FE rebuild
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Joined: Sep 2002
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From: Laramie United States
FE rebuild
I have a 360 and I was wondering if I can put a 390 crank and rods. But I would like to keep the pistons and do little or no machining. I also plan on putting a crane cam in it to top it off. Any help would be great.
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Joined: Feb 2000
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From: Sun River St. George
FE rebuild
Most likely you will need to over bore the cylinders to remove taper, so plan on new pistons. The most common is to poke it out 30 over and hone it for moly rings. You can buy good quality Silvolite pistons PN# 1130 for around 250.00. You are on the right track, budget around 2K. I am told you can buy a 390 crank at Autozone. Add a set of reconditioned rods from them or one of the other suppliers and a set of pistons and you are well on your way. Good buildable 360/390 blocks are available in the Junk Yard. Sometimes you can find a complete 390 engine to build.
William in Atlanta
William in Atlanta
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From: Laramie United States
FE rebuild
The engine that I want to use is a new stock one. Would I have to bore it .030 over if I just got stock 390 pistons, rods, and crank. I just want to make is as easy as possible.
Logistics Pro
Joined: Feb 2000
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From: Sun River St. George
FE rebuild
I never bore an engine unless it is required to remove cylinder taper. A new block will be 4.05 bore and will not have taper. Hone this for moly rings (450 stone), use new standard pistons and have at it.
William in Atlanta
William in Atlanta
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Postmaster
Joined: Nov 2002
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From: Littleton, CO
FE rebuild
The bore on a 390 is 4.052. If the current 360 you have has the same bore and you wish to do nothing other than slap in the new crank and rods, you should be set to go for a low budget CID upgrade. I do not however have the specs for a 360 bore so I cannot say it is the same as the 390. Have fun anyway!!!
--Mike G
--Mike G
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Joined: Aug 2001
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From: Collierville, TN
FE rebuild
360 and 390 have the same bore. In fact, they are the exact same block.
You will need to do a little more than just change the crankshaft and rods, however, as using 360 pistons with a 390 crank and rods would result in too much compression and may also result in your pistons poking out the top of the block at TDC -- very bad thing, that. Finally, original 360 pistons are fully skirted, and may hit the counterweights on a 390 crankshaft. 390 pistons, besides being shorter than 360 pistons, have slipper skirts to avoid that problem.
Bottom line -- you can easily convert a 360 to a 390, but you need to swap the entire rotating assembly (crank, rods, pistons). Better yet, toss the old pistons and buy new ones. 390 pistons are plentiful and cheap, so there's no reason not to. And get the assembly balanced while you're at it.
You will need to do a little more than just change the crankshaft and rods, however, as using 360 pistons with a 390 crank and rods would result in too much compression and may also result in your pistons poking out the top of the block at TDC -- very bad thing, that. Finally, original 360 pistons are fully skirted, and may hit the counterweights on a 390 crankshaft. 390 pistons, besides being shorter than 360 pistons, have slipper skirts to avoid that problem.
Bottom line -- you can easily convert a 360 to a 390, but you need to swap the entire rotating assembly (crank, rods, pistons). Better yet, toss the old pistons and buy new ones. 390 pistons are plentiful and cheap, so there's no reason not to. And get the assembly balanced while you're at it.