In my favorite junk yard, I spotted a 1953 GMC dump truck that just came in. I'm curious what kind of motor it has, can anyone help? From the plate on the door post: General Motors Truck Made In Canada Model 975 Serial Number 0975310246 CSL5062 Engine 270768053 Body serial number 65 Paint SP341 Trim 314 ( middle digit not clear, it could be almost anything ) Before the Chev V8 came out, the GMC six was the hot setup for hot rod Chevs. Just wondered what this one is.
Wonder if it would be worth getting it to rebuild for a 1942 Chev project? How does it compare to a Chev 235 or 261 for ease of finding parts, cost, difficulty of rebuilding etc? It would make a cool hot rod motor but if it is a lot more expensive and difficult to work with, will stick with the Chev sixes. Does anyone know where to find the engine number on the engine? It doesn't look like it has been changed but you never know on a truck that old.
Engine 270768053 270 768053 I don't know if you can find by year listings for the engine. There is a little bit of casting number info http://www.oldgmctrucks.com/Photos/GMC_Numbers.htm but it will only get you in the ballpark. maybe search a while, see if you can find a year listing for which engines were made what years? or look for Chevy type casting dates? I need to figure this stuff out too, I just got a 58 GMC bus with a 270 in it They do make good hot rod engines, parts are more scarce and expensive than chevys, but you can find them.
I have run 270 GMC motors in my car and I like them. The engine number is next to the distributor. 270768053 I believe you said. They were run is some pretty big trucks and are well built. If there are no cracks in the exhaust ports, go for it. I still hold an El Mirage record set with a 270. The 302 engines have a closed chamber head and large ports. The late 270H has the large ports but I guess still the open chamber. I always used 302 heads or 12 port aftermarket heads. If you go with the 302 head you need flat top pistons. 270 pistons have a big popup.
It is larger than the Chev. You will have to move the radiator to the other side of the support, I believe.
I think it's 2 inches longer than a Chevy.But the bellhousing is the same. You need to reverse the radiator as above. I think you can buy new Fenton headers for it. I made my intake. You should check out Inliners International. They have a news letter with ads both commercial and private. My 270 in '78 in color and in '84 B&W
I think that year 270 still had solid lifters? I'd like to see a picture of a Wayne 12-port head and Hornung's race car, any on the HAMB?
Check the inliners international site for numbers and history of the engine. There is even a several part history on Horning and the 12 port head.
270 is a great motor. Definitely an upgrade over a 235 or 261, IMO, and I own or have owned all three. My 56 GMC still has it's stock 270 and I love that motor. A 302 is a nice choice too, but the 270 is definitely nothing to sneeze at.
These things were pretty popular back in the day. There should be a lot of speed equipment hoarded away. Just need to locate it.
If you scroll up to post #9 you can see a Howard 12 port head, which is a Wayne 12 port with the intake ports raised to 45 degrees to give a better angle towards the valve.
Yes, they are insert bearings on rods and mains and full pressure lube system. As I recall, the pistons are aluminum. Ray
Absolutely aluminum pistons. And all the 270s I ever saw had a .990 wrist pin. Same as a BBC. Some 302s were .990 some bigger. Some with oil to the pin. Some not. I had pistons made for mine from BBC blanks. With the 302 head I used 1.94-1.600 SBC valves +.100 on the stem length. A standard over the counter hot rod part. I used the stock brazed rocker arms except for the Hourning head which Bob Dalton and I made roller rockers for. I used either a Mallory dual point or a Vertex depending on the phase of the moon. I really don't have a reason to pick one or the other. I can't think of anything else much about it. Make sure you put the rear main inserts in the right way around. Lots of GMCs got killed by people being careless about that.
Theres a chrome valve cover in IE CL for a 248/270/302 and an Ellis Intake manifold on ebay right now.. I just picked this up last week: I dont know why! I just like them. I have 2 of them,one with the H head.
I know! I asked the seller what was the deal with that,he said it was a project for a cancer survivor.
Rusty I wish I could help you with info on the mill bit alas I cannot. I do have a lot of respect for the big Jimmy as hot rod fodder. I would sure build one if I had one to play with.
Rusty, if it's practical advantages you want, the later model 292, into'd in 1963, is the best choice. 7 main bearings, full flow oil filtration, V8 bellhousing block pattern, etc. Doesn't have the "nostalgia" vibe of the earlier Jimmy 6, but practical it is. Ray
I am not a wealthy man so sometimes constraints on the wallet require something more practical. I have never met Rusty's bank account so this is no reflection on him, I am just speaking from personal experience. Anyway back to it financial constraints aside sometimes fun trumps practical.
Amen to that brother......and my financial condition has suffered steadily as a result! Just posted in the interest of offering alternatives........... Ray
The idea is to have a street cruiser I am not afraid to take on the interstate. I was thinking of a mildly hopped up 235 or 261 with insert bearings, and a little higher rear gear ratio. Nothing sensational. Then the GMC turned up and got me thinking.
Rodders Journal #65 has a couple of six powered 31 chevys in it. One is a bored and stroked 261, the other is a bored and stroked 302 jimmy. Neat cars, I got to hang around while they were being built. And I got to drive them. The GMC took a bit more work, and it was probably worth it. But they're both really neat cars.
Pistons are a problem, at least for me. I sent all required info & a chamber casting to the company known for making the finest, most popular forged racing pistons during the heyday of GMC popularity. They lost the casting, & were going to provide me with wrist pins 2.9" long for a 3.875 bore engine. We didn't do any business ... Another famous, leading mfr. was then contacted, & agreed to make them, for well over $700 ... sent chamber cast & half payment in May, & still waiting ... Some info worth noting - Wrist pins were increased to 1.052 during 1956 production. Both .990 & 1.052 wrist pin bushings are hard to find & expensive. The camshafts were both cast & steel - cam grinders I've dealt with prefer steel. Refaced Chev & GMC milkcan lifters work fine. 1.94 Chev intake & 1.60 Pontiac exh. valves are near perfect replacements for the 302'' Korean war heads. Hard seats will need to be installed or stock seats ground to 45 degrees. When looking at a builder core prospect, buy one with a 6 bolt crank flange. Stock flywheels are getting scarce. Ring gears are same as 235 Chev, so no problem there. If you plan to wind them much over 4000 RPM, tube pushrods are a must. If hooked to stock Chev 3 speed, don't dump the clutch in low ... If hooked to torque tube axle, maintain an inventory of u-joints & RH axle shafts.
Im sorry if Im high jacking this thread but Is there a reason not to keep the 270/302 stock for a driver? How about just a intake and split manifold leaving the rest stocc?
The Jalopy Journal
