TR2/3/3A rough idling TR3B

[pace]

I can't seem to get the roughness out of the idling. This winter, I put new pistons, sleeves, etc. The year before, I put new valves. Can't figure out if this is due to carbs or something else.

 

[AltaKnight]

You will have to take a systematic approach to this.
Look at the spark plugs after a good long drive to see if they are really sooted up, if so then carb/mixture is a likely culprit. Look for any vacuum leaks.
I would start with the ignition system just 'cos thats where most problems lie and it's the simplest to check.
If you haven't already done so replacement of old plugs, ignition wires, dist cap, rotor, points and condenser is a good investment.
Then make sure the points gap is set right, then check and experiment a bit with the ignition timing.
Check/reset the valve clearances.
The last thing to start fiddling with is the carb(s).
But, if that seems to be what's needed then try adjusting the mixture based on the spark plug condition. Rebuilding the carb(s) might be called for if all else fails.
Worn carb throttle linkages can leak vacuum, check by spraying carb cleaner around as the engine is running, if it slows down or stalls then you've found a possible reason.
Of course it could be a bunch of these things all together.
Good luck.

 

[pace]

Graham

Thanks for the input. Have you tried replacing the points with a electronic ignition? If so, how did it work out?

 

[Geo Hahn]

I prefer points, others don't... but in particular I don't much care for the idea of installing points because the current set-up isn't working right. I would favor figuring out the stock set-up then, if you think points are less trouble, more reliable or whatever give them a try.

I too would start with the ignition. In my experience there is a very wide range between 'way too rich' and 'way too lean' where the engine will idle just fine. Leaks around the throttle shafts or elsewhere are another matter and will affect idle... but ignition parts are cheap, you can always use good spares anyway and can usually be tested/eliminated by something as simple as trial & error.

 

[waltesefalcon]

I'm with Geo I prefer points over electronic ignition. They are easy to check, cheap, and easy to change. I'll also say start with the ignition, its much more often the ignition, than the carbs when you have a rough idling car. Make sure to check the ohms on your plug wires, check your points, rotor, and cap, and double check your timing. If all that is cool, then look for a vacum leak. I bet you find it in ignition somewhere though.

 

[Guest]

Mike, check out my post about the Sun diagnostic machine. Rough idle was also one of my symptoms.

Bill

 

[pace]

When you change the gap on your points, do you have to retime your engine? I am using a homemade static light and it seems that when you change the gap in your points, you would have to retime the engine.

 

[pace]

I have suspected the distributor to be the culprit. Now, how do I find a crusty old mechanic with a $30,000 Sun Machine? Thanks for the info.

 

[Geo Hahn]

[ QUOTE ]
When you change the gap on your points, do you have to retime your engine?

[/ QUOTE ]

Yes. Increasing the gap advances the timing (points open sooner and stay open longer) & vice versa.

 

[waltesefalcon]

You don't need a Sun diagonstics machine. Just pull your distributor if you think thats the culprit. Then give it a good once through looking for slop, etc. They really aren't very complicated pieces and are easy to check out.

 

[pace]

I am considering going to the Mallory dual point distributor. Have you had any feed back on this dist?

 

[JFS]

I have run a Mallory dual point distributor on my TR3A for about 20 years and it has performed flawlessly. Its construction is superior to the original; it seldom needs regapping unless the points are worn. I have been very happy with it.

 

[pace]

When you installed the dual point, did you have to install the resistor with it?

 

[Alan_Myers]

Hi,

I've installed the Mallory dual point distributor on my TR4 and am impressed with the quality (although the engine won't be running for a little while yet... so I'm glad to hear others are enjoying good long-term experience with it). I was just emailing info about Mallory to someone else, will repeat some of it here.

For the 4-cylinder TRs here are several Mallory products to consider:

Mallory #2332001 is the non-vacuum advance dual point dizzy that's best used with Weber DCOE carbs. Various advance curves are possible with a kit that's available separately.

#2732001 is the vacuum advance version of the dual point dizzy, most appropriate for use with SU and ZS carbs.

#4532001 is the Unilite electronic dizzy without vacuum advance (Weber DCOE).

#4732001 is the Unilite *with* vacuum advance (SU & ZS).

Physical installation is pretty much the same on all of them. You need to install a drive dog on the bottom of the dizzy shaft, that meshes with the slot in the dizzy/oil pump drive shaft in the motor. At first glance it looks like the dog can be installed two ways, but it can't because the tab and slot are slightly offset. So, watch the orientation if you are concerned where the #1 cylinder wire from the dizzy will be positioned.

Using the dual point will allow running a hotter coil, and in turn can allow a larger plug gap and stronger spark.

The Unilite electronic will also allow hotter coil and stronger spark, along with minimal moving parts and no concerns about points adjustment or wear.

There is a module avail. from Mallory to convert a dual point to an electronic ignition (#562, about $110). I plan to do this eventually, and in several stages to add a multi-spark controller with rev limiter and an even hotter coil.

One of the real advantages of Mallory is that there is a complete line of matched parts that can be used to set up whatever level of ignition you wish. I always get nervous when I see a Lucas distributor fitted with a Petronix module, powered by a Crane coil and controlled by an MSD ignition box, sending juice to the plugs over a set of Magnecor wires! All these items are likely excellent in their own right, but I can't help but wonder and worry if they will play together nicely as a complete system. I'm more confident with a matched set of components from a single manufacturer.

Do watch what coil you use if you go to Mallory. They offer coils specifically for points, for points and electronic ignitions, and for electronic ignitions only.

If installing a new (or rebuilt) dizzy, I strongly recommend taking a close look at the dizzy/oil pump drive shaft, its bushing and the drive gear and its key. The tab on the end of the shaft that drives the oil pump can wear and in extreme cases break. The key can get loose, allowing some slippage of the drive gear. A worn bushing or shaft can introduce some slop in the distributor and lead to faser wear in the other areas already mentioned.

A replacement shaft might be a little hard to find, but I got an upgraded (hardened) one from Moss a few years ago. The drive dog is pretty easily purchased from all the usual Triumph vendors.

I'd shop around for a better deal on the Mallory parts. Last time I looked the Triumph vendors were making a pretty exhorbitant profit on the distributors.

www.summitracing.com stocks or can get most any Mallory part. I've also been recommended www.centuryperformance.com

Cheers!

Alan