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I am stripping down a 12G2940 big valve head (1300GT type) which appears to have had a 'recent' overhaul and looks to be in generally good condition. I plan to clean it up, de-coke, re lap the valves etc. and probably have a light skim to clean up the head face.

I have found that a number of the valves were difficult to free off from the spring caps/collets and required considerable pressure to release. The same valves appear to have deformed tips which are worn at an angle as well as some marks on the end of the stems just above the collet groove. They will not withdraw through the guides.

What might have caused this and how can they be removed without damaging the guides which appear to be in good condition? Do I need to cut them off?

I am just looking to re assemble as a competent spare head for road use. I have a number of spare low mileage valves from a similar head which I may use as replacements where required - are they any do's and don't in putting used valves into another head (subject to re cutting the seats or lapping which I expect to have to do)?

Cheers

Jon

Perhaps the collets used were not the right ones for the valves.

It sounds like you have been able to remove the springs and keepers. That means all you need to do to extract the valves is remove any burrs from the top end. You should be able to do that using a new (flat) wetstone or a flat diamond file. Once the burrs are gone you should be able to easily withdraw the valves. Since the area around the collet grooves never goes into the seal or guide when in use, you could ask a machine shop to polish the stems and dress the worn ends flat again if you want to re-use these valves. If you decide to use valves from you collection of spares, just make sure they lap in well before final assembly of the head.

Thanks Doug,

I tried a diamond file last night without success but I probably just need to persevere a bit more.

Cheers

Jon

Probably 99% of the Valves I remove, the collets are stuck as you've described to the spring keepers, that's pretty normal in my books. I have some small timbers I cut to fit in to the combustion chambers so I can sit the head, deck side down on the bench, but sitting on these timbers, then I have a small tube I fit over each spring keeper in turn and give them a tap with the Nylon hammer to release them.

In regards to the valves, probably 1 in 2 heads, that have been run, that I've taken apart I find the valves to be like that. It appears to be from material deposited on to the valve stems. I just punch them through, occasionally though rarely it does any damage to the guide, but most of the time they are fine.

If as you suspect, the valves have been damaged at the tips, which sounds like a poor rocker geometry set up or extended use with roller tip rockers, the guides will have had it in any case.

For the valve tips to have a burr on them that will increase the diameter overall the rockers will have had to slide (or roll) off the tips and this usually also bends the valves, though it depends on whether that occurred at valve open or closed, in either case, the valve tips always have a chamber ground around the tip, so they would have had to 'wear' for a very long time to produce such a burr, or been re-dressed by a clown.

One of the main stages of stripping any head should be the releasing of the valves from the collets, usually done with a socket and a tap from a hammer.

I agree with most comments above.

A bit of deformation above the collet grooves is perfectly natural, this can be removed with a fine file. If you have pulled the valves through the guides, check for damage to the guide bores (scratches etc).

The situation is aggravated by badly adjusted rockers.

M

Thanks for the tops tips chaps

The guides seem to be okay - 8 thou maximum waggle using a DTI when I push the valve stem tips flush with the top of the guides and read from the valve edge. Does that seem alright?

Jon