valve stem oil seals!

[richandhazel]

I was actually planning on using my compressor and using the compressed air technique to do the Audi. I suggested the rope trick just as an alternative, for those that don't have a compressor.

So let me get this right as Steve, I do value your experience and opinion:-


I plan to tackle the job by moving the relevant piston to TDC, locking the flywheel, as it will obviously rotate to BDC with 100 psi bearing on it, as you have already stated (I guess I took that bit for granted ). Chucking 100psi through the spark plug hole and changing the valve guide oil seal. The piston won't move to BDC as I have locked the flywheel (already have a tool made for the job). What I don't know, as I have always assembled a head before fitting to the block, is, if I should lose compressed air with the piston at TDC will the valve drop down so far that I need to remove the head to retrieve it?

I'm thinking that if it is possible for a cambelt to snap and valves to meet piston crowns, that must mean that the valve will not drop down too far if the piston is at TDC for this job
Or am I forgetting about such things as inertia and valve bounce?

[mk1]

If you have the piston at TDC, I think the valve will touch the piston and not drop down to low. I have done a few and have let the piston go down to bdc, I dropped a valve on one because I switched the compressor off and the air pressure dropped down to nothing (about 1 hr) and there was nothing to hold the valve closed .
Steve.

[richandhazel]

That must have been annoying when you were obviously trying to avoid removing the head in the first place

I think I will leave mine at TDC, just in case...........hopefully if the same thing happens, the piston will save it dropping.

Thanks for your advice