Hi Ferrari chatters. last week when adjusting my valve clearances(83 308 QV), I was working on the front bank and after using my leaver tool on one of the exhaust valves to change the shim, I realised I leavered down the wrong valve.....(yes I know) The cam was showing that the valve I levered down had only just closed. The manual tells me that the valve closes at 10 degrees after TDC. So I'm guessing that the piston is very close to the top, on its way down. Is there some way of testing to see if the valve is bent? I have access to a leak down tester, but it requires the engine to be running temperature. Could it still work to see if the valve is leaking from being bent, would I be able to hear air escaping through the exhaust manafold? How much force would be required to bend a valve if it hits the piston,using the shim lever tool? Also how much over lap does the valve have if it was tò push through the piston when at TDC? Just trying to work out if I possibly could have missed the piston.. Any help on this matter would be much appreciated. Dean NZ.
I do not think you bent the valve. However, an easy way to check is by the valve clearance. If indeed the valve has bent, the clearance is much bigger than normal (compared to others)
I totally concur. It is extremely unlikely you could bend a valve in that manner. but the clearance check will work as described. Leakdown test will also but it could be confusing - if there is leakdown from the valve is it because the valve WAS bent or because the valve is not sealing well? Generally you would expect a valve that is not sealing well to have much less leak down then a bent valve but it's all a matter of degree. Of course if the leak down identifies a valve problem - whether bent OR just not sealing well - the head has to come off anyway to correct the problem so it doesn't really matter. But, as St@ven stated, I doubt you bent a valve.
Thanks very much for the replies guys. I have checked my work sheets of the valve gaps before my boo boo and the gap size does seem very close, (but I have since removed the cam and shim to do the seals)I will put the old shim back in and Re check the gap. If it is still correct I will do a leak down test on it after I have fired it up and got the engine warm. Any tell tail signs if a valve is not sealing when the engine is running? Thanks Dean
A vacuum gauge will show a valve not sealing when the engine is running. You will get a pronounced drop in vacuum each time that cylinder "fires." It will be a very obvious drop. A vac gauge can diagnose a wide range of problems and this is one of them.
I doubt you bent or tipped a valve. But I sure would want to know before I put it all back together. It is perfectly acceptable to run the leak down test on a cold engine. Airplane mechanics do it all the time.
