I've got a civilian 52-54 302 that I am putting in a 53 Bel Air in the place of the 216. I will be converting this to 12 volt so that may make this a little easier, I'm not holding my breath. Now I know about the size differences between the 302 and 216. But what is giving me fits is the flywheel situation. I do know that the bell housing will bolt up but I've heard so many thing about the flywheel. The stock 302 6 bolt flywheel is too big to fit into the 216 BH which I don't have anyway, so I have to use a different one. Can I use a V-8 FW and if needed drill out the bolt holes and mill out the center hole if so what years and flywheels? What years GMC 270 FW will fit onto the crank.Will a 228 or 248 fit and if so what years, heavy or light duty trucks? Someone said a late 50's Pontiac FW will fit. What is right, what in known to be the truth. I would like to know for sure before I start chasing parts and waste time, money, and stress. The last one should be capitalized. If had more hair I wouldn't worry about it, but it is taking me longer to get ready in the morning because I have more face to wash. Thanks ahead of time.
Where did you get the engine that you have now? There are two (maybe more) sizes of 302 flywheel. I pulled my '55 GMC civilian 302 out of a 450 series dump truck with a 5 speed clark, and it had a huge flywheel with a 13" clutch. This definitely will not fit inside a 216 bellhousing. I was able to source a 6 volt pickup truck 6 bolt flywheel from a guy at the www.oldgmctrucks.com site that fits inside my 216 truck bellhousing. I'm not sure if it will fit into a car bellhousing or not. My understanding is that the 6 volt GMC 6 bolt pickup flywheel is fairly rare since 270's and 302's weren't commonly used in smaller trucks. Another option would be to use a 12 volt 6 bolt flywheel from a '55 or later GMC pickup and use a 12 volt starter with it, if you don't mind converting to 12V. A post onto the gmctrucks website will give you an answer, I'm not up on what exactly fits what year. My 302 is going into my '50 Chevy pickup.
I had a standard '55 Chevy 6 bellhousing on my 302 with a 12 volt GMC flywheel and starter from a pickup or light truck. Not the big killer flywheel. Worked fine, Used the '55 Saginaw three speed for years untill I stepped up to a Saginaw 4 speed.
Not to hijack, but aside from exterior add-ons, what were the differences between the civilian and military 302s?
There is a boss on the military 302 that has to be ground down to clear the bellhousing mounted starter, which is not there on the Civilian 302. The military 302's used an electric fuel pump so the casting may not be drilled out. I'm not sure if the military cam has a fuel pump lobe or not. Some military 302 crankshafts were apparently not drilled for a clutch pilot bearing as they were intended for use with a Hydromatic. I think the PCV systems and harmonic balancers weren't the same either, but you probably consider those exterior addons.
The military blocks have bosses on the sides of the block by the front for motor mounts. These can be taken off and you can use a Chevrolet 216 or 235 front motor mount plate. I took a lot of these apart and never noticed any difference to civilian camshafts.
I did post over on old GMC trucks a few days ago and they didn't care for me posting asking about this consisering what I am putting it in. Pretty much told me that I was in the wrong forum. Told me ask here. I am converting to 12 volt so what year light truck did the flywheel come from? Was it the '55 or a different year? Just trying pin down the specifics. Like I said I've been told this and still don't have a set of years to look for. Thanks Again
The flywheel you want is for second series 1955 through 1959 GMC 248 and 270. It has 168 teeth on the starter ring gear. The six bolt crankshaft flange bolt pattern is the same as the GMC 302. If you have a machine shop re-drill the clutch pressure plate pattern for the small Chevrolet clutch you can use the stock Chevrolet bell housing. Some people have the machine shop change the crankshaft bolt pattern to the six bolt small block Chevrolet V8 pattern but this means removing and replacing the GMC crankshaft. It is much easier to find a Chevrolet flywheel. If the flywheel is off the engine and at a swap meet or wrecking yard most people will think it is a Chevrolet so take a paper pattern with you.
I think I bought my flywheel from Jack Clifford. But that was in 1978. Jack and many of my brain cells have p***ed away since then.
Hi fnla39. There is a lot of info about this swap here and at stovebolt.com, but the people who you really want to talk to is Patrick's. They've been doing this for a long time, and really know the ins and outs. Someone here recently said that they called them, and a female answered...but she was extremely friendly and knowlegable. Ask for their catalogue also...it's got some excellent info concerning 6 to 12 volt conversions, etc. Patrick **** is the owner...a good guy. And he's got good people working for him. http://www.patricksantiquecars.com/chevrolet.htm
sure is nice when they think they are better because a GMC 302 is going into a GMC truck. as much as i love old GM trucks i got the same response years ago. i think anyone that has been there heads over to www.stovebolt.com because they figured out its douchbag central!
I saw this post over at OldGMCtrucks and there's more to the story. You actually ended up getting a lot of help and nobody asked you to move on. Neil (a moderator) only gave you more websites to try since most of the guys there have more expertise in stock solutions. BTW, in case you forgot, here is your last of three posts over there
Whoa Gregg! I've never seen anyone attacked there the way that often happens here when something is off topic. Its a pretty good bunch of guys who admitted to this guy that the group's focus and thus expertise is really the trucks and not the other vehicles the motors might get swapped into. It may not have felt warm and fuzzy but it was an honest acknowledgment of the limitations of the information available. I see it as similar to someone coming here and asking about putting an LS7 motor into a Camaro. Yeah some of us might have some knowledge that will help, but there are places online focused on that kind of thing and you might get better information if you ask there. Who there offended you? I know a number of them personally and a number of the most active members are here on a regular basis too.
Check the bolt pattern and center hole. If it’s the same diameter with a 168 ring gear you have a chance. A 168 tooth of a BBC with the GMC 6 bolt pattern will fit I’m told. I have one that’s done but not used it. I believe you would need an engine adapter plate like Buffalo Enterprises sells so you could adjust the depth of the starter gear with shims in the starter head of one of the Hitachi style starters. The bolting circle of the 302 is not equidistant between holes... fits only one way for the timing mark just like all the old Chevrolet Six’s.
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