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#1 |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Good localtime forum friends,
I created a post a couple weeks back (http://67-72chevytrucks.com/vboard/s...d.php?t=733313) regarding my 64 C20 (283), and how she appears to be burning oil to the tune of a quart every 50 miles or so. I performed a compression test this weekend on a cold-ish engine and here are my results: 1. 120 PSI - 6 revs 2. 125 PSI - 6 revs 3. 125 PSI - 6 revs 4. 130 PSI - 5 revs 5. 125 PSI - 5 revs 6. 125 PSI - 5 revs 7. 130 PSI - 6 revs 8. 120 PSI - 5 revs I performed the above test with a couple of squirts of oil added to the chamber, and the numbers were similar, though it often took 8-10 revs to max out pressure. So my question is, do these number make sense if I am burning oil? I thought for sure I would be low on a cylinder or too, but these numbers look pretty awesome. I have white smoke coming out of my pipe when I drive her around and I do not seem to be leaking a lot of oil. What could be the culprit? I learned this weekend that I def have matching numbers, and I know that doesn't matter so much for old trucks, but I would like to fix my stock 283 instead of throwing in a 350 crate. Last edited by cshanek; 04-03-2017 at 12:25 PM. |
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#2 |
Registered User
Join Date: Dec 2016
Location: Lacey, WA
Posts: 190
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Re: Burning oil and compression test results
pull all the plugs and redo the test with 3 second cranks or 3 revolutions. maxing out is not accurate. and no oil squirts either.
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#3 | |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
Quote:
Use oil for a wet test to check for rings sealing. |
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#4 | |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
Quote:
My shop book says I should be at 140 PSI or so. |
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#5 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
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#6 |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
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#7 |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
I also noticed the plug #2 was completely different than all the other plugs, see attached. I am assuming it is a "performance" plug the previous owner had and just threw in.
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#8 | |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
Quote:
The important number is the first crank. You like to see at least 75-80. Your wet test shows your rings are good. Oil leaks. One oil drip every 100 feet equals a quart in a 1000 miles. Multiply yours. What do you have for a pcv system? |
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#9 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
And what do you have for a pcv system?
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#10 |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
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#11 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
Take pics!!
Air cleaner off so we can see the whole motor. |
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#12 |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
A coworker of mine just mentioned that I am probably burning oil from valve stem links.
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#13 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
Maybe!!
But could be from excess crankcase pressure too! |
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#14 |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
Attached are my images
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#15 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
Appears you have an inline pcv off the road draft connection and a breather on the intake so likely not a crankcase pressure problem.
So your coworker could be right. If your sparkplugs are all oil fouled then your valve seals could be the culprit. |
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#16 |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
They were pretty oily.
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#17 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: Burning oil and compression test results
Likely you had o-ring seals that are toast now.
Maybe a head refresh is in order. New guides and seals and a valve grind. Or replace the heads. You'll need the casting number off yours to decide what to replace them with. The casting numbers are between the rockers. Easy to find. |
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#18 |
Registered User
Join Date: Nov 2016
Location: lowell ma
Posts: 750
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Re: Burning oil and compression test results
I'd put a wrench on the intake bolts and see if they are loose?
valve seals would be my next guess.. or a stuck ring.. Might be worth putting a 1/2 to 1 qt of marvals in the engine and run it for a week then drain and new oil and filter.. |
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#19 |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: Burning oil and compression test results
Agree...the intake leak (gaskets), can pull the oil up....the marvel might take care of the sticky rings? But I had one, with a fresh top end, that used 14 quarts, from mid Ill to the southern point & back. My bud said bad heads....but the same shop had done my heads for yrs. The same heads went on the fresh bottom end, & used 1 pint of oil in 2000 miles on the break in! A stuck oil ring, will give you some problems....even tho you have good compression/good power.....longhorn
__________________
69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#20 |
Registered User
Join Date: Jan 2013
Location: Calgary Alberta
Posts: 1,166
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Re: Burning oil and compression test results
Any other leaks like crankshaft seal? If so maybe worth it to pull for an overhaul.
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#21 |
Registered User
Join Date: Jan 2013
Location: Calgary Alberta
Posts: 1,166
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Re: Burning oil and compression test results
Diesel fuel, I've heard let it idle for some minutes before dumping it. I've also heard of using transmission fluid. Another guy swears by revving it fast like almost wide open and pouring a liter of water down the carb. Apparently that frees stuck rings. What have you got to lose?
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#22 |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: Burning oil and compression test results
If you play with the water "trick", be careful....water does not compress! I have set an engine to 1800-2000, & misted , or dribbled water in to clean carbon deposits. Just dont let the engine choke down or die! This will clean carbon from the combustion chambers/pistons/valves, but a soak in Diesel or Marvel... let sit, may do more for sticky rings. Longhorn
__________________
69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#23 | |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
Quote:
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#24 |
Post Whore
![]() Join Date: Mar 2013
Location: Southern Oregon
Posts: 10,384
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Re: Burning oil and compression test results
If your gonna pull heads....pull the motor and go through it. Why put a new top end on a 50 year old engine? If the cylinder walls are in good shape a quick honing and new rings will only be more cheap insurance. If your gonna spend all that money on head rebuilds, intake, and carb....may as well make sure the bottom end will hold up long enough for all of that.
SBC parts are cheap so I'd be looking at standard bearings, oil pump, timing chain, and rings. If your gonna do an engine...make sure the whole thing is internally fine or you'll just have more problems down the road. 50 year old rings are 50 year old rings weather it has good compression or not. ![]()
__________________
1966 Chevy C10 "Project Two Tone" http://67-72chevytrucks.com/vboard/s...d.php?t=596643 1964 GMC "Crustine" semi-build:http://67-72chevytrucks.com/vboard/s...d.php?t=665056 My youtube channel. Username "Military Chevy": https://www.youtube.com/channel/UC_h...fzpcUXyK_5-uiw |
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#25 | |
Registered User
Join Date: Mar 2017
Location: Colorado Springs, Co
Posts: 35
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Re: Burning oil and compression test results
Quote:
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