Gerald Morris
Senior Member
Greetings Moparians!
I started getting some carburetor backfiring yesterday, and am checking This and That in search for a remedy. I thought this particular set of symptoms most likely caused by air horn warp, but NOW have a wholly different hypothesis.
Just to make sure my timing had NOT slipped from the canonical 12.5 degrees BTDC I set this past March, I got out my timing light, put the pickup on the #1 plug wire, and got NO response from the timing light.
So, I checked how well the old molex connector was plugged into the light, seated it firmly, STILL DARK until I goosed the throttle a bit and ECCE, FIAT LUX!
So, I diddled with this a few times, consistently observing that #1 doesn't give me any inductive pulse strong enough to trigger the timing light until I goose the motor up to around 1000 rpm, twice what I like my curb idle to be. SOOOOO... I surmise that I'm not getting very good spark voltage on #1 at idle. This is consistent enough, seeing less than 12V on the dash voltage meter I normally refer to for the overall electrical health of the car. My alternator doesn't charge well until I get the engine turning over ~700 rpm. Those old roundbacks are like that, and I want to replace the thing some day.....
So, just to check my timing, I put the inductive pickup on Plug #6, and saw that nothing had changed since my March timing job. THAT read JUST FINE at curb idle.
As soon as the damned heads cool down enough, I'm going to inspect plug #1, to see if it has crapped up so badly as to have a resistance beyond the fuel-air mixture at power stroke pressure.
Wise Thoughts VERY welcome at this time.
Thanks in advance (12.5 BTDC of course)
I started getting some carburetor backfiring yesterday, and am checking This and That in search for a remedy. I thought this particular set of symptoms most likely caused by air horn warp, but NOW have a wholly different hypothesis.
Just to make sure my timing had NOT slipped from the canonical 12.5 degrees BTDC I set this past March, I got out my timing light, put the pickup on the #1 plug wire, and got NO response from the timing light.
So, I checked how well the old molex connector was plugged into the light, seated it firmly, STILL DARK until I goosed the throttle a bit and ECCE, FIAT LUX!
So, I diddled with this a few times, consistently observing that #1 doesn't give me any inductive pulse strong enough to trigger the timing light until I goose the motor up to around 1000 rpm, twice what I like my curb idle to be. SOOOOO... I surmise that I'm not getting very good spark voltage on #1 at idle. This is consistent enough, seeing less than 12V on the dash voltage meter I normally refer to for the overall electrical health of the car. My alternator doesn't charge well until I get the engine turning over ~700 rpm. Those old roundbacks are like that, and I want to replace the thing some day.....
So, just to check my timing, I put the inductive pickup on Plug #6, and saw that nothing had changed since my March timing job. THAT read JUST FINE at curb idle.
As soon as the damned heads cool down enough, I'm going to inspect plug #1, to see if it has crapped up so badly as to have a resistance beyond the fuel-air mixture at power stroke pressure.
Wise Thoughts VERY welcome at this time.
Thanks in advance (12.5 BTDC of course)