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At wits end

R

Ron816

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Newley rebuilt 440 from the get go had popping thru carb on acceleration re jetted carb changed power valve go timing set thought I had it all sorted out went for test ride everything was fine after about 20 minutes started back firing thru carb was barely running limped back to the garage, it felt to me like it wasn't running on all cylinders and I don't mean just one or two it felt like only 3 or 4, I put a timing light on each plug wire and found only 3 cylinders were firing could this be the ignition module
 
If it was still running, it was firing more the 3 cylinders. It may be easier to get a pair of sissy pliers and go around the cap pulling 1 wire at a time while its running and see how it reacts. You will be able to see spark, and you will see if rpm drops or not when a cylinder is dropped
 
Did that no change, definatley not firing on all cylinders I mean it's barely idling

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Did that no change, definatley not firing on all cylinders I mean it's barely idling
 
Long shot, but if you had head work done, are the pushrods not too long causing valves to be slightly open? I had this happen to me after rebuild. HTH.
 
it would help to tell us what ignition , what carb , etc etc.
 
Did have the heads done, length is good car ran fine until it got to operating temp and them abruptly took a nose dive
 
Ron,
Pull the site plugs on the Holley and see if fuel surges out. Could be something got stuck in one of the needle/seats and is acting like an ignition problem.
 
Already checked out carb everything checks out dizzy okay coil okay at this point of frustration I feel like I should have let it die in the field I found it in 2 year resto nighrmare
 
Fuel pump push rod bad? or electric pump and or regulator bad or clogged? can you see fuel at the normal level in the bowls? Bad wires? I had bad insulators on my spark plugs before causing shorting, micro fractures in the porcelain. Bad or melted boots or wires causing dead cylinders?
 
Everything is new, tried different carb,distributor,new plugs, plug wires, cap, rotor, rebuilt motor was popping thru carb tried to rectify by usual process jets, timing , power valves etc got it running great then took for test ride today ran great for about 20 minutes then started running like crap, i put a timing light on all plug wires and only strobbed on 3 wires and it acts like its running on only 3 cylinders all I'm asking is could a bad ignition module cause a bad miss fire? When I tell you I checked everything I checked everything
 
We need more details on the engine. Stock build or modified?
Assuming you dont have an oscilloscope, you will have to resort to some basic diagnostics. Do you have a vacuum guage? That will give us a pretty good idea of whats going on. If not, pulling all the spark plugs and checking their condition followed by a compression check maybe.
 
Well did you check the signal from the box to the distributor? Or just try another box?
 
Did you adjust idle mixture? If its a holley DP all screws need to be set the same.
 
Mild build 30over stock cam Holley 850 primary jets 74 secondaries 76 pv 6.5 did not replace module yet parts store was closed will replace tomorrow vacuum was fine @15 timing good, set curb idle to max vacuum, car was running fine so how could any of those settings change and cause the car to barely run? engine shakes give any throttle and explodes thru carb
 
ron hang in there i have that same blackcloud you have check your ecu/ign mod/wiring could be something totally diff from what youve done shut it down and clear your head....its happened to me see my posts ive chased ghosts plenty of times few beers bed and restart
 
Thanks man I really appreciate the support I found this car dying in a field I Vermont big block 4 speed doesn't get any better than that in my book car needed everything when I tell you everything I mean everything floors quarters wheel houses trunk drops rockers firewall fenders I rebuilt the entire car including the motor and that's been the down fall of this whole build at this point I'm just burned out I know I'm a damn good mechanic but I feel like this one might have beat me
 
Backfiring back thru the carb could be timing or valves not closing completely. Are you sure the valves aren't too tight. Bad vacuum leak can cause backfire in the carb too.
 
It was running fine then start going down hill
 
And it has chrysler electronic ignition? Orange box? Sounds like it could be ignition crapping out. Also, carb jets should be spaced out more. 8 jet sizes between primary and secondary. What how black were the plugs when you changed them? How black are they now?
 
Ron,
Hang in there. Your car is talking to you. You mentioned it runs fine for 20 minutes and then goes down hill. If it's consistent like that, the common denominator is heat. If you let the car cool down completely, does it start and run fine without having to fiddle with it? Are the cylinders that quit the same ones every time? I agree with a possible vacuum leak although the backfires could just be a result of all that raw fuel from dead cylinders. The other thing that comes to mind is the coil. Coils will quit at high temperatures. I might have missed it but I didn't see where you mentioned trying a different coil.
 
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