TR4/4A I'm Trying to Tune, Again

[KVH]

You'd think I could do this by now. Forty-four years since my first TR4.

I've got pre-ignition (run on) worse than ever, fast overheating at long idles, jumpy idle speeds (fast, slow, whatever the mood might be), and smell of fuel too strong.

So, I'll check timing again, point gap and all that. But with the overheating, am I too lean on the carbs? I opened the jets 14 flats and balanced the air flow correctly. Wouldn't the jumpy idle mean something is wrong at the carbs?

As usual, thanks in advance for the good help around here.

 

[TR3driver]

When you check the timing, look at it what the mark does as you slowly rev the engine up and back down. It should advance smoothly, as a direct result of engine rpm. If it puts on a light show, your distributor needs attention.

Otherwise, it's just the usual detective work. Be assured that, no matter what, the problem will be the last place you look.

 

[tdskip]

Did anything change on the car right before this happened? If no, would a torn carb diaphram do that?

 

[KVH]

I think the only change was me fiddling with idle speed and mixture. I have SUs so no such part. I think I set mixture right but maybe not.

 

[sp53]

The run on might be carbon build up from running to rich because one of the jets did not return. Or maybe a needle did is not closing on the float and is letting too much fuel in. I am think carburation.