390 new points now backfiring

[390owner]

My 390 just died today when pulling into a parking lot at work. I replaced the points and condenser and it fired right up. Got it home doubled checked my gap .17 . Then I stared it up and reved it up and it starting cutting out then back firing real bad. Re checked the gap still .17. What is the problem. It idles fine but when I rev it a loud backfire.

[jayb]

I've had them do that when the condenser is no good.  Try reinstalling your old one.  Back when I was running points, I got a few brand new condensers that were bad...

[cjshaker]

I've had them do that when the condenser is no good.  Try reinstalling your old one.  Back when I was running points, I got a few brand new condensers that were bad...

x2
I still run points in a couple of my engines.

[wayne]

Jay is right keep your old parts new ones are junk even points file your old ones as you can.I get on ebay you can find some nos autolite some times.

[390owner]

  that is about what I thought. I get sick of buying junk. It cost me 30 dollars for the set at the local part store. I will install the old condenser and see what happens

[chilly460]

Helping a buddy get his early Bronco running, we've replaced a condensor and two sets of points in it....and it's moved maybe 2 miles.  Amazing. 

I'd heard the horror stories, now deciding if it's worth the trouble to go Pertronix or just file the old points and do what I can to stockpile a set or two of NOS Autolites. 

[wayne]

I was on ebay to day they have some nos autolite and some blue streak l have had good luck with them also if you oil the wick they stay gapped  a long time.

[badcatt]

I have a 72 Cougar XR-7 with a 351C 2V that I rebuilt the engine in a few years back. This one I did all stock. I had to replace the first set of points and condenser before getting it out of my shop. The second set only lasted about 25 miles. The 3rd set got about 250 miles. I then swapped to a pertronix II. No more problems.

[oldiron.fe]

                                                                                                                                                                           
 in 67/68  put a lot of miles on my top oiler 66 fairlane filed points/ matchbook cover on the road to set gap ! fords points for dual dist. had very high spring pressure even with lube would not last but could rpm very high as long as gap was in order --- longest lasting points were with mallory dist. and points in the 60s - did run mallory 4 lobe dist. hard to set points accurate even on dist. machine but with the big old coil - almost square and about 3x5x5"or so had a hell of a spark-standard/blue streak points were longer lasting as they didnt have the high spring pressure -- for 6000rpm + i like optical or crank pickup best- still use some points -            carried spare condensor /file/matchbook in the day - john/oldiron

[BattlestarGalactic]

Junk condenser.  Typical.  Last one I got new a few years ago only lasted about 100 miles til it shorted out.  I dug in my toolbox and found a crusty old one from decades ago and it ran for the next couple years without issue.

[427John]

Another common problem with vacuum advance distributors is failing to reattach the braided ground strap when replacing the points.I've even seen distributors that were missing the ground strap,the pivot for the movable breaker plate doesn't always provide a reliable ground.

[390owner]

Ok now I am really confused. I replaced the condensor with 3 different ones, replaced the coil, replaced the points with an old set I had laying around, replaced the dist cap and the coil wire. I double checked the plug wires they are in correct order, then checked the top dead center to make sure I have jumped time or something but no it was spot on. It starts before you can get your hand off the key revs fine until about 2500 then starts popping through the exhaust. I can hold it wide open and it will only rev so high then just pops and cuts out. What am I missing. Oh I took it to town this morning it was fine as long as I did not give it to much throttle.

[allrightmike]

You might check your neutral start switch (if auto.) and your ignition switch and any other wiring in the ign. circuit between the switch and coil.

[oldiron.fe]

                                                                                                                                                                  are you 100% sure of dist./engine to frame body /battery/frame grounds --use dwell meter to make sure dist. plate /bushing is not moving -vac/advance weights moving to change dwell -- last/old school go outside after dark- really dark have someone rev. motor -look around dist/plug wire any grounds for good old lighting bugs -do you still have full voltage in system and good resister in system -after all checked are you going lean in fuel system /carb/fuel psi --good luck  john/oldiron

[frnkeore]

With all that you've done on the ignition side, it sounds like it might be running lean.

Put a pressure gauge on the after the fuel pump and fuel filter, then drive it. If the pressure doesn't fall below 3#, it should be ok but, you should do a volume test, also by pumping it into a bottle, while running on the carb on the fuel bowels (be ready to shut it off quick if the bottle fills fast). If it has a screw in filter, at the carb, replace it or by pass it, if the first check is good.

Next checked out the power valve.