Chevy manifolds are To short for a GMC. Actually to make a 270 into a 292 you need to bore it .156 which will make it a 3 15/16 by 4 inch engine. Which is exactally what I did with mine as have many before me. The thing survived several years at Bonneville and El Mirage running up to 22 lbs boost and honed 3 or 4 times to remove remains of pistons that gave up on me. Never killed it.
Rich, Thanks for the clarification on the over bore. I know it is at 292 now, but didn't remember how much boring it took to get there. What kind of compression did you start out with when running a turbo? And what is realistic running pump gas with a turbo? Ken
A couple of books to pick from that are reprints from the 50's. tp://www.amazon.com/Chevy-GMC-Buick-Speed-Manual/dp/1931128057/ref=sr_1_1?ie=UTF8&qid=1297090514&sr=8-1-spell This one by Roger Huntington can be found on Ebay with this number in the search 150553314752 1951 tech in it. Link to it on Amazon too in the Amazon link. And at less money.
we picked up another 270 this morning. i need some help here.they both have the serial no. that begins with 270. one has the gmc logo on the valve cover with the circle around gmc. it also has a small fan belt. the guy said it was locked up. the harmonic bal. is missing and the crank does not have a tapped hole in the end, but it does have an oil filter system.theres a tag on the left bottom of the engine that says gmc truck and coach division and under that it has the bore and stroke and the no. of cylinders. the other 270 has a newer gmc logo whereas the m under lines the g and c. it has a wide fan belt and the crank is tapped to hold the balancer on.it does not have an oil filter system. this one looks worse than the other one, but its not locked up. could someone educate me on these engines. thanks
I was running 7.5 to 1. It was built to be run at WOT for three miles at a time. So bottom end was not my interest. Living through the three and comming back was. Most of the time it made it. The only thing I worried about with buying a 270 was if it had a six bolt flywheel flange or the early 4 bolt. Get the six bolt. Otherwise who can tell what has been swapped around in the last 60 years?
for what its worth. the truck that the last 270 came from is ***led as a 59 gmc long bed stepside, but it has single headlights. anyway the guy wants 500.00 for it and aint in that bad of shape. he says its going to the crusher in a couple of days and i would hate to see that happen.
Richfox is correct. Make sure you get a 6 bolt flywheel flange. They are much stronger cranks and less tendancy to have the flywheel come loose. As for the keyway, I'm not sure when they started putting the keyway in. Mine didn't have it so I had it machined in for the balancer. I don't think it really matters if it doesn't have it since you can just have it machined in anyway. You can go to inliners.org and look up the serial number there. It should tell you what year the engine is etc.
I gotta agree here. The newer 6cyls are just not the same. They just don't have the same feeling, history, heritage...etc.
You'd be better off with sbc valves. They're easy to find, inexpensive, and are pretty close to the correct length. You'd have to cut about four feet of valve stem off a 235 valve and cut new keeper grooves in what was left.
I think he means intake manifolds. And no they won't work. The engines are different lengths with different port spacing.
somebody help me !!! how to you get the bellhousing off the 270 gmc engine. i've got the top 2 bolts out. are there bolts on the bottom ? i cant find any, but the damn thing want budge.
i've got all the bolts out of the clutch and pressure plate but i cant get the pressure plate to slide past the bosses on the fly wheel so it can drop out.there does not seem to be enough room in the bell housing for it to clear. how the hell do you get this thing out ? i've been fighting it all day. what am i doing wrong ? lord, some body help me !!!
Can you hold the pressure plate back enough to remove the clutch disk and thereby gain enough room to remove the pressure plate?
Besides this open message board, try the "communities" then the social groups, then "inline motors" and "six offenders". It kind of pinpoints you in a tighter catagory, even though you are doing damn good with this for info.
you have to push the pressure plate upto the top of the bell housing and let the clutch disc slid out first the the plat will come out. ***emable in revirse order.
thanks guys. we are not going to reuse the pressure plate so i took my trusty 4 inch grinder with a cutting wheel and proceeded to split the pressure plate in 2 pieces. worked like a champ. we have another 270 that i'm taking apart, so on this one i'm going try to raise the pressure plate and let the clutch fall out like bob308 said. we will see what happens.
What? You didn't like the way I said it? You are definitely going to have to come up with a better way if you ever want to re***emble one with the stock bellhousing.
rich, it looks like those bosses on the flywheel are protruding out at least .75" and the clutch disc or the pressure plate cannot slip p***ed it because its jammed up at the top of the bell housing where it tapers down. i hope i'm making since. we are not re using any of this stuff, we are going to get and adaptor and use a 700 or 200 r4. but dammit, i got to figure out the trick to getting this stuff out. somebody put it in there !! so far, its cut my *** big time.
Well I and Bob308 got ours apart that way. I understand that you don't need to save the parts or reinstall them. But I had lots of GMCs. Always used Chevy six bellhousings and mine always came apart. Like you say. They got it together. I don't remember "Bosses" on my flywheel.
what's a GMC piston look like ? have 6 remaned rods and pistons I don't know what they fit?....from a closed machine shop....
Once I had a flywheel get a little loose and the vibration friction welded it to the crank flange. So I removed the main caps and pulled the crank with the flywheel on it. Put it in a hydraulic press and broke it apart. Can you try to get your crank and flywheel out? What's the deal with these bosses? Are they part of the flywheel? Can they be removed? This is killing me.
ok rich, i feel like an idiot. there are no bosses on the flywheel.maybe i'm making a big deal out of nothing, but 2 other guys [ that are decent gearheads ] and myself COULD NOT get the pressure plate and clutch out. like i said, i've got another 270 to take apart and i will get this stuff out the right way. oh yea. how can i tell what year engines these are ?
The only thing I know is the early motors have the four bolt flywheels, like yours. The later six bolt crank and flywheel is a better deal. I did make a jig to redrill my first 270 for 6 bolts.
There are some numbers cast on the block. Could be low on the p*** side. One will be 6 or 7 digits, block casting no. Another will be probably a letter and 3 or 4 digits. The letter is the month of manufacture of the casting. The next 1 or 2 are the day of the month, next 1 is year. Example: C = March, 12 = twelfth of the month, 4 = 1954. http://www.inliners.org/ubbthreads/...54&PHPSESSID=38de1eb7ff8b10dce6745937282b070a
The Jalopy Journal
