Block and crank questions.

[Black Car]

What is the best way to tell (by looking) if a block is On or Off?
I know the casting numbers will sometime work but not always.

On a crank, how do you measure it to determine the stroke?
I know the most popular ones are the 3.590 or the 3.625 but exactly where do you measure to get this dimension?

Thanks,
Gary

[KendallF]

If the casting numbers fail you then here are some generalities:

Dry sump blocks are on-center. Wet sump blocks are off-center or very early on-center. Cross-bolted mains are on-center. If the front of the casting where the front cover bolts is not flat like a production block but instead has a 1/4" or so step, it's an on-center.

To check the crank's stroke, you need a jig made for the purpose or you can chuck it up in a lathe. The jig has two v-blocks that you use to support the crank and a dial indicator setup. You basically measure to the rod journal at the bottom and top of the stroke and account for the rod journal diameter by adding the journal diameter.

[Ted A.]

I guess I would just look at the front and back oiling feeds. If it's on-center they will be on a angle. The off-centers were straight in.

I have never heard of a 25500153 casting to be off-center, but I guess anything is possible.

[turbodave231]

The oil feeds on early On Center 153 blocks were not angled. So don't use that as an absolute rule.

Dave