Ok, I've about had it with the Mopar Performance distributor/ignition

[moparedtn]

Ok, facts first:
Pretty much stock 440 on real low miles since rebuild (less than 1k).
Comp Cams Magnum 270 cam (might as well be stock, just a tad lumpy).
Mopar Performance electronic distributor w/orange box, also purportedly new
(sure looks it, but it came with the car, so...)
Holley 3310 750 vac sec, new and working spiffy.

As you can probably tell from other old threads I started, tuning this thing has proven
to be a bear.
I'm currently running it with vacuum advance disconnected (the thing gets
majorly jumpy if I hook it up). If I try to give it any initial timing advance beyond an
indicated 5TDC, then the engine gets all jumpy and surges over 4k RPMs.
Heck, it even does it AT 5BTDC.

I just held it at an indicated 3500rpms this morning (after a few trial warmup runs) and set the timing by ear while holding the throttle steady there. ANY advancing at all and she got noticeably
rougher; when I scaled timing back, she smoothed right out.
Set it where it felt best at that RPM and then checked the timing with the light - yep, you guessed
it, exactly TDC.
Oy.

Starting to feel like the distributor might have issues beyond my ability.
Since the motor is so close to stock, I'm starting to wonder if I shouldn't just fetch a nice stock
point-type distributor and slap a Pertronix in it or something - maybe then it would tune easier
and I could hook the vacuum advance back up?

 

[texas69bee]

I came across this web site that will verify what you are saying. You may be correct on getting a different distributor after reading this. http://www.bperacing.com/ignition_kits

 

[jeepers007]

Check rockauto for a replacement distributor. Much cheaper than shelling out for a whole new kit. You can also buy another ignition controller (stock type) from them too.

No reason to go back to points though.

 

[YY1]

Are the advance springs working correctly?

I always set my timing by:

Advancing until it pings (under load, and only under load), then backing off until it doesn't.

Not "by the book technical", but works 100%.

The only time that method fails, is if the advance springs aren't pulling the weights back correctly.

 

[69a100]

I had the same problem as you in a /6. I tried my dammest to try to get it to even idle, let alone trying any throttle with it. I said screw it and installed a pertronix with the old dist. and have been trouble free happy ever since. Good Luck

 

[moparedtn]

I came across this web site that will verify what you are saying. You may be correct on getting a different distributor after reading this. http://www.bperacing.com/ignition_kits

Thanks! Bouchillon is describing pretty much exactly what's happening with the surging and bucking above 3500rpm.
Wonder if I could just slap a stock distributor from '72 in there? Is the harness the same as the MP electronic setup?

- - - Updated - - -

Check rockauto for a replacement distributor. Much cheaper than shelling out for a whole new kit. You can also buy another ignition controller (stock type) from them too.

No reason to go back to points though.

Yep, what I'm thinking too. Surely a stock unit will behave in this mostly stock engine?

 

[lewtot184]

ever do a compression check? those cams, in my opinion, make too much cylinder pressure. take the distributor apart and look at it to see what advance plate is in it.

 

[moparedtn]

Are the advance springs working correctly?
I always set my timing by:
Advancing until it pings (under load, and only under load), then backing off until it doesn't.
Not "by the book technical", but works 100%.
The only time that method fails, is if the advance springs aren't pulling the weights back correctly.

Never even made it to pinging...

- - - Updated - - -

ever do a compression check? those cams, in my opinion, make too much cylinder pressure. take the distributor apart and look at it to see what advance plate is in it.

Nope, sure haven't. It's a mid-70's block with the '68 magnum internals and heads swapped into it is all I know.
Distributor is (well, was 5 years ago) new right in the MP kit. No idea what plate is in it, whatever they came with.

 

[69a100]

What voltage reg are you using? It could be the problem as mentioned in the middle of the page here. Again Good Luck
http://www.imperialclub.com/Repair/Electrical/charging.htm

Early Charging System modified for use with a 70 style VR

There are a number of reasons one might want to upgrade a per-1970 system to a transistorized voltage regulator. The list of reason include
•Chrysler recommends you switch to a transistorized VR if you upgrade to an electronic ignition from a points style ignition.
•If you have to buy a new voltage regulator, the difference in cost is only about $5-10 more for the transistorized unit. Not to mention, the quality of replacement early style VR's is spotty.
•The transistorized VR will have a longer life.

 

[moparedtn]

What voltage reg are you using? It could be the problem as mentioned in the middle of the page here. Again Good Luck
http://www.imperialclub.com/Repair/Electrical/charging.htm

Early Charging System modified for use with a 70 style VR

There are a number of reasons one might want to upgrade a per-1970 system to a transistorized voltage regulator. The list of reason include
•Chrysler recommends you switch to a transistorized VR if you upgrade to an electronic ignition from a points style ignition.
•If you have to buy a new voltage regulator, the difference in cost is only about $5-10 more for the transistorized unit. Not to mention, the quality of replacement early style VR's is spotty.
•The transistorized VR will have a longer life.

It's an electronic unit. Mandatory for use with the MP electronic ignition, pretty much.

- - - Updated - - -

Will a stock/rebuilt unit from a '72-up go right in place of the MP distributor? Is the 2-pin connector the same?

 

[monaco66coupe]

Take the distributer apart, and see if there are even springs there. I bought an electronic kit direct from Chrysler once, and there weren't any springs, period. If there are, tighten them up some to get them to be more responsive.

 

[mopar 3 B]

Stock distributor will sit right in. I would pull the orange box and replace it with a stock unit first.

 

[texas69bee]

Will a stock/rebuilt unit from a '72-up go right in place of the MP distributor? Is the 2-pin connector the same?

YES... Leave everything the same and ditch the distributor. To be reassured, call bperaceing.

 

[bigmanjbmopar]

Just throwing this out there but I had a similar issue with surging and jumping, turned out to be cracks in the insulators of the spark plugs. Have you checked the firing at night to see if you can see any sparks being thrown out to the side? Plug wires all good?

 

[moparedtn]

Just throwing this out there but I had a similar issue with surging and jumping, turned out to be cracks in the insulators of the spark plugs. Have you checked the firing at night to see if you can see any sparks being thrown out to the side? Plug wires all good?

Yessir, all brandy-new Autolites and the expensive MSD "heavy" wires.

- - - Updated - - -

Stock distributor will sit right in. I would pull the orange box and replace it with a stock unit first.

Guess that would be the easiest/cheapest first course of action if it actually would make any difference here. Is there really that much difference in the stock unit vs. the orange (or chrome) MP ones?

- - - Updated - - -

YES... Leave everything the same and ditch the distributor. To be reassured, call bperaceing.

Awesome, thanks again. A1/Cardone has a rebuilt unit for like $50 at the local parts joint. Can't hurt to try it if it's simple plug n play.
So leave the orange box in place?

 

[red 69 runner]

Ok, facts first:
Pretty much stock 440 on real low miles since rebuild (less than 1k).
Comp Cams Magnum 270 cam (might as well be stock, just a tad lumpy).
Mopar Performance electronic distributor w/orange box, also purportedly new
(sure looks it, but it came with the car, so...)
Holley 3310 750 vac sec, new and working spiffy.

As you can probably tell from other old threads I started, tuning this thing has proven
to be a bear.
I'm currently running it with vacuum advance disconnected (the thing gets
majorly jumpy if I hook it up). If I try to give it any initial timing advance beyond an
indicated 5TDC, then the engine gets all jumpy and surges over 4k RPMs.
Heck, it even does it AT 5BTDC.

I just held it at an indicated 3500rpms this morning (after a few trial warmup runs) and set the timing by ear while holding the throttle steady there. ANY advancing at all and she got noticeably
rougher; when I scaled timing back, she smoothed right out.
Set it where it felt best at that RPM and then checked the timing with the light - yep, you guessed
it, exactly TDC.
Oy.

Starting to feel like the distributor might have issues beyond my ability.
Since the motor is so close to stock, I'm starting to wonder if I shouldn't just fetch a nice stock
point-type distributor and slap a Pertronix in it or something - maybe then it would tune easier
and I could hook the vacuum advance back up?

Thats exactly what I did,took my original points distributor and added the Pertronix Ignitor II.car runs better than ever.

 

[texas69bee]

Just make sure you buy electronic ignition. The remans come in brown. I didn't much care for the look. You can buy through autozone, pick up at store. If you don't like it then refuse delivery without paying for shipping.

 

[Shorthorse]

Cam changes will affect your vacuum. Check your plenum vacuum at idle. What may be going on here could be a combination of lowered vacuum at idle which would affect the power valve in your Holley and the vacuum advance of your distributor.
http://forums.holley.com/entry.php?430-Holley-Power-Valve-Tuning
If you must maintain the stock look of your car, I would try what is suggested above for Mopar distributors.
Personally, I switched to a "ready to run" distributor for my race car 10 years ago (shift at 6500 rpm's). Got rid of the ignition box and the ballast resistor. These distributors can be made mechanical or vacuum advance. The advance curve is easily changed for tuning and performance. Simple, clean, easy and generally less expensive than a distributor and box combination.

 

[lewtot184]

the older mopar electronic distributors had 13 degree advance plates which means 26 crank degrees. i usually run 8-10 degrees initial with these to get a 34-36 degree total. stock springs will bring it all in around 2800rpm. basically good enough for that cam. the comp 270 is a short cam ground 110lsa with 4 degrees of advance ground into it. the 270 along with comp cams magnum replacement and xe268 close the intake too early with anything over 9:1 compression. this does make for very good vacuum, maybe too much for the vacuum advance; but thats fixable. the stock magnum cam is ground on 115lsa and closes the intake at 71ABDC. the 270 will close the intake at 61ABDC; very noticeable difference. the summit 6401 cam is ground on 114lsa and closes the intake valve at 74ABDC (very good choice for stock or near stock engines. has about 10 degrees more duration at .050" lobe lift and .200" lobe lift, with a little more lift at the valve with absolutely no bad driving characteristics). from my experience these big cube engines in near stock condition don't want short cams with tight lsa's and early intake valve closings; unless the compression ratio is down around 8:1.

 

[moparedtn]

Just make sure you buy electronic ignition. The remans come in brown. I didn't much care for the look. You can buy through autozone, pick up at store. If you don't like it then refuse delivery without paying for shipping.

Reckon since the car is set up for electronic already, that's easiest to do at this point. Thanks.

- - - Updated - - -

Cam changes will affect your vacuum. Check your plenum vacuum at idle. What may be going on here could be a combination of lowered vacuum at idle which would affect the power valve in your Holley and the vacuum advance of your distributor.
http://forums.holley.com/entry.php?430-Holley-Power-Valve-Tuning
If you must maintain the stock look of your car, I would try what is suggested above for Mopar distributors.
Personally, I switched to a "ready to run" distributor for my race car 10 years ago (shift at 6500 rpm's). Got rid of the ignition box and the ballast resistor. These distributors can be made mechanical or vacuum advance. The advance curve is easily changed for tuning and performance. Simple, clean, easy and generally less expensive than a distributor and box combination.

The car is making very good vacuum now, around 11-12hg @ idle. So much so that I put the original 6.5 power valve and 72 jets back in the Holley, just like it came with (I had a 3.5 and 75's in it with the lumpy purpleshaft it had before the cam swap).

Interestingly, this motor exhbited the same higher rpm jitters/stutters with that old cam (that wound up with wiped lobes, hence the swap). It got somewhat better with the bigger jets and PV, but never quite cleared up.

Starting to think the thing is possessed. Never had a 440 act sooo sensitively to tuning.