401 425 head numbers

[jhonjhon]

I recently found 2 nail heads in a junkyard. I don't know if it is a 425 or 401. The #'s on the heads are 1374603 on what I think is a 66 Electra 225. The other car has 119614 on head. Can any one tell me what these are and an easy way to tell them apart. Also , is a 425 just a bored out 401. Thanks for any help. John

[NailheadinCA]

The 401 and 425 are not the same block. The cranks, heads, rods, rockers, flywheel, dampner, timing cover, exhaust and intake manifolds all interchange but the blocks are cast separately. The thing to note is that you can't necessarily bore a 425 block more than .040" unless you do your ultrasonic testing first. I bored my 401 .060" over and had plenty of material left over.

[BlownNailhead]

You can not tell by the head casting numbers, both of your head castings were used on both 401 and 425 engines. You must check the block casting number, or can also check the code on the front of the engine, a stamped 2 digit number/letter on the passenger side right by the valley pan.

NailheadinCA gave you good information as well. Unless you are absolutely set on a 425, the 401 makes as good of an engine for most cases.

[jhonjhon]

Thanks for the help, but once I get the #'s , what do they mean. I still don't know what they are. Where can I find that out?

[dualqwad]

jhonjhon said: Where can I find that out?

Here;

http://www.buicks.net/shop/engine_ident.html

[jhonjhon]

Thanks again ,that was a great help. John