The Stovebolt Site Forums The Shop Area Engine Shop GMC engine (vs Chevy)

Hi all,

I came across a (reportedly) low mileage GMC 6-cyl engine from the 50's. I was told it came from a 57 panel truck, but i wonder about that as it does not have the oiled rocker assembly that my '56 Chevy 3100 235 motor has. The valve cover is held on with 2 studs sticking out of the top, which is also different from my Chevy motor.

Here are the numbers cast in the side of the block:

CWC
G317
GMC4 2324003

is there a resource for decoding GMC block #'s? or are these numbers recognizable? Does anyone have any comments or thoughts as to what this motor is (year, displacement, parts interchangeability with a '56 235, rarity, value, etc)

Thanks for any info!

Tom

According to the casting # chart at http://www.inliners.org/ it is a 270 engine. It is a highly desirable engine with the GMC crowd as a replacement for the earlier 228s and 248s. It has few parts that will interchange with a Chevy engine.

X2 on what Cletis said
The bellhousings are interchangeable from the chevy to gmc, but the gmc engine is about 2 inches longer. It is possible to put the gmc engine in a chevy, but the radiator will likely have to be relocated forward. This is not a simple drop in swap, but it ain't a difficult swap either from what I have read... never done one myself.

thanks Gents.. I can have this motor - it has 12,000 miles on it - for a very low price.. From what I learned here, I don't want to use it in my truck, but if I can buy it and flip it, i might be able to add to my restoration budget.. any swag on value?

I've got a 235 in my 58 GMC. Want to trade?
Larry

Maybe Larry. I have a running 235 that came with my truck, but of unknown condition. Looking to get a low mileage motor (maybe a dream) so I know what I have in my truck. What are the particulars on your motor?

So what kind of vehicle do you want to put it into? If its a Chev pickup it is rather simple. If its a passenger car, it runs into a lot of work with the front suspension. The 270 is a very good engine and would be a nice upgrade in a Chev pickup unless you want to stay original.

I think the block was cast July 31, 1957.

i have a '56 chevy 3100 that I want to keep original. The 270 motor is in a pile of parts to a military/civil defense panel truck that I can get as a lot. Just wondering now what to do with the engine.

Do you know if the 270 turns or will run as it sits?
Ive got a 248 in my truck that's locked up from having water in it. I'm trying to decide weather my engine is worth rebuilding or replacing. It's not the original engine to the truck anyway.
I might be interested.

not locked up - ran a few months ago. always stored inside. send email to tom_casale *at* hotmail *dot* com and I can send a couple of pictures.

good ??? I'd like to know more about GMC motors Iam kind of up on 216 and 235'S I know s%th about GMC's other than they are the same only differant.

Floyd, you sure know how to anger a gmc guy. In many years the gmcs are much more different than they are the same. GMC was a step above chevy trucks, much the same as Cadillac was a step above a Buick or oldsmobile. There was more value in a gmc.

Swingdaddy is right about that. If you wanted a pretty truck you bought a chevy. For heavy duty you bought GMC. Seems like GMC was always flirting with heavy duty and different ideas on the same chassy. I've met an owner of a 56 GMC here in Richmond with a nicely restored GMC with a couple of major mods from GMC. One being a cab brace which goes from the top of the firewall to the front of the frame. The other was a hydraulic dampner on the end of the axel where the kingpins are. Odd looking stuff but shows what GMC was trying to do.
Larry

from my experience with motors, chevy and gmc is that until proven otherwise they are worth only scrap price to $100. to me. i have had people say they were good running engines only to find out they didnt run, couldnt run or they would have blown up within the the first 100 miles of running. after tearing into them only to see that a total rebuild was in order. either the seller was a complete liar or was talking out his [censored] but regardless the engines werent good running as advertised.

Something to check out first would be the mounting on the engine block. I don't know about 270's but the military 302'a had a difference that made them difficult to install in a civilian chassis. If the "military/civil defense" unit is in a commercial vehicle then I wouldn't be concerned but if it ia a tactical militay truck then it would be worth knowing and understanding. Hope I'm not causing unnecessary concern but I do know the 302's are different.

This is all great stuff to learn. The truck it came from looked to be an ordinary 57 panel truck, not any kind of tactical military vehicle. It is a NAPCO 4WD, however, I don't think i mentioned that before if it is of any relevance.

coming out of a 57, the engine will have side mounts and use that funky horse shoe mount in the front. In order to bolt this in an earlier 1939-1955.1 gmc truck, the front timing plate needs to be swapped with the earlier style plate. This means you have to pull the valve cover, the rocker assembly, the side cover, the push rods, the lifters, the harmonic ballancer, the oil pan, the timing cover, the distributor, the fuel pump, and the camshaft. After doing all that work, one would have a much better idea of weather or not that engine would require a full rebuild.

John

tomctomc, The casting number that you gave us, 2324003 is the correct casting number for a 55-63 270 with side motor mounts.
If you go to the GMC site and look at the casting numbers you will see it there.

My truck uses the earlier style.

OK OK I said I do'nt s@th about GMC althougth I do own a few big bolt's GMC's.

GM's Atlas division built the 270s for gmc. Funny thing is my wife drives an 05 Envoy with an atlas built inline six developing 270 hp. Wish I could steal her engine and put it in my 58 gmc but she would never go for that.

Oh, that engine is a terrible, terrible model. Nobody want's them. As a matter of fact, you should just let me take it and turn it in for the recycling money