Valley Gasket Popping

[jon haines]

I have just replaced my valley gasket and it now appears to be popping as if it is expanding and shrinking when reved. Didnt do this before just leaked. Checked the breather pipes which are all clear and car is running well so any ideas?

[adam quantrill]

Sounds like you might have some blowby on a ring.

Unscrew the breather canister and check the gauze.

Sometimes you get a blockage between the breather hose intake to the throttle body and the opening near the butterfly, this is a sod to clean out.

If you run the car with the breather hose disconnected (might need a tad more throttle) does a load of steam come out and/or excess gases?

Check the compression, or, remove the injector wiring one at a time while running and see if it goes away, to identify which cylinder.

[jon haines]

Thanks Adam. I have cleaned out everything with an airline but wasnt much crud in anywere. If i run it without the breather there is stuff that comes out that looks like gas. So i will do the next things you suggest and see what happens,

[rev-erend]

That should be oil vapour when warm.

[Englishman]

I had similar symptoms on my wedge about a year ago. Compression and leak-down tests showed two cylinders in particular were leaking badly and causing the valley gaskets to leak 'steam' under load. Piston rings/oval bores were the reason, a rebuild sorted the issue

[Boosted LS1]

yes, it sounds like blowbye from the piston rings causing crankcase pressure. A compression test kit's not that expensive from halfords and easy to use. Or a local garage could do it for you.

[adam quantrill]

If you are lucky it's just a cracked ring, which you can replace and leave the rest alone (once you have identified the cylinder causing it).

I had blowby on a Rover P6 and it eventually expelled a gallon of oil every 150 miles!

[rev-erend]

You probably had this issue before but the old gasket was stuck fast and did not show the issue.

Is your oil consumption than is normal?

The compression test is the way to check. Leak down is even better.

Edited by rev-erend on Thursday 12th November 10:52

[jon haines]

Had the results of compression test today and i have 95psi on number 3 and 120 psi on number 7 rest are all 160 psi. the mechanic recons its rings on these two but as always until you strip it down you don't know.
That will have to wait no pennies for that job , might sorn the car and do in spring when hopefully we are in a more certain place.

[rev-erend]

Such a shame.. but at least you know what the issue is and can plan its fix.

[adam quantrill]

Look on the bright side - only one head to remove ;^)

You might want to start researching which rings to get as they might be "special"...

[LLantrisant]

adam quantrill said:

Look on the bright side - only one head to remove ;^)

You might want to start researching which rings to get as they might be "special"...

only 1 bank is botch...all cylinders need to be done.

engine out, strip, minimum is re-honing, if not even re-bore.

as the engine is out the camshaft should be replaced, plus all the big-end and main bearings.