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| | | | Joined: Mar 2013 Posts: 176 Shop Shark | | Shop Shark Joined: Mar 2013 Posts: 176 | I recently tore down the engine to re-seal it. It's all back together now but before I put the valve cover back on I wanted to adj. the valves. I've been reading that your supposed to do this with the engine warm??? I've always been taught to do it cold? Regardless I need a cold baseline to adjust from. What should they be adj. to cold and is it necessary to adj. them again when warm?
Thanks,Nick. | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | You can set them cold to the given settings.
After warming up the engine (30 minutes at operating temperature), adjust them again.
| | | | | Joined: Mar 2013 Posts: 176 Shop Shark | | Shop Shark Joined: Mar 2013 Posts: 176 | What are the correct settings? I thought they were .0015-.003in. and .002-.0037ex. Then I read about warm at .012? That seems really sloppy.
I did however make a handcrank to turn the engine over. It works well and should speed things up a bit. | | | | | Joined: Jan 2008 Posts: 4,961 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,961 | The intakes should be at .012 and the exhaust at .020. If they rattle a little, don't worry about it. GMC is notorious for burning valves that don't have enough clearance. And they will get tighter after running because the valves will settle down into the seat. | | | | | Joined: Mar 2013 Posts: 176 Shop Shark | | Shop Shark Joined: Mar 2013 Posts: 176 | So, what I'm hearing is to set them at 12&20 cold.Then after I get her fired up again bring her up to temp and reset at 12 & 20 while the engine is warm.
Thanks for the replies,I don't think I've ever adj. valves with this much slop? I'm more of a shim under bucket kinda guy. | | | | | Joined: Feb 2004 Posts: 29,798 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,798 | These engines were made to work for a living, and people didn't care if they rattled a little bit. Running an engine all day long with a full load on the truck and wide open throttle was what a GMC was designed to do. The exhaust was too loud on most of them to hear a rocker arm making a little noise.
Jerry
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| | | | | Joined: Jan 2015 Posts: 914 'Bolter | | 'Bolter Joined: Jan 2015 Posts: 914 | So, what I'm hearing is to set them at 12&20 cold.Then after I get her fired up again bring her up to temp and reset at 12 & 20 while the engine is warm.
Thanks for the replies,I don't think I've ever adj. valves with this much slop? I'm more of a shim under bucket kinda guy. Why set the valves twice when you can plan ahead and have a chance at adjusting them once? .012 In and .020 Ex is for an engines that are subjected to heavy duty operation such as "log hauling in swamp country, tractor work, etc" taken from the Chevrolet manual. Normal valve clearance for a hot engine is .006" - .008" In .013" - .015" Ex The manual says cold valve clearance can decrease by up to .005" when the engine fully warmed up. Makes sense that if when cold the In valve is adjusted to .011" then the engine is allowed to reach proper temperature the clearance should then be some where between .006" - .008". Same for the Ex valve. Start with .o18" for a cold engine and you should be in the .013" - .015" range. | | | | | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | We aren't discussing Chevrolet engines here. A lot of what you read in a Chevy manual doesn't translate to GMC. | | | | | Joined: Jan 2008 Posts: 4,961 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,961 | Cletis is right. GMC is has very little in common with a Chev engine. If you own a GMC, I would suggest buying a GMC service manual instead of trying to compare it to Chev. The GMC manual is pretty straight to the point on how they want the valves adjusted. https://plus.google.com/u/0/1126369...0779876610&oid=112636930370126476644 | | | | | Joined: Mar 2013 Posts: 176 Shop Shark | | Shop Shark Joined: Mar 2013 Posts: 176 | Thanks for all the information. Now I just need to get out and do it. It's been raining this week so I haven't got to it yet.
Yes I could use a manual. I have been using the info on the sites so far. | | | | | Joined: Mar 2013 Posts: 176 Shop Shark | | Shop Shark Joined: Mar 2013 Posts: 176 | Got the valves adjusted and the valve cover back on. Thanks for all the help. Need to clean up the Dist,Starter,Gen then she'll be ready to fire up again. | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Great on the rain. If you come across a 302, parts are cheap and will bolt right up, give you a boost in power.
'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: Mar 2013 Posts: 176 Shop Shark | | Shop Shark Joined: Mar 2013 Posts: 176 | Thanks for the tip. I'm trying to stay stock for now, but later on,,, who knows? | | |
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