3-litre inlet valve guides again!

[djm16]

Is this 3rd or 4th time I have now had the head off?

This time was to replace the damaged inlet valves and guides (and yes Vince, the damage was done by a large specialist engine shop with a previously good reputation).

This time I replaced the O-rings not with the ones from the gasket kit, but with some expensive 1.5 x 8mm Viton rings from Transeals. Regrettably after only 400 miles I am blowing smoke again.

Rather than pull the head YET again, I am considering umbrella seals (I have a tool for removing the valves springs with the head on the engine).

Question is, does anyone know what the clearance is above the valve guide when the springs are fully compressed? I would need a little over 3.3mm for fitting umbrella seals, or 1.5mm if only fitting external O-rings (like I had in my Morris Minor).

[enigmas]

If you can remove the inlet valve springs in situ David (and obviously not drop the valve into the cylinder), then by using a simple calculation (inlet camshaft lobe lift x rocker ratio) you can physically assess the clearance available. With the spring removed refit the cap and collets, mark the valve stem at the top of the guide then lower the valve to the amount of calculated lift. The remaining clearance is the available margin for the seals.

[djm16]

Looking at wear marks on a used valve, there should be room for an umbrella seal. However it will not fit inside the inner spring, nor over the valve guide. So if I do go that root, I would have to trim off most of the skirt.

[enigmas]

Why not then replace the dual valve springs with a single outer with a similar spring pressure . Do you really need 2 valve springs on the inlets? I assuming you don't routinely rev the engine high enough to induce valve bounce. 😉

[djm16]

"I assuming you don't routinely rev the engine high enough to induce valve bounce."

Umm, err, well I do occasionally floor it to pass a truck. The 3-litre is not exactly the fastest accelerator in the Rover stable, in fact I am sure my Morris Minor was faster in some speed ranges, so it does occasionally go up to 5,000 rpm.