Checking VHPD valve clearances

[Englishmaninwales]

Should this be done with the cylinder head torqued down to the rest of the engine (and so allow for any head distorsion) or can the clearances be checked reliably with the head off the engine?

 

Malcolm

[oilyhands]

The difference between on engine and off is less than the tolerance specified so it can be done either way. Check on a cold engine though.

 

Oily

[Englishmaninwales]

Thanks Dave. How much tolerance do you allow... +/- 0.001"? I guess the shims are case hardened, so grinding them not permissible?

[SLR No.77]

Malcolm, I did mine to 0.0005" but even then I think I have one that 's a little out

I measured them with the head off, and again with the head fitted and a couple changed. Can't work out why, they just did!

Be aware when you're measuring that when you've all the shims and followers fitted the cams run in the carrier and not in the head.

 

Stu.

[oilyhands]

Stock shims are case hardened so you can only grind 1 or 2 thou from each side.

 

The ones I have made are silver steel which is through hardened so these can be ground as much as is required.

 

Nomrally the tolerance is 7-9 on the inlet and 9-11 on the exhaust, I normally shim them to bottom tolerance on an unfitted and cold head and they are near spot on when fitted, clearance in the bearings can increase the gap and the oil film when running can alter it too.

 

Oily

 

Edited by - oilyhands on 22 Jul 2012 22:27:14

[Englishmaninwales]

Stu and Dave - thanks for your replies.