mrfeeney

I bought a used motor to repower my 84 and have a question for the group.

Can anyone tell me why the piston top would have more clearance on the exhaust side than the intake side?

Could the previous owner have decked the block this way on purpose, or possibly the Mahle flat tops were manufactured this way for extra valve clearance?

I've got around .010 below the deck on the outboard or exhaust side of the piston and around .040 on the inboard or intake side of the piston.

Need A Vette

Having built a few SBCs in my day, What are your intentions for the motor? What would you like it to do? What HP are you looking for, and what kind of torque are you looking for? Planning on keeping it as a 350? or Stroking it and going to a 383? Keeping the TPI, or going to something else?

These are all questions you need to answer first, then build the engine around those parameters. It really isn't that hard. I used to be ALOT easier when PAW was still around, as you could source all of your parts from one single source. But it can still be done.

Personally I would get a nice roller cam with nice lift, and duration, a decent set of heads that are port matched, which isnt that hard, go with about a 10:1 compression ratio, and a set of long tube headers.

So check it out, there are websites out there as well engine builders that post everything online it really isnt that hard, and can be quite relaxing

D.

mrfeeney

Yep, I've built a few myself....the question remains has anyone seen a piston that has more deck clearance on the intake side than the exhaust?

The engine is brand new with only three passes on it but I tore it down to make sure what I had and that there were no issues.

It has Mahle SBC250060F05 pistons, I plan to replace the heads with a set of Dart 180 runners 64CC chamber 2.02/1.60 dual springs for a roller cam setup, which according to Mahle will make 10.6-1 compression.

Cam selection still not settled.

Street/Strip application

Will be keeping the CFI with a Renegade intake upgrade and some work on the TBI's and programmable ECM.

mrfeeney

More checking of other pistons revealed there is that much slop of the pistons in the bore, now Ill check to see if they are in tolerance....now I feel stupid

C409

..... The fact is : pistons are purposely not cylindrically round ... its not very apparent looking at them with the naked eye but if you looked at a piston from the side with the pin hole on center , it would have a barrel shape ... when cold ..... also , some forged piston alloys expand more than others and therefore need more piston to wall clearance allowing for more rocking in the bore ... again , when cold .....

Hot Rod Roy

I can't imagine that much "slop" is good. I sure can't see that in my '84! The '84 FSM specifies "production" piston clearance of 0.0025 - 0.0035, with maximum wear clearance of 0.0045. What are you identifying as the "outboard/exhaust/inboard/intake" sides, since the intake & exhaust valves are arranged e/i/i/e/e/i/i/e?