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  1. #1
    Poop GRM-REPR's Avatar
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    Car still missing intermitently

    I'm still having trouble figuring out why this engine seems to have a mind of its own sometimes.

    It's a 75' Firebird with a 355, E-brock 700cfm, E-brock Performer RPM intake, fuelie heads, mild build, brand new MSD dizzy, Accel 8.8 wires, MSD 6a and some other tricks.

    The #6 boot kept burning melting against the header tube cuz the header design sucks, so I got a new boot and trimmed it a bit to clear it, I don't think this is causing anything anymore.

    I put my friends E-brock carb on last year before putting it away and it seemed better.

    The car just seems like it will miss or backfire at anytime. Today it was bubbly at the intersection when I drove thru it, and when I got onto the freeway and accelled, it backfired out of what seemed to be the pass side tailpipe, then seemed to "clear" up.

    I'm rusty with carb'd cars due to having EFI for the last 5+ years. I'm out of ideas and whatnot.

    It has roller rockers that haven't been adjusted since the engine was built, roughly 3k on it. I figure if it were a rocker, it would do it all the time. The car feels like it isn't at full potential ever.

    Any suggestions would be appreciated, or if anyone knows a good tuner/diagnoser....

    Thanks, Jon.
    WIP

  2. #2
    RTCTTFMF 2SLOW's Avatar
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    it's popping out of the exaust, or carb? also how close it the distributor pickup wire to the power or coil wires? they shoud at least be 6" to eliminate radio interference. bad ground, almost seems like if it i popping through exaust like a miss or detonation it could be a loose wire? if it has a mind of its own it has to be ignition?? what is the initial timing set at, and total advance?

  3. #3
    This is entertainment. Myles's Avatar
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    Check the plugs, find out if you are running lean/rich on a random cyl. Then check the timing. Check a ground that may be lose.

    If all else fails put an LT1 in it. Its not that hard.
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  4. #4
    Poop GRM-REPR's Avatar
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    I believe the wires are right next to the dizzy.

    The plugs are new, along side a new dizzy.

    The backfire was out of the exhaust. Trust me Spool, I've gone over the ignition system a million times, however, I never knew that the pick-up wires, (I'm assuming you're referring to what would be the black/orange, or pink MSD wires from the box) could play interference on the ignition, MSD never mentioned this.

    Timing is roughly 9*. I thought it seemed better when I swapped the Holley for an E-brock carb, but it still runs goofy when it wants.

    Myles, I'd rather stick a Ponti 455 into it before disgracing the car with another chevy block....
    Last edited by GRM-REPR; 04-16-2007 at 11:46 AM.
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  5. #5
    RTCTTFMF juicedimpss's Avatar
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    sounds like the carb is fat.
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  6. #6
    Formerly known as Yellow Wagon jbiscuit's Avatar
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    gurgling/bubblin = carb is WAY too fat. When you go WOT it probably isn't AS fat which is why it "clears up."

    Why did you switch the Holley out for?
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  7. #7
    RTCTTFMF 2SLOW's Avatar
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    Quote Originally Posted by GRM-REPR View Post
    I believe the wires are right next to the dizzy.

    The plugs are new, along side a new dizzy.

    The backfire was out of the exhaust. Trust me Spool, I've gone over the ignition system a million times, however, I never knew that the pick-up wires, (I'm assuming you're referring to what would be the black/orange, or pink MSD wires from the box) could play interference on the ignition, MSD never mentioned this.

    Timing is roughly 9*. I thought it seemed better when I swapped the Holley for an E-brock carb, but it still runs goofy when it wants.

    Myles, I'd rather stick a Ponti 455 into it before disgracing the car with another chevy block....
    hmm yeah well thats the first place to look is the ignition but if it's good then i dont know. poping through the carb means lean and it is a soft pop compared to a
    hard pop from the exaust.

    what rev limiter chip do you have in it??? it will start to miss 500rpm before the rating on the chip some times put in a higher chip and see what happens. but you said it "clears up" after the misfire? hmmmm well what weights do you have in the dizz whats the advance curve? all advance in at 2500? or 4000 ect. might need a slower ramp if it momentarily happens then clears out at higher rpm. just some suggestions.

    below is a statement from an msd Tech.


    "Make sure the fist dial on the 6 is set to 2 for the 8-cyl engine. If this is set incorrectly the rev limiter will not work correctly. Another possibility is that the MSD unit is picking up noise on the power leads being that they not connected directly to the battery.

    Also verify that the magnetic pickup leads are routed at least 6" away from any other wires running in parallel with them. These leads may be picking up interference if they are routed in parallel and within 6" of other leads carrying 12V or more."
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    Last edited by 2SLOW; 04-16-2007 at 01:03 PM.

  8. #8
    Poop GRM-REPR's Avatar
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    Yeah I'm pretty sure it's not the carb, I switched the Holley out for the E-brock to test to see if it made a difference, didn't. Besides, the power valves on the Holley I believe popped, due to a rusty dizzy (which is now replaced) and is sitting in my garage.

    I believe the MSD box is NOT wired to the battery because it's in the trunk (previous owner) so I think he has it grounded and powered elsewhere, that I was told is NOT the way to do it. But when my younger bro owned this car, I can't exactly say it was doing this, unless it was and he accepted it.

    Spool, its a 6A, no soft touch chips. I thought the magnetic pickup wires aren't used unless you have a crank-trigger dizzy?
    WIP

  9. #9
    Poop GRM-REPR's Avatar
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    Quote Originally Posted by yellow wagon View Post
    gurgling/bubblin = carb is WAY too fat. When you go WOT it probably isn't AS fat which is why it "clears up."
    Problem isn't just WOT, a lot of times just idiling at the line and leaving normally it will ..babbaaabbaaa.....(sputter, stutter)....very annoying...
    WIP

  10. #10
    RTCTTFMF juicedimpss's Avatar
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    so its not missing,its stumbling....
    its in the carb.
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  11. #11
    Ol' School Nix's Avatar
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    This all started back last year, I can't remember exactly when. the Holley on the car was brand new out of the box when I got it and then the I believe the power valves went due to it backfireing a few times while I was trying to diagnose the problem.

    The ignition coil replaced, wires ran the way they should be to my knowledge (execpt for the MSD box cause of the previous owner having the battery in the trunk) wires brand new, plugs brand new, dist brand new also MSD to match the other components.

    After the new dist was introduced to the car is corrected the problem for sometime as far as I know. The Holley was a 650DP, if that wasnt drowning the motor I don't see how the Ebrock could be doing it. Back when the motor was rebuilt it orignally had a Holley 700 on it and I cant remember if it was a DP or not, but the car ran fine with it on there. I switched it out for a 650 cause I didn't want to take a chance of "washing the bearings" in the motor and whiping it out with too much fuel. After the 650DP was put on the car was great for the rest of the summer it was on there. Then when the car was brought out next year it was fine with no issues and then all of a sudden this came up out of no where.

    The thing is when it did come up nothing else was changed before hand that may have some how screwed anyhting else up. Its pretty crazy and Im actually at a loss for ideas on how this is happening.

    What we should do Jon is see if anyone on here would be willing to stop out and we all put our brains togther and try to figure this out once and for all man.

  12. #12
    RTCTTFMF juicedimpss's Avatar
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    drive it over and a few of us can listen to it
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  13. #13
    Formerly known as Yellow Wagon jbiscuit's Avatar
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    Quote Originally Posted by GRM-REPR View Post
    Problem isn't just WOT, a lot of times just idiling at the line and leaving normally it will ..babbaaabbaaa.....(sputter, stutter)....very annoying...
    re-read what I wrote. the primaries are jetted too fat I'd bet....which is why when you stand on it and the secondaries come in, it runs better....that would tell me that the secondaries are tuned somewhat decent.

    ITS THE TUNING IN THE CARB

    do some google research on how to tune out the off-idle stumble. Also don't think the carb is too big....I have a Holley 750 on my little 327
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  14. #14
    A regular know-it-all Tetris Champion Snake Champion Lasagna From Heaven Champion Mac Man Champion Mahjong. Champion Mini Putt 3 Champion Plastic Saucer Champion Ratman Ralph Champion Prince Valiant's Avatar
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    I'm betting that the idle mixture is probably what's most off...have you ever tried adjusting the idle mixture screws?
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  15. #15
    Dusting off my knick knack... MurphysLaw88GT's Avatar
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    Quote Originally Posted by juicedimpss View Post
    so its not missing,its stumbling....
    its in the carb.

  16. #16
    Poop GRM-REPR's Avatar
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    To address most of you, the dizzy was replaced and it fixed the backfiring and killing issue.

    Then I bought the car from my lil bro and it never seemed to run "right" since. It got so bad it would kill coming to a stop, and WOT on the freeway once made it run like total shit, when I got off the freeway to pull over, it killed. Everytime I tried to start it cold, it would flood. So I took it to Hopson in Waukesha (my buddy knows the owner pretty good), and he found a bent float. It still didn't run right eventually.

    So then I took the Holley off to see how it would run with the E-brock on it (700cfm), and I thought it felt better. But the more I would drive it it would still exhibit the sputter off the line, backfire under half accel. Once I got it on the freeway yesterday it purred just f'n fine.

    I can see why some of you think it's carb, but the only reason the Holley came off is cuz the p. valves are blown from a few good backfires thru the carb from when the dizzy was bad.

    An E-brock carb is easy to tune, I have it a bit on the lean side with an idle that purrs at 825rpm hot. But then again, I'm not a master carb tuner, so maybe its off like Juiced said. No one seemed to agree with the rollers being a bit out of adjustment.

    So I guess I'm thinkin', what would be the chances of 2 carbs being bungled up? The E-brock has idle miles on it, never driven, basically brand new!

    I would appreciate it if someone wanted me to stop out close by and putz with it, but remember, it seems to have a mind of its own. Some good help from some bcm'ers would be nice

    Thanks for the replies so far, keep them coming.....
    Last edited by GRM-REPR; 04-16-2007 at 08:09 PM.
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  17. #17
    A regular know-it-all Tetris Champion Snake Champion Lasagna From Heaven Champion Mac Man Champion Mahjong. Champion Mini Putt 3 Champion Plastic Saucer Champion Ratman Ralph Champion Prince Valiant's Avatar
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    Well, most would agree that trying to dx a car over the internet can be pretty dificult just because how one describes and one interpets a problem can be vastly different. I'd suggest actually bringing it over to someones place...if you can get to someone elses sooner, fine...but if not, I could probably look at it on sunday morning at my house.
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  18. #18
    Poop GRM-REPR's Avatar
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    Yeah I'm starting to think carb now too. I took it back to storage and trompt on it hard, it sorta did a Q-jet bog and burp, then hauled pretty good, as I kept the throttle thru all gears it never missed a step.

    I was talking to my younger bro and he drove it today and said it never did any of this before. Just seems like ever since I put the new dizzy in, it started doing this.

    I checked out the wiring for the MSD box, the black and ornage wires were by the coil wire, and the power wire for the MSD. The previous owner has the MSD main ground going to the back of the pass side head, and it appears he has the main power wire going to the f'n starter wire?!?!?!?!

    Stupid moron, I will need a couple of hours just to re-wire it the right way.

    I may take some of you guy's up on your offer to help me tune this sucker right, as long as there is no rain. Will keep thread updated.

    Thanks again. Jon....
    WIP

  19. #19
    Praise the Lord. Reverend Cooper's Avatar
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    Quote Originally Posted by Myles View Post
    Check the plugs, find out if you are running lean/rich on a random cyl. Then check the timing. Check a ground that may be lose.

    If all else fails put an LT1 in it. Its not that hard.
    coming from the guy that has ron fix everything for him lolololj/k myles

    special thanks to: Marv @ C&M performance 262-993-6605

  20. #20
    RTCTTFMF juicedimpss's Avatar
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    how much intial timing are you running?you may want to tighten the curve and add more initial to it.
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