1955 or maybe 56 GMC farm truck. It says 300 on the grill and model is 303 on the id tag. ID tag also says 130 gross horsepower and 120 net horse power. It is headed to the crusher and I want to save it if it is a 270 or 302. How can I quickly identify the engine? thanks.
On the right side of the block,by the dist. there is a flat, machined surface. This will have a ID code but more importantly, the engine size.
Why not? If nothing else it has all the accesory stuff you can use for a larger GMC engine. If my memory is right, the following is correct: 228 = smallest bore, same stroke as 248 270 = same bore as 248, same stroke as 302 302 = largest bore The 248 may be down a bit on cubes, but if it is good condition you could just run it. The other parts like bellhousing and flywheel could be useful as well. Pretty sure GMC has same bellhousing pattern as the 235/261 Chevy.
These sizes are all correct, but there are also two others in this line-up; a 236" and a 256". Pretty rare, I've only seen one of each, stamped numbers down by the distributer shaft, resting in junkyard GMC's, but they are listed in my motors manual. Don't recall how the bore/stroke relates to the other engines. Later, Kinky6
Thanks, it's a 248. I haven't had time to see if it will pop off yet but supposedly it was running 3 years ago. I bought the truck to save it from the crusher since it had a pretty decent set of 7.50x20 rubber that is getting a little hard to find. Will strip it of any good parts and let it continue it's way to the crusher.
If you ever see another one consider saving the oil pan, oil pump pickup and flywheel because they fit the 302 and big truck 270 and make it easier to install the big truck engines in pick up trucks and passenger cars.
My first 270 was very stuck when I bought it in '77. Been outside in a junk yard, uncovered without a carburator for about 10-12 years. Very hard to get apart. Went 158 mph in my stock roof '32 Ford 5 window and still holds it's class record at El Mirage. Don't crush GMCs just because they are stuck. Flex a mussle