Trying to start the engine on a '56 GMC 1.5 ton after who knows how long. I thought I had a 270 I-6, however after looking up the block casting numbers it appears I have a '53 or '54 248. So guessing it's not the original engine to this truck, which is kind of a bummer. Still hoping to get 'er started up. I have spark and now I have re-installed the carburetor with new gaskets. I installed new gaskets in the Carter Ball & Ball carburetor, which came from Chrysler (still leaking fuel from accelerator pump linkage - darn). The engine backfires through the carb, so now I want to verify the timing.
So here's me question: what is the firing order for this engine? Thinking it would be cast into the intake or somewhere else but couldn't locate it. Hoping someone reading this can also comment on the engine/truck relationship as well. Is there a chance this engine was original to the truck? Still not sure what to even call this old girl. '56 GMC 250? I was told by the previous owner it is for sure a 1.5 ton, so who knows. Starting to think that it's a bit of a "Frankenstein", but hard to imagine a guy would swap the 270 out for a 248 and then put a Chrysler carb on it. But maybe it's what he had laying around.
A quick response would be appreciated as I wanted to drive it to dinner tonight! Just kidding...
Engine SN stamped on machined surface behind distributor on right side starts with displacement, I.e. 270xxxx, etc. Front wheel is 8 lug, so rear is probably same. Probably has SM-420 trans. If front hub is pipe thread that would fit for one ton. What is GVW? If engine is 248, it has been changed for sure. I have several 270 and 302 engines.
Ed
Last edited by EdPruss; 12/30/20213:21 AM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
The block casting number in your third image (if I'm reading it right) "6107328" looks like it's a 1953-1955 248. This is from the Mark Allen casting numbers book.
-David
1953 2-Ton GMC
I'm a machinist... because engineers need heroes too.
The block casting is a '53-'54 248. The head casting should be 2194819, Normally the displacement of the engine would be the first 3 digits of the engine number. However this doesn't always hold true because it was common to change the engine number to match the title because many states titled vehicles by engine number until the mid 50's. There is nothing wrong with a 248 and this one has the later flat pistons and small combustion chamber head. However parts unique to the 248 such as pistons are getting hard to find.
Hy Derek S., welcome. the firing order for the 228 through 302 series engines is 153624, that is also true for the Chevrolet inline sixes as well, hope that helps.
Hy Derek S., welcome. the firing order for the 228 through 302 series engines is 153624, that is also true for the Chevrolet inline sixes as well, hope that helps.
Old instructor at OIT taught 1st year students "easy way to remember in line 6 firing order, 15 is too young, 36 in to old & 24 is just right".
BC 1960 Chevy C10 driver 261 T5 4.10 dana 44 power loc 1949 GMC 250 project in waiting 1960 C60 pasture art Retired GM dealer tech. 1980 - 2022
The distributor rotor turns clockwise as you look down on it, so be sure you get the firing order right- - - -numerically and direction-wise. Pull the #1 spark plug out and "thumb" the hole for compression whlie someone else taps the starter, then put the #1 plug wire into the distributor cap wherever the rotor is pointing when the compression pops your thumb off the hole. Any cap tower can be #1. The engine doesn't care as long as the firing order is good and the ignition timing is set right. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I was able to get the engine running. The cap, rotor, and plugs were all set up correctly, but the distributor was 180 deg. off. For some reason I always doubt this and look for other issues, but backfiring through the carburetor was a good clue. Just weird how it can be rotated. I guess it may have been loose, and then pops out? I don't know but I was sure happy to hear it fire off - after it got really late and cold out and I had given up, but thought well might as well try. So spun the distributor 180 deg. and it started right up. Next issue is the carb., which now leaks like a sieve, even with the new gaskets. Since it's not the original carb., I will start looking for a good replacement. Thanks everyone for the comments. Here are a couple of additional photos of the rear wheel, and of the stamped numbers on the machined surface near the distributor.
For now I am going with a 1956 1 ton, with a 1954 248! Making progress
Tim - I love your 2 ton, pretty cool project making it an extended cab. Pretty cool Photoshop job too, or whatever you used!
Ed - I may want to consider getting a 270 from you.
