GMC V6 engine info
 

I am having a problem ID-ing the serial # on my GMC 401 cu V6.
The serial # is as follows: 401-011246. It is stamped on the passenger side front of the block close to where the head meets the block. What year is this engine?
Does anybody have any info on these engines?
Auto parts stores don't even list this engine for tune up parts. Maybe I'm looking under the wrong truck size/heading. What size trucks did these engines come in & what years did they have/make them? Auto parts stores have the 305 V6 listed. Do they take the same points, condenser, cap, rotor?

Re: GMC V6 engine info
 

Welcome to the site. I'm by know means a person that knows very much about the GMC engine but I do think the points and stuff would be the same. I would say from your numbers that you have a 64 model but that is just how I see it I would [guess] it was built Jan 12 64. Some one that knows a lot more thane me can [and will] come on here and help you out. Once again happy to have you . Jim

Re: GMC V6 engine info
 

Thanks Jim!

Re: GMC V6 engine info
 

Look here!
http://6066gmcguy.com/

Re: GMC V6 engine info
 

http://6066gmcguy.com/401v6.html

401= Engine CID
011246 = Build sequence number or unique engine ID

The date code should be cast into the block. Probably on the top of the bell housing flange (sorry I'm not up on the GMC v6s)

Re: GMC V6 engine info
 

Double check to see if there is an M next to the 401. Mine was hard to read but it is there. Also check the intake and exhaust manifolds for dates as well although those parts could have been replaced.

Re: GMC V6 engine info
 

You can't beat the 6066 site for info on those years. My 1969 Data book from GM shows that in '69 the 401 V-6 was standard in HM80,JM80 and TM80 vehicles, and was optional in no other.
Horsepower was up to 237 gross (202 Net), torque was 372 gross (348 @1600 RPM Net).

Re: GMC V6 engine info
 

Thanks for the help!
The 401 GMC v6 is in a 1952 Diamond T fire engine. The engine is a super mega tight fit, and you cant see any casting #'s. That's why I was hoping to ID by serial #.
The 6066GMCguy I tried to contact, but to no avail.
There is NOT a M next to the serial #. M= Magnum motor, mine is not.
Since it isn't in a GMC truck, the V.I.N. # on the Diamond T cab doesn't give any specifics for the engine.

Any more help would be greatly appreciated.
If I got a mirror on a stick, where would I look for casting #'s specifically on the block?
Would they be stamped on like engine serial #'s, or are they raised #'s on the outside of the block?
Would they be on drivers side up high, passenger side down low, etc?

Thanks in advance!
Have a great weekend!

Re: GMC V6 engine info
 

There is a casting number on the rear driver-side of the block just below the head. Yours may have a draft tube but the photo shows the canister. I have seen a number by one of the freeze plugs too.

The intake is dated as well; I've seen by the 1&3 cylinder area and 4&6. Also the exhaust manifold has a date. My 401 was reportedly a replacement engine so I have different dates; 74 & 79.

Re: GMC V6 engine info
 

The 401 was not used in pickups, usually found in 5 ton trucks. You might want to ask in the Heavy Haulers sub forum on this site. I believe the 401 used the window in distributor cap with allen wrench access to point adjustments. The 305 that was used in pickups has the non window distributor cap. I recommend a shop manual like this one ( heavier duty trucks) 5500 and up.http://www.ebay.com/itm/1960-1962-GM...ccd04e&vxp=mtr

Re: GMC V6 engine info
 

Not sure when they changed but my 61 305 has the window distributor and the 401M I have, does not have the window.

Re: GMC V6 engine info
 

Thank you Musicman70!
The pics and info was just what I'm looking for!
I will try and Id it tomorrow!

Re: GMC V6 engine info
 

What type of distributor does you 401 have gsmeier?

Re: GMC V6 engine info
 

My cap has a window.
Does that help?

Re: GMC V6 engine info
 

also, I think the caps will interchange....

Re: GMC V6 engine info
 

Thanks for all the help!
I have a 1962 401!