distributer reluctor air-gap check?

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pjc360

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today, i fired up my 360 magnum, and some of you guys know that i had a miss fireing issue that i thought i had tracked down. But i guess i was wrong about finding the problem because it the miss firing while at an idle was back today.
It didnt last for long.. One the engine was warmed up it stopped. But i am begining to wonder if this issue is inside my distributer? i'm thinking there is a good chance the air gap on the reluctor and pick up coil being off could cause a miss fire at idle. My distributer is brand new with less then 1000 miles on it, i purchased it from Don at fbo systems, and he curved and phased it with his distributer machine. He suggested i set the initil timing at 16 degrees wich would land the total at 34 degrees because there is 18 degrees in the distributer. And he suggested i hook my vaccum advance up to manifold vaccum.
So i do as he instructed when i first got the distributer and it never ran right that way, thudding out the exhaust while at an idle. It runs fine thru out the entire rpm range doesnt miss a beat, but at an idle i'll be damed if i can find whats causing this stuid little miss fire. It does it more noticeably when the vaccum advance is hooked to manifold vaccum. Right now i have my vaccum advance on ported vaccum And i have my initial set at 14 degrees and total timing at 32 degrees with vaccum advance on ported.
I have crane cams lx91 ignition coil a wells ecu box a wells 2 prong ballast resistor at 1.0 ohms. My wells ignition box is grounded good, i have aa 10 gauage ground wire running from the ignition module mounting bolt to the engine block. All of my ignition wiring is brand new including my ecu ignition module connector and wires pick up coil wires coil wires its all brand new and done up real nicely. My spark plugs are brand new ngk v-powers zfr5f11's i also have 8 brand new autolite 3923 plugs all of them gapped at .035. My plug wires are new borg warner select 7mm's they have about 500 ohms of resistance per foot.
Everything on this is brand new ignition wise and is wired up correctly and i still have this miss fire out the exhaust, i am so frustrated with it because it shouldnt be doing this. I tried the autolite 3923s to see if that would help, and it did help it run a little better, but after about 3 or 4 days of running the 3923 plugs this miss fire is back? and it came back today because i tried turning up my initial timing from 14 degrees to 16 degrees and thats when i noticed the miss fire was back, i put the ngk v-power plugs back in it and set my initial timing back to 14 degrees and it seemed to go away once it warmerd up?
When i had the distributer cap off i pushed down on the pick up assembly plate and that did something to it because once i put the cap back on and fired it up it was running crummy, thudding out the exhaust.
I thought i read online somewhere that don sets the air gap differently on his distributers, does anyone know this for sure?
 
You set a stock [email protected],with a brass feeler gauge,thank Badsport for that info.As for Don's stuff,I don't know.If the reluctor rubs/grazes the pickup,my guess.You have not stated if new,or not.If possible,run matched cap/rotor from the same supplier.
 
i guess what i should have asked is what in the hell causes a miss at idle but no where else? from 800 rpm all the way to 6200 rpm there is no miss at all, it dont miss a beat. But then once im at an idle i can hear it thudding out the exhaust. Take off and there is no miss. This only happens while its idleling.
Is this most like an exhaust valve sticking or something? should i try dumping some atf down the carb while its at an idle? I mean a sticking exhaust valve or the air gap on the reluctor not being right is the only 2 things i can think of. If it was ignition related wouuldnt i have the miss somehwere else too other then just at an idle?
 
i have a wells gold distributer cap it has copper contacts, rotor is a standard blue streak. Ecu is a wells same with ballast resistor coil is a crane cams lx91. distributer is brand new curved and phased by don at fbo. I mean what can this be? seriously i do not get it. virtually everything on this engine is brand new.
 
Good response.What has been done to this Magnum?Head swap/reground/new bigger cam,carb /intake? I threw a couple answers,the other day.Don't know your combo.Working,on the same silly on my Magnum.
 
I doubt gap is the problem. The trigger signal is RPM related, the engine is starting. Since starting happens at at about 200 RPM, 800 RPM is well above that.

Here is a trick to test your ignition. Use a timing light, move to each plug wire. It should provide a consistent blink rate on each cylinder. Don't look directly in the light, just shine on a dull surface.

If all seems well then, consider doing a compression test.
 
i have already done a compression test, 150 psi on each cylinder.
my guess is its ether something in the ignition or an exhaust valve, if its in the ignition my guess is distributer or ignition module.
Because when i put in dons distributer from fbo systems in it thats when this all started, but it very well could be plug wires too. It's kinda hard to keep them from being corossed. I dont know its just a strange issue.
 
the strange thing is this issue only happens at an idle, no where else in the rpm range does this happen while driving or sitting still. Only at an idle.
 
so what can be the cause of this? what can make it miss while at an idle but not miss anywhere else in the rpm range? Maybe its the wells ignition module i have. Been thinking if i got an aftermarket cd ignition like a crane or a mallory that it would most likely solve whatever this is, ifits ignition related.... It could be a sticking exhaust valve iv'e been told.. Maybe i will try dribbling some atf down the carburetor while its at an idle and see if that quiets it down.
 
pjc360 said:
so what can be the cause of this? what can make it miss while at an idle but not miss anywhere else in the rpm range? Maybe its the wells ignition module i have. Been thinking if i got an aftermarket cd ignition like a crane or a mallory that it would most likely solve whatever this is, ifits ignition related.... It could be a sticking exhaust valve iv'e been told.. Maybe i will try dribbling some atf down the carburetor while its at an idle and see if that quiets it down.
Click to expand...

its sounds to me like it may be a rich or lean mixture miss and not a solid misfire. is this thing running on 7 cylinders at times or is it a kind of puff or thud slight miss?

this may be unrelated, but here is something to ponder...

http://www.forabodiesonly.com/mopar/showthread.php?t=203055
 
Do I understand that this happens ONLY when the vacuum is hooked to manifold vacuum? If so, that should be the really big clue right there. Either it is OVER advancing so far as to cause stumble (the same thing would happen if you crank in enough initial WITHOUT vacuum) or else the vacuum advance is changing the air gap in there enough that the thing will not trigger.

It's been awhile since I've played with a single point Mopar (yes I realize yours is breakerless) but my recollection is that on a dist. with ANY amount of wear, the vacuum will tend to OPEN the points gap, which causes over--advance, as opening the points further advances the timing.

It might be that you have the wrong (way too much advance) vacuum can

Worn parts in the dist, such as the advance plate pivot

Or a weak pickup coil. I ran into one tune-up mechanic who CLAIMS this happens more than you might think
 
We were working on one the other day tried two new distributors and when we on hooked vacume advance and the miss would go away, so we no longer run vacume advance and have no problems.
 
So what was the outcome of the timing light test for each cylinder? Seems like you have been working on the ignition for months, based on all the past posts.
 
no this miss happens wether the vaccum advance is on manifold vaccum or ported vaccum. it dont matter if its on ported vaccum or manifold vaccum. and it is like a small thud/puff while its at an idle.
strange thing is this only happens when its at an idle. I dont think the idle air/mixture is too lean or too rich, i adjusted them with a vaccum gauage and set them for the highest vaccum reading.
And one of my ngk v-power zfr5f11 plugs did quit working on the number 5 cylinder but i replaced it with a brand new one and it seemed to help it outt alot. Then i purchased 8 brand new autolite 3923 plugs to see if a colder plug would help and it seemed to help, so then i decided to turn up my initial timing from 14 degrees to 16 degrees and thats when it started thudding out the exhaust while at an idle real bad, so i turned it back down to 14 degrees and it was still doing it.... So then i put the ngk v-power zfr5f11's back in it and it almost completley went away but it still does it occasionally.
This is a strange issue for sure, i have never seen anything like it before.
Just to make sure everyone is on the same page i have my initial timing sitting at 14 degrees total timing is at 32 degrees running the ngk v-power zfr5f11's and i have my idle air mixture on thee carburetor set for the highest vaccum reading on my vaccum gauage.
When i try to run my vaccum advance off of manifold vaccum the thudding out the exhaust becomes even worse no matter how i set it, I did have my vaccum advance set to add 10 degrees of timing at an idle with the initial set at 14 degrees and the total at 32 degrees and it seemed to do ok like that, but then the thudding out the exhaust returned and ever since then i have put the vaccum advance on ported vaccum and left it there and i still have the thudding out the exhaust when its at an idle.
 
this never happened untill i installed the distributer that i purchased brand new from don at fbo systems, i did notice that the prong on my rotor is a little loose....Its a standard blue streak rotor, i have a different rotor that i can try real quick to see if thats what the isssue is?
But my ignition module is new and it is grounded, ballast resistor is new and reads 1.0 ohm resistance, the coil is new crane cams lx91 coil. All my ignition wiring is brand new, the connector to my ignition module is brand new my coil wiring is new. alternator field wires are new. I just cant seem to figure out what the hell this is and its extremeley frustrating. It runs great just has that slight little thudding out the exhaust when its at an idle and it doesnt always do it, just every once in awhile, but when the vaccum advance is on manifold vaccum the thudding out the exhaust is even worse.
I called don at fbo systems to talk to him about this issue and his answer was for me to throw away my brand new edelbrock carburetor and purchase a quick fuel ss series carburetor with vaccum secondarys and a 4 corner idle circuit. He said my edelbrock carburetor is whats causing this issue. and of course the carburetor he thinks i should have is 500 bucks brand new, i call BS on that. i really dont think its the carburetor.
 
Today, i fired up the engine and let it warm up and took the air cleaner off and dribbled a little bit of atf down the carburetor while it was running just to lube up the valves or break anything that might be in there loose and i also dumped a littl bit of atf into my gas tank. So that should help if its a valve.
The only other ecu box i have to substitue for the wells ignition module is a mopar gold unit wich cant be ran on the street. I have tried multiple ignition coils, a borg warner select canister coil and a wells canister coil and this crane cams lx91 e-core style coil so i dont think its the coil causing this, i have tried an echline and a wells 2 prong ballast resistor and changing them out doesnt change it.
 
well i run a 1406. im not an advocate for edelbrocks, i love my holleys, but i do have an eddy on my 318, that carb works perfect in just about every way. BUT , this is the 3rd edelbrock i have been through before i got one that would run good.... . if it were me, i would try another known to be good running carb just for ***** and see how the engine re-acts to it before i went out and bought another carb.
 
I have also used 2 big bottles of carburetor cleaner and checked for vaccum leaks, i sprayed around the intake manifold and the carburetor nothing made the idle jump up, so i dont think this is a vaccum leak. I have also done a compression test, each sylinder was at 150 psi.
I did a resistance test on the pick up coil in the distributer, and it checked out at 300 some ohms, i have done resistance checks on my plug wires they are at about roughly 500 ohms of resistance per foot. I have fired it up in the dead of night and watched for cross firing, couldnt see any cross firing.... I just dont kno what else i can look for here. I really dont think that 14 degrees of initial timing is too much for this engine. Its the 300hp crate 360 magnum and it has under 25 thousand miles on it. I have triple checked my floats in the carburetor , they are correct, my firing order is correct. Triple checked that too.
 
i dont have any other carburetor that i can try.... Truth is i would like to get a better carburetor and its in my plans for the future, thinking about getting ether a demon or a quick fuel slayer series carburetor. i just cant swing that right now, so the edelbrock will have to do for now. I just really cant see the edelbrock being the cause of this issue, its brand new. And i know how to tune the edelbrocks. i have owned severalof them over the years had them apart a million times.
I am running the edelbrock rpm air gap dual plane intake manifold too and i have a 1 inch 4 hole phenolic carburetor spacer on it. I have taken the carburetor spacer off to see if that helped and it didnt make a difference, in fact it runs better with the spacer, has more low end grunt with the spacer and throttle response is better and it starts better with the spacer.
 
i have a holley 600 on my 360. i have tuned it to vacuum. with it at the highest reading , it still puffs a tad from a lean condition. im also at 6200 ft in elevation. if i turn my mixture screws out another 1/2 turn, i richen the carb enough to get a damn near perfect idle even though im losing a little at the vacuum gauge. just something to consider
 
I'm kinda of jumping in here late but from what I read and gather out of all your posts is.
one, either your balancer is not showing true readings as in it slipped or maybe your using the wrong pointer/balancer combo. Because the traits your describing sure seems to point to over advancing.
 
balancer is not off, i'll garantee you that. this engine dont have near enough miles on it.
my dial back timing light pretty much proves the balancer is right. And I have used my friends dial back timing light to check the timing and his light reads the same as mine.
 
I guess i could by some tming tape to make absolutely sure, but i am about 95 percent sure this balancer is eading correctly. It has the numbers marked in the balancer.
 
pjc360 said:
I guess i could by some tming tape to make absolutely sure, but i am about 95 percent sure this balancer is eading correctly. It has the numbers marked in the balancer.
Click to expand...

Unless you have actually CHECKED TDC with a PISTON STOP you are making assumptions that may not be true.
 
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