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MG TD TF 1500 - Bronze inserts for Valve Guides

I am in process of rebuilding the head of my TF. My re builder has suggested using Phosphorus Bronze inserts instead of replacing the old iron guides with new ones.
Has anyone had experience with this process?
Are there any pro or cons on this method?

He has also suggested the application of a an attached valve seal to the top of the guide like a modern engine and eliminating the o-ring/deflector all together.
colin stafford

To my way of thinking these are a quick-and-dirty repair, like knurling pistons. My one experience with thin-wall inserts was not good - they wore out in about 10,000 miles.

I use new iron guides on the intakes and bronze guides on the exhausts, and have the bronze guides honed a bit oversize to avoid expansion problems that could lead to valve seizure. The cost of new guides and their installation is part of what you have to do to obtain a leak-free head.

Tom Lange
MGT Repair
t lange

It is common to have to hone the bronze guides oversize to eliminate the possibility of seizing a valve. But in addition to expanding inward the bronze guides expand outward. This is due to the coefficient of expansion of bronze is different than that of cast iron. If the expansion is great enough the result can be cracks around the bore in the head. This has been known to happen.
Save yourself the trouble and expense, use cast iron guides.
Lew3

Should you choose to use phosphorous bronze guides then if you don't ream them out to at 0.003"then within 100 0r so miles they may seize up as Lew3 stated. However a good friend of mine who specializes in overhauling cylinder heads mainly for the racing fraternity uses the standard guide with a small bronze insert in the top of the guide.
He said it is the normal procedure here and you do not have to reamer it out.
Hope this helps and if you need any further information let me know and I will be able to put you in contact with him. Unfortunately he does not use the internet.
John...Sydney
John Walton

Colin,

How many miles do you do on average per year ? If you are doing low mileage,and I suspect you are, I would recommend sticking with new,
original type valve guides with original seals. If the seals are fitted correctly a la the Factory Manual,they work perfectly.

Cheers
Rob Grantham
TF3719("Aramis"),TF9177("Arhos").
Rob Grantham

Phosphor bronze valve guide inserts are normally fitted by opening out the bore in the original guide, pushing in the bronze sleeve, and then sizing this to the valve stem by pressing a suitably sized steel ball through the sleeve. How a thin walled bronze sleeve will react to heat I don't know but original guides are the safe bet. There is another issue though. To fit modern stem seals (from a BMC A Series engine) you have to machine a groove towards the top of the guide. The prevents the seal running up the valve and becoming useless. The only way to cut this is in a lathe before the guides are pressed into the head. Maybe your machine shop has made up a special tool to cut the grooves in situ and I would ask them.

Jan T
J Targosz

This thread was discussed between 15/12/2016 and 16/12/2016

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