Thread: Piston swap
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Old May 6th, 2022, 02:18 PM
James James is offline
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Default Re: Piston swap

The following is base on my own observation, measurements, research, and opinion. Your results will be different.

I have measured the wall thickness on a GMC 305 V6. This is what I have found (see attachment):

Base on my research a minimum wall thickness for a naturally aspirated engine is .100", thicker if turbo/super charged/NOS injected, running near stock compression.

You will need to have the cylinder walls ultrasonically tested and base on the minimum thickness you find, of the cylinders, and subtract .100" this will be the most material that can be remove.

Example:
Thinnest measured wall thickness: .232"
▼▼▼▼Minimum wall thickness: -.100"
▼▼Material that can be removed: .132"

▼Minimum wall thickness times 2: .264"
▼▼305 V6 stock bore diameter: +4.250"
Maximum cylinder bore diameter: 4.514"
▼GMC 351 V6 cylinder diameter: 4.560"

I do know some natural aspirated racing engines will go down to a lower minimum thickness depending where it is located in the cylinder. Also some machine shop will offset bore the cylinder in favor of a thicker thrust side.

Bottom line it depend on the engine and if you want to risk boring it out that far. No two engine are alike.
Attached Files
File Type: pdf Cylinder Wall Thickness.pdf (34.5 KB, Multiple views, 11 clicks)
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