Help with numbers on my 401

[Mike Caldwell]

Finally getting started opening up my 401. It came out of a "New Idea" harvester, that's all I know.

Here's some pix of the numbers I've found on the top of the bellhousing. Will post more when I can get to the front of the engine.

Questions: is it a 401? any idea what year?

[Funky61]

Check the Intake manifold and the exhaust manifolds as they should be dated and that may give you an idea

[Mike Caldwell]

Third pix in OP shows the numbers on the intake manifold.

Any help?

[Funky61]

That looks like the rear portion behind the carb area. I have similar numbers on my 401.

Here is the driver side front pad that shows the firing order and a date


New Idea Harvester repowered section from Jollys Page
http://6066gmcguy.com/V6powered.html

[Mike Caldwell]

Pix shows entire intake; only numbers are the ones in the closeup and the firing order on the other side.

[Funky61]

It could be a 401, but not a magnum based on the intake manifold but,

The numbers you have in your first picture are the same stamped on my
401M: CWG4 2476579

So it may very well be a 401.

Here is what I have stamped on the front engine pad just below the right-side head.

[Mike Caldwell]

I'll try and get to the front end tomorrow and see what I can find.

Thanks for the help!

[Funky61]

You're welcome and since the intake is off post a photo of the head passages to see if they are magnums.

https://6066gmcclub.com/album.php?albumid=107

[Mike Caldwell]

Here's the stamped numbers on head and good closeup of ports.

Couldn't get real clear look at numbers but it's a 401!

[James]

Here is a link for 401 piston .030" oversize:
https://www.ebay.com/itm/186901885269?mkevt=1&mkpid=0&emsid=e11021.m164380.l178264&mkcid=7&ch=osgood&euid=e82d05f89c574d2d8a3d14a4d10d8b86&bu=43104789955&ut=RU&osub=-1%7E1&crd=20250119035312&segname=11021&recoId=186901885269&recoPos=1