Oil Gets Dirty fast

May 4, 2021
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Here's my build:
'81 Pontiac Firebird, 468 cu in Olds, 224/[email protected]/2", .507" lift 110 LSA Hydraulic Roller cam, 1.6 Roller Rockers, Edlebrock Heads, Dual Plane Edlebrock Air-Gap Manifold, 3:73 gears/positracton, 750 Holly HP, built TH350, 28" tires, Hooker Long-Tube Competition Headers, MSD-6AL-2 & Distributor, 10.1 Forged Pistons, runs 11.3s @ 115 mph in the 1/4 mile, 399 RWHP & 430 RWTQ.

1- I change my oil (Valvoline VR 20/50 w/zinc} once a month, before each monthly Summit Series race, and it always pretty dirty by then. Of course, my question is why so dirty after about 500 miles as I drive it almost every day (daily driver).
2- I recently did a compression check and all cylinders were 210 psi. In an older test they were all 190 - 205 ... FYI.
Is this causing any problems in regards to the dirty oil?

Thanks guys/women.
 

Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
I just saw this. Check your carb tune, it may be running rich. It is obviously running nice and strong. What kind of air filter set up fo you run?
 

455 [email protected]

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May 4, 2021
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M air cleaner is a 3" K&N drop down air filter with an open top. It's so old that I call it a "spark arrestor" because all the cotton is gone it's so old. I have a 4" cowl hood.
It idles a little rich but the plugs look great at WOT. I'll do some city driving today and look again. I'll let you know.
 

Olds 307 and 403

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Oct 4, 2018
877
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Melville, Saskatchewan
It sounds like a really nice setup. The carb can't be too far off with your 1/4 mile times.
 

Rocketman269V

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Feb 26, 2020
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South Central Florida
............why so dirty after about 500 miles.........I recently did a compression check and all cylinders were 210 psi. In an older test they were all 190 - 205 ........

I would do a "leak down" to see if you have any blow-by passed your rings. That would account for the increase in "compression" (cranking pressure), as the oil would seal the rings better during a compression test. You didn't mention if it used any oil in between changes or if there is any smoke out the back or wet black residue in your tailpipes.
 

455 [email protected]

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May 4, 2021
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Good inquiry.
1- Haven't done a leak down test yet. Will do this as soon as possible
2- Yes it uses oil between oil changes, especially when racing. We built it to Bracket race and I figured I'd "burn some oil".
3- No smoke is visible while starting or driving
4- No wet black residue in tail pipes. Sparkplugs burn clean and light brown
5- Idles great at 900 rpm but will idle at 650 rpm if I wanted it to.
 
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455 [email protected]

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May 4, 2021
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Well, if it's using a quart ~every 500 miles, it's got to be going somewhere. Are you running any PCV system?
Yes I have a PCV "valve" from the valve cover attached to full vacuum on my carburetor base.
I also have a hose from the other valve cover to the underside of the K& N air cleaner.
 

Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
Is it is using a quart every 500 miles of 20W50? What piston, piston to wall and ring gap? If the plugs aren't black, the tune can't be to far off. Do you have valve cover baffles?
 

455 [email protected]

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May 4, 2021
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Is it is using a quart every 500 miles of 20W50? What piston, piston to wall and ring gap? If the plugs aren't black, the tune can't be to far off. Do you have valve cover baffles?
Pistons are Ross 10.1:1 forged. I don't think I have valve cover baffles. They were on the engine when I got the car. I've had them off a number of times and don't see baffles. I never knew that valve covers had baffles. I'm going to pull the intake manifold, replace the gaskets, and check out the lifters and adjust the valves next. See what I find?