TR2/3/3A valve guides and piston clearance

[TFB]

I thought I posted this earlier but--
What are the recommended clearances for bronze exhaust guide with 3/8 stem and cast iron piston skirt to bore?
Currently I am thinking .005 guide,.004 skirt.
Thanks

Tom

 

[sp53]

Glad to see you posted this Tom because I wonder myself. I have a couple of older complete heads and was going to tear them down and try to lap the valves and try and use the guides if within tolerance. Hopefully somebody adds to this post.

Steve

 

[CJD]

Well, nobody else seems to want to dive in, so guess I will. Stock clearance, using iron guides is .001 to .003" intakes, and .003-.005" exhaust. Again, those are with iron guides. There have been several threads over the years of owners trying to use the stock specs with bronze guides...and they end up with sticky valves. There is a chance they were using the same tight clearance on both the intakes and exhaust, causing the sticking. So...I would say .005" would be minimum for the exhaust with bronze guides. The good thing is this engine is not an interference engine, meaning that if the valves stick, they will not get hit by the pistons. It will just run rough.

 

[mctriumph]

My considered advice is to make sure the guides get knurled . So old valves/new guides or new valves/old guides.DO NOT
howl and scream, it is to reduce oil consumption and it will work. My old tr4 could go for 1500 miles on one quart counting leaks.
Mad dog

 

[TFB]

Thanks john and MD ,I thought I replied earlier but I guess not.The speed shop I use installed 4 new bronze 3/8 exhaust valve guides reamed to .0035 and new valves.
When I told them I had a recommendation of .005 ,after they were already done,said he would cry if he had to do .005.
This was kind of funny because the motorcycle cylinders he has been doing for me for years have .005 as stock clearance,cast iron guideSo I will find out if .0035 is enough.
Pistons were fit to .003
Tom

 

[charleyf]

Thanks john and MD ,I thought I replied earlier but I guess not.The speed shop I use installed 4 new bronze 3/8 exhaust valve guides reamed to .0035 and new valves.
When I told them I had a recommendation of .005 ,after they were already done,said he would cry if he had to do .005.
This was kind of funny because the motorcycle cylinders he has been doing for me for years have .005 as stock clearance,cast iron guideSo I will find out if .0035 is enough.
Pistons were fit to .003
Tom

I previously had bronze guides installed and much later determined that the shop did not use the correct reaming. Result was a new cam. Bronze guides apparently expand when hot so need a greater reaming space.
Find out what is correct . You will be money ahead to pay to have it redone, IF it should be the higher number.
Charley

 

[mctriumph]

I agree , bronze is for racing and must NOT be too tight. This will make you burn more oil. The best result on a fresh head
was new guides knurled to fit the old valves.This head did not burn oil at all .Drove 5500 miles on a big road trip in 2000,
consumed 3 qts total on the trip.Had one flat tire and the tach cable failed. Not bad for a 63 tr4.Packed a but load of spares
and never needed one!
Mad dog