Bronze valve guides

[pfenlon]

How true is it that some people say they cause the valves to stick?

Have you any info please.

[Andy Moltu]

Shouldn't do.

Unless incorrectly reamed or, dirty assembly.

The idea is the phosphor bronze is slippery and can be used with seals.

Chris Witor supplies them for the 6 cylinder cars with a groove machined on the inlets to retain the seals. However these are not present on.his exhaust seals.

I had my 4a's head done by Rik Wood who machines his own bronze guides to fit and were supplied with seals for both inlet and exhausts.

Neither standard or bronze guides should stick up.

[Nigel Triumph]

Many engine reconditioners fit bronze sleeves into the old guides to overcome wear. Bronze has lower friction than traditional cast iron guides.

Nigel

[Waldi]

Pete,

I heard that too.

When I installed the bronze guides from Goodparts including his seals and I had reamed them with a nice sliding fit, almost no play.
But before final assembly, an experienced friend (Andreas)  told me they needed a bit more clearance, so he helped me and we increased the clearance (and he cut the valves seats too, danke Andreas).

I have a very low oil consumption (almost nothing), so the seals apparently work well.

Waldi

[RogerH]

I would have thought that  oil seals would not be needed on the exhaust as there is only pressure blowing

the oil out of the guides - not sucking into the cylinders. 

Can seals be fitted to standard steel guides?

 

Roger

[Andy Moltu]

In theory if they are slim enough and can either grip the guides or be held down by the springs if of top hat design.

There is a thread on fitting the Elring 010250 a few months ago.

These were on a 4 pot but I think the outside diameter of the 6 cylinder guides is the same. The spring diameter of the 4 cylinder engines is greater so if you try fitting them to the 6 pots make sure they don’t foul on the inner spring.

[Jim F]

somewhat tangential comment - I recently replaced bronze value guides with steel guides on my TR5.  Bronze sounded like a great idea when I had the engine rebuilt but after ~10k miles I discovered a couple of the guides had moved in the head.  Differing expansion coefficient is the likely cause and, while I understand the risk of this happening can be limited by knurling the outer surface of the valve guide, I've decided that I'll stick with steel in the future.   To your question I didn't experience any sticking issues.

Jim

[Andy Moltu]

Even on modern alloy headed cars the guide material is different to the head material so differential expansion is to be expected, so the question should perhaps be as to why some of yours moved and not others?

Were the guides made to the correct diameter (if so, why hadn’t they all moved) or had the cut outs in the head been over zealously cleaned/honed prior to fitting or at some time in the past meaning there wasn’t enough interference on some?

[Andy Moltu]

On 10/9/2023 at 9:45 AM, RogerH said:

I would have thought that  oil seals would not be needed on the exhaust as there is only pressure blowing

the oil out of the guides - not sucking into the cylinders. 

Can seals be fitted to standard steel guides?

 

Roger

If that is the case, why are they fitted on modern engine’s exhaust valves?

Granted they may well be bathed in more and thinner oil but do other factors contribute to oil going down the exhaust guides?

I suppose I could remove them from the 4A and see if it starts using oil but that’s too much effort.