409 truck pistons.

[deans 64 ss]

Hey, I'm a new 409 owner and a new member. Seems to be alot of knowledge here. Could anyone tell me what size overbore a gm casting # 3788108 piston is? The only number stamped in the face of the piston is z-18 w. It came out of a 1965 truck 409. Thanks.

 

[Phil Reed]

Welcome aboard!!!!
Thw part number will not tell you what you want to know. GM pistons did not have a "stamp" with the oversize. You will have to mic your piston to be sure.

 

[64ss409]

Welcome! Glad to hear from a new W owner.
I have a parts book for cars that shows the part numbers for std and os pistons, but no truck pistons. As mentioned, mic is the best way.

 

[deans 64 ss]

Welcome aboard!!!!
Thw part number will not tell you what you want to know. GM pistons did not have a "stamp" with the oversize. You will have to mic your piston to be sure.

 

[deans 64 ss]

Welcome aboard!!!!
Thw part number will not tell you what you want to know. GM pistons did not have a "stamp" with the oversize. You will have to mic your piston to be sure.

Ok. This is what the piston mic'd at. 4.2805 at the top of the piston and 4.312 at the bottom of the skirt.

 

[Don Jacks]

Those would be standard size pistons.

 

[Howard Hull]

Did you ever find out any more information on your pistons? I have the same 1965 truck block with same camz18W pistons and cast# on inside is 3788108. I am still looking also.
Howard

 

[63 Biscayne]

Welcome to this awesome site !!!