Diameter Chevrolet 216 pistons?

[Lynn Eades]

Hi Alex. I'm not sure how much you know, so don't be offended if you know all this.
If I recall correctly, ).010" wear, or 0.003" oval, and it's time for a rebore. Those old tollerances were the deal back in the day, for a patch up,but today they're hardly acceptable.

Piston to bore clearance is such that the bore is honed so that the piston slips on a 0.002" feeler, but locks up on a 0.003" feeler. (feeler sitting down the thrust face of the bore)
So a 0.002" piston to bore clearance.
The piston is measured on the thrust face (90 degrees to the gudgeon pin) just below the oil ring. This is the biggest measurement you get on a cam ground piston.
My info covers 1935 to 1951, but does not say anything about the difference between cast iron and alluminium pistons. Each should have a different spec.
Measuring the bottom of the bore will tell you what the bore size was, but what you need to know is what the maximum measurement is. That tells you what you have to do. For example if you have 0.012" wear, you need to find some 0.020"O.S. pistons, for your motor re-conditioner to bore and finish hone to.
For me, I would buy some good quality modern piston rings for it.

[Mike K]

One good aspect of the old domed cast pistons is the upper ring grooves usually don' t wear ( widen ) , unlike the softer Al. alloy pistons which often have worn top ring grooves that require machining and spacers fitted ( expensive) . George Russell did a set of Ford pistons 85hp for me years ago, machined the grooves and supplied spacers for the top ring groove.

Down side is the domed chev pistons can be weak around the crown area and they have been known to fracture , the crown flies off . I think this tends to occur if you are a harsh driver eg constant high revs .


In the 50's there were a few after market manufacturers of the Chev 216 pistons ( and valves , springs, and other engine parts ) . I bought a set of Al. domed pistons ( when the US postal service had sea mail ) , weighed them and they are 25% lighter than the cast iron ones. I believe POLSON here in Aust. made 216 pistons ?

I sandblasted the original C8 cast standard pistons with a fine abrasive , I think its called 'peening' . Had no issues with it so far.

[Alex van de Wetering]

Mike, Lynn, Richard,

Thanks for your ideas and suggestions, very much appreciated!

Hi Alex. I'm not sure how much you know, so don't be offended if you know all this.

No worries, Lynn. I think most of you have noted already ,by the questions I asked, that I am a newbie to rebuilding engines , which is also the reason why I will have a specialist look at my engine. I only have a caliper, but he has proper kit to measure accurately. First up will be to examine all the parts for damage and wear, which is why I was looking for measurements, so we have something to compare it with. Somehow it's difficult to find the nominal diameter of the pistons, to me that seems odd, but it might be due to my lack of knowledge on the subject.

I am not planning to go to the races with my C8, but I do want to have a reliable engine without blue smoke. My budget is tight, so if the pistons can be re-used I will, if not, ....well..I will have to wait and see.

Alex