help with a bad miss

[valley firearms]

New to this site. A lot of you guys seem very knowledgable as I read through your posts. I purchased a 68 coup several months ago and thought I'd re-live my teenage years again. I have owned half a dozen stangs 19+ years ago and my 65 fastback was my favorite. Here is what I started out with component wise in my 68 coupe.

Fresh 302
shorty headers
GT40-P cast iron heads
Edelbrock performer
Holly Street Avenger 570


After purchasing the 68 I installed a comp cam and gear drive two weeks later. It is their 280H-10 with 512 lift and 280 duration. I love the sound of a nice cam. Everything was good. I then put accel 8.8mm wires, new cap, rotor, and points. Started to miss slightly then progressed over a period of several days. Switched from my Holley to an Edelbrock a friend had. Ran OK without the miss but a little rich. Found out it was a 750. Didn't like the mini turbo mufflers so I had thrush glasspacks installed and had the tips run out in front of my rear wheels like the 65 GT350. Still running like crap. Tried several other carbs and still runs like crap. Ingition right? So the other day I purchased the Accel pointless conversion kit from Schucks. Also purchased an Accel coil, what the heck. It was a snap to install. Followed the directions to the T. Got her started and timed(about 34 degrees advanced). Started popping throught the carb and exhaust. I saw this coming so I dipped my avenger the night before. Went back to Schucks and got a rebuild kit for the Holley. Rebuilt the Holley and stuck it on. Ok, it's going to scream now. Now it idles crappy and pops out the exhaust when I accelerate. I used to be a good shade tree mechanic when I was younger. I have done so much to the mustang it's hard to pin point one thing. I think it's the ignition. Has anyone had problems with the Accel? I did pull the cap and found burn spots next to all the copper terminals. I changed the cap and it is not having the hot spot problem now. I don't know exactly when that occured though. I hate to put the points back in to see if that is the problem but I may have to do that just to start a process of elimination. I took #5 wire off and stuck it on another plug I had in my tool box. I looked like it was not getting hardly any spark at all.

I'm at my witts end :damnit: Please help. I hope this all makes a little sense.

Thanks!
Mike.

 

[bnickel]

i think the accel ignition kit is supposed to run on a full 12 volts, if so you'll need to bypass the pink resistor wire that runs from the igintion switch to the coil under the dash.
also if you have installed an external ballast resistor because the accel kit calls for it and you haven't removed or bypassed the factory pink resistor wire delete the ballast reisitor as you already have enough resistance with the factory pink wire.

i had a problem with my mallory unilite conversion because of the external ballast resistor and the factory pink resistance wire, once i removed the ballast resistor it was fine

 

[valley firearms]

Thanks for the response. Is this the same type of problem with the pertronix? How do I bypass the problem in detail please.


Thanks!
Mike.

 

[gsxrken]

I'd bet the problem is as bnickel advised too. You need to check your voltage at the coil, you should be getting direct battery voltage. Ford used a pink colored wire that dropped the volts down somewhat to the 7-8 volts range. If you have less then 12V, run a super-temporary jumper from battery to coil to see if it cleans up. I hope that is your problem b/c then you have identified the cause and the fix is straightforward- run direct 12V to the coil when the key is on. You may have to search www.vintage-mustang.com for more references to the "pink wire".

 

[bnickel]

Thanks for the response. Is this the same type of problem with the pertronix? How do I bypass the problem in detail please.


Thanks!
Mike.

first off what do the instructions say the voltage requirements are for the accel points conversion kit? shoot me a reply and we'll go from there

 

[valley firearms]

Here is a link to their directions.ACCEL eliminator instruction sheet

As you will read, they do state that if you don't have a resister wire than you must use a aftermarket resister. BUT, if you use their coil(I purchased the 8140C) neither is required. Maybe the coil and the resister wire are tag teaming my system? I have read that some have used the pertronix and had to use a direct 12V current. I will try the temp bypass and see what happens.

Thanks!
Mike.

 

[bnickel]

yeah you definitely need to get rid of the pink resistance wire for sure in this case. the coil you have is designed for a full 12 volts and probably has an internal resistor of some kind. using that coils and the pink wire is definitely going to cause some problems. i'm sure you'll find that you will still have to do some tuning after you bypass the pink wire but the engine should be a lot easier to tune and more responsive afterwards

 

[valley firearms]

I ran a wire from the battery to the + on the coil and it still has the popping and missing.

 

[bnickel]

have you played with the timing at since you did the bypass? try backing the timing off to about 28 degrees total, the p heads like quite a bit less timing than a regular head. also try swapping one of the other carbs you have back on see if that helps.

 

[valley firearms]

Well, I figured it out. I am embarrased to say it was the plugs. The 750 I was running must have fouled them. They didn't look that bad but I decided to clean them anyway. It runs now with no hesitation and is very responsive. I will have a problem with my idle in gear until I get a stall converter. Can I put just a MSD box on to increase the spark? Will a better spark help in performance? It runs good but just doesn't have much power. I figure low gears and a 3000 stall will help. I did not do anything with the pink wire as of now. Is the pink wire under the dash?

Thanks for all the help!
Mike.

 

[bnickel]

a better spark will almost always help performance. the pink resistor is under the dash and is the ignition hot on the ignition switch, i would definitely bypass it to see if it helps the in gear idle, it may but it may not. in any case it nedds to be bypassed to get max performance out of your ignition system and if you do convert to an msd, which is definitely a good idea but not absolutely necessary, you will need to bypass the pink wire anyway.

as for the stall convertor i understand perfectly on that aspect. my cam is a speed pro unit that the catalog says is the biggest with stock convertor, however in my case i think it's a little too big for the stock unit, i have an nos trw stock replacement cam in the garage that i may swap out or i may just suffer through it for a couple years until i install my aod.