help-popping up through carb-seems to be dist/cap/rotor issue???

[john27pa]

Ok- I have a 74 Duster with a 78 360 4 bbl. My car just started to pop up through the carb a while ago. I thought and was told by many that this is a cam issue. Makes sense and sounds like it would be. Then my dad says-check your cap and rotor, replace them. ok ok, here it goes- a few months ago, I bought new/reman distributor and new cap/rotor/ wires/ and plugs. Ran great. A few weeks later-popping through carb. High mileage engine-so goes to make sense that its the cam. It would pop loudly around 2000 rpm-whether in idle or in gear.
Today- I replace the cap and rotor. I can rev up to atleast 3500 rpm in nuetral with no popping sounds heard. When in gear- it still "pops" around 2000 rpm but not nearly as bad. Now when it pops- it doesnt sound like a piston is going to explode. I bought BWD brand cap and rotor-same as last time. Thing is this time- I cant seem to align the cap on right- that square chunk out of cap is supposed to align with the metal tan on distributor-next to the hold down clip. The cap is 180 off, no biggie-seems to not move any and its still aligned with spring hold down snaps. When I took off "old"-only old by about 4 months??-rotor and cap- there was a brown tint around the metal band on rotor where rotor button goes up against from dist. Maybe burned?? arced?? whatever.
Seems like I have arcing going on inside my distributor and cap area. How do I fix? All this was replaced 4-6 months ago and worked great until 2?? months ago when I thought it was the cam.
I have my distributor advance hooked to above port on my eddy 600cfm-the left front port as you are looking at it standing in front of car. Idle seems to be just a little high-1200 or so??. Feels slightly cammed at the stop lights, but timing is good-close anyway. Not sure what else to say on here for info. Could something be bad like a coil? volt reg? the electronic ign unit? distributor?

 

[67Dart273]

This sounds like a rotor phasing issue. Is the reluctor installed correctly? There's one or two arrows on the top of the reluctor, and two places for the pin. On a small block, the pin must be in the CW arrow, in the photo, the one on the right

Also, I would NOT keep that cap. Get one that fits correctly

And, take one of your old caps and cut/ drill/ beat a hole in it so you can check phasing. Then when you get the new cap carefully mark the position of the two to confirm they are the same. One way to do that is to lay a square from the bottom of the old cap so the square comes up through the midpoint of any tower, and mark the cap. Then lay the cap on paper, trace around it, carefully mark the key and the scribed line you made, and then compare the new cap.

All kind'sa info on rotor phasing:

[ame="http://www.google.com/search?um=1&hl=en&newwindow=1&safe=off&tbo=d&biw=1366&bih=647&tbm=isch&sa=1&q=rotor+phasing&oq=rotor+phasing&gs_l=img.3..0i24l3j0i5i24l2.266796.268715.0.268836.13.13.0.0.0.0.157.1193.7j6.13.0.crnk_timediscounta..0.0...1c.1.St7AkheSK9s"]rotor phasing - Google Search[/ame]


Also check your plug wires and coil wire for opens, replace the plugs at least to test.

I would be checking the valve train, IE pull the covers, carefully pull it through a complete engine cycle, and compare valve lifts as close as you can. A flat cam should be fairly obvious, at least one bad enough to cause popping

It also could be low ignition voltage, either on the 12v end of things or the hi v. side, bad coil, etc. Check, or better yet, clean the ground point of your ECU. Use star washers, and while you are at it, do the same for the voltage regulator

Check ignition voltage with key on/ engine off. Put one meter probe on battery positive, and the other on the switch side of the ballast. You are hoping for a very low reading, the lower the better. Over .3V (three tenths of a volt) means you have a voltage drop problem in the harness.

An easy way to further check, is to test run the car temporarily with a big (no14) clip lead from the starter relay stud to the switch side of the ballast. Make sure it is not on the coil side.

 

[john27pa]

Thaats alot of good info- will check these day by day-weather permitting. My garage roof leaks real bad and the walls seem noneexistant lol. Thank you for all the good info. I do have a warranty on the distributor-maybe I will just order a new one and switch them out. Then also do all these checks as it couldnt hurt.

 

[john27pa]

To all that helped and future searches- it was the timing chain. I had about 1/2" play on it. The cam "looked" good. Didn't mic the cam. There was only a few more steps involved- so I changed the cam also- put a stock cam in it for now. No popping at all now and timing chain is nice and tight, bought a stock timing chain and sprocket set for undewr $40 from advance auto. All runs great now.