would increasing the compression ratio on an engine with worn rings increase oil burn - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-02-2012, 04:48 PM
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would increasing the compression ratio on an engine with worn rings increase oil burn

I just changed the cylinder heads on my sbc 350 from 76cc chambers to 58cc, big time compression boost with the flat tops pistons that were already inside

anywho i never burned oil before, but now it's burning a bit of oil out of the passenger side tailpipe, the same side where i noticed the rings for one of the pistons were not in too good a shape

so my question is, would me raising the compression ratio on my engine increase the strain on already worn piston rings and force it to burn oil ?

or is there something wrong with the new machined heads i bought ? because it never burned any oil before

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Old 07-02-2012, 04:55 PM
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The short answer is yes. Increased compression= increased cylinder pressures = increased blowby.
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Old 07-02-2012, 05:02 PM
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The short answer is yes. Increased compression= increased cylinder pressures = increased blowby.
I took of the heads and found forged pistons, cast would of probably of hugged the cylinder walls better when they heated up and stopped the blowby

it's smoking ever so slightly out of 1 tailpipe so whatever, thanks man
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Old 07-02-2012, 05:58 PM
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Intake manifold gasket vacuum leak.
worn valve guides. bad or missing valve seal.

Oil migrating up the PCV hose into the intake manifold.
Valve cover breather/pcv oil baffling. (aftermarket valve covers)

Last edited by F-BIRD'88; 07-02-2012 at 06:04 PM.
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Old 07-02-2012, 06:09 PM
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Intake manifold gasket vacuum leak.
worn valve guides. bad or missing valve seal.

Oil migrating up the PCV hose into the intake manifold.
Valve cover breather/pcv oil baffling. (aftermarket valve covers)
it's a new pair of cylinder heads with new seals and valve guides

i thought it was the pcv but it's only smoking out of 1 of the two tail pipes, i removed the valve and plugged the vacuum port on the carb but it still smoked
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Old 07-02-2012, 06:09 PM
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Of course, blow-by doesn't automatically mean oil consumption. Blow-by is fuel, air, and combustion gasses getting by the compression rings, and doesn't necessitate that excess oil is getting by the rings going the opposite way. F-BIRD suggested quite a few areas where oil consumption can stem from, especially on a new-to-you set of cylinder heads. It's worth checking out before you automatically fault the short block.
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