Bad miss when engine gets hot???

[Anonymous]

I have a 64 1/2 Mustang with a 71 200 engine. Holley 1bbl and Mallory dual point dizzy. It runs fine until it gets hot then it misses like crazy! I check the temp of the fuel line at the filter and it was 149* and the bottom of the carb at the bowl was 152* is this hot enough to vaporize the fuel ? If so how can i fix it?
Thanks, Joe

 

[jahearne]

Coil ?

 

[Anonymous]

I have wondered about that? Its old been on their since I bought the car in 1981! Wonder if it is?

 

[ludwig]

If you don't have an electronic ignition of some sort, you will never know. The cheapest is a salvage DSII system. However, I would suggest the Pertronix I because it is all in one package and easy to install. You skip the day in the junkyard.
When I put mine one, I had to set the idle waaaay back. You will never have a misfire.
David Vizard says that the misfire rate of a conventional points ignition is 15%. With a decent electronic ignition you can almost eliminate them.
If you got the Pertronix route, get the Flamethrower coil and you have addressed two issues.
I only suggest the Ptronix because it is relatively cheap and easy. Plus, when you move to the high-zoot DUI from FSPP, you won't be walking away from much work or money. Plus you will have a high output coil already installed.

 

[wallaka]

The DUI already has a high-output coil...

 

[jahearne]

Can you install a Pertonix kit into a Mallory dual-point unit? With a dual-point ignition, how about a high-output coil with an MD-6? Expensive, but nice set up with the Mallory dual-point.

 

[Anonymous]

I think I will do the Duraspark with a MSD 6 box.
Clifford split header and a 2300 Holley will be later!

 

[addo]

jahearne, I don't know if you could use the dual points to trigger. Certainly hooking up one set of points would fire, but two might confuse it!

 

[Lazy JW]

jahearne, I don't know if you could use the dual points to trigger. Certainly hooking up one set of points would fire, but two might confuse it!

It should work. If the MSD fires upon "make" the timing will need to be adjusted. If it fires upon "break" then the timing will remain the same, relative to the normal breaker point setup. The dual points only serve to increase dwell time (angle, duration, whatever). I would simply use one set because the extra dwell is not needed and the points will last forever.
Joe

 

[Anonymous]

Check if your exhaust header/manifold gasket is leaking near cylinders 3 and 4. I found out that mine was and was heating up my carb real bad.

 

[jahearne]

I re-read an old post where "66 Fastback 200" runs an MSD triggered by one set of points on his dual point '61 Vette. I knew I got the idea somewhere...

So, I'm curious - does the second set do anything or is it just left out?

 

[Lazy JW]

I re-read an old post where "66 Fastback 200" runs an MSD triggered by one set of points on his dual point '61 Vette. I knew I got the idea somewhere...

So, I'm curious - does the second set do anything or is it just left out?

The purpose of dual points is to increase coil saturation time. They are arranged in a staggered, configuration so that one set closes, the other set closes slightly later, the first set opens, then the second set opens. As long as either set of points is closed, current is flowing through the coil primary windings. As soon as the second set of points opens, the primary current is finally "broken", the electromagnetic field collapses, and the coil fires the spark plug.

If you use the MSD box, none of this is necessary, one set of points will work just fine.
Joe

 

[Anonymous]

OK But what about my question? What temp does fuel start to vaporize? And could it be the coil?

 

[Lazy JW]

I think I will do the Duraspark with a MSD 6 box.
Clifford split header and a 2300 Holley will be later!

You indicated above that you were going to upgrade your ignition. Jahearne suggested the coil being bad.

YES. Change the coil. A coil that old is likely to be weak. You are running a dual point distributor that increases dwell time, which increases heat, on an engine that has no need for longer dwell time with a coil that was not designed for it. The hotter it gets, the more the insulation breaks down, and it will get hotter yet. Count yourself fortunate that it hasn't left you stranded.

I doubt that the fuel is hot enough to matter.
Joe

 

[falcon fanatic]

I had a similar problem the other day. Driving in stop and go traffic and first I couldn't apply full throttle without it stumbling and dying, and then it just died. Temp guage indicated fine and the engine didn't feel especially hot, but the fuel in my little glass fule filter was bubbling. So, I parked on the side of the road, waited 15 minutes, and then the car drove fine. I think my carb got too hot and I was having vapor lock, but maybe it was my coil? Last time this happened it turned out I had a bad coil, but it was visibly leaking. I think having the coil mounted on the engine, like these usually are, is probably a bad idea - vibration and heat, etc...

Doesn't answer your question, but at least you know you are not alone!

 

[Anonymous]

With regards to the missing at higher temps, you might also try replacing the condenser if you have a points set up.

And Joe is on the money with the dual point setup. I have not had an occasion to pull the cap in years, but I think I left the 2nd set of points in the distributor, adjusted them so that they did not touch the cam lobe and placed a piece of cardboard between them to insulate them. I figured this way if the MSD box ever quit, I could return to dual points fairly easily or at least have another spare set stored under the cap. I think the MSD instructions even covered dual point distributors. As Joe mentioned, when triggering an MSD box, the points will last a long time since they do not have to carry any current to speak of.
Doug

 

[Anonymous]

Great guys thanks, Any suggestions on a coil till I get my HEI stuff? A MSD Blaster or just a cheap Wells for $15 at the Zone?

 

[Anonymous]

1 other thing to look at is the dizzy cap. It like the coil will sometimes get a 'hairline fracture' that will open up with heat while still working perfectly untill it gets hot. Ford big sixes were notorious for this 'back in the day' the small sixes were less prone but still susceptible. The cap when cracked looks fine but you can find the crack with your thumbnail. Often they crack when hitting a puddle while real hot-the plastic just cracks.

 

[Anonymous]

who was it on here that made the cool heat sheild that went over the exhaust manifold and looked like a little shelf?

that was cool...and probably would work in a situation like this

 

[Anonymous]

A lean condition or exhaust leak can cause your carb to boil and cause the problems you are having after sitting in traffic or at idle for any period of time.