valves

[marcusclive]

Evening gentlemen,
would anyone know the diameter of the valve stems. Still mucking about with the engine and the guides are worn,(valves wobble) but i need to know if the valves themselves are ok. They don't seem worn but you never know.
Marcus

[elvimto]

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I believe they are .311 the book says use a 5/16 reamer on the guides. I just replaced all my valves and guides if you are going to do guides may as well do the valves. To get the best value for your money a top end job is the best way to go.
I found that getting the guides out to be a pain I ended up heading up the head and using a pneumatic gun with a tool I made to remove them same with installing warmed up the head and used dry ice to freeze the new guides and then drove them in.
Cheers Stuart

[marcusclive]

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Hello Stuart,
thanks for that, i needed to know as you need a starting datum and the workshop manual doesn't give a size. i am having an engineering company replace the valve guides as its a bit beyond home mechanic's as far as I'm concerned.
marcus

[comeinhandy]

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Hi Marcus, are you using brass valve guides for the new ones when you change them as I believe these are better with unleaded?

When I changed mine I also tapered the ends of the guides on the bit that sticks out into the airflow, to improve the flow of air across the valve and into/out of the head.

In the spirit of trying to improve the design I also cut a groove near the top of each valve stem so that I could fit the valve oil seals from the dolomite sprint. The head and valve construction is similar on the sprint apart from having 4 valves per cylinder of course and I believe the sprint oil seals were designed to improve emissions and reduce oil consumption. I fitted these a couple of years ago to my stag with no apparent problems since and negligible oil consumption, I removed the metal spring in the seal for the exhaust seal just to let a bit more lubrication in there.

I am not recommending any particular course of action, just thought this may be of interest.
Jon

[marcusclive]

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Hello Jon, i am not sure what the valve guides are yet, i've ordered them from James Paddocks, they should be here tomorrow. This grinding grooves in the top of the guides, does it make a lot of difference? I thought the stags didn't have seals as they weren't needed or is it a case of they thought they didn't.
Marcus

[comeinhandy]

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I think Paddocks will give you the brass ones, but I haven't checked if they give you a choice. I think I got mine from them when I did mine.
The original design for the stag and therefore everyone doing this job runs without oil seals and just relies on the shrouding effect of the valve cup.
What is interesting is that for the sprint they decided oil seals were required, even though the design of the valve cups etc is the same. I have a vague memory that they had to do it in order to improve emissions for some markets by cutting oil consumption.
Before my rebuild I had a bad case of oil being sucked Into the engine on decelerating and hence high vacuum, so I wanted to not only fix the worn valve guides but improve it over the original design, by making it similar to the sprint design.
There is some risk of not getting enough valve lub, so I can only recommend sticking to the original design, as I don't want to get any blame for problems, I just like to experiment and try improvements here and there. I only mention my changes in case yourself or anybody else is of a similar mindset and may want to try a similar setup. Most modern engines use valve oil seals.

[Andy Rundell]

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I had valve stem oil seal fitted to my recently rebuilt heads heads - seemed to make sense to my (albeit limited) brain

.........Andy