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TR2/3/3A Bronze valve guides

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charleyf

charleyf

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I have a question about whether bronze valve guides are better than iron guides.
Charley
 
I do too. The bronze is supposed to wear slower, but you have to ream it larger than the cast iron on installation. So they start out already worn. And the cast iron ones seem to easily outlast a valve job or two (not to mention not having to buy that expensive oversize reamer).

I'm using them on the exhaust only because I wanted to use the smaller stem TR4A exhaust valves, and the conversion guides only come in bronze.
 
The machine shop that I have used for many years strongly recommended iron for my stock (except 87mm liners) engine. I trusted their recommendation and had the iron installed, but I am too ignorant to convey their rationale.
Tom
 
X2 what TomMull said. My machine shop recommended I purchase new iron guides for my head rebuild. They also did not recommend I purchase bronze.
 
Additionally, many machine shops today are staffed by folks who are inattentive or simply don't care what they're doing. They'll ream bronze valve guides to the cast-iron (too tight) stem clearance - even if you provide them the correct clearance figures. Then your valves bind and stick open when they get hot, and you get to remove the head and do the whole job over again. I've had this happen...not fun, and costly to put the job right.

I've also had another machine shop ream the bronze guides to an overly-large clearance on the intake valves. So even if bronze guides really do turn out to be the greatest thing since sliced bread, I'll not be using them again.
 
I'll go against the wind.

I have not had the head on my TR4 rebuilt, but when I had my 1933 Chevrolet head rebuilt back in 1974 I had bronze valve guides installed. The engine is still running fine after more then 40 years. I had a machine shop that specialized in farm tractor engines do the work. The car even sat in a garage for 6 years while I was in the US Air Force without ever being run.

I have read comments on the Antique Automobile Club of America (AACA) forum where others have stated they had iron valve guides and had valves freeze up and bend the push rods when the car sat in their garage for a year or two without running the engine.
 
The iron valve guides on many old cars, particularly valve-in-block engines, are very long and have a lot of surface area along the stem of the valve. In damp storage these long guides can rust up, but not if the car is well oiled and stored properly. Never heard of this happening on a TR engine, though, but it's always wise with a long-stored engine to turn it over by hand before running it. Easy to pop the valve cover and rocker arm assembly off to have a look at things and give them a shot of oil. A mild rap on the end of the valve stem with a hammer and brass drift or block of wood will verify that the valves are free. More troublesome, of course, is if the valve seats have rusted over time.
 
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