Early Block vs Late Block

[jpian0923]

Early block vs Late block. Are they interchangeable?

[edwardc]

Yes, with a couple of caveats when trying to use an early model block with late model parts. The two big ones I know of are:

1. Oil Fill - The early block engines had an oil fill cap on the accessory drive, and don't have one at the front of the block. Easiest fix for this is to use a reversing-gear top cover plate from a V-Drive engine, as this has an oil fil spout welded onto it.
2. Distributor hold down - On the early block engines, the bolt for the distributor clamp screwed into the accessory drive. On the late model, it screwed into the block. If you use an early block with a late accessory drive, there's no hole for the bolt! The fix is to drill and tap a hole in the part of the block where the accessory drive and water pump attach. This will also require fabricating some sort of spacer, as the late model blocks have a raised boss here and the hold down clamp won't sit properly without it.

I think there may also be an issue with the number of starter teeth on the flywheel, but I'm not sure about that one.

My current engine is an early model block built up with late model parts.

[jpian0923]

I have an early block and I’m looking to replace it with a used late block.
See any issues with that?
Thanks Ed