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MG TD TF 1500 - Bronze valve guides

Bronze bushes should be lay in oil before install them. What's about bronze valve guides?
W_Mueller

I think the bronze bushes you refer to are the sintered type and either come pre-oiled or require laying in oil before use. Sintered valve guides do exist, but as far as I know are not used in these engines, so I think its unlikely bronze valve guides will require laying in oil (though it certainly wouldn't do any harm).
Dave H
Dave Hill

I doubt the guides will be sintered bronze
If they are ,I wouldn't be useing them
You don't need to soak bronze guides
BUT-BE AWARE
Bronze guides need extra running clearance or they will grab on the valve stems when they get hot
willy
William Revit

I second the larger tolerance issue. I had to have my bronze guides honed after two of them seized the valve stems.

Tim
Timothy Burchfield

And since bronze has a greater coefficient of expansion than cast iron, a hot guide can put undue pressure on the surrounding head. Resulting cracks are not unknown. Ask me how I know.
Lew Palmer

My 2 cents worth of advice, as a Land Rover and ASE Master Technician. When valves stick due to carbon deposits it is due to air / fuel mixture too rich and or not driving the car hard enough! To correct this on new Land Rovers ( NOT a mixture issue) due to driving around town slowly and never " Putting your foot in it" the clearance was enlarged by only .0003" or .0004"!
All of the cylinder head / engine machine shops I have used recommend manganese - bronze valve guides for most applications.
So make sure the mixture is not too rich & drive them like they were meant to be driven.
Len Fanelli
Abingdon Performance Ltd
Len Fanelli

Bronze bushes should be lay in oil before install them. What's about bronze valve guides?
W_Mueller

I think the bronze bushes you refer to are the sintered type and either come pre-oiled or require laying in oil before use. Sintered valve guides do exist, but as far as I know are not used in these engines, so I think its unlikely bronze valve guides will require laying in oil (though it certainly wouldn't do any harm).
Dave H
Dave Hill

I doubt the guides will be sintered bronze
If they are ,I wouldn't be useing them
You don't need to soak bronze guides
BUT-BE AWARE
Bronze guides need extra running clearance or they will grab on the valve stems when they get hot
willy
William Revit

I second the larger tolerance issue. I had to have my bronze guides honed after two of them seized the valve stems.

Tim
Timothy Burchfield

And since bronze has a greater coefficient of expansion than cast iron, a hot guide can put undue pressure on the surrounding head. Resulting cracks are not unknown. Ask me how I know.
Lew Palmer

My 2 cents worth of advice, as a Land Rover and ASE Master Technician. When valves stick due to carbon deposits it is due to air / fuel mixture too rich and or not driving the car hard enough! To correct this on new Land Rovers ( NOT a mixture issue) due to driving around town slowly and never " Putting your foot in it" the clearance was enlarged by only .0003" or .0004"!
All of the cylinder head / engine machine shops I have used recommend manganese - bronze valve guides for most applications.
So make sure the mixture is not too rich & drive them like they were meant to be driven.
Len Fanelli
Abingdon Performance Ltd
Len Fanelli


For the life left in me , I can't see why manufacturers produce and dealers keep pushing bronze guides that have caused everyone in our community such problems. I wish someone would get the message and fix this faulty part , not continue to promote it blindly. Way too many issues for our enthusiasts!
Richard Cameron

Richard
If I may respond--
There is nothing wrong with bronze guides
The 'problem' is that a lot of machine shops now, are accustomed to working on little multi valve engines with tiny valve stems and tight valve stem/guide clearances and just won't accept the fact that these thicker bronze guides , when fitted to these larger valve stem engines need extra clearance
The clearance required cold is similar to a worn cast iron guide, and they just can't bring themselves to open them out that far
At normal running temp the clearance reduces to similar to the cast guide
The advantage of using the brass guide is that they are self lubricating and last forever
The 'problem' with these guides isn't the guide itself, it's the lack of knowledge in the running clearance required when fitting them---Not a faulty part, human error--
willy
William Revit


Willy OK, but what is the average enthusiast to do?

1. Argue with the machinist about clearances.
2. Find a machine shop with like new reamers or hones for 8mm plus stems.
3. Inspect the work and check with what hand tools?
4. Tear it down again and Take it back if valves stick.
5. Hope engine doesn't eat a valve during the learning experience.

Well, most people would say that there was a problem with this whole situation. If the bronze guides were manufactured with a bore closer to the requirement things might work better. If they included instructions for fitting, people (including machinists) wouldn't have to guess at the best minimum clearance.
However, as long as things progress as they currently are, people will get to learn a tough lesson for their selves or pay the already outrageous price including possible damages.




Richard Cameron

Basically Richard, the way I see it is that if the enthusiast is moving away from anything but standard they would/should research whatever they are going to do and find the engineer or whatever they will need to complete the conversion to non standard to the specification required-If a machine shop reconditioning cyl. heads hasn't got guide honing facilities or at least the apropriate reamers then they aren't kitted up very well and should be avoided
There have been several caught out with bronze guides fitted too tight but it all gets back to understanding the situation
If someone fits bronze guides and doesn't really know how and why they are doing it ,they will get caught out probably--
Your first three points cover it-
There is a special push/pull measuring attachment on the Sunnen hone that pushes the stem dead square to measure clearance in the guide, but if doing the reaming by hand a dial indicator on the side of the stem as close as possible to the guide will tell all
It's fairly basic engine machining practice-
The main issue is to research and as you say argue your case with the machinist till you get your way-
willy
William Revit

I have got to support Richard's arguement. Why go to the bother of fitting bronze guides when the original ones have done the job for years.

Sintered broze is porus and holds oil, hence the need to soak them before fitting. Absolutely fine for bushes in a dynamo but what happens to the oil when the bronze is heated to nearly 100 degs in a cylinder head? If you examine cast iron under a microscope you will see flakes of graphite and this gives cast iron guides inbuilt lubrication, even at high temperatures.

Jan T
J Targosz

Richard, the bronze guide clearance issue has been known in the T-series community for like 20 years. My machine shop messed them up even after I gave them the looser clearance so it happens. No one "pushes" the bronze guides and they are not faulty. Moss and Abington have carried those and steel for many years and you can pick and use whichever you want. Willy's comments are right on as well about modern shops. Bronze guides were introduced many years ago due to sticking/wear with the steel guides after lead free fuel was introduced, as well as when people started using modern tight fitting umbrella seals. If you are looking for perfectly fitting parts that require no research or thought on the owner's part, hand fitting or specialized machine shop knowledge, buy a Miata! One last comment: I had to replace my original early TD head as a hunk of the guide boss cracked off and the guide worked loose- this was with an original steel guide. George
George Butz III

Hi George,

Are you sure the original guides were steel? I have recently removed the guides from my head to machine grooves for Mini seals and they were certainly cast iron. I could tell from the way they machined and from the fact two fractured when I was too lazy to press them out and used a hammer and drift instead.

Cheers

Jan
J Targosz

Many people refer to them as steel, but they were always cast iron, in this and other period engines.
Dave H
Dave Hill

ha ha ha George
My son has a Miata and his pile of broken bits easily outnumbers my 40 plus year old pile of MG dead bits-
Jan T
Your local engine shop should have a guide cutter--there is no need to remove the guides from the head to machine them for seals, they would have been doing Chevs for 40/50 years

willy
William Revit

99% sure mine were original guides which were definitely not bronze, head had never been skimmed, etc. Willy, I have a collection of broken 280Z parts as well! George
George Butz III

Here is some information which might be useful to someone. Standard BMW bronze guides fit a T-Type perfectly, although the "umbrella" has to be cut back. They have exactly the same OD. They are even available in OD oversizes of about .002" and .005" and .010", which is helpful if the cylinder head holes have loosened (as might happen in a Laystall head). They are from old model BMWs of about 30 years ago (and so might need to be ordered from a supplier). I have been using them for about 25 years because I believe bronze conducts heat away from the stems better. If anyone is interested I will dig out the part number.

Bob
R L Schapel

Here is some information which might be useful to someone. Standard BMW bronze guides fit a T-Type perfectly. They have exactly the same OD. They are even available in OD oversizes of about .002" and .005" and .010", which is helpful if the cylinder head holes have loosened (as might happen in a Laystall head). They are from old model BMWs of about 30 years ago (and so might need to be ordered from a supplier). I have been using them for about 25 years because I believe bronze conducts heat away from the stems better. If anyone is interested I will dig out the part number.

Bob
R L Schapel

This thread was discussed between 31/12/2018 and 02/01/2019

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