Pissed off with motor, want to change

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Mopar to ya

Mopar to ya

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I have had issues with backfiring through the exhaust. I installed a new cam and it ran beautifully all day. I took it to the car wash, drove in running fine, washed the fender wells, started up backfiring. Never dried out, so I changed plug wires. No dice. Then plugs, cap and rotor. No dice. Coil. Uh-uh. Ignition module. No. I am thinking the car wash was a coincidence and I have a flat lobe or bent valve.

I was going to go with a 408 stroker this winter so I could enjoy driving all summer. Now I think I am going to push the timetable up. I need to find a 360 block. There are a few around locally pretty cheap. Does it matter if it comes out of a truck or a motorhome? I don't think so, but I don't have the knowledge base this forum has! I found a running 360 and transmission out of a motorhome for $600 and a non running motor out of a motorhome for $200 less than 15 miles from my house.

Much as a new stroker appeals to me, I would rather wait. Any advice on the popping through the exhaust would be great. I can get it to stop popping for the most part by adjusting the timing, at least until I put it in gear. It's driving me nuts.
 
Before blaming the engine, do basic checks like compression, vacuum tests, power balance (pull 1 plug at a time). Most likely it is un-related to the engine and due to the carb or ignition, especially since it sometimes runs fine.
 
I know this is a dumb question, but did you do the proper cam break in? Sounds like a cam/lifter/valve issue to me ???
 
sounds like the cam, this may sound stupid but did you change the lifters when you did the cam?
 
Did the ballast resistor get even a hint of water on it / near it ?
Those damned things like to POP when they're hot ( been run for a bit ) and water -- even in vapor or mist form -- gets on them / near them .

Take the ballast off and inspect its backside , looking for cracks . Hell , they're cheap enough ; just buy one anyhow and plug it in . If that doesn't solve your problem , it's not much money out of your pocket , and you'll have a spare around for when it does go bad .
 
Yes, I broke it in at 2500 rpm for a half hour. Comp Cam XE268H cam and lifter kit. Would a ballast resistor cause a backfire? I thought they were more start / no start problems. It ran perfectly until I went in the car wash. Drove in fine, backfired driving out. I am down to compression check now. Hoping for the best, fearing the worst.

Bill, would a carb cause backfiring only on exhaust? If it is carb or ignition related, I changed everything in the ignition, so that leaves the carb. I kind of believe flat lobe or bent valve, however.
 
What was your timing set at? Are you sure the dust. Gear was installed correctly? It should point to the contempt drivers intake manifold bolt. If these check out, the pulling 1 plug wire at a time, see if can be isolated to one cylinder, or if it is totally random.
 
Mopar to ya said:
Yes, I broke it in at 2500 rpm for a half hour. Comp Cam XE268H cam and lifter kit. Would a ballast resistor cause a backfire? I thought they were more start / no start problems. It ran perfectly until I went in the car wash. Drove in fine, backfired driving out. I am down to compression check now. Hoping for the best, fearing the worst.

Bill, would a carb cause backfiring only on exhaust? If it is carb or ignition related, I changed everything in the ignition, so that leaves the carb. I kind of believe flat lobe or bent valve, however.
Click to expand...

on the rare occasion I have seen a ballast resistor give the backfiring through exhaust and carb
 
jimmyray said:
What was your timing set at? Are you sure the dust. Gear was installed correctly? It should point to the contempt drivers intake manifold bolt. If these check out, the pulling 1 plug wire at a time, see if can be isolated to one cylinder, or if it is totally random.
Click to expand...

Just to be sure, I turned the motor to #1 TDC and aligned the timing marks. The rotor is pointing at the #1 cylinder on the cap. And my #1 on the cap is just left of center. The weird thing is that it was running beautifully before the wash. I just can't believe it would be timing or a misadjustment. You would think the problem would have been there all along if that was the case.
 
jimmyray said:
What was your timing set at? Are you sure the dust. Gear was installed correctly? It should point to the contempt drivers intake manifold bolt. If these check out, the pulling 1 plug wire at a time, see if can be isolated to one cylinder, or if it is totally random.
Click to expand...

You're on the right track, but don't PULL plug wires. Instead, GROUND them at the distributor using a probe. When you pull a wire off, it creates an open circuit, will cause crossfiring, and can actually steer your wrong

So far as the "gear" you can time these engines with the gear in there "any old way" as well as the dist, just as long as you bring up no1 cylinder 'ready to fire' and plug no1 wire in where the rotor points.

Any chance your distributor is simply loose and moved?

You need to treat this as a "one cylinder" problem to start.

Try grounding one wire at a time and RUN A COMPRESSION CHECK. Seriously consider pulling the valve covers and do a CAREFUL examination of all valves opening / closing.

Consider trying a different coil, and if you are using a Mopar ECU, it is possible that you got "junk" (water/ chemicals) under the transistor/ heat sink on the ECU.

I used to have trouble with this on my old landcruiser, running a Mopar SB and Mopar ECU. Finally moved the coil/ ECU up under the dash. We'd get out into deep snow or mud/ water, and the ignition would break up
 
Mopar to ya said:
Just to be sure, I turned the motor to #1 TDC and aligned the timing marks. The rotor is pointing at the #1 cylinder on the cap. And my #1 on the cap is just left of center. The weird thing is that it was running beautifully before the wash. I just can't believe it would be timing or a misadjustment. You would think the problem would have been there all along if that was the case.
Click to expand...


I would get a cheap point dist and install a new set of points and see what happens. Electron ignition is great when it works but can cause many headaches.

you be surprise how well a point dist can work and its so simple, cheap and easy to wire up
 
dodge freak said:
I would get a cheap point dist and install a new set of points and see what happens. Electron ignition is great when it works but can cause many headaches.

you be surprise how well a point dist can work and its so simple, cheap and easy to wire up
Click to expand...

but alot more maintnace is required, such as cleaning and gapping points every tune up, as well as having proper dwell. electronic ignition is the cats a$$ and is also easy to figure out
 
Well yeah but it can be your back up dist and dwell can be set roughly with a feeler gauge.

Electronic ignition is easy but isn't cheap. He could spend $200 on a nice msd dist and then he needs different style plug wires and a $200 msd box to fire it. That's $500--just to see if its in the ignition system and where he lives winter will soon be knocking on the door
 
Mopar to ya said:
Just to be sure, I turned the motor to #1 TDC and aligned the timing marks. The rotor is pointing at the #1 cylinder on the cap. And my #1 on the cap is just left of center. The weird thing is that it was running beautifully before the wash. I just can't believe it would be timing or a misadjustment. You would think the problem would have been there all along if that was the case.
Click to expand...

Ignition issues are weird animals Things can appear that seem related to. Some cause, but generally coincidental. I had a distrutor wire from the pickup to the ecu go bad, having 5-30 ohms resistance, depending on how I wiggled the wire. I also had problem with wiring on the dist to the plugs being off due to the location of the rotor on the shaft. FBO had installed it wrong.
 
Generally, a wiped cam lobe or the like causes popping through the carb, while ignition related maladies cause popping through the exhaust.
 
Sound's like the same problem I had with a Chebby 396 I built year's ago with a Comp cam and Rhodes lifters.engine ran awesome first 600 miles than started a slight miss that got worse.When I pulled it down the cam lost 1 exhaust lobe,only cam I ever lost,I blamed the Rhodes lifters,but.i installed a new Crane flat tappet cam and lifters,broke in properly.worked great for 30,000 miles,till I sold car.Also clean debris from engine if that happened.Good luck.
 
How new/what condition is the exhaust system? I have seen a "used" exhaust system with clogged glasspack mufflers do the same thing as well....the problem usually ends up being a plug wire breaking down or ignition related though.
 
67Dart273 said:
You're on the right track, but don't PULL plug wires. Instead, GROUND them at the distributor using a probe. When you pull a wire off, it creates an open circuit, will cause crossfiring, and can actually steer your wrong

So far as the "gear" you can time these engines with the gear in there "any old way" as well as the dist, just as long as you bring up no1 cylinder 'ready to fire' and plug no1 wire in where the rotor points.

Any chance your distributor is simply loose and moved?

You need to treat this as a "one cylinder" problem to start.

Try grounding one wire at a time and RUN A COMPRESSION CHECK. Seriously consider pulling the valve covers and do a CAREFUL examination of all valves opening / closing.

Consider trying a different coil, and if you are using a Mopar ECU, it is possible that you got "junk" (water/ chemicals) under the transistor/ heat sink on the ECU.

I used to have trouble with this on my old landcruiser, running a Mopar SB and Mopar ECU. Finally moved the coil/ ECU up under the dash. We'd get out into deep snow or mud/ water, and the ignition would break up
Click to expand...

I installed a new coil and a new ignition module. I bought a ballast resistor today but haven't installed it yet. My brother is giving me his orange box, but I don't want to install that until I have it running right. How do I ground a wire without pulling it off?
 
A compression test should show any mechanical issues. If a lobe is worn, it will show that too.
It does sound more like ignition/carb related. What is the voltage at the coil positive terminal with the key in the run position? What is the battery voltage? Is this the stock type (or MP conversion) ignition?
 
so you got it wet and it started up?

check the grounds to the box, also check how much timing you have, too lil and too much fuel will load it up and pow!
 
Mopar to ya said:
How do I ground a wire without pulling it off?
Click to expand...

Sometimes you have to pull it off, have a ground probe right there to stick in the wire

The best way IF YOU CAN (on older 7mm wires) is to stick small brands down into the dist towers beside the wires. Then you can just ground 'em.

I realize that the newer dist cap/ wire setups make this more difficult.

If you MUST pull a wire off, ground it right away.

By the way, an open, ungrounded wire CAN KILL an ignition box. Some systems are worse than others.
 
moper said:
A compression test should show any mechanical issues. If a lobe is worn, it will show that too.
It does sound more like ignition/carb related. What is the voltage at the coil positive terminal with the key in the run position? What is the battery voltage? Is this the stock type (or MP conversion) ignition?
Click to expand...

It is stock electronic ignition as far as I know. Voltage at battery with vehicle off is 12.55v. Voltage at positive post of coil key on engine off is 4.7v. Voltage at positive post of coil key on engine on is 7.2
I have it running, and when I turn the distributor counter clockwise or advanced, it pops louder and more often. When I retard the timing and can actually see the timing marks with my gun, it pops less or almost never until I put a load on the motor. I actually drove it today and it had absolutely no power and began to backfire a lot (after idling with no popping for 5 minutes). My next free time is Sunday and I am going to do a compression check. Can a carb load up and cause exhaust backfiring only?
 
dodge freak said:
Well yeah but it can be your back up dist and dwell can be set roughly with a feeler gauge.

Electronic ignition is easy but isn't cheap. He could spend $200 on a nice msd dist and then he needs different style plug wires and a $200 msd box to fire it. That's $500--just to see if its in the ignition system and where he lives winter will soon be knocking on the door
Click to expand...

If money was an issue, I wouldn't have bought a Mopar! :) Seriously, I am ready to drop a shitload of money on a 408 stroker and all the extra crap I need. I have a guy who rebuilds distributors and I would send mine to him if I thought that was the issue. I have points in my Truimph, and I can tell you that yes, they are easy, but the extra voltage at the plug alone is worth going electronic.
 
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