Dieseling when engine turned off

My 73B roadster had sat for 6 months or so before I got it, and then I only drove it short distances for the 1 1/2 to 2 years I had it. Once more comfortable with it this summer I began taking longer (a few hundred miles) drives.

The first thing I noticed was that the more I did this the better the engine ran. I'll accept that this was a result of eliminating some carbon buildup from the engine.

The car ran better for 2 or 3 of these trips, and then suddenly began to get poorer gas milage and diesel occasionally if idling a bit high before shutdown.

The spark plugs had been a nice almond color before this began to happen, but now are a deeper red/brown.

I suspect that the car is running too rich now and so leaned the mixture out about a quarter turn on both HIF4s this afternoon.

I'll do a more thorough test of the carbs this weekend.

I think any elimination of carbon should have had no effect on timing but will check that as well. Could it have effected the valve settings though?

So, what should I do this weekend? Readjust the valves? Readjust the carbs?

Thanks,
BH

I find that my 73 does not diesel much after a long run, but will often do so in use about town. Over the years I've not found adjustments to be of any value. dropping idle speed helps (but you have to let the car return to idle). I usually just pop the clutch with the brake on. AFAIK this causes no harm. But it is annoying.

I plan to look into repairing the anti-run on valve installatio that someone who was "helping me" disabled a decade or so ago.

check timing...that was my problem years ago

My 73 has that is I have run it anything more than very easy. I find letting it idle for a 20 or so seconds in the drive that is usually shuts down OK. Other than that I usually dump the clutch. I'll have to look at it thins week. The car is advanced about as much as we can take it.

Have you checked the point gap in the distributor? Its possible that the gap is closing up due to wear and the igniton is getting weaker because of it.

Had same problem -- found that adjusting and synchronizing the carbs did the trick. Turns out that I was running too rich.

Note that just fiddling with the carbs didn't solve the problem -- only fixed it when I went "by the manual", ensuring I had the carbs synched and the idle speed right.

Thanks all.

I forgot to mention that I didn't see how it could be the timing as it was fine before. But I will check it this weekend as well.

I have a Pertronix electronic ignition so unless it has somehow failed points can be ruled out.

My plan is to check the plugs and compression (just for kicks), then the valves, then the timing and finally the carb mixture.

Any other suggestions?
Thanks,
BH

Put anti run on valve back on.

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