part lines, etc.. Port match. I would modify a set of head pipes to use a 2 1/2 exhaust system. You can use the smaller flange to use the log manifolds and then use the exhaust reducers in reverse to size up off of your flange to the 2 1/2" pipe. I have done this on a couple cars making my own head pipes, but not on a 1965 GTO. A muffler shop should be able to help create this head pipe.
Use the factory cold air open hood scoop and make a lower pan to work with your carb as the tri-power did. You can also go with a modified cold air set-up as used by the 1966 Olds similar to this set-up from Spectre
https://www.summitracing.com/parts/s...SABEgIemvD_BwE
I would also suggest adding the upper/lower control arm braces to stiffen the rear chassis. These are available in a stock type used in 1967 and up, or aftermarket. I like and purchased the UMI set-up as it is adjustable and clears the floor pans.
https://www.jegs.com/i/UMI+Performan...SABEgJf7_D_BwE