Black smoke. Opinions (and facts) needed

Just completed a head gasket job on the series 2a. Had a substantial loss of power and smoke that would transition between gray and white. Found the copper head gasket was blown between cylinders 2&3. After buttoning up the engine with a new head gasket, it sounds (and seems to run) much better, but the black and white smoke from the exhaust has increased. I’ve noticed that the distributor internal LT wire has deteriorated to an extreme level, and ordered a new one, but I am not convinced that will fix the issue. I’ve set the carburetor as lean as I am comfortable with, and the issue persists. Any thoughts or advice?

Generally speaking; white smoke is coolant, black smoke is fuel, and blue smoke is oil. The only thing you may be doing with the "idle" mixture screw is leaning out the idle circuit, not the main jet circuit that comes in after idle. A stuck float may cause an over-rich condition. And various vacuum leaks can affect the mixture of the carb. also.

'99 Disco II
'76 Series III 109 hybrid

After installing a new distributor, the problem is less but still present. I adjusted the timing to 6 degrees BTDC with the vacuum disconnected and capped (using a timing light), but noticed that attaching the vacuum advanced changes the timing advance to 30 degrees at idle. My next step is rebuilding the carb, but it feels like a shot in the dark. I’m wondering if I set the timing with the idle too high, but everything seems to be running well. I drove 20 miles with 5 passengers over the weekend and it performed at a 7/10. Compression check was very good. I just want the smoke to stop.

It's been many years since I turned wrenches for a living, but as I recall the vacuum units on distributors were either vacuum retard at idle (connected to the vacuum of the intake manifold) or vacuum advance off idle (connected to the appropriate carb port). Either way the timing would advance off idle. Having 30 degrees of advance at idle seems incorrect and counterproductive, as you'd want the ignition to advance as engine speed increases.

Black smoke sounds like it's running too rich though. Perhaps a carb rebuild would help. Does it have the standard Zenith carb, or has it been retrofitted with something else that may be incorrectly jetted?

yea, agree, the timing is advancing too much, and that wire in the distributor....... another thing may be insufficient air supply. check the butterfly valve(s) in the carb throat, if you have a auto choke on there, especially a electric one that could be a problem too. If you've done a good job on the head gasket and the compression is good (and holds) you are probably confined to carb/distributor issues ........... of course there is the valve drive timing ? ... but we assume you never touched the timing chain etc?

I did not touch the valve timing. I checked it and everything seemed to line up perfectly.

A carb rebuild is coming, just waiting on parts.

I have a Weber 34ich and I don’t think I have ever taken it apart🤔 but who knows at this point. It’s been a long decade with this truck. I started with the Weber recommendation on the air/fuel screw. Tighten all the way, then back out 2.5 turns. This seemed rich, so I tried turning it in 1 turn (1.5 turns away from shut). Dare I lean it out more?

The distributor is a new electronic one now, but 6 degrees BTDC with no vacuum and 30 degrees at idle with vacuum attached is the same reading I had with the old one.

Thanks for the replies.

If you have that much advance with the vacuum line attached, you're using manifold vacuum. You should be using a vacuum source above the throttle plate at the carb., this gives vacuum to the dizzy slowly, and only when you accelerate. Your engine will tell you when the idle is too lean to run properly. A vacuum gauge will tell you the lean best idle as well, and a bunch of other things too, such as too high an idle that drops your manifold vacuum.

The distributor vacuum is attached to the carburetor above the throttle plate, which is why the extra advance is so strange. I will be adjusting the idle down and checking the vacuum when the new vacuum gauge arrives tomorrow.

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Originally Posted by Sherony

The distributor vacuum is attached to the carburetor above the throttle plate, which is why the extra advance is so strange. I will be adjusting the idle down and checking the vacuum when the new vacuum gauge arrives tomorrow.

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Not too related but back in about 1978 or so I installed a smiths vacume guage, I like the smiths of that era, nice chrome, big bright letters/colors. I got another one but it cost about $70 used and had to be imported from England. I've never had a smiths guage go bad though i've had the amp/oil light shaken out of the speedo.

Since you have a Weber carb, TerriAnn Wakeman has some things to check when you rebuild yours: http://www.expeditionlandrover.info/...weber34ICH.htm Possible yours is jetted wrong.

I remember working on Webers back in the day when Fiats were common. I recall frequently cleaning clogged idle jets, which were accessible from the top of the carb.

The mystery persists. Vacuum at idle was registering a little low at 13 (measured at the carburetor). I drove the truck about 20 miles on country roads at speeds of up to 65mph, and everything seemed to run fair. It is running a little hotter than usual, and it’s hard to remember the power before the head gasket, but I managed fine with 5 adult passengers.

I’m still having trouble understanding why the vacuum advance changes so much at idle compared to static.

Just took the carburetor apart and it is quite clean with no noticeable clogs. Still planning the rebuild when the parts arrive.

Everything seems to run well, it just won’t stop with the black smoke.

When removing the carb I noticed some smoke/steam emitting from the manifold vacuum for the break booster. Not sure if that’s relevant.

Thanks again for the replies.

did this malady come on all of the sudden? where it was running perfect then this?