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Mack

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Almost time to put my "76B away for the winter up here in up state NY, but I just can't seem to stop tinkering?? Anyway, I went for a nice ride the other day and when I got home I decided to pull the plugs to see how well tuned the car is, well plug one and two are that nice sandy brown color we are all looking for, but three and four were a little on the black,dry side is this a carb problem? or a valve train out of adjustment? for info I'm using a stock ZS carb and the motor is a rebuild with about 1100 miles on it. Thanks, MACK /ubbthreads/images/graemlins/cheers.gif
 
Do you still have emissions parts on the car? The first thing that comes to my mind is the gulp valve may be leaking a bit giving you a leaner mixture on the front two. Also, if you do a lot of down shifting, this would cause the gulp valve to open and let more air into the system, but the gulp valve is connected right next to the 1-2 intake port so those cylinders will get a slightly leaner mix compared to the back two.

Try blocking off the gulp valve, and taking it for a spin. If your plug colors aren't all the same or close to the same with the gup valve blocked off, then I'd start worrying/looking for a possible problem in the system.

I've had my gulp valve (anti-backfire valve in some circles) stick wide opena couple of times and that REALLY makes the car run rough. Recently the same valve has developed a small leak where it never completely shuts off. When it doesn't completely shut off then it's continuously leaning out the mixture in cylinders 1 & 2.

So yeah, if you still have the emissions equipment on the car blcok off that gulp valve go for a spin then recheck the plugs. If there the same after blocking it off, then I'd have to say you're doing ok... /ubbthreads/images/graemlins/smile.gif
 
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Anyway, I went for a nice ride the other day and when I got home I decided to pull the plugs to see how well tuned the car is, Thanks, MACK /ubbthreads/images/graemlins/cheers.gif

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Hi Mack,
To get an accurate plug reading that is truly representative of engine conditions, you need to start with fairly clean plugs, run the engine under load for a while, cut it off without idling, & check plug color. If you let it run under light load/idle conditions, the idle mixture which is relatively rich, will mask the true plug readings. It wouldn't be unusual for the plugs to darken unevenly during idle & then burn off to their true color when the engine is loaded.
D
 
Thanks for the response, as far as the polution equipment goes, the airpump and most of the other stuff have been removed. The gulp valve is still in place, next question, can I remove the gulp valve and plug the manifold? Also, I haven't had a chance to check the plugs as Dave suggested yet, but will forward the results as soon as I do. Thanks, MACK
 
You should be able to remove the gulp valve and plug the hole. As a matter of preference, I'd make sure the EGR valve is functioning properly and leave it in tact as it's supposed to reduce HC emissions, lower ignition temperature, and reduce ping. There's all kinds of information on the web covering why EGR valves are in use (mainly to reduce HC emissions) and many of the side effect benefits that they have. Also, there are also just as many sources on the web that will tell you what happens when they go bad. Either way, I've come to the conclusion that EGR valves are good, and don't hurt performance enough to warrant getting rid of.
 
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