The 248 GMC is a completely different engine than the Chevy six. I don't know if the bell housings/transmissions interchange however.
'48 and later bellhousing is going to accept the Saginaw transmission. (Eric, the '47 had the earlier type transmisson and bellhousing.) What is it going in? 1/2-ton trucks '54 and earlier are going to give you a problem unless you convert to an open driveline. I believe the Saginaw is a different length than any of the transmissions likely to have been installed behind the 248. I just re-read your question. No problem at all hooking the Saginaw to a SBC bellhousing. But that bellhousing will not bolt to the 248. L-6 GMC bellhousing were the same '48 through '62. When Chevy dropped the 235/261 and GMC dropped the 248/270/302 and the new Chevy L-6 and GMC V-6 arrived the sixes all started using the same bellhousing as the Chevy V-8s.
[ QUOTE ] Thanks guys. It's a late 55 2nd series GMC 1/2 ton...guess I'll have to find a 350 (eeeeewwwww) [/ QUOTE ] 350 Chevy is an easy answer, but this is a GMC, so another choice seems worth considering. In those years GM put Pontiac and maybe some Olds motors into GMC pickups. How about a 455 Pontiac with original GMC decals on the valve covers? I'm told the valve covers are mostly interchangeable. Tell everyone its orginal.
It's a second series 55? Then, it should have the modern bolt pattern bellhousing with an open drive rear. You should have no problem bolting the saginaw to that bellhousing. Driveshaft length and output shaft spline count will need to be addressed but those problems are easily solved with the saginaw/muncie/350 turbo/late powerglide slip yoke. Double check the diameter of the big hole in the bellhousing vs the diameter of the tranny's front bearing retainer so that tranny will butt-up against the bellhousing ok.
Well right now the truck's got the 4 speed Hydro, so a bellhousing from a manual box (maybe 3 speed) that will fit the 248 will also fit the Saginaw box?
[ QUOTE ] so a bellhousing from a manual box (maybe 3 speed) that will fit the 248 will also fit the Saginaw box? [/ QUOTE ] '48 and newer bellhousing for the 248 and related motors should take the Saginaw. I know more details about the '47-55.1 trucks, and not as much about the later trucks like yours. '54 and '55.1 trucks have a different mount arrangement between the crossmember and the bellhousing than the '53 and earlier. I would expect you want a '54 or later bellhousing to fit your truck, but I do not know if the crossmember on your hydromatic truck is the same as that on a manual transmission truck or not and I don't know with certainty that the mount isn't different for your truck. Lots a caveats there. I have a '54 Chevy pickup frame sitting in my yard. Sitting on the crossmember is a bellhousing I was told came from a '64 Chevy pickup. Any bellhousing after '62 isn't going to work with your 248, but based on my '64 I'd bet any '54 to '62 L-6 truck bellhousing will match your transmission, mounts and motor. Inliners.org, stovebolt.com and oldgmctrucks.com are places you might find some more confident answers. I like V-8 power. I'd go with that Olds and the hydromatic.
You should be able to bolt up a late '50's Chevy truck bellhousing to your 248; look for the one with two slanted mounting pads on the lower front corners. Call Buffalo @ 360-625-7684, in Arlington, WA, or Dick Larrowe @ 503-668-0352, Sandy, OR. These guys can get you any parts you need for this conversion. You could also put a T5 behind anything you can bolt a Saginaw to. I have a 302 with the Chevy truck bellhousing; used to have a Muncie behind it, now its a Camaro T5. Later, Kinky6
I say rebuild the Hydro, and this from a 3 pedal man. Those are rare and way cool. Low gear could launch a freight train.
I gotta go with Kinky's vote on this one, find a T5, it and the later rear end are the best thing I've ever done to my 53 as far as driveablility. Good around town gears and 95 on the highway, and a high enough rear end to get my butt kicked all night by Raven61 at the HAMB Drags . I've got a buddie who runs a 228 (same block as a 248,270) with a T5 in his 52 GMC Burb and loves it. MONGO
thanks for correctin' me OldSub. I though I remember Buffalo telling me '47 was the first year but oh well. I do know 1954 was the first year of the angled mounts! I learned that the hard way. cheaterSlick, If I were building a '55 and had a usable Olds Rocket sitting on the floor I would look no further! The roomier hood on the 47 and later trucks is crying for more motor.
Thanks for all the info, got a line on a GM bellhousing that shoud do the trick. I know the Rocket and Hydro would be cool, but as there's no one I can find who knows how to build em (truck's is tired), short of teaching myself the options are very limeted with the Rocket. I need simple and cheap. Maybe I'll make a go-cart with the 394... Thanks again for the help everyone.
While I like the Olds Rocket the truth is my '55 1st is still running a GMC 270. Someday I'll replace it, but probably not this year, and likely not next either. Good luck on that bellhousing.
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