350 chev no. 8 plug fouling up.

[mk swb]

Hey all, I have fitted a crate 350 into my mk and have done bout 3000k's since and now the no. 8 plug keeps fouling up. Every 100k's i have to pull it out and clean it up. When the plug is pulled out it looks like it has come out of an older car and is caked up with burnt oil. And if it idles for awhile then it gets reved it blows a puff of blue smoke. Which to me means its burning oil which is consistent with the plug.

Pulled the tappit cover off and fitted new valve stem seals, No Difference. I have pulled the head off honed the bore and put new rings in, No Difference. And when i refitted the head i put a new valley cover gasket on. And now i'm stumped for ideas!

Anyone have any idea why it is doing this?

Cheers Rees

[pongo]

Broken oil ring maybe.

Can you get warranty?

[KiwiBacon]

Is there any oil present in the inlet manifold?

[TUFF MAV]

Make sure your inlet manifold is sealing properly.They can suck oil down the intake if the gasket is not sealing. Does it have blowby?

Kyle

[PGS 4WD]

They are all right, also possibly a guide on the inlet on that cylinder or valve stem seal, does it smoke if you do a big downhill decel and then accelerate again? (This can indicate a guide/stem seal) A ring will usually smoke under load. Intake sealing is certainly an issue, check the bolt tensions before you pull off the intake, pop the rocker cover and check the valve stem seal hasnt popped up.

Joel

[mk swb]

Hey guys thanks for the replies. I have fitted new rings to that cylinder which rules out a broken ring.

When i refitted the head i put gasket sealer aswell as a new gasket. How do i check for blowby??

I fitted new valve stem seals to no. 8 last friday and have done bout 90k's since and it has fouled up again.

Thanks again. Keep any ideas coming.

[Chook350]

this wont solve the prob of burning oil but if u put sum hotter plugs in it should stop fouling.
mitsubishi forks are good for fouling no.1 and sum foul them all, we tryed hotter plugs and it overcame that prob

[tweak'e]

you sure its fouling due to oil?

what sort of inlet manifold and fuel system (carb/injection) does it run? i think some used to have fuel problems where the fuel would settle on the bottom of the manifold and run into the rear cylinders causing them to run extremely rich. ditto for oil coming in from the breather.

the other thing is cuz had a problem with head gaskets sealing. used to get coolant leaks. going to felpro (i think?) head gaskets fixed it (on a 283 chev).

[RUFF]

Where is your PCV Valve plumbed into? Is it plumbed into #8 intake runner?

[mk swb]

hey guys, Thanks for the replies.

Currently the plugs i have in it are 6's what should i put in it???

I have a holley street dominator manifold with holley 600vac sec carby!
When i refitted the head bought a full gasket set in the felpro brand.

The PCV valve is plumbed into a spacer underneath the carby i might try putting a new one in and see what happens.

Thanks guys keep em coming.

[PGS 4WD]

Whats your compression and camshaft? Plug heat range relates to combustion temp, which related to cylinder pressure which is a result of compression and cam, most stock type engines run 5's(NGK). If ypu have 10:1 comp or so with a mild cam then 6's but ideally plug type is assesed based on plug life. The coldest plug that dosent foul is the right plug(generalising). If you are fouling one plug its not the plug heat range at fault. A missfire due to a faulty lead will cause a plug to foul. Replacing the valve stem seal if the guide is no good is't likely to help. If you have some funky angles on the inlet manifold it may not seal, but you wouldnt expect to see that on stock stuff Does it smoke on decel or if you idle it for a while(2-3 minute) then give it a rev. That would indicate heads not rings.
I have seen faulty automatic trans modulators cause oil to foul plugs and even brake boosters sucking brake fluid in from the rear of the master cylinder. Look for any lines that run to that manifold runner and check them for oil residue.


Joel