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Triumph TR3 - coil failure

Hi guys:
Has anyone ever thought about insulating the coil from the engine block to avoid overheating the coil.I installed a super top of the line sports coil to replace my old original(which was still good by the way)and it failed within 500 miles.New is not always better.A Lucas replacement is on there now without problems over the last 2000 miles.I don't want to relocate the coil because the shorter the HT lead to the dist. the better.I was thinking of a piece of insulating material such as is used between the exhaust and the head between the coil bracket and the block.
Any thoughts?
By the way I thought tappet adjustment should be .010 across the board after the introduction of alloy rocker shaft supports Instead of .010 intake and .012 ex.or do you just use .012 ex just for safety's sake.


I set mine .010 across the board, following this advice from Randall: "For the aluminum [rocker pedestals], .010/.010 is used for all conditions. Later (4th edition) owner's manuals have only this number."

Working fine thus far.

Bill Stagg
1960 TR3A

Bill Stagg

The specification in the book when I bought my TR3A in 1958 was 0.010" for intake and 0.012" for exhaust. Even with 0.012" setting for exhaust, I had to have the head off about 3 or 4 times in it's first life (80,350 miles on leaded petrol) for badly burned exhaust valves. So I always have kept it like that. I feel that this gave me longer life at least for the exhaust valves before running into a burned valve problem.

I have driven another 43,000 miles with the next set of exhaust valves (from 1990 to 2000 using un-leaded gasoline) before valve seat recession forced me to do it all again. At this time I had exhaust valve seats installed in the head with 8 new valves and 8 new guides. Still using 0.012" for the exhaust valves, I have driven another 40,000 miles without ever needing to re-gap the valve settings and I check them every 5000 miles. Says a lot for the hardened steel valve seats and 0.012" exhaust settings.

Chuck - you are right that more recent settings are both o.010" since the intoduction of the alloy rocker shaft pedestals.

But I say, "If it ain't broke - don't fix it !"

Don Elliott
Don Elliott

My dog-eared Clymer's Handbook says:



TR2 intake .010"
exhaust .012"

TR3-4 intake .010"
exhaust .010"

HIGH SPEED: .013" for both inake and exhaust on TR2/3/4

The .013 clearance will give an noticeable increase in performance in most cases but is accompanied by considerable tappet noise. It then becomes a matter of personal choice. If the additional tappet noise is not annoying then the additional "snap" to be gained by the .013 clearance is there to be had.


Good luck and happy motoring.

I still have and use the original coil that came with my TR3A new in 1958. It is stamped and dated "LUCAS 7/57" on the bottom.

When I was passing through Penn. in June, I stopped at Roadster Factory and a chap came in with a burned out Lucas Sports Coil. He had the same results with 4 in a row over a 10 year period. After about 2000 miles, they would overheat and he had to sit it out at the side of the road to let it cool down before he could continue. Then about 1000 miles later, it happened again. Then 500 miles later. Then 300 miles later. Then 150 miles later. And so on. Then it wouldn't work at all so he bought another new one.

And it was the same story for the new coil, then the next 2 coils.

Any suggestuions ?

Don Elliott

Don Elliott

When I was in the Singapore Army 30 years ago, we would routinely relocate the coil away from the engine block on the Land Rovers because the coils would fail otherwise. However, I've had my coil on the TR3 on since 1989 (about 25,000 miles) with no problems at all

Harpal Singh
H Singh

I have a Lucas Sports coil which was installed by the PO approx. 20K mi ago. I have put on 4500 miles of that, some in very hot conditions. No problems...yet.

There are also Borg/Warner replacments available at modern parts stores. I bought one because I thought I had a coil failure awhile back - turns out I isolated the points from the LT lead on the mount because I put the plastic washer on first instead of after while changing them. Good one, huh?

So perhaps it's just the sports variety, since both Don and Chuck's originals are still good...

Don, this chap in PA, were the next 3 coils all sports?

Mike Gambordella

Mike - Yes all the coils were Lucas Sports coils with the green and white label on them.

Since no-one has offered a suggestion as to why they may have copped out, I was speaking to a chap at TRA in Ohio in June and he explained the fowwowing to me.

1. If you leave the key on in the dash, and providing the points are closed, the power from the battery into the coil will all appear as heat inside the coil.

2. If the points are open (or if you stuff a bit of clean plastic or cardboard between the points when you do this), there should be no power into the coil therefore there should be no overheating of the coil.

3. I had always heard that arcing of the points was a natural thing to happen amd that metal will transfer from one flat face of the points (leaving a cavity) and the metal will become deposited on the other flat face leaving a hard metal spike. He went on to say that if the capacitor under the distributor cap was the exact value for a given set-up, there would be no transfer of metal and the spike would not occur, thereby giving you longer points life.

Maybe that chap in Penn has a wire somewhere that a previous owner installed (for some stupid reason) that leaves power going to the coil all the time.

Don Elliott
Don Elliott

Can someone please explain what is meant by "snap", as in, "If the additional tappet noise is not annoying then the additional 'snap' to be gained by the .013 clearance is there to be had."

Makes it sound as though "snap" is a handy thing to have...

Bill Stagg
1960 TR3A
Bill Stagg

I took a hard guess and came up with the following.

You get more snap = you get faster acceleration.

Don Elliott
Don Elliott

Makes linguistic sense, Don. Mechanically, why does the higher exhaust clearance provide faster acceleration?


Bill Stagg

Bill, I think it affects the valve timing a bit. I love the term. Just thinking about it makes me want a little more valve noise..

Just hit me...head snapping acceleration..

Ahh...that kind of snap intrigues me. What is it that provides said snap? Is it the .013 on the exhaust, the .013 on the intake, or both? Is Don getting more snap than those of us using .010/.010 because of his .012 on the exhaust? Any downside to running snappier on a regular basis?

Let the heads roll...

Bill Stagg

My engine is only 1991 cc displacement, so side-by-side, you with 2138 cc would have more snap than me based on displacement. But it might be interesting to try somewhere someday.

Running for 46 years with 0.010" and 0.012" has not shown me any problems that I can attribute to the settings. I can't compare if mine got "snappier" because I always ran them that way.

Don Elliott

Geez, Tom - look what you started!

Here's my theory on what's creating the alleged (no one's actually tried this have they?) "snap".

Increased clearance - same as increased lift.
Now a greater volume of air/fuel is being exchanged thereby creating more power.
Like bolting on larger carbs and "hotter" cams.

But a thousand of an inch on a worn motor?

2 cents from a rookie...
Mike G.

I have to confess I only discovered I had any "snap" at all two weeks ago. I adjusted my valves for the first time in a year and half (.010/.010), and I can assure you I'll never wait that long again. They were way out of adjustment. I also rebuilt/cleaned up my grungy distributor, providing me with a working mechanical advance for the first time. This really brought the planets into alignment with my no-longer-leaking carburetor I only finally learned to set with the Colortune acquired a year ago.

Now I know where the "sport" in sportscar comes from.

The snappier, the better, I say.

So, .013, here I come, even just for a quick test. For me, Mike, it's a yawning .003 on each set of valves. Who knows what snap is yet to be gained?

Accelerating in Indy,

Bill Stagg

Bill - The snappier it gets, you will gain confidence that you can drive it (her) (him) etc. 794 miles in one day like I did in June with no sweat. Make a list of all the items you have done, repaired, fixed etc. Then you can say, "The rear axle, carbs, distributor, radiator, starter, clutch, front steering, etc. etc. have all been attended to." Therefore with all this in tip-tip shape, it will not only be snappier but your confidence level will get way up there with mine.

Now don't ask how good is "tip-top" or what it means.

Don Elliott
Don Elliott


You are my road warrior role model. My list of things attended to on the rolling restoration is lengthy, and my confidence in the TR grew enough for me to make a one-day 695-mile run to Richmond, Va., to touch base at VTR last month. With the distributor and valves now on the list, I'm ready to head north to Montreal for one weekend to see how you're coming with that rebuild.

Bill Stagg

This thread was discussed between 12/08/2004 and 17/08/2004

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