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Triumph TR6 - Low speed miss

I have a 1976 TR6, actually the second last one built, complete with Coventry brass plate, saying it's one of the last 6 built.

Its in immaculate shape and fully original. It runs like a brute at high speed! However it has a low range miss/hesitation that I cannot find. It only does this in low range of each gear while under acceleration and the other hint only does it after the car has warmed up. While its cool it works great!

Even when warmed up at speed it runs great! It just happens under low speed acceleration.

I've done everything I can think of including:

- all new plugs, wires.
- new Pertronix Ignitor
- new vacuum advance and va line and connectors
- removed and thoroughly cleaned and inspected carbs.
- removed, inspected and resealed carb temperature
compensators.

Does anyone have any advice?

Gary
76TR6
Gary Arsenault

Gary,

I had the same problem. Turned out to be timing related. Did you check this yet? I would get poor accelleration/hesitation/missing in the low range. Properly setting the timing did wonders.

When I converted to Pertronix, I opened my plug gap to .035. I'm told you can go to .040.

Since you're having this issue while the car is warmed, you may have an issue with your coil. If you can borrow one for a day, it's a simple test to rule out a potential problem.

Hope you get it sorted out. Car sounds like a beauty.

Don
'74 CF19053U
D Hasara

Gary,

I gotta go with Don.

Electrical components change value with heat.

Coils can do it.

I've got one I can loan you to test it out but the freight back and forth would be a pain. We can do it though.

Is yours set up to go around the ballast resistor and use 12v to the primary side or are you still ballasted?

Jim
Jim Deatsch

Or the carbs could be a tad too lean. Since it only seems to happen when the engine's warm, I tend to think the setting is too lean. You could also try a restrictor in the "coolant" intake manifold line - a clamp will do.

It could be the Temperature Compensators, too. The VTR site has an article on how to adjust them, I believe. I disabled those buggers, however.
Brent B

Hi Gary
Sounds like a great car.

To test if your running lean give it a bit of choke not a lot when the problem occurs. The chokes on the Zs add fuel rather than restricting mixture air. American carbs have an accelerator pump that gives a shot of gas under high torque load. Low end of each gear range. Thats what you will be doing with choke.

Do a read of second and 5th plug to find out if rusty brown in colour. Whiter means lean blacker rich.

Timing to far advanced or coming in to fast will affect but the plug read should give you an idea of were to start.

One bit of advice try one thing at a time and return it to original setting before trying next. When everythings close tweakings cool.
Bill



Bill Brayford

Gary
In the last year of production the compression ratio was lowered to 7.5 to 1 which will slow down flame burn rate. Try optimising the ignition timing on tick-over as the book values for ignition timing dont seem to take CR into account- you need more advance to counter the low CR. My guess would be that a static timing of around 15-18 BTDC will prove about right. I use 18 BTDC with a 8.5 CR head.
Peter
P H Cobbold


Sorry I'm late responding but have been away for these last few weeks. First of all I'd like to thank all those who suggested an alternative to what I've already done. You can bet I'll try all these until I get this remedied.

Again, thanks everyone. I'll let you know in the coming weeks as to how it goes.

Gary
76TR6
Gary Arsenault

Gary,

I had a very similar problem with my '71.....and my suggestion is going to go the other direction form those posted.

Check your fuel pressure, you should only have
1 1/2 - 2 lbs. I had 3 + with the mechanical fuel
pump.....put in a pressure regulator and my carbs
leaned out.

The problem was that at low speed or idle the pressure
was flooding the carbs.

Good luck!

Jeff
Jeff Shirhall

I have had that problem on two occasions. Both times were faulty plug wires. The repair shop went through two sets of plug wires the first time so don't discount the fact that the plug wires you installed may be faulty. Try another set.
Mike Strong

I always travel with a spare set of plug cables already connected to a spare distributor cap. If I run into such a problem, it takes less that 2 minutes to switch dist. caps and cables. This usually happens after I do a 1,500 psi power washall over the engine and ancilliaries under the hood, usually just before I'm going to put "TRusty" in the concours show.

Don Elliott, 1958 TR3A, Montreal
Don Elliott

This thread was discussed between 23/09/2003 and 10/10/2003

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