390 ignition help
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390 ignition help
Ok, maybe you guys can help me out here....back story... Bought a 74 F250 Crew Cab 4x4, was told it had a rebuilt 390 in it. It ran but backfires through the carb and the exhaust. My issue I'm working on as of now is the ignition. The wiring is a mess on this truck as it has been through many hands. When I bought the truck it was converted from points to electronic ignition. There is no ignition module or anything like that hooked up. Do I need one with the conversion? Also I had to connect a wire from the battery to the coil (red wires in first few pics) to get it to run. Right now I have a wire ran from the solenoid to the coil that goes hot once I turn the key on. (small red wire last pic) Am I doing this right or what needs to be fixed?
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That looks like the typical Pertronix module, which doesn't require a separate module.
The MSD Blaster 2 coil, I'm not sure if it needs a ballast resistor or not - it might overheat of you don't have a resistor, but for now, that's probably not your problem.
More likely, timing, wires and plugs are the cause of your issues, as long as the engine is OK - might be worth a compression check.
The MSD Blaster 2 coil, I'm not sure if it needs a ballast resistor or not - it might overheat of you don't have a resistor, but for now, that's probably not your problem.
More likely, timing, wires and plugs are the cause of your issues, as long as the engine is OK - might be worth a compression check.
Lead Driver
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From: Ohio
Yup, looks like a Pertronix module.
The instruction say it needs a ballast resistor if used with points:
http://documents.msdperformance.com/8202.pdf
It looks like the motor has been apart by the bolts and mismatch paint. With the backfiring, I'd be curious if you have some valve issues. If nothing seems wrong with ignition(wires, plugs, etc) then I would pull the covers and check for proper rockers, lash, everything moving like it should, etc.
The instruction say it needs a ballast resistor if used with points:
http://documents.msdperformance.com/8202.pdf
It looks like the motor has been apart by the bolts and mismatch paint. With the backfiring, I'd be curious if you have some valve issues. If nothing seems wrong with ignition(wires, plugs, etc) then I would pull the covers and check for proper rockers, lash, everything moving like it should, etc.
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I started messing with the wires cause they didn't look like they were wired up right. So I found #1 on the cap and redid the wires and it wouldn't start. So I found TDC on #1 cylinder and pulled the cap but the rotor was pointing to the #5 on the cap. So I'm going to pull the distributer out and turn it to point to #1 and reinstall and redo the wires. Hopefully that will help. I also pulled the plugs and they were covered in gunk so I brushed them off for now (I'll buy new ones soon). When I get a chance, I'll see how this goes.
Post Fiend
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Yup, looks like a Pertronix module. The instruction say it needs a ballast resistor if used with points:
http://documents.msdperformance.com/8202.pdf
http://documents.msdperformance.com/8202.pdf
I agree about a compression test. If that checks out okay I'd remove all the BS wiring that previous chuckleheads installed. Start from scratch, assume nothing. Check that TDC of #1 piston on compression stroke results in the timing pointer to "0" on damper balancer, that it has not slipped, rotor points to #1 tower on the cap, no slop in the timing chain etc.
Cargo Master
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From: Harned, Ky
It's been a while but I'm pretty sure the oval rubber plug hanging down at the back off the left valve cover is what the factory engine harness plugged in to. It should have three wires in it, one for the coil, one for the oil pressure sender and one for the temp sender. Turn on the key switch and see if one is hot, if so that goes to the coil and the truck should start off the key. The pcv valve on the right valve cover is not connected to the hose going to the carburetor so there's a vacuum leak that may be causing part of the popping.
A picture of the engine without the breather on would help.
Engines painted a non stock color indicating it's been out of the truck so I'd guess it's been worked on, Edelbrock intake, valve covers, four barrel carburetor and fender well headers along with the heater hose outlets plugged tells me someone was building a play toy.
A picture of the engine without the breather on would help.
Engines painted a non stock color indicating it's been out of the truck so I'd guess it's been worked on, Edelbrock intake, valve covers, four barrel carburetor and fender well headers along with the heater hose outlets plugged tells me someone was building a play toy.
Lead Driver
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From: Ohio
Yes, the module replaces the points. My statement was the fact that the coil only calls for a ballast resistor if used WITH POINTS.
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Ok, I finally got around to working on the truck the other day. I Put the truck to TDC and pulled the cap. The rotor was pointing to the #8 location on the cap. I pulled the dizzy out and rotated it and got it to point at #1 now. I put all my wires back on and got the truck to fire up. I still need to set the timing better, just did it by ear for now. It is nice to not have the truck backfire all the time.
I'm going to get a pic tomorrow of the wires from the cap to the coil. Both wires are going to the coil from the cap. I cannot figure out if that is right or is just the red wire go to the coil and the black go to ground. I keep finding illustrations of both ways it's driving me crazy!
I'm going to get a pic tomorrow of the wires from the cap to the coil. Both wires are going to the coil from the cap. I cannot figure out if that is right or is just the red wire go to the coil and the black go to ground. I keep finding illustrations of both ways it's driving me crazy!
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Brett Foote
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http://www.pertronix.com/docs/instru...heets/1281.pdf
See page 2. Not sure this is exactly what you have, but it's a Pertronix Igniter for a 1970 Ford distributor. Looks correct to me.
Wiring is simple. Since you have an aftermarket coil, it probably doesn't need/require the ballast resistor so you can ignore that part.
Red from Pertronix to (+) side of coil, black to (-) side. (+) side of coil also needs switched 12V from the ignition switch (has to get voltage in both start and run position).
See page 2. Not sure this is exactly what you have, but it's a Pertronix Igniter for a 1970 Ford distributor. Looks correct to me.
Wiring is simple. Since you have an aftermarket coil, it probably doesn't need/require the ballast resistor so you can ignore that part.
Red from Pertronix to (+) side of coil, black to (-) side. (+) side of coil also needs switched 12V from the ignition switch (has to get voltage in both start and run position).
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