[pa140flyer]

I do have a set of 1973 4X heads with pressed in studs but I think they have the smaller valves but it would solve the dished piston requirements! This is all getting way more complicated than I had intended!

JayS thanks for the input more food for thought. I get what you are saying but it sounds to me like you have headers on the engines you are running and I wanted to stay away from that headache as I have not seen a set of headers that fit in a GTO without denting up a tube or something to get them to fit. Now if I have to run the log manifolds what does that do to your theory of the higher compression and still burning lower octane gas? I did want to run the ram air manifolds but apparently you cannot find them.

[Joe's Garage]

Originally Posted by pa140flyer

I did contact rock and roll engineering and apparently he has some custom JE pistons that he says will work with stock cast rods but from what I have read he may not be the most reliable person out there.

THAT is a major understatement! Run far, far away from the Flupper!

[Jay S]

Originally Posted by pa140flyer

I do have a set of 1973 4X heads with pressed in studs but I think they have the smaller valves but it would solve the dished piston requirements! This is all getting way more complicated than I had intended!

JayS thanks for the input more food for thought. I get what you are saying but it sounds to me like you have headers on the engines you are running and I wanted to stay away from that headache as I have not seen a set of headers that fit in a GTO without denting up a tube or something to get them to fit. Now if I have to run the log manifolds what does that do to your theory of the higher compression and still burning lower octane gas? I did want to run the ram air manifolds but apparently you cannot find them.

IMHO, 670s belong on your car. If your doing dishes pistons I think that means automatically it is time to do forged rods, and rebalance it. The pistons and pins are much lighter than stock, the balancing will not be close to the factory balance anymore, then you get a lighter rotating assembly and less friction with the thinner 1/16” or metric rings.

The summit 6402 is a pretty proven pump gas combo on RA 3 type engines with flat top pistons and manifolds. But, it is a 91 octane combo unless you make some other changes.

On your engine with stock 670 heads and below 10:1 compression, going from Headers, to RA manifolds to log manifolds won’t make much difference at all for changing how it runs on a particular octane. Headers might gain some, but not much pushing through a full exhaust (a point at most). The 068, 744, 041, summit 6400, summit 6401, and summit 6402 are all pretty friend cams for having pretty restrictive exhaust systems, and headers really would not effect much other than make more power.

If you want to drop the compression down less than 9, the 068 still works ok, but there are going to be better cams than an 068. The smaller summit 2801 would be better.

[chiphead]

Autotec pistons, 4032 alloy, Can be used with whatever rod you want. Call Paul Knippens.

You can use the TRW forgings for pistons, but I would strongly advise 91-93 octane over 9.5:1. You've got to be spot on with the tune or you'll hurt the motor, if you try to run 89 mid grade at 9.5 or higher. Heat soak on a 100+ day, 9.5+ compression is going to want the higher octane .

I build a motor on paper first:

Decide power level desired and RPM range
Decide size of motor (informs bore, stroke, rod for later decisions)
Decide fuel to be used (mostly what octane, any nitrous or boost?)
Decide head (iron or aluminum) and confirm chamber size
Decide cam type and parameters
Decide compression
Decide piston type and any dome/dish, ring pack
Decide crank and rods (circle back to piston design for pin height and type)
Somewhere in there is intake/carb/exhaust considerations

Work it all out on paper before you buy anything.

Since you have the 670s, you know the head. You've decided you want 89 octane, and you want 400CID. Next thing to do is have the heads gone through to determine chamber. Chamber size determines piston design to get desired compression ratio.
It's not that hard once you build a few on paper and judge pros/cons of each combination of parts. Whatever you do, please pitch those stock rods in the bin. I personally know of 3 stock pontiacs that were destroyed because the stock rods let go at crusing RPMs.