flywheel question- one piece seal vs. two piece seal. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**crossy** · 07-28-2007, 08:03 PM

Hey guys I have a bit of a problem solver question here. I'm trying to install a 1979 350 in place of 1986 engine. the 86 engine had the one piece rear main seal. the truck is a stick shift truck and has the 13.5" dia. flywheel in it. the 86 flywheel will not fit the back of the 79 engine. the bolt pattern is totally different and and the center hole on the 86 flywheeel is smaller in diameter than the back of the 79 crank. I thought i could just get the crank hole bored out on the 86 flywheel, but the bolt pattern is different also.
QUESTION is simply this. can i just install the 85 and earlier style flywheel ?? the truck has the hydraulic clutch. I was pretty sure the trucks started using the hydraulic clutch BEFORE they went to one piece main seals so this should just be a simple swap right???
At the present time i dont have an early flywheel here(usually do), but i want to be sure before i purchase one somwhere.

thanx , crossy.

07-28-2007, 08:03 PM	#1
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	flywheel question- one piece seal vs. two piece seal. Hey guys I have a bit of a problem solver question here. I'm trying to install a 1979 350 in place of 1986 engine. the 86 engine had the one piece rear main seal. the truck is a stick shift truck and has the 13.5" dia. flywheel in it. the 86 flywheel will not fit the back of the 79 engine. the bolt pattern is totally different and and the center hole on the 86 flywheeel is smaller in diameter than the back of the 79 crank. I thought i could just get the crank hole bored out on the 86 flywheel, but the bolt pattern is different also. QUESTION is simply this. can i just install the 85 and earlier style flywheel ?? the truck has the hydraulic clutch. I was pretty sure the trucks started using the hydraulic clutch BEFORE they went to one piece main seals so this should just be a simple swap right??? At the present time i dont have an early flywheel here(usually do), but i want to be sure before i purchase one somwhere. thanx , crossy. __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks. Last edited by crossy; 07-28-2007 at 08:04 PM.



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