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TR2/3/3A tr3 and unleaded gas


Freshman Member
I have got a tr3a and i was wondering what the thought was on running unleaded gas without the new valve guides and valve seats? or if anything else needs to be done to run unleaded gas


Luke Skywalker
Country flag
FWIW, I run my '59, w/ 64k miles, and use unleaded premium, 91 Octane here in L.A. The car is completely original, I don't think the engine's ever been apart. No knocks, seems to run fine, and I've had her at 90mph for short bursts here and there. Every now and again, I'll put in a little lead additive... I might use more if I ran it for extended runs, but I rarely put on over 100 miles at any one time. If I ever do the head, I 'd probably have the upgraded valves put in then. Of course, YMMV!

Don Elliott

Obi Wan
I drove my TR3A 43,000 miles on unleaded gas with the original head in good condition without the steel inserts for the exhaust valves before I had to have them added. Toward the end of that 43,000 muiles the cast iron was receding so the valve gap was closing down from 0.012" to 0.002" every 1000 miles. This is what tells you that you need to do the conversion. I had an engine re-build shop do the job. I supplied him with 8 new valves for unleaded, 8 new valve guides for unleaded and he put in the inserts he was familiar with and he had them in stock. He preferred this because he has his own tooling for his machine and he knows that when he presses them into the head, the interference fit will guarantee that they will stay in place. I have heard of several TR3A owners where an insert for one of the exhaust valves has become loose and fallen down to ruin the valve and seat area, usually with a lot of noise. You don't want this to happen while on a long trip from home. I did this in 2000, just before I drove Montreal to Portland Oregon for VTR. That trip was 7250 miles. There were no problems. Since 2000, I have driven another 51,000 miles and never had to re-set the valve clearances - but I still check them every 5,000 miles or so.

Andrew Mace

Staff member
Country flag
So far I've put 25,000 miles on my Herald (with an untouched, original engine) using Premium Unleaded, and with no ill effects. And a Herald engine is far more stressed than any TR3 engine.

Do any "conversion" WHEN you need it. Until then, enjoy the car!


Jedi Knight
"Most" lead substitutes or additive contain no lead.
I did a wack of snoopin on this for the last two driving seasons. Don't worry about it, see Andrew and Don's responses above

Don Elliott

Obi Wan
I never believed in "snake oil". So I never used any additives for unleaded gas. The TR Register in England did an extensive study of many products and came to the result that there were 6 that helped. These products are available in UK.

Will it hurt ? Probably not. Will it help ? Who knows ? Will it cost you ? Yes.

You'll have to bite the bullet some day and do the exhaust valve seat inserts. If that's 3 years down the road or 4 years, it'll be more expensive to do it later than now. It depends how hard you like to drive and how many miles you plan to do over the next year or years. Don't leave it too late.


Jedi Knight
stupid question,
is there a reason to put in inserts on the intake side other than if you have an aluminum head?

Geo Hahn

Country flag
I drove 25 years on unleaded and noticed no significant recession... finally did the hardened exhaust seats when I had the head off for other work.

I would think just doing the exhaust makes sense. I think if you do both the seats would overlap so they would have to do the intake seat first, then the cut for the exhaust seat taking some material out of the intake seat.

Don Elliott

Obi Wan
The intake valves do not suffer from the problem of valve seat recession. The cool air/fuel mixture coming into the combustion chamber prevents the cast iron head from wearing away at the cast iron intake valve seats. It's the exhaust valves that need the inserts. When I had mine done after 43,000 miles on unleaded gas, I took the valves out and the exhaust valves were razor sharp on the edges. Once it was off, I changed all 8 valves. Some of those I took out at 123,000 miles from new were still the original valves.

Don Elliott, Original Owner, 1958 TR3A

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