360 to 390 conversion.

I'm gonna pull the junkyard motor out of the Howard this winter and do a quicky upgrade. Drop in a 390 crank and rods. What kind of CR will I see reusing the stock 360 pistons and C8 heads?

depends on the combustion chamber I reckon, probably 9:1 though...

You gotta get diffrent piston's too, the pin height if diffrent from 360 to 390... 390 as has a pin height of 1.66 and the 360 has a 1.76 height, you do not want to hit the head

Originally Posted by FEandGoingBroke

You gotta get diffrent piston's too, the pin height if diffrent from 360 to 390... 390 as has a pin height of 1.66 and the 360 has a 1.76 height, you do not want to hit the head

NO. The 360 and 390 use the exact same replacement pistons. The 360 uses a longer connecting rod.

This is an EXCELLENT conversion! The 360 has crap for compression, and crap for quench! The compression is only around 8:1, and the piston is around 1/8" from the top of the bore at TDC! The 390 conversion adds 30 cubes, bumps the compression up to livable levels, and restores quench by bringing the piston right up to TDC for better efficiency! Chances are, it wil have more power AND get better mileage after the swap.

As a bonus, the ONLY things you need are the 390 crank and rods. Both engines use the same balancers and flywheels... and even the same replacement pistons.

Good Luck!

Originally Posted by n2omike

NO. The 360 and 390 use the exact same replacement pistons. The 360 uses a longer connecting rod.

This is an EXCELLENT conversion! The 360 has crap for compression, and crap for quench! The compression is only around 8:1, and the piston is around 1/8" from the top of the bore at TDC! The 390 conversion adds 30 cubes, bumps the compression up to livable levels, and restores quench by bringing the piston right up to TDC for better efficiency! Chances are, it wil have more power AND get better mileage after the swap.

As a bonus, the ONLY things you need are the 390 crank and rods. Both engines use the same balancers and flywheels... and even the same replacement pistons.

Good Luck!

That's what I was told too. So what will the final CR end up being? I'd like to stick a cam and springs in it while it's apart and this is an important factor.

right on, cause if i aint mistaken, the 360 uses a 352 crank and rods with a 390 bore, i may be off on this but thats what i remember when i used to screw with FE motors

Originally Posted by n2omike

NO. The 360 and 390 use the exact same replacement pistons. The 360 uses a longer connecting rod.

This is an EXCELLENT conversion! The 360 has crap for compression, and crap for quench! The compression is only around 8:1, and the piston is around 1/8" from the top of the bore at TDC! The 390 conversion adds 30 cubes, bumps the compression up to livable levels, and restores quench by bringing the piston right up to TDC for better efficiency! Chances are, it wil have more power AND get better mileage after the swap.

As a bonus, the ONLY things you need are the 390 crank and rods. Both engines use the same balancers and flywheels... and even the same replacement pistons.

Good Luck!

You sure about that? I think almost all FE's use the same length connecting rod at 6.489". I think there were a very few 352's with a longer rod at 6.52"??? I think it's the pistons and crank that are different not the rods.

I think you need the 390 crank and 390 pistons to make the conversion.

paulie

Originally Posted by plovett

You sure about that? I think almost all FE's use the same length connecting rod at 6.489". I think there were a very few 352's with a longer rod at 6.52"??? I think it's the pistons and crank that are different not the rods.

I think you need the 390 crank and 390 pistons to make the conversion.

paulie

Very sure. The 360 uses the longer rod. When converting to the 390, the more common shorter rod is used, and is what allows the standard 360/390 piston to be used.

I believe the compression comes in around 9:1, but don't know exactly offhand.

I am confused now and will have to go to the machine shop in the morning...

I do believe the 360 had a longer rod though...

Thanks Mike, now I got WORK to do

330, 332, 352, 360, 361 all use the longer 6.540" rod...except the ones with the C3AE-A numbered rods...those ones were the shorter 6.488" rods. Pretty much all the other FE motors used the short rods.

Mike

Seems to me that you cannot use the same piston for two diffrent rod lengths...

Unless the crank makes up the diffrence in stroke...