ok, i hadf it running beautifuly this afternoon, actualy went 6 miles to the walmart and back with no issues aside from a steadily increasing metallic rattle. i pulled back in still idling great and shut it off, imediatly thought it could be a lose heat shield...nope, pulled the valve cover to check the rockers...nope, all still in spec, looked the carb over, no signs of leaking. put the valve cover back on and started it up and idled and then the rattle got louder and the idle speed was no longer constant, i shut it off, checked the distributor rotor, put it back together and no will not even start. i reset the timing to factory 7 times before i got fed up. no matter where we put the timing it cranks strong and only backfires and can smell the gas in the exhaust system. this is going from annoying to aggrivating. please help. this seems to be an ignition issue now.

 

oh and forgot if you need to know, 1987 mazda B2000 2liter 4cylinder carburated with the 5 speed manual regular cab long bed.. bone stock whopping tire tearing 80hp.

 

A metallic rattle and spark at any which time would indicate a mechanical problem with the distributor itself. So I looked for a picture of the distributor and found this one:


There is the mechanical advance device with two little springs and fly weights. Then there is the worm drive at the bottom (right end in the pic).
These are the 2 places I see that could cause metallic rattles.
I bet your advance devise is shot. Open up, tap it with a wrench or screw driver. If it sounds similar to the metallic rattle you heard then the odds are you found it.
There is also a vacuum devise. See if the vacuum line to it is o.k. If it is o.k. replace the distributor with a known good one.

 

Backfire is timming. As suggested investigate the distributor rattle. You are on vacuum advance till what time (high rpms) you are on mechanical advance, thats the two springs on the top. Racers talk about curves refering to distributor spring mechanical advance. I'd suggest take #1 cylinder to TDC compression stroke, put the distributor rotor to #1 with the firing order rotor point to plug, in this case I do not know Mazda rotation, I belive looking down on top of it clockwise. Then set the timming at idle with a timing light.

 

well i decided to haver my friend crank the engine over with the cap off and the distributor was skipping around like it wasn't fully meshing with the cam gear. i took the upper cover off and noticed when the crank is set to ! TDC the mark on the cam spricket points between A mark and B mark... well that just ain't right. so i stripped the radiator, fan and other goodies off, pulled the lowewr cover off and saw the crank sprocket notch lined up and manualy turned the engine around and watched the belt skip a tooth..... belt is in good shape but the tensioner spring is weak!!.... so seems i'm in need of a new spring. i'll be pulling the belt off and the cam sproket to check the dowel and removing the distributor drive housing to check the gear. i hope the gear is fine.. otherwise i may need a junkyard cam... gotta love these engines.

 

so things gone from bad to worse this morning.. these pix will explain.

 

Up late I see. My logical observation:
First pic: middle smooth pulley looks a little off centre.
Second pic: Teeth worn.
Third pic: this is what teeth go against. Mind as well replace that one since teeth worn.

 

I kind of think you found the problem, nikkie!

 

the smooth pulley is the tension pulley and is off center because its free hanging, the worn teeth are due to the angle of the camera, the teeth are actualy deep, but is getting replaced any way due to the fact that its warped. now my next trick is to ask my boss for a $150 advance and order a new camshaft from rockauto.

 

update. new cam on the way.