GMC engine identification

[chris j]

I have a GMC six cylinder with the number B228292777 stamped on the block just behind the distributor. I'm trying to figure out exactly what motor I have. I was told it is a 270 when I bought the truck. The truck is a 1950 1 ton dulie flatbed. Can anyone help
Me figure this out?
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[FirstNation]

It would appear to be a 228ci. The first three numbers in the serial number tell the tale as far as the cubic inches on the GMC motors..

[dwcsr]

The problem is that they never used a B in a serial number. It was A then C skipping B
Your serial number for 1950 should start with an FC and most all in that year were 228 CI except the FC 350 series. Look on the door post for a plate
it could have been swapped out for a 270 at some point. get the casting number on the block

[chris j]

Where do i find the casting number? The number in my original post was just behind the distributor stampped on a flat platform

[Sim6]

I believe it will be raised numbers below that platform to the left.

[joedoh]

the leading letter, at least by what I have read on stovebolt, is the crank/bore/rod sizes.

http://www.stovebolt.com/ubbthreads/...1832#Post11832

so the bore on a B prefix engine is +0.005" and standard crank and rod bearings. 228 is the size, you cant make a 228 block into a 270, the deck heights are different, and 1950 definitely came with a 228, so chances are excellent that you have a 228.

FC could be 1947-1950, my 1947 is an FC, with a three digit serial. see if your last 4 digits of your serial plate inside the cab match the last 4 digits on the engine block.

this is everything I have learned about the GMC engines from stovebolt, so dont crucify me if my parroting of information is incorrect.

[FirstNation]

Cmg !

[FirstNation]

Originally Posted by dwcsr

The problem is that they never used a B in a serial number. It was A then C skipping B

GMC engine numbers will often, but not always, begin with a letter which denotes the bore and crank journals other than "standard" and then three numbers for the engine size, which in your case would normally be a GMC 228.

Sooo....

If no code letter then the engine bore and crank is standard. IF it has a letter, the following apply:
LETTER..........Cylinder Bore Crankshaft Journals
...............................Main.......Rod
A .............+0.005".....-0.010"....-0.010"
B .............+0.005".....Standard...Standard
C .............+0.005".....-0.010".....Standard
D..............+0.005"......Standard...-0.010"
E............Standard......-0.010".....Standard
F............Standard......-0.010".....-0.010"
G............Standard......Standard...-0.010"

[Gypsyman]

Rather than start a new thread I'll kick this one back to the top. Engine is believed to be a 426 c.i. I-6 in a '47-'49 800 series truck.

S/N AC4266526

Any idea what would the AC prefix stand for?

[mr48chev]

You are always way better off to start a new thread than stick your question on the tail end of a long dead thread. Guys will answer the first question again but never see your question. We don't care how many times a similar question gets asked but you usually don't get the best answers being a tag along.

I am not well versed in GMC engine serial numbers except that knowing the first three numbers denote engine size. There isn't much on the early GMC engines in the http://www.oldgmctrucks.com/index.html website that as far as I know is the go to GMC knowledge base. He doesn't have big truck numbers on those pages though.

[dsraven]

you could try the GM heritage center as well. get as many numbers as you can then send them an email
https://www.gm.com/heritage?evar25=gmhc_redirect

[Rickysnickers]

I know you two are sharp guys, but I'm curious why are you answering questions from a seven year old thread? Did I miss something?

[mr48chev]

Originally Posted by dsraven

you could try the GM heritage center as well. get as many numbers as you can then send them an email
https://www.gm.com/heritage?evar25=gmhc_redirect

There is nothing on GMC trucks in the GM Heritage center archives. Only Chevrolet. Actually only Chevy, Cadillac Oldsmobile and Geo and a lot of the info on some is sales media. https://www.gm.com/heritage/archive/...tion-kits.html

I go to the Chevy truck section almost daily to answer someone's question on the net.

I did find this on the Gregwapling site

2135412 GMC 46-54 200, 270 =3D 4
2193980 GMC 52-54 302
2324002 GMC 55-62 248, 302
2324003 GMC 55-63 270
2324004 GMC 55-62 302
2404929 GMC 55-63 270 =3D 4m

https://www.gregwapling.com/hotrod/c...indercast.html

Then more searching finds this from the OLD GMC site that I have looked on a number of times and hadn't seen. Hope it's on the bottom here is the link to go with the image. http://www.oldgmctrucks.com/Photos/GMC_Numbers.htm

The casting number will be on the side of the block (I'm not sure exactly were) and between it and the stamped serial number you can get about as close as you can.

[dsraven]

hey snickers, thanks for pointing that out. I didn't check the dates, just went by the newest threads that come up on the 47-59 message board. I figured somebody was resurrecting it for some reason. lol.

[Rickysnickers]

HAHAHAHA!!!! I've done the same and then realized, uh, what am I doing here???