Help with backfire and smoke

I got my Spitfire running again, and not only does it smoke out the tailpipe, but it backfires when you let off of the accelerator. Otherwise, the motor seems to run pretty well. It doesn't miss or anything. I really don't know much about these cars, so can anyone give me any suggestions here? I really need to get it cleaned up in order to smog it. My girlfriend and I would like to take it on a road trip in a couple of weeks, and I need to get it registered first.

------------------

Originally posted by Mojo:
I got my Spitfire running again, and not only does it smoke out the tailpipe, but it backfires when you let off of the accelerator. Otherwise, the motor seems to run pretty well. It doesn't miss or anything. I really don't know much about these cars, so can anyone give me any suggestions here? I really need to get it cleaned up in order to smog it. My girlfriend and I would like to take it on a road trip in a couple of weeks, and I need to get it registered first.

Click to expand...

Well, of course checking the timing would be a good place to start. The smoke could be over-rich fuel OR burning oil (bad valve guides and/or rings). But since you mentioned the backfire, I would suspect over-rich fuel mixture first. The over-rich fuel situation would be a lot easier (and cheaper) to fix of course.

Best place to start is just to do a proper tune up - change plugs, distributor rotor/cap, check timing, etc. (The backfiring really does sound like a timing issue). I'd also, of course, check the carb. Rebuild kits are not too expensive. You should also check that your carb float/ needle valve is not sticking. You can have a simple compression check (wet/dry) done to determine (to some extent) the condition of your valves and rings as well. First do a dry test, then if the compression is low in one or more cylinders, do a "wet" test. The wet test is where you put a couple teaspoons of oil in the cyls (pour it in through the spark plug holes), then check compression. The oil seals the rings, so that if the compression comes up to near normal, you can suspect the rings are the problem. But, if the compression stays low, the valves are likely at fault, and if it come up a bit, but not to "normal" then suspect both.

Oh, one more thing...you can determine if your running too rich by pulling the spugs and looking to see if they are very black and sooty. If they look nice and brownish, with not a lot of excess black carbon soot, then the carb mixture is probably not the problem.
Without seeing the car, the actual color of the smoke, etc., its hard to diagnose, but I'm just trying to give you a few ideas to try. Also, if the smoke is blueish - suspect rings and/or valves/guides (expensive to fix). If the smoke is black - suspect rich carb mixture (less expensive to fix). If the smoke is WHITE - oh dear, you are burning anti-freeze/water and probably have a blown head gasket.

Good luck and keep us posted
George.

All of the regular tune up parts are new. I've already set the timing. I have a feeling that there's a vacuum leak somewhere as I hear a whistling sound when it's running. I hope it's not the diaphragm in the distributor. I have a feeling that my problems are coming from the carb, and unfortunately I know very little about these side sucking strombergs.