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Old 01-07-2007, 07:23 AM
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Piston preference for a 350 with 305 heads

Greetings Elder Gearheads and Master motor buiders,

I'm an offroad enthusist, I'm building a motor to assist my '78 3/4 ton 4x4 chevy modified trailrig through anything the trail might dish out. It has a stock 350, which just did get me through my first run through the Badlands of Attica, IN. It left me to be winched the final 1/4 of the way up a long, steep hill climb in deep soft pea gravel.

I know many would say that it was the carb being starved out for the angle of the grade. I would say that I was amazed at the quadrajet. It gave me no real trouble all day. On this climb, I took 3 runs at it with different gear combinations and did no worse than 75% of the jeeps in the group. They had EFI. My truck never stalled out until I killed it either, and once they secured the winch and started the pull, I had to put her in granny low, in low range, and punch it. It never show any signs of starvation. I just did not have the horseys.



I did kill it at the top of the climb, but it refired right off and pulled well for the winch. I might have done better had I been able to get a real run at it, but I started from the base of the hill.

So, back to the drawing board. I bought an old pickup off a guy so that his PT Cruiser wouldn't get repoed. It was beat. I've sold enough of the parts off to make my money back, cut it in half to make a pickup bed trailer, and pulled the engine as a donor for my first build.

It was a 350 with 305 heads! After much study, I've come to realize that this is just what my trailrig needs. I've watched too many guys have to rev up high to build their power and as soon as the RPMs drop or they have to take their foot out of it, they have nothing.

The name of the game is low end torque and throttle response. I've also watched guys with this accomplished take the same line as the High RPM guys and make it all look like a walk in the park with half the RPMs or less. You can tell the power is there. Gear selection and reduction does play a part, but it seems that if anything the High RPM crowd is in a lower gear.

I'm on a budget, and the 350 donor was a most recent rebuild, so I'm going with it. I found a spun bearing, but the motor was clean, and no piston ridge. I test drove the truck and it had serious torque, but a lot of noise up top. Why? Every compression ring was broke in half save 2.

The pistons look alright, they are stock flats, but I'm warned that they will burn through. I've heard that this is possible, but not always the case. I'm thinking that some of this damage might be from detonation. The CR's were around 11:1 or higher. They are the "601" heads without any work done. I keep hearing that these are 53 cc heads. I calculated for 58's so the CR might even be higher.

I plan on a careful and mild pocket porting (I'm not too greedy) and a deshrouding, which should help a few issues and allow for 1.94 intakes.

What do you all suggest for pistons and rings? Can I run my stock flats? Which rings will hold up this time? Moly's?

Thanks for the advise, sorry for the long post, but I wanted to set the backround. Peace.

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