Hi guys , just got my mk7 head back , again ! , from Fiennes performance after a complete rebuild , and did a compression test . No compression at all on no 3 . Checked the valve clearances , zero clearance on inlet no 3 , and all the others save one , half , or less what they should be !!! Save me from bloody professionals.
Looked inside with a camera , just in case a hole had had appeared in the piston overnight . Nope, all ok, must be the valve letting by . What do you think ?
Somebody might have bent a valve.
Hi Kris , engine spins over fine though .
A bent valve stem will not prevent engine spinning , just won’t seat well. So cam clearance will be affected. Look for tell tale marks on valves to see if intake valve came in contact with exhaust valve.
If it was bent then there would be excessive clearance.
Zero clearance can mean less than zero clearance, and the valve would be open. If you remove the cam shafts you can do a leak test (don’t spin the engine, reset the cam shafts per the book) and if it’s tight readjust the clearances (let them do it/pay for it).
Probably all they got wrong. If they even did it, or did they just lap them in and put it back together… what do they say?
Yes excessive till the shim bounces out of its recess under the cam follower and gets lodged on the spring as you spin the engine over. Checking under the cam follower would be my first step. Assuming the vales were set correctly at some point, something ugly s keeping the valve open.
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Great theory apart from the 10 with small clearance (provided Kenny didn’t assume 12 - 14 thou to be correct) and the other valve that’s different as well
No, I didn’t assume that David , clearances on this engine ,as you know , are 4 & 6 thou for inlet and exhaust respectively . Only no. 1 inlet was correct , all the others , as I said, achieved half , or less than half the requirement .
I bet they didn’t to do the clearances… what do they say?
I wonder if they have recut the valve seats so deep that they can’t get adequate clearance with the standard shims and so just left it at that.
If that’s that’s the case you could fit the later X500 buckets which are thinner and oversized shims to get things right. That’s assuming the valves aren’t bent.
Let’s hope they haven’t ground the valve stem ends as that can lead to a whole lot of trouble.
I have , just this minute sent them a long E mail .
Actually , this the latest installment of a long running saga which goes back many months . The head went back for them to do some blending work to the ports , which they hadn’t done . When it came back I discovered that the time sert that they had installed in one of the camshaft oil feeds was the wrong size , so they had to fix that . Also one of the helicoils broke up the first time I put a plug in . So , off came the head , and back it went . A 360 mile round trip !!! Told them I thought there was a problem with no 3 inlet , I encountered very strong resistance when turning this camshaft at that point , with a spanner . The other camshaft was released at the time. I went back to
collect it , another 360 miles , after being told everything was ok . That brings things up to date .
So the head has to come off yet again , more gaskets , more time and effort , more bloody stress .
So David , innocent untill proven guilty you say .well , that is the case for the prosecution .
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I really don’t suspect that , but anything is possible .
„Professionals“.
My…
I know why I do everything I can possibly do myself…
I suggested the later clearances not because I think you were stupid but because it would have fit in so well with half clearance, and you didn’t specify the values. At the very least you should get all your money back and it’s still a loss… not good
Some news . When I rock the camshaft gently back and forth by hand , both are still bolted down , a quite loud metallic click can be heard , emanating from the suspect no.3 inlet side . Any ideas ?
If the chain is still connected, could be a chain guide, or slack in the chain.
No , it’s definitely from no. 3 valve , tappet , shim area . I had my earole , that’s cockney , close to the source .
Could be the tappet rocking in the bore or a mechanical problem you need to have a look at.
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