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Thread: Help!- 86' CJ-7 w/350 chevy SB swap... engine misses once warmed up

  1. #1

    Default Help!- 86' CJ-7 w/350 chevy SB swap... engine misses once warmed up

    Hope someone can help...I am new to this forum, please bear with me and give me any advice you can.
    I have an 86' CJ7 w/ a 350 bored 30 over, standard distributor, an RV cam (don't know the brand or specs unfortunately), and a brand new Edelbrock performer 600cfm carb.
    It runs beautifully while cold, but once fully warmed up, it seems one of the cylinders isn't firing 80-90% of the time.. every once in a while it will catch, and I can feel the surge in power, but mostly it misses and sounds like a 2 stroke engine

    Here's where I have looked for as far as solutions/ remedies:

    1. new remy dist. cap and rotor; have vacuum advance set to ported (passenger side) vacuum port on the Edelbrock carb (tried the full vaccum port, but it would die sometimes when shifting out of idle)
    2. new plugs
    3. new wires
    4. played with timing (don't know where exactly I should have it since I don't know the specs on the cam) anywhere between 8-16 BTDC after it is fully warmed up (runs much better at idle at the higher advance, but poorer under load) (anyone know what I should set it at?)
    5. all vac. hoses are new, as well as carb gasket, so no vac. leaks.

    also what's a good idle speed for this set up.. I have it at around 950 rpm

    please help!!!! and thanks in advance

  2. #2
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    my friends chevy truck(350 cid) did that he had 2 of the sparkplug wires backwards
    IOWNCJS

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    Registered hozercj7's Avatar
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    If you have a timing light you can clip it over any spark plug wire and itll blink.
    When its missing put the timing light on each wire and watch for missed blinks.
    86 CJ7 RE4.5 Extreme duty lift OBA TSL33 SuperSwampers 2400watt power inverter Winch Woody CV driveshaft 4.56 gears detroit in the rear
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    Are you still run’n a points type distributor?
    I had battled a similar problem for months until I converted it using a Petronix ignition conversion.
    Corveep = ’60 CJ-5 + ’65 L-76 Corvette.

  5. #5

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    I have checked the wires, no crosses... I will check w/ a timing light to see if any/which cylinder is missingm, but like I said... it seems to run fine at idle, it's under load it misses.

    Corveeper, yes I still have a points distributor... what Petronix ignition conversion did you get?

  6. #6

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    if its not a cylinder getting no fire then it sounds like your advance curve is way off for that cam. i just read alot about that in a book but cant explain a fix. this may be way off but ive also seen guys have a similar problem with a bigger cam and too small of a carb. seems like a 600 is plenty big but i dont know. mabye someone can dispell or help out with what ive said.

    good luck...... youll get it


    ok so i read your post again and im gonna have to put my money on the timing+high advance+big cam= your problem! big cam+high advance makes your timing have to be dead on and have your advance curve dialed in. would help alot if you knew what that cam was but you should still be able to get it driving.
    76 cj5 AMC 304 d30 amc20 dana 20 t150 complete resto.

    SPEND MORE TIME THAN MONEY!
    some assmonkeys keep makin that red bar up there bigger! am i really an asshat?? LOL

  7. #7

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    Thanks for all your help. I will play around with it some this weekend and let you know how things turned out...

    how difficult is it putting in one of those pertronix ignition conversions? poking around on the net, showed me a lot of praise has been given to them solving ignition probslems.
    just a thought

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    Dude yank that points dissy out and get a hei. Performance Distributors would be a good one to buy. Just give them a call and they will hook you up. If you have a RV cam it is not going to be big. The idle is a little high if you ask me. Mine idles at 800 rpm in park. I have a Comp Extreem 268 in mine.

    clicky here
    84 CJ7 383 sbc 350 trans d300 tcase short shaft 4"skyjacker lift 35" BFG'S.warn 8000 winch front/rear bumpers w/tire carrier & grill guard. woody c/v d-shaft
    MORE SRS 1" BL "swing out fenders"

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    Quote Originally Posted by mille239
    I have checked the wires, no crosses... I will check w/ a timing light to see if any/which cylinder is missingm, but like I said... it seems to run fine at idle, it's under load it misses.

    Corveeper, yes I still have a points distributor... what Petronix ignition conversion did you get?
    Petronix Ignitor electronic ignition conversion kit.

    This one is at J.C. Whitney but you can get them several different places including your local parts store.
    You might try swapping points and condenser before jump’n into a conversion kit since it’s a cheaper way to trouble shoot.
    My problem was I kept blowing the contacts off the points. Could’a been the hot coil I run or the RPMs my engine’ll hit, but either way the problem was cured with the ignition conversion.
    You will have to remove the distributor to install this kit, just FYI.
    Corveep = ’60 CJ-5 + ’65 L-76 Corvette.

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    Quote Originally Posted by jeep450
    Dude yank that points dissy out and get a hei. Performance Distributors would be a good one to buy. Just give them a call and they will hook you up. If you have a RV cam it is not going to be big. The idle is a little high if you ask me. Mine idles at 800 rpm in park. I have a Comp Extreem 268 in mine.

    clicky here
    A GM big cap HEI won’t fit unless he cuts a pocket into his firewall.
    Keep this in mind when shopping for distributors for a GM V-8 converted Jeep, it has to be the remote coil type unless you clearance it.

    As far as idle goes, if you have the specs for your cam it should say there. Most GM V-8’s will idle right ‘round 800 RPM, + or - 50 RPM. I’ve idled mine down to 900 RPM even though the cam specs call for a 1000-1100 RPM idle, but I’ve got a pretty hot cam (.490 lift intake & .510 exhaust).
    Corveep = ’60 CJ-5 + ’65 L-76 Corvette.

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    stupid question but is the choke opening all the way as the engine reaches operating temp?

    how did the plugs look when you changed them?

    if the choke is remaining partially closed it will cause the cyl. which runs the richest to run even richer which could cause a miss and fowled plug.

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    Quote Originally Posted by Corveeper
    A GM big cap HEI won’t fit unless he cuts a pocket into his firewall.
    I had a HEI in mine before I went with a complete MSD set up and had no clearence problems with the cap clearing. The firewall wasn't beat in or cut out.
    84 CJ7 383 sbc 350 trans d300 tcase short shaft 4"skyjacker lift 35" BFG'S.warn 8000 winch front/rear bumpers w/tire carrier & grill guard. woody c/v d-shaft
    MORE SRS 1" BL "swing out fenders"

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    Quote Originally Posted by jeep450
    I had a HEI in mine before I went with a complete MSD set up and had no clearence problems with the cap clearing. The firewall wasn't beat in or cut out.
    Did you mount the engine forward or something? I can’t even get a finger between the firewall and distributor base. This is a pretty common problem for GM V-8 converted CJ’s.
    Corveep = ’60 CJ-5 + ’65 L-76 Corvette.

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    Quote Originally Posted by Corveeper
    Did you mount the engine forward or something? I can’t even get a finger between the firewall and distributor base. This is a pretty common problem for GM V-8 converted CJ’s.
    I used the bolt-in kit from 4WD. It bolts right up to the factory engine mount holes in the frame. It allows for 1" adjustment up or down to help with driveline angles. Here is a link to it clicky here
    84 CJ7 383 sbc 350 trans d300 tcase short shaft 4"skyjacker lift 35" BFG'S.warn 8000 winch front/rear bumpers w/tire carrier & grill guard. woody c/v d-shaft
    MORE SRS 1" BL "swing out fenders"

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    Performance Distributors also has a small cap dissy for tight clearences.clicky here
    84 CJ7 383 sbc 350 trans d300 tcase short shaft 4"skyjacker lift 35" BFG'S.warn 8000 winch front/rear bumpers w/tire carrier & grill guard. woody c/v d-shaft
    MORE SRS 1" BL "swing out fenders"

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    Quote Originally Posted by jeep450
    Performance Distributors also has a small cap dissy for tight clearences.clicky here
    That’s along the lines of what I’ve been looking at, ‘cept I’ve been shopping Mallory, and that’s what I’m talking ‘bout when I posted “remote coil”. For now though, the Petronix conversion is work’n great so I’m in no hurry to spend more $$$ there.
    It’s interesting that you had a big cap HEI without clearance issues. Did you have any problems with clearance in front, have to move the radiator? Mine doesn’t look like it could move forward at all without get’n into the radiator, ‘course my radiator is a 3 row out of the Corvette the motor came out of, so maybe that’s where my clearance issues are.
    Corveep = ’60 CJ-5 + ’65 L-76 Corvette.

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    No I had a dua 1.25" core aluminum rad built for it. I have the long style water pump and the plastic flex-o-light flex fan. What year vette did it come out of? You may be able to switch to the short style water pump and get more clearence in the front. Some years had the short water pump factory.
    84 CJ7 383 sbc 350 trans d300 tcase short shaft 4"skyjacker lift 35" BFG'S.warn 8000 winch front/rear bumpers w/tire carrier & grill guard. woody c/v d-shaft
    MORE SRS 1" BL "swing out fenders"

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    Quote Originally Posted by jeep450
    No I had a dua 1.25" core aluminum rad built for it. I have the long style water pump and the plastic flex-o-light flex fan. What year vette did it come out of? You may be able to switch to the short style water pump and get more clearence in the front. Some years had the short water pump factory.
    It’s from a ’64 Vette. The L-76 with the “fuelly” motor, if you happen to know what those were.
    The motor mounts are welded pretty solid to the frame so I’m in no hurry to go shift’n the motor around, but thanks for the input anyway. I’m just gonna work ‘round what I’ve got and eventually go with a small cap HEI with the remote coil.
    But for right now the Petronix is do’n a hell of a job for me.
    Corveep = ’60 CJ-5 + ’65 L-76 Corvette.

  19. #19

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    Just thought I would add to this, but I have 2 buddys running 350's and both have no problems with the HEI clearing the fire wall.
    "Run what ya brung, and hope ya brung enough"

  20. #20

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    sorry but a L-76 fuelly kicks ass! thats some beef... :nutkick:
    76 cj5 AMC 304 d30 amc20 dana 20 t150 complete resto.

    SPEND MORE TIME THAN MONEY!
    some assmonkeys keep makin that red bar up there bigger! am i really an asshat?? LOL

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