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Old 11-30-2006, 08:41 PM
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changed plugs and now the motor is missing

i could hear the car miss while driving but not under hard acceleration. well i found two wire boots with holes in them. there's are msd 8.5 wires. i replaced the two boots and took it for a test drive. i didn't hear any more missing. so then i did a search on here for plugs to use and found a post with a motor like mine and it said to run autolites 144's. the car had motorcraft asf42c that shows for a 82 mustang gt. i gapped the plugs to 40 and put them in. test drive and i can here the light pop pop of a miss. but don't hear it under hard acceleration. i don't hear the miss at idle but at light acceleration or putting at low rpm's

here's my setup- a 2 bolt main 454 bored to a 468. msd 6al box, molory dist and coil, trw forged pistons, merlin 320cc rectangle heads, 10 to 1 (pump gas), victor 2-r intake, solid 248/258@.050 recommended power range 3800-7000, th400, 3800 stall and 4.10 gears.

i just ran the car in the dark looking for a spark jump but didn't see any. i'm thinking of changing the the wires. any other idea's? it's missing more now than it did before i fixed the two boots. i'm going to pull the plugs in the morning and see what they look like.

anyone know if the old plugs i had are hotter or colder than the plugs i put it. am i running the wrong plugs for the world heads?

thanks for your time.

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Last edited by 71javelin; 11-30-2006 at 08:47 PM.
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Old 12-01-2006, 05:51 AM
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changed plugs and now the motor is missing

changed plugs and now the motor is missing

I'll bet it's still there....

Have you looked at the fuel/air ratio?
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Old 12-01-2006, 11:36 AM
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Don't want to state the obvious.. BUT why not just use the same brand of plugs as you have been using if it never gave you problems before? If it ain't broke, don't fix it.
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Old 12-01-2006, 11:57 AM
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check your connections. Its a good possibility that you fractured porcelin on one of the plugs if you're getting a steady miss. Take the plug boots off and grab the end of the plug and try to wiggle it up and down. if it moves at all its broken, if not, you're good. Check the obvious thigns first. I'm not saying it can't be the problem, but when you change a component (plugs) and you have a problem, you need to look for your problem there. I dont think if you change plugs your air/fuel ratio is suddenly going to be off. That's like losing your keys in the armchair and going out side in the yard to look for them!

Had this problem once before too, hope you get to the bottom of it-

K
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Old 12-01-2006, 03:08 PM
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i only took it for a short ride after i fixed the boots. so maybe it was still there? but i just changed the wires and it's still there. it's not a even miss and you can just hear a very light pop pop. i just looked at the cap and it doesn't look too bad but i'm going to change it anyways.

the old plugs where gapped at 45 and i only gapped the new plugs to 40. the big difference i see between the plugs is that. the old plugs center electrodes protrudes out and the new ones are recessed.

maybe i'll try the old plugs if it's still there after i change the cap. the reason i changed the plugs is because i wanted a cooler plug. the old plugs where glazed and i've got a little run on problem too. it looked like i could use a cooler plug.


i checked the plugs today and they where clean with a light tan color in the middle. shouldn't they carbon up if you let the car idle?
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Old 12-01-2006, 03:49 PM
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With the MSD-6 box you shouldn't get any carbon buildup unless the fuel ratio is very very rich. MSDs will fire .100 gap easily even with very high compression.

Killer's right.

I would be sure those aren't carbon core wires. MSDs won't stay inside carbon wires. They should be helical (spiral) core.

You could also have a bad coil.

Definitely check to see what plugs Merlin recommends.

Also I would be sure the plug thread reach (length) is correct for those heads.
I don't know what they require, but short thread plugs installed in long thread holes do cause a problem. ........ Saw it, but I didn't do it.

No offence intended, but I don't know anybody who would run a Mallory distributor even if they were given one for free.
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Old 12-01-2006, 07:44 PM
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LOL, well the mallory distributor came on the car. don't forget it has a mallory coil too i've only had the car for a few weeks so i've not done much to it yet. it had the msd 8.5 wires and i put new msd 8.5 wires back on it.

i checked the plugs merlin says to use. there the same size and reach but the center electrodes protrudes out and the ones i installed are recessed.
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Old 12-05-2006, 09:05 PM
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ok, i changed the cap and roter and the miss is still there. i'm going to try putting the old plugs in tomorrow. anyone else got any ideas of what else i should check? would a bad cam do it or lose rockers? but i don't hear any ticking. it goes like this- pop,pop---pop--pop----pop,pop,pop---pop but i can only hear it at low cruising speed. pedal has to be steady for me to hear it around 2000-3000r's

maybe too little or too much timming at that rpm?

i'll try another coil after i try the old plugs.
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Old 12-10-2006, 06:30 PM
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update,
i put the old plugs back in. i took it for a test drive and i didn't hear any popping. looks like my heads/motor doesn't like the recessed plugs. when i pulled the plugs, 7 looked used and one looked almost like new. #1 cylinder had very little gray on that plug. the other 7 looked the same.
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