Questions and Answers

Dodge Charger Backfiring Q. Having a problem with intake backfire. It only does it when I "punch it". 1968 Dodge Charger 383 - 4 barrel (Carter AFB) Auto Transmission Factory A/C

Following is a list of things that I have done:

• Rebuilt carburetor
• Compression check - 120 to 130 psi each cylinder
• Vacuum test - 15"
• Distributor and oil pump drive gear. Notch is parallel with crank with #1 at TDC
• New points, distributor cap, plugs, wires, condenser, rotor.
• Points set at 30° with dwell meter.
• Pulled plug wires one at a time - still backfires on every one of them.
• Accelerator pump - Looking in carburetor. I can see gas coming out of both discharge jets.
• Timing - supposed to be 5° BTDC @650 rpm. I have the idle screw turned all the way out. If I set the timing at 5° it idles at 850 rpm. Can't get it to 5° and 650 rpm.

Help!
Buddy

A. The vacuum is a little low but that is probably due to the low compression. I would like to see the vacuum around 18" or 19" on this engine. Compression should be, at least, 160 psi.

So basically I'm seeing a tired engine, nothing seriously wrong in any one area, just a lot of little things that when combined, leads to a bigger problem.

I think the main problem here is the timing chain. It is probably stretched out and flopping around. One way to check for this is to, by hand, rotate the engine until the mark on the crankshaft pulley lines up with the 0° timing mark.

Now, slowly turn the engine backwards, watching the distributor rotor. When the rotor just starts to move, note where the pointer is. If the engine has turned back more than 2°, it's timing chain time.

Another possibility is weak valve springs. This, too, will cause backfiring on hard acceleration. I think in addition to everything else, the carburetor may be bad. Each mixture screw should only be out 2½ to 3½ turns.

Dodge Charger