Hi, maybe you great guys can help me with this one, as i`m mostly into Fords... I just got a `57 chevy 3100 pick-up as a trade for another car. I`m thinking about putting a 302 GMC that a friend of mine has, into the chevy for the endless torque, and was wondering if this is an easy swap. How do i identify a 302, just to make sure it is what everybody says it is? What cool toploader could i use behind a 302? Does the 302 have the familiar smallblock bellhousing boltpattern? Where can I find cool parts for 302`s, like dual exhaust, dual intake, nice street cam, etc.. All these things should be priced relatively reasonable, as most of what i make goes into the Fords.. Any help appreciated.. Thanks.
The 302 GMC six is getting kind of rare around here. I have found several of the smaller ones 228cu but no 302's in a long time. The 270 I had and the 228's I have found were stamped with the cu right on the machined pad that the distributor mounts in. There is some speed equipment floating around and prices are about the same as flathead Ford stuff. I'm sure someone on here will have a source or two for parts. Fred
Size number should be on the pad near the dist. It's longer than the chevy six but moving the radiator and using extensions on the mounts worked 30 years ago. As I remember it 57 gmc mounts worked but were hard to find then. I does not have the chevy v8 belhousing pattern.
it does have the same bellhousing pattern as the Chevy 235 though, which makes it pretty easy to deal with the back end of the engine, just use a stock 6 cyl 55-59 truck bellhousing.
I wrote this post on our oldGMCtrucks forums pages about how to look for a good candidate 302. This might be helpful: A lot of us have gotten into our motors and have collected some prospective spares, and I thought it might be interesting to discuss some of the things we look for when prowling for a project or replacement motor. The Service Manager and I were fortunate enough to have found and recovered a couple of 302s and bunch of spare parts for 302s and 270s. The 302 I got came out of the '54 COE. It was totally buried in 50 years of grease cake and other than s****ing the pad adjacent to the distributor to confirm it was a 302, and pulling the dip stick to make sure the crankcase wasn't full of water, I did very little but remove it and park it in my shop. Over past two weeks, I've had a small army of s****ers lying next to it and I've been scratching on it every free chance I've had to clean it up enough that I felt it was safe to begin dis***embly without fear of putting cake/rust/schmega junk in the motor during the breakdown period. I have been using a s****er and screw driver for the most part, but it's been VERY slow going so I decided I needed to up the ante. I went to Sears yesterday and picked up a pack of three s****ers which have totally changed the level of effort required on my end of the deal. These s****ers are worth their weight in gold as far as I'm concerned. So back to the topic: What clues to look for when searching for a prospective motor. The basic things I encourage everyone to check prior to considering any junkyard or junked engine are as follows: 1) AntiFreeze/Freeze Plugs - check all the visible freeze plugs for any sign they have popped, adn see if there's any antifreeze in the motor/radiator. Is the block drain plug open/closed/in place? 2) Oil - check the oil for any indications of water or contamination 3) Was the hood open or closed on the truck? An open hood can allow water to enter the engine through the rocker vents (*if so equipped) and it will end up in the oil pan after dripping through the oil p***ages. 4) Broken or obvious signs of why this motor is in the junkyard to start with; is the truck crashed or is there some obvious failure that might have led to its being put in the yard? 5) Casting numbers: ALWAYS check the casting numbers on the head and block to make sure the engine is what you think it is. Further clues.... Andy has a great post in the the Hall of Fame on how to read date codes. I found that the 302 from the '54 COE had a 1956 date code. How is that possible? It's possible because it's a replacement engine. First a close exam of the numbers on the pad adjacent to the distributor revealed that the block at least was a replacement block; it did not begin with a letter code (customary on original engines in my experience) and the font/type set of the numbers following 302 are different and bigger clearly showing the engine was re-stamped with the original serial number: OK, so now I know the engine was re-numbered and the block replaced. The intake/exhaust manifold date codes are '54, but the head and block show 1956. Here's the date code off the block. It is J 25 6 which corrolates to October 25 1956 Here's the date code on the head which read G 17 6 and corrolates to July 17, 1956. So that tells me that both the head and block were replaced, but the manifolds were apparently re-used. Here's where I'm pulling these numbers from for anyone interested: First, the manifold side of the engine: All of these clues were helpful in determining if the likelihood of a useable motor is there. I have still not yet opened this engine up to see if something catastrophic happened and took it out of service, but I am pretty confident that this one should be ok. Only time will tell and I have still a lot more cleaning on this before I'm ready to open it up and see the inside because I want to go straight to a rebuild on this one and it's a lot easier to clean the outside when engine is still sealed and you don't risk dropping a lot of metallic crud into it. --------------------------------- Here's Andy's post from our site on how to read the date codes: Several people have asked here and through my email about how to tell what year an engine really is. Here goes: I attached a picture of what is used to determine the casting date of the GMC engine blocks and heads. The first digit is always a letter of the alphabet A-L. A=January, B=Febuary, C=March etc, etc all the way to L=December. The next digit is a number 1-31 which is the day of the month. The last digit is always a single number and represents the year of the casting. For example, the one casting date in the picture would read: March 5th, 1952. What gets tricky is that the "2" for the year could mean 1942, 1952 or 1962. In this case, you have to look at the casting number and/or engine model to narrow this down. The example in the picture is the 302 head that's in my truck. 302's were only made from 1952-1959 so the "2" can only mean 1952. Same thing with the 270, the casting number of the heads and blocks changed over the years so this has to be used along with the date code to pinpoint the year if there are multiple possibilities. The date code casting for the block is usually on the same side if the block as the casting number. The cylinder head location is usually outside the valve cover near the center. Some of the later 270 and 302 heads had all the casting numbers and date castings under the valve cover down near where the pushrods come through. The raised area with the date almost looks like a small plate attached with two screws and they are often mistaken for something that can be removed. They actually are part of the casting. The slotted screw impression is there because that's likely what they used to hold the tag on the inside of the mold when the casting was poured. Other GM products use the same method so you may see the same thing on Chevrolets, Buicks etc, etc. Here is one for a Chevy 261 from January 7th, 1959
Thank you I got some free time this weekend gonna see if the 59 gmc 100 270 has tat special head.My uncle also has a 54 gmc fuel tanker with a 270 tat I will go check out. will also try to start the 302.
Why do you want an H head? It will have the same ports and valves as any 302 head, but will not have the small combustion chamber with a squish surface. So you get the same ports and loose compresion and turblance. Whats the up side?
Hi morning. I was reading other threads and wow I gotta say you guys are serious builders/racers.I didnt know I was talking to a Boneville record holder!!! This is awesome.I respectfully bow down to your experience. Now this is the first time I mess around with engines. I love hot rots and old cars and trucks in general.But I like stock engines and I want to get to know them better before I try to "soup up"any engine. I need experience. My plans for the 302 are: Leave it stock with the exception of a 12 alternator and mate it to an automatic transmission or a 4 speed.Which ever is closet to my ability and availability. I dont plan to race,drag,burnout But I would like a highway friendly truck/car. The 270 H head would be just a nice thing to have,Maybe a nice hamber could teach me how to mate my 302 to a decent transmission if I provide the parts and I could give him a nice 270 with an H head in return.(hint hint)That is if I had a 270 with an H head. I was just thinking that It would be sweet to find these cool old parts in the backyard thats all.
I used a '55-61?) Chevy 6 bellhousing and a Saginaw 4 speed on mine. Bolts up with no mods. Worked great.
Yes. I picked a flywheel for my 302 from a 270 out of a 1/2 ton pickup. The 'wheel on my 302 was way too large--it used a 13 inch clutch as the engine came out of a school bus--and the 270 unit uses an 11 inch setup.
As mine was a race car I had to buy a billet SFI flywheel. I would guess any GMC 6 cylinder pickup or small truck that was 12 volts would have the right flywheel. Not many of them around these days. Post on Inliners International. Somebody there may have one.
You post on "OldGMCtrucks", yes? List your want ad there,I know some of those old farts are sitting on piles of GMC stuff.
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