Running rich

[Geoff]

Hi all, I have an S4 elan, SE engine, distributor new from distributor doctor, carb chokes, jets etc. are as per
Lotus workshop manual, engine runs well no flat spots idles fine accelerates well, adjusted mixture numerous times by ear and with a colour tune plug, flame turning from orange to blue, problem is sooty exhaust and black spark plugs, tried weakening mixture slightly and engine spits and pops and won't accelerate, any advice on how to solve this would be appreciated,

cheers Geoff

[pabbage]

What plugs are you using and have you checked the timing?

[billmoore42]

My 67 S3 with DCOE 31 Webers. When I first got it, I had to switch to a one richer idle jet (50 F8) to keep it from spitting and popping at low speeds (I am using California gas 91 octane with ethanol added, and the previous owner was using 89 octane pure gas and did not have this problem).

I then balanced the carbs and tuned it for highest rpm without the benefit of a Colortune with the mixture screws. I found that my plugs fouled if I spent too much time idleing in traffic, so I switched to NGK BP5ES from BP6ES. This switch has stopped my fouling problem, and the plugs are not as sooty.

I have driven about 2000 miles with this setup, and it seems to work pretty well on my 1700 CC tall block motor. Gas mileage is not very good around town, around 17mpg.

I am not an expert, but believe the Elan is a bit overcarburated for idling and city driving, and tends to run rich at idle. I hope this helps!

[2cams70]

If your car is running well why fiddle with it? That should be the golden rule for a lot of people on the forum.
Sooty deposits are entirely normal for cars designed to run on leaded fuel now running on unleaded.

In my many years of dealing with old decrepit cars I've discovered that it's the fiddling that causes the most issues rather the vehicle itself. By all means relieve the fiddle itch by polishing your cam cover but think long and hard about tampering with deeper things when everything is working well as is - especially when it comes to replacing original OEM parts with substitutes.

[Dellortofan]

Driving at 55 does not keep a lotus alive!
Seriously - idling and cruising about is not it's style...