i need to know how to find out if some motors i have are 360 or 390. i have ran some of the numbers and have found out some info but none on the bore and stroke

 

Here's the numbers:

360 = 4.050" bore X 3.5" stroke

390 = 4.050" bore X 3.784" stroke

 

I believe that the 360's have a key-way type notch and a half-moon cut-out on the crank flange (on the outer area) where the flywheel bolt's up. And the 390's just have the key-way cut.

 

I have seen in the past that the 360's that I have had have raised enbossed "ribs" along the sides of the block, next to the soft plugs. They are not very high and they are of varying whith. 360's also have square cut troughs on the crank and the 390's have chamfer cut troughs on the crank. This may not be the way all of the engines are, but the ones that I have had run along these lines.

 

If the engines are apart, post the casting number from the crank, if not, you have to measure the stroke. You can do that using a dowel poked through the spark plug hole. Bring the piston up to the top and mark the dowel. Rotate the crank untill the piston is at the bottom and mark the dowel again. Measure the distance between these marks - 3.5 inches is a 360, 3.75 or so is a 390.