6066 (1960-1966) GMC Truck Club

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-   -   High compression pistons (https://6066gmcclub.com/showthread.php?t=51185)

Prowbar August 4th, 2021 06:45 PM

High compression pistons
 
Have read here and there that the 305C's used in forklifts for propane use, and the V12's for irrigation that ran on natural gas came with different, taller pistons that raised the compression from 7.5:1 to around 9:1. Does anyone have a picture of these so called high compression pistons?

Would be interesting to see; also a nice upgrade for an existing gasoline engine.

BobBray August 7th, 2021 06:49 PM

Re: High compression pistons
 
Yes, industrial GMC V6's and V12's had high compression pistons when set up for gaseous fuels. I believe the pistons were flat-topped compared to the truck pistons that were slightly dished. 'High Compression' in this case was a relative term, I believe they were only about 8.5 to 1. I always wondered if GMC made a higher compression piston for the 637 gas V-8. That piston had the combustion chamber built into it.

Prowbar August 8th, 2021 12:34 PM

Re: High compression pistons
 
Quote:

Originally Posted by BobBray (Post 74459)
Yes, industrial GMC V6's and V12's had high compression pistons when set up for gaseous fuels. I believe the pistons were flat-topped compared to the truck pistons that were slightly dished. 'High Compression' in this case was a relative term, I believe they were only about 8.5 to 1. I always wondered if GMC made a higher compression piston for the 637 gas V-8. That piston had the combustion chamber built into it.

Thanks for the reply. Not sure if the 637's came as industrial engines, have not read much about them being used for industrial vehicles or pump use etc.


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