Further to my thread on engine rust: I am now ready to assemble the intake valves in the cylinder head and have a question regarding the seals. I once heard a discussion re the O rings in the guides being inadequate. I have found some "universal" neoprene valve stem seals in the shape of an umbrella. They are a little too deep and will require trimming, so not to contact the top of the valve guide. Is using such a seal a good or a bad idea? Or is it even necessary? Could it starve the guide of lubrication and spoil the guides? I do have the old seals out and new O ring type seals came in the gasket kit I purchased. I appreciate your advice. Thank you. David.
Post by Phil Nottingham on Nov 15, 2005 16:13:07 GMT
Rover designed the inlet guides with the O ring seals which do allow a certain amount of oil seepage so I suppose unless you fit self lubricating phosphor-bronze guides which would have to be made specially I would think it better to keep the original set up.
They do harden with age but then this is not aproblem confined to old Rovers as may modern cars with the top hat seals suffer from this as well
Phil - 1964 P5-Coupe PMB***B & P5B-saloon LHO***L & other classic Rovers & Land-Rovers
I have a 1961 3l. The engine was reconditioned 12 months ago but within a month the stem seals had failed sufficiently to cause carbon build-up on one side of the exhaust valves resulting in missing at slow idle. The re-conditioning firm offered to fix the problem with the comment that this was 'par for the course' with this engine. There had been problems in the past with this engine in this respect. In this part of the world the 'japanese solution' with hoods is commonly employed with these engines... the same solution used in the land rover engines.
Your point concerning lubrication is valid but here it was always a case of too much and so the common solution which has stood the test of time in many engines in this part of the world, including the Land Rover 6 cylinder; very common in years gone by.
I also own a P5-MKI-1961 and I also suspect that the inlet valve guides are worn, because of the oil consumption, bleu smoke and oily sparks. Therefore i am considering to have this fixed. What about the exhaust valve guides? I would expect these also to be worn, but what are the symptoms of worn exhaust valve guides? These are much more difficult to access for replacement. Can I leave them as they are? Frans
Inlet valve guides are the source of most of the oil contamination that gets into the cylinder. It is not clear from your post what was done when the head was "reconditioned". I suspect that valve guides were not replaced or sleeved. If so, then wide clearances allow the valve to rock around and wear out the seals.
An effective recondition would be to have phosphor bronze liners installed. This should not be an expensive job, as a skilled recondtioner ought to be able to do that in 30 mins with the right tools. However that will usually obstruct the groove for the O-rings. No worries though. The phosphor bronze liners can be left with a close to interference fit to the valve stems, in which case little oil will get through. The alternative is for the reconitioner to machine the top of the valve guides to take top-hat seals as in a modern car.
Oil will come through thr exhaust valve guides on the over-run if they are heavily worn. Symptoms are blue smoke on over-run despite a good head job, + - rattling under power.
Exhaust valve guides are not that big a deal once you have done them before, but see this thread: Valve guides
Lastly, oil in the cylinder does not create carbon deposits (that is rich mixture). Oil burns to leave a dense and hard brown ceramic coating that eventually causes pinking, gets on the valve seats and contribiutes to exhaust valve failure.
Blue smoke from the exhaust pipe on the over-run, for example during a closed/off throttle descent down a steep gradient is caused by high vacuum on the inlet stroke drawing oil past worn guides and/or guide seals if fitted. When the throttle is opened again after the descent a large puff of blue smoke is emitted. If the smoke is continuous...then it's obviously a ring seal issue.
3 litre Rover engines utilize inlet over exhaust (IOE) design. The negative aspect of this like a side valve engine is by virtue of the exhaust valve being in the block beside the cylinder. This overly heats one side of the block/cyl causing poor ring seal due to cylinder distortion.