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| | | | Joined: Dec 2023 Posts: 36 'Bolter | | 'Bolter Joined: Dec 2023 Posts: 36 | Hi, I am new to these old motors. I have a 270 I am installing in my 53 1/2ton GMC I removed the bell housing, flywheel etc to install a new clutch and pressure plate and bearings. Of course we rotated the motor to remove the bell bolts, My question is how do I figure out the correct position to reinstall the flywheel, in order to time it ? Sorry if this has been ask before. I did several searches and couldn't find this info.
We were thinking we could bring the #1 piston to top dead center, and line the flywheel up with the marking on the flywheel, But we aren't even sure of the pistons. Do they run in order front to rear 1-6 ?
Any help would greatly be appreciated!
Thank you! | | | | | Joined: Feb 2004 Posts: 29,774 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,774 | Check your PMs- - - -A Chevy six has dowel pins in the crankshaft flange that won't allow the timing marks to get misaligned, and I believe the GMC is set up the same way. I've got a 248 disassembled in the shop- - - -I'll check it to see if the crank is doweled the same way. Cylinders are numbered 1 through six, starting at the front.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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| | | | | Joined: May 2015 Posts: 11,040 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,040 | Your method of turning the engine to TDC on #1 with the valves closed and lining up the timing mark with the pointer would work. But If you just put the flywheel in place and the dowels don't all line up, just turn it 1/3 rotation and try again. If that still doesn't work, 1/3 more turn and it should go right on. No real need to turn the engine to any specific position. I just drilled and tapped some crankshaft snouts using a flywheel to hold them and just turned the crank till the dowels lined up with the flywheel.
It took longer to type that than to actually get them together.
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: Dec 2020 Posts: 1,960 'Bolter | | 'Bolter Joined: Dec 2020 Posts: 1,960 | Thats what I was going to say when I first read this. If thats the flywheel that came off it, there should
only be one way it will go back on.
~ BD.
"You won't find me in an old folks home" Pioneer Florida Cracker
1958 Apache Stepside
1958 Apache 1/2 ton Panel
1959 Apache 1/2 ton Panel
| | | | | Joined: Jan 2022 Posts: 2,446 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,446 | I have a 270 flywheel that I removed from a 57 GMC myself. I just measured the bolt circle. One of the holes is offset. If you install all 6 bolts, there is no way to put it on wrong.
Last edited by Bill Hanlon; 01/05/2025 12:33 AM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| | | | | Joined: Jan 2022 Posts: 2,446 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,446 | Bad news if you are trying to use your '53 248 flywheel. It has 4 bolt holes. Depending on the heritage of your 270, it likely has 6.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | I seem to remember someone redrilled their 4 bolt flywheel to 5 bolts, no need to do that on yours, Joe.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jan 2022 Posts: 2,446 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,446 | Before you mount it, paint the flywheel engine side black. Then use a fine artist's brush to paint the BB (5 degrees before TDC) and the U|C (TDC) marks white. On mine I counted 56 teeth (1/3 turn) either direction from the TDC mark and used an engraving tool to make "TDC" marks for cylinders 2&5 and 3&4. Paint them too. I don't know what I'll ever need them for, but I'm ready if I do.
Last edited by Bill Hanlon; 01/05/2025 3:10 AM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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