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| | | | Joined: Jun 2010 Posts: 170 'Bolter | | 'Bolter Joined: Jun 2010 Posts: 170 | My 46 216 has always spewed blue smoke when revving the engine but ran fine in the past and was quite "perky". I haven't used it the past year, only started the truck 2-3 times over the winter/spring in the garage. Then drove only once this summer - at that time the power felt like it was not close to what it had been before. I checked the vacuum and it flutters erratically between 11 and 16 inches at idle. Today I checked the compression, from 1 to 6 it was: 110, 20, 115, 115, 45, 95. When I put oil in #2 and #5 they only went up by 5 pounds each. I pulled the valve cover and all valves and rockers are moving when running. I haven't tried adjusting the valves. Does that hideously low compression on the two cylinders along with the vacuum flutter point more likely to valve guides? Or a possibly some shot valves? Thanks for any insite! | | | | | Joined: Aug 2012 Posts: 1,214 Shop Shark | | Shop Shark Joined: Aug 2012 Posts: 1,214 | definitely try loosening the valves for 2 & 5 a full turn then test compression on them again.
If no change, odd's are it's either burnt valves or pitted seats.
Good luck
Dave
| | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | 2 and 5 could also be stuck thanks to alcohol in the fuel. Try some acetone on the valve stems, tap with a piece of wood or brass, see if they move at all, if they do, keep tapping gently, up and down.
'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: Feb 2000 Posts: 5,228 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,228 | Does it have extra valve clearance on the two cylinders that are low?
Do you hear more lifter "click" then before?
Seats, guides, and valves do not go bad from setting.
Do they stick shut, yes
Can you bend a pushrod, very easily
Will it still run, possibly,
Can they stick open, sure can,
Any of the above can happen from setting, but you should hear more noise then usual.
Clean the stems as suggested above or add some internal engine cleaner to the oil and let it idle for awhile. Recheck compression once up to temperature after the oil has had some time to work
Joe
| | | | | Joined: Jun 2010 Posts: 170 'Bolter | | 'Bolter Joined: Jun 2010 Posts: 170 | Thanks for the tips - I'll be trying this weekend. | | |
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