1975 D100 400/727 misfiring problem

[CaseyMoparRoss]

I just put the engine in after painting it and new transmission, I hooked up all the wires right and made sure that it was ready to fire up and it ran pretty good but has a bad misfire at 650rpms up to about 3000rpms and on. It ran smooth before I took the engine out and I have it set at 14 degrees BTDC like it should be and no matter where I time it it still misses. Its not a bad miss but very noticable. Ive checked the plugs and they were somewhat black. I pulled them out and hooked one into the wire and grounded against my intake and theres a very small and weak looking flame. The plugs are accel shortys and they have less than 300 miles on them. Also I have a single point distributor and MSD blaster coil. I have tried nearly everything with the same results. Please help

[GHS]

First thing I'd suspect is a bad wire. It's very easy to break the carbon core or loosen one of the connectors when you remove the wires.

[CaseyMoparRoss]

I have checked evey single wire for leaking and such but all of them spark, But I noticed the spark was very weak on most of them

[moe7404]

moe in wichita ks double check the fireing order. all of this gos for both big blocks and small blocks. big blocks the dist turns counter clockwise, small blocks turn clockwise
#5 is in front of #7 on the engine, and #5 is before #7 on the dist cap. dont run them next to each other they should be crossed at right angles. if your dist cap has a vent in it plug it with j-b weld, when the rainy season comes youl be glad you did. been doing it for years no trouble.

[bherder]

Just out of curiosity, why would you want a points-type dist?

Black plugs usually mean 'too rich' a fuel mix, but, if your getting a weak spark, that could result in the same thing. Got another coil you can swap for testing purposes? Is the spark weak on every plug wire?

[moe7404]

moe in wichita ks for me i dont want a point dist but the electronic dist with the advance in the dist is a very good one. as a mater of fact i dont like ANY chrysler computer igintion. the electronic dist not only is a good dependable one but when it does give trouble its easy to trouble shoot and fix. my dad had a 1977 chrysler new yorker 440ci but it had that stupid lean burn system, that didnt last more that couple mo. it ran so much better.

[CaseyMoparRoss]

Yea it looked kind of weak but it was on every wire. I had another coil and put it on there with same result. firing order is right,timings right, no burnt wires. Could it be my plugs? and wih the distributor its a mallory dual points and I have had best performance with it plus Im in high school so I aint got a yearly salary... lol I guess you could say allowance

[CaseyMoparRoss]

I kind of have my mind on the plugs tho because they are black as ever.

[bherder]

Check to see what kind of voltage you're getting to the '+' side of the coil ..
(Pull the coil plug wire during this one..) During cranking, you should be getting full voltage to the coil. About 12-13 volts.

Does your present ign system still use the ballast resistor? If so....

(OK, plug your coil plug wire back in ...) Start it up ... Check your voltage at the '+' side of the coil again ... It should be about 9 volts. If it's anywhere around 7 volts, I'd try replacing the ballast .... Reason I say that is,
Low voltage going into primary side of the coil will = lower voltage (And a weak spark) out of the secondary side of the coil.

[CaseyMoparRoss]

well earlier I took the ballast resistor out completely and just bypassed it. but still runs the same. but while I pulled one of the plug wires after running it the number 3 plug boot pulled off really easy with the terminal

[dodgensince74]

did you recheck the gap on the points, they could be your problem, get a nail file and run it between the 2 contact points to clean them up. Check your engine ground to make sure its good.

[moe7404]

moe in wichita ks i used to put a ground wire from the points plate to a good ground on the engine, made a big difference in coil output. and the points lasted a lot longer.

[bherder]

Did you check voltage at the coil? Try running a jumper wire from the positive batt post to the + side of the coil and see what happens. You may be getting a voltage drop somewhere down the line.
Also, it sounds like you'll be buying a new set of plug wires anyway, which should eliminate that off the 'suspect' list ... Mmmmm I suppose it could be plugs, but my hunch is it's something else. Have you had someone else confirm 'Yup... Spark looks pretty weak' or does it just look weak to you?

[CaseyMoparRoss]

well in my view and what I have seen there is only a tiny partially blue spark. And from the coil it is sparking pretty good. So I think its either points, or my plugs because this engine ran great 4 days prior to pulling it out

[CaseyMoparRoss]

But I had no idea my choke flap was sticking open and I thought it was timing when I first cranked it and Im pretty sure I ran it like that for a hour or so and thats what caused the fouling. I am gonna try checking the voltage today at the + side of the coil. and on the ground side of the coil do I have to have the distributor hooked to that? in reference to moe in kansas

[bherder]

well in my view and what I have seen there is only a tiny partially blue spark. And from the coil it is sparking pretty good. So I think its either points, or my plugs because this engine ran great 4 days prior to pulling it out

Ahhhhh ..... Now we may be getting somewhere ....
So, if you pull the coil wire off where it goes into the dist cap, you're getting a pretty healthy spark from that? I'm guessing probably plug wires then especially since you said one fell apart on you, just from pulling one of the boots off. But also check to make sure the rotor or the inside lugs of the dist cap aren't scorched also. Also check the dist cap for any cracks (However small) which could lead to 'carbon arcing' and grounding or semi/grounding of the spark going to the plugs...

Oh, just thought ... Seeing as you may have 'less than good' plug wires ... Maybe could be just the coil wire....

[CaseyMoparRoss]

well they are fairly new mallory 9000 plug wires but I think I bought them a little too cheap if you know what I mean. but I will have brand new points and cap and rotor and plugs and wires by wednesday. So we shall see how she is runnin thn

[Speed Dragon]

The points are just a switch, if you have spark they are good. I put 20k miles on a set and they looked like new still (changed them anyway at the time just cause I had a new set). I'd put a full set of new Champion RN14YC plugs in it, make sure the choke is working properly (or just wire it open for the time being) and see how it does.

[CaseyMoparRoss]

well regular champion plugs wont leave enough room between th ewires and my headers. So what plugs besides accel has some less bulky plugs? I was wonderin on some bosch platinum 4's or somethin like that

[bherder]

well regular champion plugs wont leave enough room between th ewires and my headers. So what plugs besides accel has some less bulky plugs? I was wonderin on some bosch platinum 4's or somethin like that

Huh???
I've had headers on BB's SB's 6's and 4-bangers ... What kind of headers are you using that restricts the actual size plug you use? (Remind me to never buy them...)
Yeah, I've had headers where you had to use an 'angled' boot rather than a straight one ... and high-temp silicone .... but never 'shorty' plugs...

Maybe I've been out of the game too long, but this all sounds very freaky to me.

[Speed Dragon]

well regular champion plugs wont leave enough room between th ewires and my headers. So what plugs besides accel has some less bulky plugs? I was wonderin on some bosch platinum 4's or somethin like that

Use heat boots on the wires maybe? And don't use platinums unless you have a good hot coil (like 40k+ volts).

[CaseyMoparRoss]

well They are 2" prmary headers and theres barely any room.. I was just wondering if there is any other smaller plugs

[Speed Dragon]

What are you using now, Accels?

[CaseyMoparRoss]

well they will probably clear but its very hard to get a socket or a wrench to tightenthem.. I am wanting some bosch platinum4's but Idk what part number they are for the BB

[Oldblue1978]

well they will probably clear but its very hard to get a socket or a wrench to tightenthem.. I am wanting some bosch platinum4's but Idk what part number they are for the BB Casey, I run the RC14YC short champion plugs in my 400BB with big tube headers. they work nicely but you need to use a box wrench on a few to tighten them as theres no room to do the ratchet. You need a plug socket with a "hexed" end so you can turn it with a box wrench :)

You could have a bad condensor in the dist if you have hot spark at coil but weak spark coming out of dist. I have also seen worn dist bushings causing too much sideplay and erratic gap operation which in turn will cause weak spark because the gap constantly changes with rotation. Check dist bushings by holding onto reluctor and with moderate force, try to move the shaft sideways and see if it slops. it shouldn't move sideways hardly at all. very little movement, like less than .010" is tolerable, but more than that and its time for a new dist. good luck and let me know what you do :D

[moe7404]

moe in wichita ks if you drive hard 14s are way to hot. if you drive hard you should be at least 2 heat ranges coolder better 3 heat ranges. toss the champions, get ngks or densos. and get one that pulls the gap back to the threads, that will let you run 2-3 degrees more advance without pinging and keep the center out of the heat. i have found that small block chryslers like a gap of .045. but remember each .005 wider gap will cause the plug to act 1/2 heat range hoter but not to worry it just LOOKS hotter it realy isnt.

[CaseyMoparRoss]

I bought NGK fr5's they are the V powers and are 5/8 threads I talked to a guy wwith the same problem, I ordered new heavier points so I can finally rev it past 5000 rpm, and new MSD wires and some nice bolt on wire looms, I will get a new condensor why Im at it because I dont want to put everything else on and a 4$ part being the problem. Thanks everyone on here. aAnd sometim ein the near future Im gonna put a msd box and MSD billet distributor

[Oldblue1978]

true Moe, but when you have high compression as I do, 14s are whats required. I dont race the motor so I dont want it fouling at low revs.

Casey, I have learned the hard way about all those splitfire, v power , whathaveyous, whatchyamacallits, with big block mopars, those funky spark plugs do no mix well with them. I tried a set of those thingybobber plugs and the 440 ran great for 500 miles, then started backfiring like crazy. Too much spark is NOT a good thing especially if it lingers after the valve starts to open. The factory used Champion plugs for a reason :D

[Speed Dragon]

The NGK V-power are good, they aren't really a split electrode, they just have a groove in it. They are all I use in my turbo cars, haven't tried them in a V8 yet though.

[CaseyMoparRoss]

Well we shall find out tommorow ;) ha ha the parts will be here when I get home to put in my truck

[moe7404]

moe in wichita to:oldblue1978. "true Moe, but when you have high compression as I do, 14s are whats required." why do you need a hot plug when you are adding even more heat, i have NEVER seen that work, the more heat your engine makes the colder plug you want. been there done that bought the tee shirt. thats why i stoped useing Champion, they screwed there plugs when they put copper in them in the early 80.

[CaseyMoparRoss]

summit sent me the wrong wires, Or the MSD description says multi angle spark plug boots. But everyone of them are straight and they wont work with my headers so now waiting on some taylor mades

[Oldblue1978]

moe in wichita to:oldblue1978. "true Moe, but when you have high compression as I do, 14s are whats required." why do you need a hot plug when you are adding even more heat, i have NEVER seen that work, the more heat your engine makes the colder plug you want. been there done that bought the tee shirt. thats why i stoped useing Champion, they screwed there plugs when they put copper in them in the early 80. Whoops! my screw up, thanks Moe for calling me to task on that, hehehe! I am sorry for mix up, you are indeed correct, colder plugs, absoluteley. I was wrong on my 14's, in fact, I just checked my plugs in the Power Wagon and they are RJ12YC. I put them in there because I run Edelbrock RPM Aluminum angle plug race Heads, and that is whats reccomended. I did try a pair of Bosch platinums when I had the original manifolds and heads still on it, it ran great. but to my dissatisfaction, Bosch does not make a equivalent "short" style platinum plug when crossing it with the RJ12YC. The Edelbrock Heads have a heart shaped chamber and totally different plug position than the factory heads. I've had bad luck with those so called multi-spark plugs and I just dont' think much of them. I run 95 octane in the Power wagon and it currently pumps over 300 HP to the ground, via the all wheel drive system :D

[moe7404]

moe in wichita ks to: oldblue1978 thats ok your alowed one mistake a year, that was yours. the different plug position in the head might need a different heat range then again it may not. on the small block dodges in used to run even colder plugs, cant remember the numbers. they had the gap pulled back to where it was next to the threads. and i used ngk and denso. and i found i could run .045 gap. but if it starts dropping cylinders at hi rpm close the gap back.