Suggestions for non-Magnum 360 that started running badly?

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Bill Crowell

Bill Crowell

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One day I went to start up my '62 Valiant resto-rod with a non-Magnum 360, and it had a huge miss. Wouldn't idle. It will run if you hold the RPMs up, but still seems to have a miss.

I've squirted carb cleaner into the idle jets and carb throat, with no improvement.

Sure would appreciate it if you guys would suggest some other things to check.

Thanks very much.
 
Vacuum leak on intake manifold. Check intake bolt torques and then Vacuum guage it.
 
Also check timing
Fresh cap/rotor/plug wires
 
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Sure seems like a vacuum leak to me, too, but I'll be durned if I can find it so far.
The engine won't keep running, even with the idle cranked way up, so I can't check the manifold vacuum!
Thanks for the suggestions. I will try them and report back. But I may also have to have a friend who's smarter than I am come over and advise me.
 
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Egr equipped? If so block it.
 
I have thrown some parts at it over the past year, thinking that it might be electrical: MSD cap and rotor, Accel wires and new plugs. The only other spark issue I'd like to check before focusing completely on engine vacuum is the reluctor gap in the Mopar EI distributor. Now I'm an amateur mechanic, and am finding this pretty hard to do because the distributor is at the back of the block and the reluctor is toward the rear of the distributor, pretty close to the firewall. Have any of you guys figured out a way to more easily measure the reluctor gap on the LA small block?
 
Pull the distributor? That may be easier for some....but maybe not for everyone. Probably not a good idea for a new mechanic.
Rotate the distributor a lot and then re-set timing afterwards? You need a timing light and know how to use it right.

BTW, you are supposed to use a non-magnetic feeler gage (not steel).
 
I was scratching my head on a similar issue a few months ago, and found it was a vacuum leak. I had checked all areas multiple times that I suspected had leaks at and around the engine, but as it turns out the leak was on the brake booster. Mind you I have had booster leaks before, but this time the leak was not bad enough to be detected in a lack of performance or noise at the booster, but was large enough to where it was causing the poor running engine. Leak was at the booster check valve seal. No booster likely on a 62 abody, but thought I would share since it is a resto-rod, good luck.
 
Bill Crowell said:
One day I went to start up my '62 Valiant resto-rod with a non-Magnum 360, and it had a huge miss. Wouldn't idle. It will run if you hold the RPMs up, but still seems to have a miss.

I've squirted carb cleaner into the idle jets and carb throat, with no improvement.

Sure would appreciate it if you guys would suggest some other things to check.

Thanks very much.
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How many miles on the timing chain?
 
"Probably not a good idea for a new mechanic."

I'm not really a new mechanic, Mark. I am moderately skilled, but not nearly as smart as a lot of the guys on here, so I guess it won't kill me to be honest about it.
 
Gotcha and good deal. I really don't have any tricks for that unless it is pull the hood and climb up on the fender!
 
Bill Crowell said:
One day I went to start up my '62 Valiant resto-rod with a non-Magnum 360, and it had a huge miss. Wouldn't idle. It will run if you hold the RPMs up, but still seems to have a miss.

I've squirted carb cleaner into the idle jets and carb throat, with no improvement.

Sure would appreciate it if you guys would suggest some other things to check.

Thanks very much.
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What led up to that "one day"? Just fill up with fuel? Sat for a couple years, maybe moved it around once or twice? Also, to avoid a lot of guessing, it is best to list Your
equipment as completely as possible up front,....OK now I know You have an OE dizzy type, orange box, chrome box, what coil, ballast,MSD.....carb type, etc...........?
1) Fuel quality....check it.
2) Fuel pressure...check it.
3) Timing light on it..........dropping out or steady flash?
4) Timing mark......where You left it?......Jumping all over?
5) Vacuum gauge.........for Gods sake get a long enuff hose and sit there in the seat and keep it running......what does it read and what is it doing?
6) Battery............voltage B4 & after starting.....12.7.......then steady & around 13.5-14.5?
7) Voltage at the ballast resistor wire from ign. within 1 volt of the Batt.? Or at the MSD if using that?
8) History of this engine..........built recently?.....mild/wild?..............adjustable valvetrain/stock?
 
I got it running pretty well. I found two problems:
I forgot to change the ballast resistor. I had used the old 1.6-ohm ballast for a points system rather than the correct .8-ohm ballast for Mopar EI with an MSD Blaster 2 coil, so I was getting twice as much voltage drop in my ballast as I was supposed to have, my coil primary voltage was too low and my spark intensity was poor.
Then the fuel tank vent was clogged, so I'd get an intermittent lack of fuel in addition to the poor spark.
I still need to figure out how to make the accelerator pump on my ThermoQuad give it a better shot when I goose it. I have all the books on TQs, though, so I will figure it out some day.
 
Bill Crowell said:
I forgot to change the ballast resistor. I had used the old 1.6-ohm ballast for a points system rather than the correct .8-ohm ballast for Mopar EI with an MSD Blaster 2 coil, so I was getting twice as much voltage drop in my ballast as I was supposed to have, my coil primary voltage was too low and my spark intensity was poor.
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There ya go...
And FWIW to anyone interested.... the OEM Mopar ballast resistor is 0.5 to 0.6 ohms cold, points or electronic. So even the MSD 0.8 ohm cold ballast is not quite right for most of the stock Mopar ignitions. I always look for an OEM ballast on ebay. (And yes there is a 2 part ballast used for a year or 2, with the 5 pin modules, but the primary coil half of that ballast was still 0.5-0.6 ohms cold.)

I have to wonder how many perfectly good stock Mopar ignitions systems got/get pitched due to the wrong ballast resistor....
 
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