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MG TD TF 1500 - Bronze valve guides
|A question for the group. |
When I purchased my MG-TF 1500, I was told that the engine had been modified to run on unleaded gas.
I know there has been an on going debate as to whether Ts' should run ONLY on leaded gas or if the addition of appropriate head modifications is necessary or even effective in order to use unleaded.
Not wanting to open up the old argument too much - does anyone know if there is an easy way to verify if the head has been modified to work with unleaded (bronze valve guides??). Will pulling the valve cover give me any insight into such modifications?
I'm wary of taking the word of the dealer I purchased my TF from......it's the "Trust but Verify" factor -
|No way to tell without pulling the head. The modification for unleaded gas is to install hardened valve seats, and you can't see whether you've got them unless the head is off the engine.|
That said, the whole unleaded gas thing is greatly overblown. I don't know where you are located, but here in the US we've been on unleaded for decades. In all that time I've only heard of /one/ instance of valve recession. I've never run a lead substitute and have never had issues. Eventually it comes time for a valve job, and that's when I have hardened seats installed.
Run it, don't worry about it, but check your valve clearances regularly. If the valves start receding, the clearance will close up. If that happens, then you will have to have the valve seats replaced -- but no sense doing it before you have to. There's no gain in doing it early.
|I have a TF 1500, Stage 3 tuned, 9.5 / 1 compression ratio that I have run on unleaded since it was introduced. NO INSERTS no recession, and I drive it over 3000 miles /year frequently on long trips at 65 MPH |
Bob Wagner, our Vintage race car guru says that he doesn't recommend anyone with cast iron heads put in seats unless the head can't be fixed without. He has built many MG T, A, B engines.
"Just add some lead substitute if it makes you feel better, BUT don't run too lean"
|You did ask about bronze valve guides. I run them, the important thing is that they are opened up slightly from stock cast iron guides, or it is reported they may expand at a different rate and cause a push rod to stick.|
I also run hardened valve seats, because I wanted to be sure that they would tolerate unleaded fuels. With the seats I fill up anywhere, and don't worry about aditives. I think it is highly unlikely that a seat will loosen, so I'm fine.
Hope this helps,
|Also some modified heads have cast iron valve guides that have been modified to have bronze sleeves inside. This I am told is a motorcycle trick and mine were done that way by a shop that did a lot of motorcycle work.|
I suspect that not only would you have to remove the head but also a valve to see if it had been done.
|"Back in the days" -- I had a 1952 TD, bought & rebuilt the engine in Winter 1961-2. Magnafluxed to check, & turned the crank journals for new bearings, bored to clean up, installed slightly higher compression ratio pistons, took enough off the head to insure flatness. It was my/our only car from Jan. 1962 - July 1964. I don't remember how many miles, but would guess probably 25-30,000 mi. at least. Always ran Amoco premium gas, unleaded. No problem ever noted with valve clearance, cyl. wear, etc. It did tend to "run on" when shut down, unless the throttle was opened as the key was shut off, probably due to a hot spot in a cylinder & the higher compression.|
your mileage may vary,
54 TF "Emma"
|A W Parker|
|Primary concern on unleaded fuels used in older vehicles is valve seat erosion - particularly the exhaust seats. Some engines have more of an issue than others. Never had an MG with heavy erosion issues that I can recall, while is is quite common on older small block Chevys and Fords. That being said, we commonly replace seats in MG heads due to multiple valve jobs and poor machining techniques sinking the valves deeply in the head. We always use hardened seats during this process and blend the new seat with the original casting. Proper installation will keep replacement seats in place for the life of the engine. Not a great believer in bronze guides for street engines. As Dave mentioned, increased clearance is needed to keep lubrication on the valve stems and avoid galling. Stock guides and proper clearances are working well for us. |
No real way to verify mods on youe engine from the outside - sometimes we use a borescope to examine internals, but that is not always 100% proof. Like Rob suggested, watch valve clearances for decreasing lash amounts - that is a good clue on erosion issues. Dan
This thread was discussed between 09/10/2011 and 10/10/2011
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