Advice needed on flash burn on distributor cap please.

[Bob T]

Hi Guys, I recently installed a new 440 source h.balancer as the old stock one had shifted and I couldn't get a good timing mark. This led to finding out that the old dizzy was failing with play in the shaft and spark scatter.
Next up was a new Accel dizzy, coil and Rev-N-nator trick ecu.

Its a 440 HP2 with a mild ( unknown spec ) cam, Torker manifold, 750 Holley vac sec, 2" Headers by Doug.
We set it up at 20' initial and all in at 35' around 2200. It also has a 3.23 rear and I'm guessing stock converter.
On the way back from my mates workshop, I chopped it down at 95/km and it broke traction, sweet. It ran strong for about a week and then the performance dropped away a bit.
We went away for the weekend and although it ran good, it just didn't feel like it had that crisp bark and power to boot.

I dragged it last weekend and the best I could manage was 15.1 @ 97.25, a bit dissapointing but no breakages at least.

I have noticed the contact tips on the underside of the cap have slight flash burns at the extreme tip and the rotor has dulled out a lot, it only has less than 500 miles on it since new, maybe the rotor is slopping around??

Any clues or tips would be much appreciated, thanks

[John_Kunkel]

Could be a rotor phasing problem. For a discussion:

http://bangshift.com/blog/video-msd-s-todd-ryden-explains-rotor-phasing-and-distributor-differences.html

[Bob T]

You're probably right John thanks , I just got off the phone from a dyno guy I know and also suggested phasing. I have noticed that the rotor is not a very snug fit vertically on the shaft but it is difficult to guage how much free play laterally it should have. Any ideas how to measure it  
Or to reduce or stop the phasing??

Short clip from the drags last weekend

http://www.youtube.com/watch?v=pk43ACGmisg

[firefighter3931]

There should not be any lateral play on the rotor....once seated on the shaft it should not move fore/aft. 

Check your ignition wires for resistance....250ohm/ft is the maximum you should see. Less is better 

It doesn't hurt to check the spark quality. Ground an ignition lead and turn the engine over allowing the spark to display itself. What you're looking for is a blue/white color when it jumps to ground. If you see orange or yellow that's an indication of excessive resistance somewhere in the ignition system. Carbon tracks inside the distributor cap are not uncommon when used in conjunction with high resistance ignition wires. 


Ron

[Bob T]

There should not be any lateral play on the rotor....once seated on the shaft it should not move fore/aft. 

Check your ignition wires for resistance....250ohm/ft is the maximum you should see. Less is better 

It doesn't hurt to check the spark quality. Ground an ignition lead and turn the engine over allowing the spark to display itself. What you're looking for is a blue/white color when it jumps to ground. If you see orange or yellow that's an indication of excessive resistance somewhere in the ignition system. Carbon tracks inside the distributor cap are not uncommon when used in conjunction with high resistance ignition wires. 
Ron

Ok, thanks Ron, I will check the leads tonight, they are Moroso 8mm ,new in Jan 2012 and I only have 6700 miles on them .
With what you mentioned about high resistance in the circuit, I checked the ballast resistor last night and its 2.5 ohms, I seem to remember seeing a rev n nator spec recommending 0.8 - 1.0 ohms, I will see if I can hunt one down somewhere.
I have a new rotor to pick up today and will refit a different cap and also check the spark.

Its quite frustrating when it had heaps more grunt in it a couple of weeks ago and now its just vanished. Quite odd. Still starts and runs ok ,but nowhere where it was previously.

I appreciate your replies guys, cheers

[Bob T]

Ok, sort of an update..
I have rechecked the timing ( which was fine) and replaced the rotor with a very similar after market one. We then went to a car & coffee parkup today which was about 40 miles. I checked the cap again and there's a new flash mark which I presume lines up with . Will lightly sand the contacts in the cap with 400 grit to clean them up a bit.
Picked up the correct ballast resistor and will fit it tomorrow night and check the leads then too Ron.

Just guessing here, but does a higher resistance induce a higher voltage or higher current at the coil?? I would've thought higher voltage = lower current, with the inversely proportional rule???

[rt green]

so, you won the race in the vid?     do they make a clear dist cap for mopars?  or do you have to still  have to window one to test?

[Bob T]

so, you won the race in the vid?     do they make a clear dist cap for mopars?  or do you have to still  have to window one to test?

I red lit, bit I still got him haha.
I've never seen a clear window cap for one but I assume they are out there??

[firefighter3931]

Picked up the correct ballast resistor and will fit it tomorrow night and check the leads then too Ron.

Just guessing here, but does a higher resistance induce a higher voltage or higher current at the coil?? I would've thought higher voltage = lower current, with the inversely proportional rule???

It certainly won't hurt to check the lead resistance and install a low(er) resistance ballist resistor.  

Too much resistance will place an incresed demand on the coil and cause it to overheat and eventually burn up. Same thing can happen if you throw too much voltage at it.  

Electricity will take the path of least resistance so if the ignition wires are in bad shape the spark will scatter inside the distributor cap....seen it before. Carbon tracking is usually the result.

What is interesting about this scenario is that originally it ran quite good but now performance has dropped off. We need to figure out why this has happened and correct it.

Have you looked at the plugs ? Have you checked the spark color ?


Ron

[A383Wing]

the rotor tip & cap contact lugs do not touch each other ever...it like a spark plug gap...you will always get a "flash burn" on the tips of rotor & cap lugs....think of lightning striking something...it's gonna leave a mark. Which is what the spark is doing inside the cap

[RECHRGD]

Hey!  That looked like me in the yellow '68 coming down the return road.  What did I run??