missing 390 :-(

[happycamper]

Not a happy camper!
My 390 has been running great until recently... I just put on a new 2 1/2" exhaust, manifolds to tailpipe w/ glass packs. Sounds great! However, this is where things start getting weird.. it was okay for a few days; maybe I didn't get into it hard, but now I am experiencing missing on acceleration and missing while cruising 40 plus mph. I have a pertronix points eliminator and accel coil and the carb is the stock 2bbl. All new cap, rotor, wires and plugs. Fuel filter replaced too. Running stock air cleaner w/new element...Gets worse at the engine gets warmed up. Did check to see if the vaccuum advance plate was binding, (no).

Thinking the following unless otherwise... Fuel pump "circling the bowl," Accel coil putzing out, not enough cfm's from the carb, or (too lean?). Any suggestions?

I was thinking to install a new performer RPM manifold and a new 4bbl performer carb on the backburner, but didn't want to spend the bucks unless necessary...

[happycamper]

Forgot to add that I did rev it up in the driveway, 500 and hold, 1000 and hold, so on and so on, up to 2500 rpm and hold. No missing. Back out on the road it started missing again.
Could the torque converter be slipping too?

[convincor]

try tighening up the air gap on the pertronix.
had mine at the .020 they recommended and got a skip. closed it up just a little and cleared it up.

[70_F100]

Have you checked to make sure your breaker plate isn't worn?

[BRUTUS_T_HOG]

i don't know if this applies, but i worked on a fairlane with a fresh built engine that did this. after putting it on an ignition scope i found an almost invisible crack in 1 spark plug, i replaced the plug and it ran great. we think it got cracked when the headers were being installed

[happycamper]

I'll look into the plug issue. Maybe the amigos bumped one when the headpipes were being bent and installed. I think the passenger side donut is leaking a little anyhow. I've checked for vaccum leaks as well; didn't find any. Replaced some suspicious hose and sprayed carb cleaner around other things that looked suspect. No change in idle; no fix so far... retiring for the night. By process of elimination, the only other suspects can be: a plug, the coil/wiring, or the carb. BTW, the carb always smells gassy, makes the garage smell gassy, and it is a PIA to start when the truck is warm. Hmmm. Thanks for the help so far.

[Dragon]

Not a happy camper!

Thinking the following unless otherwise... Fuel pump "circling the bowl," Accel coil putzing out, not enough cfm's from the carb, or (too lean?). Any suggestions?

I was thinking to install a new performer RPM manifold and a new 4bbl performer carb on the backburner, but didn't want to spend the bucks unless necessary...

The Accel coil will not go out that way it will make you sick at the bottom end or just die. I had my coil get damaged when I followed Accel's instructions to eliminate the ballast wire. It caused my coil to start acting up. Well today it bit me. 2 blocks from a customer on a no parking street the truck died. I checked it had fuel. I pulled the coil wire and laid it on the engine and hit the solenoid(eat your hearts out chebie fans) and the spark at 1/8 an inch was barely visible. The truck tried to start then I probably flooded it. The customer drove me to buy another Accel coil and I fixed it.

Like it was said the pertronix gap could kill top end. A Pertronix air gap is critical as is a Duraspark air gap. If the gap is too great the pickup coil won't see a sharp trigger event until late in the timing event. To close and it fires early.

How old is the 2V? I lecture about older carbs all the time. After about 80,000 miles or twenty years the throttle shaft is a major vacuum leak and is not fixable at home with any rebuild kit. At least on a Holley you can buy throttle bodies.

[happycamper]

I thinking to just scrap the whole top and start fresh. I love my rig, so a little money spent really can't hurt. I'll probably get it back in fuel savings anyhow. I've decided to put on a performer RPM manifold and a performer carb, (600 cfm elec.choke), put the pertronix back in, and a K@N filter. The 2bbl carb is something I have not liked since I bought the truck and the 2bbl manifold must be made out of kryptonite, (feels like it weighs 40-50 lbs). The engine is about 5 years out from rebuild, 390 pushed out to 411, with a 428 crank. I probably have an opportunity here to make some power and should take advantage of the "missing" as the opportunity knocking. The Lord works in mysterious ways, no?... I have pics in the photo album if anyone is curious of what I'm dealing with.
Thanks everyone.

[Dragon]

Don't put that Performer carb on it is just a poor copy of a carb everyone tried to get rid of in the 60s and early 70s. No one in the winners circle ran Carters. Carter is gone because Holley makes a better product. LOL the intake weighs, get this, 92 pounds on low risers and 96 on medium risers.

For a 411 at 4500 rpm max a 480 is the largest carb you would need for daily driving.

I am running a 2 Stage Holley power Valve test and today I fill my tank for my first real check. But my 750 at one time got a mere 5 mpg and with work I think I am at 12 now.

[cdeal28078]

I would not over look the coil. I have seen several coils fail after people installed Pertronics points eliminator kits.
Not sure which kit you have but one is very finicky on the input voltage and what type of coil you run. Did you use the resistor wire from the ignition or by-pass it. I would stick a known good coil on there and see if the miss goes away. Would cost nothing if you have a spare coil and only $20 or so around here if you have to buy a coil. Cheaper at a pull a part.
Cheap enough to try.
I won't get into the Holley versus Edlebrock subject. Nothing but an argument there. To each his own. If you like to tune to get the best results I say get a Holley. If you want to stick it on out of the box and it run OK get the Edelbrock.
That is all I have to say about that. Said I wouldn't say nothing didn't I? Opps
Don't go TOO large on which ever carb. you get. If you are not going to race the truck smaller is usually better as far as a crisp running truck that gets decent mileage goes. I run a very mild low compression 460 in my 71 F100 and run a 600 Holley. Runs great low end and great top end. Has a very responsive throttle and gets around 13 to 15 mpg over all. I think I can get better.
I know for wide open performance I am leaving HP on the table with a 600. A 750 would run better at top end. My truck is a daily driver and sees wide open only once in a while when I an goofing off.
Clint

[happycamper]

Thanks for the tips eveyone. I took a little bit from everyone, but the root cause was found after a good nights rest and a good cup of coffee. The carb just needed adjusted; I forgot that I had been farting around with it the night before and now it was out of sync. I am currently 3 1/2 turns out on each side, running smooth as silk. Put the original dis back in with some new points and condensor, .017 gap, timing @ 6 BTDC and tuned the adj on the vaccuum advance. Purring like a singer.

Still have issues w/ hot starts, but if it aint broke, I'm not going to screw with it. Like to keep my rig original as possible.