Ballast resistor with a Crane XR700 YES or NO

[conkitchen]

According to the internet the answer is no. However in the Crane instructions it says yes if the box feels hot after 15 mins of use.   

 

Currently have a black coil with a BR which gets kinda hot, but the coil and ignition box remains normal in temp. What seems to be happening though are the plugs fouling. Running BP7ES or some other W7ES perhaps. I know it's a #7 heat range. They were black and sooty when I removed them. Cleaned'm up and threw them back in. Ran good for a little but now it's back to back firing. Likely fouled. I know old plugs, should get new ones. That's next I guess but what heat range? Stay with 7 or perhaps 8 with a Crane box.  Gap is per the spec @ 28+/-. I have heard with electronic ignitions one can run a bigger gap. Bigger gaps mean fatter spark, So there is that to ponder.  

Granted I have only just started to work out what's going on so no real in-depth information just yet.  I did not do this original install, but it fires right up and idles fine. Just gets rough running when you give it gas.  Carb and timing have not been verified so that's another glitch in the future diagnosis.  New wires wouldn't hurt although they appear fine.   Anyways, the first answer sought is the Ballast Resistor issue.  

 

I have a new Blue coil which I understand is internally resisted. Thinking of swapping that and foregoing the external BR and hook up coil directly to the 12+ source from the key on/run.  

 

OR

 

keep the black coil and just undo the BR.  

 

 

 

Edited August 22, 2023 by conkitchen

[paulyg]

There was one of these on my car when I got it. No ballast resistor with some MSD coil, which I'm sure was very low resistance. Since you haven't verified timing I would start there. 

[dlacey]

Run a hotter plug? Leave ballast resistor alone?

[Tdh]

Personally, I think you’re barking up the wrong tree. If you’re running a Bosch black coil (newer made in North America) it should have a resistance of 3.2 ohms and is fine for use with the ignition you’re using sans resistor. I’ve put those things on a ton of cars with no issues. I typically use Bosch blue coils, but that’s just because I like blue better. Either way check the resistance between the poles of your black coil with a multimeter. You should get around 3.4 or so. 
 

My first go to for fouled plugs would be a carb check and timing. Jetting, clogging, all the things you know to check already. Hell, an excessively dirty air filter can cause a car to run rich. 
 

Good luck. These things can be frustrating. 

[visionaut]

Kinda concur - if it's something that gets worse with time - then that's typically NOT electrical...

 

I've no experience with Cranes, but for MSD - with the analog MSD 6A it's not necessary to bypass the ballast, but for the Digital MSD 6A/6AL, it says it's recommended to eliminate it.

 

And I do gap my plugs wider running the MSD. I've played with it, and have tested up to .050. I'm currently set at .040...

 

FWIW, a known CDI (and Pertronix) failure mode is not enough voltage - when that happens, the unit can constantly turn on/off under load. If it's experiencing a miss or hesitation at higher rpm, it is usually not directly ignition. So like Tdh said, check other stuff.  

 

But if it is electrical, and only at higher rpms, some other possible ignition-adjacent possible causes can include coil or coil plug wire failure, arcing from the cap or boot plug to ground or spark ionization inside the cap.

 

 

[conkitchen]

Okay, a mild update. Pulled the plugs and black soot after just idling and throttle reving for like 15 mins. Besides the hot BR when running, I'm gonna just swap out the blue coil I have and forego the black coil and BR per the standard 73 set up.  

 

The big change I'm looking at is the carb. Currently it's a 38/38 which is likely way too much fuel delivery for this engine. Nothing about it tells me it needs it. Don't want to buy different jets and other things to make it run better. So I gonna swap in a 32/36 and report back next week.  after the change in coil, plugs, and carb. I'll fiddle with the timing too.  I like to base set my timing with a vacuum gauge and then tune by ear.  

 

Who needs a stinkin timing light? 

 

 

['76mintgrün'02]

19 minutes ago, conkitchen said:

Who needs a stinkin timing light? 

 

Not you!

['76mintgrün'02]

Apparently.

 

 

But, if you change your mind!

 

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Are you trying hotter plugs this time?  I read that lower compression engines prefer hotter plugs, so I went from BP6 to BP5 on my '76.    BP7 seem chilly.

[Son of Marty]

46 minutes ago, conkitchen said:

Who needs a stinkin timing light? 

 

Jeez, Tom just died a little inside🤢

[conkitchen]

2 hours ago, '76mintgrün'02 said:

Are you trying hotter plugs this time?  I read that lower compression engines prefer hotter plugs, so I went from BP6 to BP5 on my '76.    BP7 seem chilly.

Yeah gonna pick up some NGK bp6's or 5's but will try running the 7's (cleaned up again) with the different carb as a base line first.  

 

[JohnS]

[conkitchen]

30 minutes ago, JohnS said:

This is good stuff. I have a pack of W8DC, may just throw those in however I think they are Platinum's so maybe not.  

[conkitchen]

SO, running without ballast resistor makes no difference. However putting a 32/36 carb on there did.  The 38/38 was just too much carb.  

 

Installed the blue coil also without the resistor. Same NGK7's and no fouling, but gonna run a hotter plug down the line just because these have been fouled and cleaned and reused several times. For now gonna see what happens. 

 

Tuned it with the vacuum gauge and tweaked the timing per, and it was basically set where it needed to be at the get go. 

 

In summary kid's if you are fouling spark plugs when just idling and blipping the throttle, you need to check your carb.  

 

Check out that cool manual choke device.