The TH350 swap with a higher stall will feel like a 100 added horsepower with the much better first gear and launching in your new cams powerband. What gear ratio is in the car? Even with good used 3.08 gears with the Yukon posi, it had to be close to $1000 US just for parts, the posi alone is $700. That posi needs 3.08 or 3.23 factory gears or Richmond 3.42 or 3.90 gears. The factory Type O 12 bolt cover with 10 bolt ring gear with bolt in axles, is expensive to build. Good luck on the overhaul, make sure the shop puts enough valve to guide clearance when they rebuild the head, especially if you aren't filling the exhaust crossover. Mahle has a nice piston 1mm ring pack pistons, if you want to end up in the 9.5 to 1 compression range. DSS and Speedpro are your other forged options. See what overbore it needs, the 4.065" hone to fit Mahle pistons didn't work in my 350, needed more removed, went to the 4.100" oversize.

 

Did you notice much change in the cars ride when going up in diameter? I think the 18s might look too big, I had been thinking about 16s, but it sounds like the tire section for 16 is worse than 17s. Car looks great btw

 

Thanks...that's my driver/survivor. I never drove on those wheels, the tires were shredded and I was just checking them for clearance and offset before getting new rubber and mounting on my '70 project. I had planned on running 14" front and 15" rear with 255/60R15 and 205/60R14 tires. When I got these rims I checked the tire width and diameter specs to get my 17" wheels matching closely to those sizes (primarily for rear end gearing but also for appearance) and went with 255/50R17 rear, 205/50R17 rear. I'll find out how they handle in a few months (I hope!) but the entire suspension has been redone as well, using UMI springs, sway bars and rear links.

 

I believe the rear is a 278. I haven’t opened it yet. It has 12 bolts on the cover, and I thought it was open, but when I spin one side, the other side spins with it… it’s got a jetaway trans in it now.

 

doing a leak down test on a cold engine isn’t correct to start with.

can you tell us your procedure for testing each cylinder? walk us through it

 

Which way does the other wheel turn, the opposite way? There were some 68 and 69 Canadian built cars with chebby 12 bolt rear ends.

 

I was taking each cylinder to tdc of the compression stroke and running compressed air to, and looking at the percentage that was leaking out. Some head about 90% while others werent holding anything.

 

Where does the air pressure escape on the cylinders that don't hold air? Exhaust, carb and/or oil fill cap and valve cover breather holes?

 

It was smoking from the exhaust. And sounded like the air was coming from the valves and rings. I looked at each cylinder with a bore scope, most of the looked glazed, and one had a vertical score. Hoping it’s not beyond repair! My grandpa told me he was running regular fuel in it, not sure how long he’s been doing that for.

 

Air from the leak down tester was leaking out the exhaust not smoke from the car running correct?

Air leaking out of the exhaust indicates a problem with an exhaust valve. Glazing on the cylinder walls is to be expected. Can you post a picture of the scoring?

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It was smoking while running, so didn’t put my ear next to the exhaust once I heard all the other leaks. I felt like the motor was tired after hearing the oil and intake. The motor just go picked up by freight today, and is on its way to S and J engines in Spokane. Hopefully it’s not wasted money, but either way it will give me peace of mind.

I didn’t get any pictures before sending the motor out.