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Oil on #4 Plug

General engine tech -- Drag Racing to Circle Track

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lekid
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Oil on #4 Plug

Post by lekid » Fri Sep 06, 2019 9:08 am

Need help. #4 plug shows oil (almost looks like it is unburnt oil).
Car puffs a cloud of smoke on startup after a run when it was left hot to cool down and does not smoke after other startups until it is hot after a run.
Plug shows slight oil but the electrode is wet but does not have oil burnt on it.
There is some oil residue in the exhaust port, but header tube end shows no oil at all. There is a little bit of oil on the floor pan on the side of the motor that #4 is on, so oil obviously comes out the header.
Did a leak down and it is dame as other cylinder. Changed both valve seals and both guides appear tight enough. Also re-sealed the shaft mount bolt that goes into the intake port. None of those have helped at all.
It seems like it is only pulling oil on deccel (even though we see no smoke at all out the back) or oil dripping in chamber when engine help.

Any thoughts??? I will take intake and possibly head off this winter, but trying to pin-point it. This is frustrating!

I can try and post pictures if it would help.

P.S. Car has never made so much power and it is running stronger than ever, so obviously no power loss.

mag2555
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Re: Oil on #4 Plug

Post by mag2555 » Fri Sep 06, 2019 12:16 pm

Can you post up what kind of heads these are?

novafornow
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Re: Oil on #4 Plug

Post by novafornow » Fri Sep 06, 2019 12:30 pm

Points toward intake gasket. Surprised that it runs the same. Been there, done that.

Racer71
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Re: Oil on #4 Plug

Post by Racer71 » Fri Sep 06, 2019 12:35 pm

Intake could be a possibility especially depending on how much block is decked etc. does it show any crankcase vacuum at idle if you block off your breathers etc

lekid
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Re: Oil on #4 Plug

Post by lekid » Fri Sep 06, 2019 2:52 pm

Would be awesome if it was just an intake gasket!
I will check the logs to see what vacuum I have at idle and report back.

lekid
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Re: Oil on #4 Plug

Post by lekid » Fri Sep 06, 2019 4:31 pm

Cylinder heads are RHS casting that have been CNC ported and new guides installed. Less than 40 runs on heads since new.

1972ho
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Re: Oil on #4 Plug

Post by 1972ho » Fri Sep 06, 2019 5:40 pm

Maybe you should first try and torque down your intake a little more and see if that helps.

ProPower engines
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Re: Oil on #4 Plug

Post by ProPower engines » Fri Sep 06, 2019 9:06 pm

So do we have to guess what engine it is???
Sounds like a common BBC issue intake sucking oil but thats a guess without engine details.
Real Race Cars Don't Have Doors

CharlieB53
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Re: Oil on #4 Plug

Post by CharlieB53 » Sat Sep 07, 2019 12:01 pm

Can you do a clean shut off then pull the plug and inspect for oil?

Compare that to pulling the plug immediately after decelerating and high intake vacuum.

High vacuum on deceleration may be pulling oil past intake asker yet not leaking enough at wot to show a problem yet.

Have heads/intake surfaces been milled to fit well?

77cruiser
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Re: Oil on #4 Plug

Post by 77cruiser » Sat Sep 07, 2019 12:42 pm

ProPower engines wrote:
Fri Sep 06, 2019 9:06 pm
So do we have to guess what engine it is???
Sounds like a common BBC issue intake sucking oil but thats a guess without engine details.
I think it's at a 4 cyl. :wink:
Jim

lekid
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Re: Oil on #4 Plug

Post by lekid » Sun Sep 08, 2019 8:53 am

Sorry guys, forgot to say that it is a SBC 23deg head engine on nitrous.

When I shut the engine off at the too end to read plugs, there is always oil on #4. I did change both intake & exhaust valve seals. The intake manifold is tight. I have tried to re-tighten it twice and it was still tight.

I guess I will pull the intake and go from there.

Lizardracing
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Re: Oil on #4 Plug

Post by Lizardracing » Mon Sep 09, 2019 10:29 am

PCV valve if equipped
Intake gasket
Valve seals
Valve guides
Rocker stud threads
Piston rings/bore

In that order

lekid
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Re: Oil on #4 Plug

Post by lekid » Tue Sep 10, 2019 10:50 am

PCV valve if equipped - Dont have, have a vacuum pump
Intake gasket - will pull the intake off this weekend
Valve seals - intake and exhaust valve seals already changed, no changes
Valve guides - checked guides and no excessive wear or clearance
Rocker stud threads - already resealed, no change
Piston rings/bore - if everything else is good, I will re-ring with a hone job

Thanks for the recommendations!

CharlieB53
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Re: Oil on #4 Plug

Post by CharlieB53 » Tue Sep 10, 2019 10:54 am

While the intake is off check the gasket surface with a straight edge .

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