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**Bob B.** · 07-15-2006, 06:12 PM

As far as increasing the compression ratio on the GMC V-6, you are really limited. About all you can do is mill the head. Stock pistons are hard enough to find, and to my knowedge high compression pistons were only availble for a short time in the 60's, when they were made for industrial V-6's running on propane or natural gas. Good luck finding a set of those! No doubt the 'Magnum' heads and manifolds are better than the stock 305's, and the 500 cfm Holley is a big improvement, too. But I wouldn't try making a hot rod out of a GMC V-6. It just wasn't designed for it.

07-15-2006, 06:12 PM	#15
Bob B. Senior Member Join Date: Aug 2005 Location: Los Angeles Posts: 1,396	Re: GMC V6 engine compression ratio As far as increasing the compression ratio on the GMC V-6, you are really limited. About all you can do is mill the head. Stock pistons are hard enough to find, and to my knowedge high compression pistons were only availble for a short time in the 60's, when they were made for industrial V-6's running on propane or natural gas. Good luck finding a set of those! No doubt the 'Magnum' heads and manifolds are better than the stock 305's, and the 500 cfm Holley is a big improvement, too. But I wouldn't try making a hot rod out of a GMC V-6. It just wasn't designed for it. __________________ 1967 GMC CM-2500 Camper Cruiser, 351E V-6, NP 435 4 speed, Dana 60, and factory A/C. 2012 GMC K-3500 WT regular cab, 6.0L Vortec, 6L90.