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Stumped on an engine "miss"!!! 390 FE Ford

Discussion in 'The Hokey Ass Message Board' started by Ken Carvalho, Jul 25, 2012.

  1. Ken Carvalho
    Joined: Dec 22, 2004
    Posts: 1,608

    Ken Carvalho

    Working on a 390 FE motor for a friends wife (he passed of cancer last year) as she is having a hard time being around the car, but, I want to get her back to driving it. NO sexual liaison, or ANYTHING like that!!! Just helping out a widow of a friend of mine.
    Last "mechanic" changed the head gaskets and used --copper coat-- everywhere including the head gaskets!!! The car smoked like a chimney, and ran like shit. I pulled the heads and the copper coat was still gooey, all cylinders had oil and coolant in them. She is lucky it didn't hydro lock!!!

    Here is what I have going on:
    At idle; car runs, is smooth, and sounds, PERFECT!!!, I set the idle mixture & idle speed, (your standard issue Edelbrock 650 with electric choke opening correctly) set the timing per book specs., and put a vacuum gage on it and has 16-16.5" of steady vacuum. Compression is 135 at lowest cyl. 150 exactly at 6 cyls. and 155 at highest cyl., has pertronics ignition and coil, with a FULL 12 volts at the coil, Dist. advance starts at 5" of vacuum and is working, (used a vacuum suction with gauge), have the vac advance hose on the LEFT port (passenger side) of the carb, have checked and double checked for vac leaks everywhere. used spray bottle to shoot a stream of water onto the headers induvidually to get a, "back yard" feel for the cylinders getting hot from firing and all looks good with steam vaporizing off fast and evenly. Plugs seem clean and have a white insulator with a nice even hint of tan all around. (Plugs wires, cap rotor etc, all new I believe from Pertronics she said as it was a gift package that had everything together, includinc the electronic conversion for the dist.)
    At idle in the driveway the engine is PERFECT, putting it into gear backing out and slowly going to a stop sign, car is fine, but upon giving it gas and driving the car, it spits and sputters and hesitates, while under load. Off the line is fine, but once the car is going and you give it more gas it starts popping thru the EXHAUST, and I can feel the popping in the seat of my pants.
    I'm stumped!!! I have no way to check the pertronics module or coil but don't "seem" to think it is ignition?!?!? And the carb seems to be functioning fine so don't see fuel related either, BUT obviously something is going on. I usually SWEAR by a vacuum gauge, while "tuneing" a car but my gauge is telling me the motor is GREAT!!!
    Any ideas or places to point me towards??? Did I miss or forget something??? This is my first 390 repair job, but ultimately it is still a mechanical engine!!!
    I am open to ANY legitimate suggestions.
    Soory for the looong post, but usually when someone asks for help the posters always have to ask for MORE info, and I wanted to cover everything I could think of that I did.
    The car is an off topic '67 Galaxie Convertible, but it is truly female owned and she does as much as possible, on her own to it, She does also own a STOCK '53 Ford, so let her slide on this O/T car please
    Thanks, Ken
  2. henry29
    Joined: Sep 5, 2007
    Posts: 2,837


    I would swap out the ignition module for a set of points
  3. Dyce
    Joined: Sep 12, 2006
    Posts: 1,926


    Check and make sure you have mechanical advance, or the fuel filter.
  4. Rbt603
    Joined: Jul 15, 2012
    Posts: 4


    Just a shot check the firing order I had two wires mixed up on my 390 it did the same thing
    40fordtudor likes this.

  5. nick_c
    Joined: Apr 27, 2011
    Posts: 149

    from texas

    If its not the firing order I'd say burnt exhaust seats.
  6. Old Dude
    Joined: May 12, 2006
    Posts: 193

    Old Dude

    Is the Timing Gear in Correctly ? Has it got Bad Gas in it ? The backfire tells me it isw one or the other.
    I always use Stabil, during the Winter, when not in use!
  7. RayJarvis
    Joined: Oct 11, 2010
    Posts: 209


    i whould make shur carb is sprayin fuel into intake . engine off, then recheck float level. ploease let us lnow what the problem turns out to be. tks
  8. kracker36
    Joined: Jan 21, 2012
    Posts: 756


    Brain is sore now
  9. Sounds like a partialy restricted fuel suply or weak fuel pump.
  10. the popping alone tells me,either plug wires crossed .
    40fordtudor likes this.
  11. 58custom
    Joined: Jan 1, 2009
    Posts: 398


    In addition to what Old Dude wrote, I would take a good look inside that carb for any blockage of the main metering circuits. And check the float height.

    After that I might wanna know if the valve springs are correct and have sufficient seat pressure. Do we know if the hack meachinic did any work to the heads? Maybe he did something with the valves, seats or springs that would be the equal to his stunt with the gaskets.

    I don't think this is a part of the problem, but the coil should be preceded by a ballast resistor. Full 12 volts to the red lead of the Pertronix, ballast resistor for the coil.
  12. ironpile
    Joined: Jul 3, 2005
    Posts: 915


    Broken valve spring?Is it an automatic?you might load test it.Put in drive ,hold the brake and slowley raise the rpm. Sometime the problem will appear and you will feel it in the gas pedal and maybe the seat.:D
    Legends47 likes this.
  13. yes id put a ballast resistor in the wire going to the positive side of the coil

    on the poping my truck (72 f100 360 fe) started that when i installed my pertronix found out that some applications need a shim under the reluctor shim it to where the top of the reluctor is evenwith the module on the pertronix i made my shim out of a heater hosepull the reluctor slip the shim down to sit on top of the old points cam and put the reluctor back on sounds funny but it worked on mine

    my truck ran EXACTLY as you describe
  14. Ken Carvalho
    Joined: Dec 22, 2004
    Posts: 1,608

    Ken Carvalho

    O.K. O.K., Kracker your brain is hurt!!! Why, because I gave all the info possible and you had to read it???? If I hadn't laid it all out, I would have been asked...Did you check for vacuum leak, did you check your timing, you didn't say if it was a 4 bbl. or not...ETC!!!!
    Anyways here is what I stumbled across...The "Hack" mechanic is a --certified-- ASE repair person ie: her friend also, and a Female mechanic, the female part doesn't bother me at all, but the certified and using Copper coat DOES!!!!!
    It has 20 gallons of NEW "last night" gasoline in it. I didn't open up the front timing cover so am ONLY, -I know, I know-...assuming the gearset is fine as it ran before his passing and her storage of it.
    I don't want to say it is a "backfire" per se', just a --stuttering-- as you give it the gas, (tiny backfires, if you will)...BUT!!!!!
    here is what I did...Took out the pertronics and bought a NEW set of points and a condenser, swapped them and SAME THING!!! So put Pertronics back. Test drove and FORGOT to put the dist. vacuum advance line back on and it ran good but had a stumble, so when I looked again, thats when I realized the vac. advance line wasn't hooked up. Hmmm. I plugged BOTH vacuum ports on the carb and left the dist. with -NO- vacuum advance and it runs PERFECT!!!!
    I just put about 10 miles on it with NO vacuum advance and it purrrs down the road. I hooked the vacuum back up to the carb and I get the same stumbling!! Unhook it again and it is back to running and puring like a kitten.
    Whats my problem???? Do I have an engine that runs off of mechanical advance ONLY and someone stuck a vacuum advance dist. in it???? Very confused, and now MY brain hurts!!!
  15. Ken Carvalho
    Joined: Dec 22, 2004
    Posts: 1,608

    Ken Carvalho

    57ford/60thunderbird:, can you explain that again??? I am not following what your describing but if you have the EXACT problem I'd like to try it out if my above post turns out to be another issue?!?!?
    I have the box the Pertronixs came in and the instructions don't mention what your reffering to, BUT there is a semi clear plastic "disc" about a 1/16" thick with a hole in the middle that would slip over the dist. shaft in the Pertronixs box that I, nor her have any idea what it is for!?!?!?

    ironpile:, I did that exact "load test" and it does not mimick the problem, I pulled the valve covers off and watched all 16 move up and down in perfect order when I did the compression test.

    58custom:, Mechanic did nothing to heads other than replace gaskets, then intake gaskets that sort of usuall stuff, but DID have copper coat all over the intake gaskets too!!! There is NO ballast resistor in the ignition circuit!!! Shouldn't that Pertronixs coil be getting a FULL 12 volts and then the module hooked up directly to the coil with no ballast there either? I have taken the Ballast resisiter out of the equasion since it is NOT there and didn't think a Pertronixs coil and module used them!!!

    Fuel pump and filter are strong, and wires are NOT crossed
    Last edited: Jul 25, 2012
  16. DFH-GMC
    Joined: Dec 24, 2011
    Posts: 108

    from Texas

    It seems that if it only acts up when the vacuum advance is hooked up, then that would be your vacuum leak.
  17. JimInrADFORDva
    Joined: May 14, 2012
    Posts: 41


    OK- put the vacuum line back on the carb, but leave it plugged and disconnected from the distributor. How does it run? If it runs OK, then the vacuum line is good.

    Next, check the vacuum advance diaphragm to see if it will hold vacuum. It may have a partial leak. If it will not hold vacuum, then replace the diaphragm.

    If the diaphragm is OK, then check the linkage from the diaphragm to the breaker plate to make sure it's correct.

    Many of the "Idles OK, runs like crap under load" issues I have worked wound up being vacuum related.
    Last edited: Jul 25, 2012
    Jersy71 likes this.
  18. Ken Carvalho
    Joined: Dec 22, 2004
    Posts: 1,608

    Ken Carvalho

    JimInrADFORDva: Thanks for that, I "think" the diaphram is good, but NOT positive. I'll check it out tomorrow and go from there.


  19. tjmercury
    Joined: Oct 22, 2010
    Posts: 589


    Weak fuel pump, clogged fuel line, valves sticking, plugged jets in carb, etc. etc...
  20. Depending on how the mechanical advance is set up it may be getting too much total timing when the vacuum advance comes into play. Do you know what the total advance is when the initial, mechanical and vacuum advance are all added together?

    You mention where the vac advance is connected on the carb, but do you know if it's manifold or ported vacuum? Hook up the vacuum gauge to some different ports and see if it reads full vacuum at idle (manifold vacuum) or no vacuum at idle (ported vacuum). If the stutter occurs with the vac advance connected to ported vacuum, try connecting it to full manifold vacuum. This way when the engine is under load the vacuum should drop off and back the timing down a bit.

    Also check for good, clean, tight ground straps everywhere they're needed. Battery to chassis, battery or chassis to block, intake to chassis or firewall. Have you run into any other seemingly unrelated electrical issues with the car?
  21. snaptwo
    Joined: Apr 25, 2011
    Posts: 696


    Check to see if there is a small bare copper cable from the plate to the dist. housing, it's a ground . I had an old Merc. "y" block that gave me fits until a friend spotted that cable---broken , looked fine at first but when the vacuum moved the plate--well you get the idea.
  22. barstowpo
    Joined: Jun 27, 2012
    Posts: 232


    So it sounds like a timing issue. Have you tried timing it with the vacuum gauge? My charts say it should be 6BTC. Does the vacuum pot on the distributor have 2 ports? If so, 1 is advance and 1 is retard. I can't remember which is which.
  23. Ken Carvalho
    Joined: Dec 22, 2004
    Posts: 1,608

    Ken Carvalho

    ClayMart:, I honestly have no idea what the parameters are of this dist,. its a NAPA factory replacement with just ONE port on the diaphram. It is hooked up to the LEFT side (passenger) on this Edelbrock. Has LOW vacuum at idle and slowly "ramps" up as I give it gas. It is NOT hooked up to the full vacuum all the time port on the drivers side.

    snapto:, that wire is there and in PERFECT shape and is hooked up to both the breaker plate and the dist. body.

    barstowpo:, I got the timing set at first with my timing light and had 14" of vacuum, and then put the light down and adjusted the dist to get my 16.5" of vacuum, by using the vacuum gauge. No pinging, no hard start after warm up, I "-believe-" I have it at the optimal timing potential, but I may be wrong. just going by what my usual steps are in tuneing an engine?? and its a "single" port dist.
    thanks again all, Ken
  24. Commish
    Joined: Jan 9, 2010
    Posts: 379

    from NW Ok

    Ken, your first description reminded me of a 67 or 68 that had the same symptoms and drove me nuts for about half a day until I found the problem. The factory wiring harness as I remember came over the corner of the top of the engine and had been rubbing on the underside until it had a bare spot. Ran perfect until it had a little load on it going down the road and the engine torqued over just enough to intermittently ground the hot wire to the coil and caused the missing and stuttering. If you look there and don't find any problems, I would be going through the distributor with a fine tooth comb, checking wires and breaker plate, bushing, etc.
    Good Luck
  25. Try hooking it to full manifold vacuun once just to experiment with it. This will give you a little extra advance at idle which helps keep the vacuum up. Under acceleration or a heavy load it will retard the timing a bit and maybe help keep it from missing or pinging. Unplug the vac advance when setting initial timing with a light to get a true reading then plug the vacuum advance back in and see how much the timing and manifold vacuum increase.
  26. lewislynn
    Joined: Apr 29, 2006
    Posts: 1,659


    I got the timing set at first with my timing light and had 14" of vacuum, and then put the light down and adjusted the dist to get my 16.5" of vacuum

    Was this done before or after the problem?
    If the vacuum is 14" at timing specs, why do you think it needs 16.5"? What is factory spec timing and what is your timing @ 16.5"?Also, I have a 460 with the same firing order, somewhere in my research it was suggested to be sure and NOT run #7 and #8 plug wires parallel because of cross firing. Probably nothing to do with your problem but I thought I'd through that out there.
  27. RidgeRunner
    Joined: Feb 9, 2007
    Posts: 906

    from Western MA

    Quick check for timing drive slop: Pull a battery cable and the dizzy cap, slowly turn engine back and forth a bit to check for lost movement between crank and rotor.

  28. outlaw256
    Joined: Jun 26, 2008
    Posts: 2,023


    im not going to say this is it but i had a customers car drive me crazy because of this, crossfiring. i caught it by raising the hood once at nite in front of the shop. i could see the 2 wires trading fire.went to grab one and i got grabbed. and it had the symptoms of yours. mr. chopper, why does the copper coat scare you?thats what its made for. ive used copper coat(lightly) on our racing engines on the head gaskets for yrs and yrs. i hold the gasket and lightly spray it down. when it gets tacky i put it on. never have had a problem. but if there are problems that can arise from this i sure would like to know.
  29. Bad Eye Bill
    Joined: Sep 1, 2010
    Posts: 841

    Bad Eye Bill
    from NB Canada

    The point about # 7 and 8 cross firing is a good one but I think it would still be there with or without vacuum advance. Like someone else said, I'd look for a broken wire in the distributor that flex's when vacuum is applied.

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