TR4/4A Tune Up Order - Fuel and Ignition

[RJS]

Hi All

I will be installing new plugs and plug wires and thought I'd use that as an opportunity to fine tune fuel mixture, plug gap and ignition timing. Is there a right or preferred order to adjust these three things?

Thanks

Bob

 

[Hamish Racing]

I’d start by starting and running the car as normal just to know it does start and run. (useful later if you run into issues !)
Gap the new plugs, gap the points, clean the rotor arm contacts (the top and the arm), clean the dizzy cap contacts inside, replace the plug wires 1 out 1 in so you retain the correct positioning. ( so many instances of people pulling the lot off and then inadvertently putting one or more new ones in the wrong order !)
then start the car get it running and nice and warm.
you may wish to check the valve gaps
i’d then do the timing dynamically ie running.
then the mixtures /carb balance and set tick over.
would be my starting point. And be prepared to revisit carbs and timing as required.

 

[RJS]

Thanks Hamish. Everything is in very good nick - car starts and idles at 650RPM. Car runs terrific other than an ever so slight rhythmic drop in engine note pulling up a steep hill in 4th gear. Also, fuel mixture appears to be spot-on but, MPG's seem down about 10% (which could be many things). Thinking my 21 year old ignition wires could do for replacement, and while I am at it, renew spark plugs too. Then I realized I have not touched the ignition timing in the 23 years I've owned the car so, may check on that too.

I think I will start with setting plug gaps, then double check fuel mixture, then fine tune ignition timing.

Bob

 

[CJD]

Always do the electrical work first, followed by the carb work. The book requires you to set the timing based on road tests, to get the most advance you can without detonation. Once the final timing is set, you may need just a "tweak" of the mixture and idle speed to bring it back down.

 

[sp53]

Do the points before the timing because setting the points can change the timing and not the other way around. I set the timing with a timing light at a low idle about 800 rpm and about a ¼ inch past the mark toward the driver side. I set the carbs running the best I can and then after that I pull the plugs and look at them for carbon. I have found around here in colder Washington that warming up the car too much with the choke out can carbon up the plugs, so I get moving and baby the car to let more air in until it is warm. Once the car is warmed up and driving around for probably 20 minutes or more. i stop the engine, and I let the car cool down and pull the plugs. If I see carbon, I lean the mixture by turning the richness nut up a turn or maybe 2 turns depending on the amount of carbon. Sometimes this procedure takes a few times to get the fuel mixture correct. If the car performs poorly after the fuel mixture is correct. I look at the timing with a light again and watch to see how much the timing advances when I rev up the engine. The timing mark should move probably an inch and come back reasonable quick.

Like said you might need to tweak things like idle and timing. Some things I look for is how the car performs a little cold compared to totally warmed up. The car should not take off easily in second gear from like 5 mph when the engine is a little cool. The car should hesitate until it warms up more. When engine is cool , and I go to start the engine, the engine should need a small amount of choke or the engine is running too rich. I find sometimes the engine needs an hour to totally warm up around here anyway, or the idle setting will need adjustment to a totally warm engine.

Steve

 

[Sarastro]

You're doing, in essence, a full tune-up, so it would be a good idea to adjust the valves at the same time. Do this before adjusting the carbs, as the carb adjustment depends on it somewhat.