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MG TD TF 1500 - valves MS vs SS

Facts & opinions, + or - please. My speed shop doing the head sez no to SS valves and hardened bronze guides. Scott
SM Scott

Why do THEY say that. It seems they must have a rational for a statement like that.
JWP Policastro

Bronze guides need a bigger clearance than cast iron or they can seize.
Dave H
Dave Hill

Bronze guides need a bigger clearance than cast iron or they can seize.
This does not happen very often, it is usually caused by:
Only when running too rich, & or driven too lightly.
Then the guides are reamed out larger by only .0003"!
Scott, time for a second & 3rd opinion from experts who do this for a living.
Len Fanelli

Yes, that is basically what they said about the guides, seizure. What about SS valves, that shouldn't make a difference vs mild steel, longevity ? Scott
SM Scott

It sounds like they know what they are talking about. Certain combinations of valve material and guide material are incompatible, and there is an issue with the valve seats as well (assuming you have those fitted for use with unleaded fuel). Its not my area of expertise, though I have had issues with bronze guides. As Len says, get a second opinion from experts, there are plenty who frequent this forum.
Dave H
Dave Hill

The coefficient of expansion between the cast iron head and bronze valve guides is different. Thus when the engine is hot, they will expand at different rates. The bronze guides will expand more to the point where they CAN cause binding on the valve stem and in an extreme case have been known to cause cracking in that area of the head. I have personally had the former happen. The guides expanded causing the valve to hang up.
My local specialist in cylinder head work refuses to use bronze guides and will only use cast iron guides.

And, valves are not made of mild steel, but rather a rather special steel alloy. And yes, they can be made of stainless steel, as well as a bewildering selection of other materials depending upon use.
Lew3

What kind of engine are you having built?

Maybe he just don't use bronze guides ever at all, in any engine, period. Or could be he feels "SS" is a vague term? 21-4N and Inconel (for instance) are two specific alloy's sometimes used for exhaust valves. A number of Inconel alloys to choose from, just like a number of SS alloys out there.
Maybe he uses a specific coating or treatment on the valve which requires a certain MS alloy?

While SS is (depending on the SS type) rated for higher temps than most MS valves, that is a good thing because SS dies not dissipate heat as well, so they will be hotter running than MS- in the same engine. As such, many don't like SS exhaust valves in bronze guides, as noted above the bronze can act up in such high heat.
D mckellar

I had this issue between my machine shop (good background in MG engines) and the person that supplied my parts (Builds MG racing engines) Shop wanted brass, supplier said steel.

Shop said that the fuel used in CA was the reason they preferred brass. Went with steel and have not had any issues.
Bruce TD4139 Cunha

They met me half way, we used cast iron guides & SS valves. Thank you much for all that threw their two cents in, I learned something again. Scott
SM Scott

Please refer to http://www.nemgtr.org/images/stories/Research_Lib_Files/Tuning_The_T_Type_Head_V3.pdf

Len Fanelli

Wow, thank you Len !! Scott
SM Scott

For the record, all TDs (and earlier) came with MS valves. The TFs came with Tranco SS valves.

SS is heavier than MS, but the difference would only be noticed on an engine that is used at higher revs.

I've had SS valve inserts put in. Is there any alternative material?

Gord Clark
Rockburn, Qué.
Gord Clark

This thread was discussed between 15/09/2016 and 29/09/2016

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