3 ring pistons?

[surfamtn]

IMG_3180.JPG

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


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[BobBray]

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

[TJ's GMC]

That's a Real set of rings to. haha

[bigblockv6]

Originally Posted by BobBray

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

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 After 1969 when the 305E was discontinued in light duty trucks, GMC replacement pistons for the 305E were superseded to 4 ring pistons for standardization purposes.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.

[BobBray]

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.

[Quigley]

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

[BobBray]

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

[BobBray]

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.

[Quigley]

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

[TJ's GMC]

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.