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MG TD TF 1500 - Fuel type

I'm restoring a 1950 MGTD and am at the point of starting the engine for the first time in about ten years. What octane of U.S. fuel is recommended for these cars? Any need for lead additives? Thanks!
Robert

Unless the compression ratio has been increased to greater than 9:1, 87 octane regular unleaded will work fine. I don't think that lead replacement additives are worth anything, and I am of the minority opinion that fifty year old engines that are not being hammered don't require hardend valve seats, as they are probably as hard as most "hardend" seats by this time anyway. When hardend seats fall out it is always a catastrophic failure, while valve seat recession is not.
George B.

Hello Robert,

About a year ago, I got a call from a gal with a TF that I had known for quite a few years. Long ago (when we were switching to non-leaded) she asked my opinion. I suggested that she either use a lead aditive, or install hardened valve seats.

Last year, her husband had checked compression and found it low on 2 cylinders. He removed the head to find tiny cracks in the valve seats that a local machine shop had advised were too deep to machine-out.

Its the old story " . . . ya can pay me now, or ya can pay me later"

Sorry to disagree with George, but why take the chance? The chap that did my head, told me he put the inserts in his freezer over-night them forced them into a heated head, then finish-machined them. But you're dead right. A dropped insert is an expensive if not a difficult repair.

Regards,

Gord Clark
Rockburn, Qué.
Gord Clark #100

One thought on valve seats falling out.

I would suspect that the valve seat is much hotter than the place in the head that it is positioned. The head is being cooled. The valve seat is being heated by exhaust gases. Unless it flops around upon installation, I suspect not too many would fall out.
Bill

My head had about 10,000 miles since it was re-done when I was in high school in '75 or so. One exhaust valve was burned, and the seats hammered in somewhat. Due to a broken valve guide boss and loose guide (must have been broken when guides were knurdled years before), I replaced the head, and had hardened exhaust seats installed. Another guy in town had his trashed seats cut to the TF size and uses the lead additive. I think you have to "hammer" these cars to keep up with traffic! Just make sure you have an excellent machinist! As George B says, you need to know your CR-I use mid-grade- bored .060, block deck and head have been shaved, no knock.
George Butz

So we don't misslead any one,I think we should be calling this stuff a "lead substitute" as I believe it has been illegal to use or sell any type of "Lead ADDITIVE" for a few years....
SPW #8893
Steve

Thanks for the info...I placed a pint or two of 87 octane in a jar and dipped the fuel line in it, turned the key, the fuel pump purred nicely, and the 87 ocatane leaked out of several places in the carbs just as fine as the more costly 90+ octane would have!! :-)...aaarrgghh!!
Robert

Robert

We have been running our 1954 TF 1250 on 92 octane unleaded for 2 years now using the Castrol phosphide / cyclopentadienyl additive which various tests here showed most nearly emulated the effect of lead additives. It is said that the phosphide additive also tends to leach out traces of old lead additive trapped in the cylinder very slowly over many thousands of miles - so maybe the engine is not yet "seeing" unleaded!

Whatever - our strong impression is that the engine runds markedly sweeter on Castrol additive plus unleaded than it ever did on 97 octane leaded. Certainly, cold starting is easier.
Paul

This thread was discussed between 31/01/2003 and 04/02/2003

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