so the other day while doing a burnout, i was told it sounds like the engine was misfiring.

looking inside the distributor cap, i see there is a fair amount of carbon scoring, sounds like things are jumping around in there.

it is a mopar electronic distributor with the tan cap, and it is vented, and an MSD system.

how do i go about fixing this? is it just possible that the vent isn't enough and i need to drill some more holes in the cap?

Check the carbon ball on the center.. see if its
there.. a lot of those will tend to disappear and
people dont catch it... the diameter of the dist
is the biggest problem with high output ignitions
and the timing curve where it moves the timing
a fair amount

Vents not the problem. Mopar distributors are poor quality these days. Just installed one in my street rod. Distributor cap button was 1/2 gone?? One advance spring was rubbing on the under side of the advance plate. Pick up magnet was not parallel to the reluctor - about .010 variance top to bottom. Surprisingly, when I spun it up, signal variation was less than 1 degree, so I am using it - but it's a turd. BTW, the curve out of the box is extremely slow - all in at like 4K.

distributor has been recurved, so i'm good there. i come in when i want and get to full advance. reluctor gap is good also.

it may be a turd, but it is usable. i just need to figure out how to fix this.

Just found this problem on a 69 nova I did a carb and other work on. The center for the coil was pretty much gone but still ran poppin and spittin. I drill holes between each tower which helps EXCEPT for when you`re setting your timing and grab the cap...........

I spray my stock style cap out every couple
of months with brake cleaner and wipe it out
good to get rid of the trails.. make sure its
dry(blow it out with air)before you fire it up

aluminum inserts in the cap? try and find a cap with copper inserts....brass is even better for conductivity...

misfire fix???

http://www.ebay.com/itm/MOPAR-Electronic-Ignition-MISFIRE-FIX-Modd-Distributor-Reluctor-440-340-Hemi-/322031143791?hash=item4afa8d4b6f:g:xqUAAOSwBahVGW~j&vxp=mtr

OEM Mopar Modified Distributor Reluctor Stops Misfires!
Gennie Mopar, modified to cure a common problem! Read on....

Smallblock, Big Block, and Hemi owners - listen up! If you've got either an OEM Mopar electronic distributor, or a MP aluminum distributor, here's a cure for that all-too-common, hard-to-diagnose, misfire problem! This can be intermittent, and cause you to drink (or, drink more, as the case may be.)

Frequently, due to a myriad of problems, your distributor rotor tip is NOT POSITIONED SQUARELY UNDER THE CAP LUG (terminal) when firing takes place! Result: an intermittent misfire that can drive you nuts; no amount of external fiddling can fix this. The cure is re-phasing the reluctor on the shaft, so that when the plug fires at, say, 35 degrees BTDC, the cap terminal is aligned with the rotor tip. This is accomplished by re-indexing the reluctor, which requires a reworked reluctor with additional locating slots. And E-berg's got one for you, CNC precision machined, complete with detailed instructions.

NAPA # M020 for cap with brass inserts. #M013 for rotor

vent holes. copper terminals. adj phasing so the arc swing is equidistant with dead center on the terminal if using vac adv and that is the only system that changes phasing in operation & in a killer setup I'd actually like to have the terminals (their operating arc) the closest at WOT (no vac) when the required voltage is the greatest) but with the gap reduced having the arc distance centered is OK & far better than it was prior. Burning comes from high resistance which is not the issue in a dist cap (one that ain't carboned up) and the other is gap which is always present in a dist cap by its' design but minimize it by reducing the rotor blade tip to cap terminal clearance to .015" (best). NAPA has an Echlin rotor MO3000 with a .060" longer blade for $8 & change out the door (NAPA ain't never cheap) or make your own (better cuz you can get the gap just right). As said the center button & I like a light smear of dielectric grease on top of the rotor blade where it will contact the center button

I bought one a few days ago. The instructions recommend drilling a hole in your "spare" cap ( just below #1 tower) and shining your timing light in there to verify rotor position re the #1 terminal. Vacuum disconnected and full advance - 3K or above. I will try it this morning. Reluctor looks like a quality piece.

This fix, does it work on MSD dist with locked timing


Steve

For "Rotor Phasing" only vac adv alters the rotor position when running (IE a 11 deg (stamped on arm) can will shift the rotor 11 (dist) degrees around the cap terminal circumference arc. I would drill the (1/2") hole on the cap on top in between the center terminal and the #1 terminal then shine the light on it & you'll see it in action. The can shifts it CCW on a SB and CW on a BB. easiest cure (if needed) is to widen the slot in the top dist metal shaft where the rotor locks into then JBweld the opposite wall to restore the width back to where it was for a snug fit on the rotor so you can shift the rotor around however much is needed.

No. Mechanical advance does have an effect on rotor phasing. Any advance be it mechanical or vacuum changes rotor phasing.
I think you are mixing rotor to reluctor phasing. The post is about cap to rotor phasing.
You want the cap to be phased perfectly at peak tq rpm with 100% load. To test you must simulate low manifold vacuum(if you have a vacuum advance or load sensing ignition.)
The less load, the less important rotor phasing becomes.

I respectfully stand by what I posted. Lets do this: drill the 1/2" hole in dist cap flat top 2/3 of the way between the center terminal and #1 terminal and cap off the vac adv. with your light ready, start it/rev it up & see if the rotor moves.

If the rotor doesn't move when doing what you describe, the distributor is locked. The reluctor and rotor are mounted on one piece, AFTER the mechanical advance. If the rotor doesn't move, you have no centrifugal advance.

If we were closer I'd make a (cash) bet! Alright, since I'm making the statement I will go out tomorrow & recheck

No problem... I accept paypal
Seriously though. If you look at how the mopar distributor is made, if the weights are giving you advance, then the rotor has to move. It should move half of what the timing on the balancer indicates.

I'll tell ya what bro, since I'm feeling frisky today lets make a 10 dollar bet on this! I do PP too & I will (even) include the 3% (if it comes to that). And the bet will be (& correct me if I need to change the wording). "a non locked out "regular" type dist, if you cap the can, the rotor phasing position will be the same at idle as it will at 3 or 4K RPM". And we are assuming that at 3 or 4K it WILL be into the springs. Feeling gutsy! EDIT in other words the rotor will be pointing to the same position in relation to the cap terminal, the rotor will NOT move when you "freeze" it with the timing light