Oil Gets Dirty fast

May 4, 2021
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6
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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

Well-known member
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]

New member
Thread starter
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

Well-known member
Oct 4, 2018
855
254
63
Melville, Saskatchewan
It sounds like a really nice setup. The carb can't be too far off with your 1/4 mile times.
 

Rocketman269V

Member
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]

New member
Thread starter
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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