3 ring pistons?
 

Attachment 5596

Three rings? I guess I was expecting three plus the oil ring.
This look right?


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Re: 3 ring pistons?
 

Yes, later 305E's used 3 ring pistons. Most V-6's have 4 rings (3 compression, 1 oil ring set).

Re: 3 ring pistons?
 

That's a Real set of rings to. haha

Re: 3 ring pistons?
 

I think that pertains to the 351E, some early versions came with 4 piston rings and later switched to the 3 ring. After 1969 when the 305E was discontinued in light duty trucks, GMC replacement pistons for the 305E were superseded to 4 ring pistons for standardization purposes. I'm sure they did the same for the 351E as well. Piston sets that I bought for both 305 and 351 engines have all been 4 ring type.

Re: 3 ring pistons?
 

FWIW, the original pistons (and the replacements) in my '67 351E were 4 ring. I'll have to look around, I seem to remember a service bulletin that said something about a production change to 3 ring pistons in some V-6's. Thought it was 305's.

Re: 3 ring pistons?
 

My 66 305E had original 3 ring pistons and the replacements were 4 ringers. Dave

Re: 3 ring pistons?
 

The book 'GMC Light Trucks' says the 305E had 3 ring pistons when it came out in 1963.

Re: 3 ring pistons?
 

I am thinking the 3 ring pistons were one of the modifications to increase fuel economy of the 305. Lot less drag than the 4 ring piston.

Re: 3 ring pistons?
 

While we are on this subject, what do the bigger V6s have for rings and are the magnums the same as non magnums? Thanks,Dave

Re: 3 ring pistons?
 

From what I know the bigger v6's were 4 rings and no difference between Magnums and Non-Magnums. Magnums were bigger ports, valves, carb, and manifolds.