360/390 ?

Zorm · Post by **Zorm** » Sun Aug 02, 2009 11:49 am

how can you if you have a 360 or 390? In my Dad's truck, I know he has had at least 2-3 engines. When I was younger I remember helping him build a 390 but I think he said that is a 360 now. I know he has gone from a 390-360-390, or visa versa. So, how can I tell the diff between the two?

TNIceWolf · Post by **TNIceWolf** » Sun Aug 02, 2009 12:09 pm

You have to measure the stroke. As I understand it the engines are identical in external appearance.

fordman · Post by **fordman** » Sun Aug 02, 2009 10:15 pm

the 360 stroke is 3.50 and the 390 stroke is 3.78

Zorm · Post by **Zorm** » Mon Aug 03, 2009 7:16 am

heads are the same if they are stock?

convincor · Post by **convincor** » Mon Aug 03, 2009 8:22 am

yes.
crank, rods and pistons are the only things different.

fordboy69 · Post by **fordboy69** » Sun Aug 09, 2009 11:17 pm

I thought the only things different were the crankshaft and rods. Pistons are the same because the engines are the same bore, right?

fordman · Post by **fordman** » Sun Aug 09, 2009 11:37 pm

well the pistons are the same but they arent. the 390 piston marked 410 usually. has less of a skirt on it than the 360 full skirt piston. so in theory. as far as i know the full skirt 360 piston can hit the rod or the crank when running and mess up the piston. so in order to be safe you put in a 390 half skirt piston so that doesnt happen. they are the same bore. you are right. its just the chance ( i heard) that the 360 skirt can hit the rods or piston when you use the 390 crank and rods to build a 390.

frankensteined_67 · Post by **frankensteined_67** » Mon Aug 10, 2009 3:12 pm

if you cant get the stroke you can look at the back of the crank where the flex plat gos. if there is a half moon cut in it it is a 360 crank if no cut it is a 390 crank

fordboy69 · Post by **fordboy69** » Tue Aug 11, 2009 5:31 pm

ok thanks.

sideoilerfe · Post by **sideoilerfe** » Thu Aug 13, 2009 10:15 am

fordman wrote:well the pistons are the same but they arent. the 390 piston marked 410 usually. has less of a skirt on it than the 360 full skirt piston. so in theory. as far as i know the full skirt 360 piston can hit the rod or the crank when running and mess up the piston. so in order to be safe you put in a 390 half skirt piston so that doesnt happen. they are the same bore. you are right. its just the chance ( i heard) that the 360 skirt can hit the rods or piston when you use the 390 crank and rods to build a 390.

The compression height is different and the rods are different lengths.

fordman · Post by **fordman** » Thu Aug 13, 2009 6:24 pm

i forgot about the compression height. oops thanks.

ToughOldFord · Post by **ToughOldFord** » Thu Aug 13, 2009 9:24 pm

frankensteined_67 wrote:if you cant get the stroke you can look at the back of the crank where the flex plat gos. if there is a half moon cut in it it is a 360 crank if no cut it is a 390 crank

This is so, here's a shot of the 390. My extra 360 still has the flywheel on it so no pic there, but instead of the round hole you see in the 390 pic it'd be a crescent cut for a 360:

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