Spark plug gap question?

[jasonL78]

On the L79 I am running a pertronix street ready distributor. My question is do I have to open my spark plug gap from factory specs because of the electronic ignition. I know every car seems to start different but normally I would pump the gas 2 or 3 times then try to start the car. But it seems the car cranks alot before even tring to fire? It has the stock carb with original style choke. Any ideas....

[RPOLS3]

Does it start after you let off the key (key in run position- not cranking position)?

May have something to do with not getting a full 12V while cranking.

Jake

[jasonL78]

Good point. The car seems very cold blooded. This motor has only been started about 6-10 times so I am still working out the bugs. Tonight when I went to start the car cold it cranked a while before firing. Since I had the car running for about 20 minutes on Sunday. I would think I could pump the gas 2 times and it would start quicker than it did. Once the car warms up it starts fine. Just looking for a couple of ideas.

[Lynn]

You do not have to widen the gap. You get to.

Point being that the limits of the point type ignition dictated the smaller gap.
With hotter spark, you can widen the gap which will give you a little more spark.

Either way, it should have no effect on your starting condition. I still have points in my Z for now, and it cold starts in a nano second. I would say less than one revolution of the engine.

I would check to see what the voltage is with the key on, then make sure you have good voltage while cranking.

Also, before starting next time, remove air cleaner and look down the carb. Hold the choke open with your finger and give it some gas. Make sure you are getting a good squirt. Then let go of the choke plate and make sure is "sets" firmly.

Hard starting could be either gas or spark issues.

One more tip. I am guessing that car had either 43 or R43 plugs. It will run even better on R43S plugs. The "S" plugs have a slightly extended tip putting the spark farther out into the cyl. However, and this is IMPORTANT, you should index the plugs to the gap is down just to be sure there is no piston interference. But then, I am one of those screwballs who always indexes the plugs.

[scuncio]

I am not a Pertronix fan, but when I did use them I always set the gap at .035". As Lynn mentioned, this is unlikely to be your problem for cold start issues. Does your L79 have a Q-jet? Sometimes the fuel will bleed out of the bowls if you don't use epoxy during the rebuild, making cold starts difficult.

[jasonL78]

Ok thanks guys I will check the 12 volts while cranking. Yes it does have a Q-jet and was rebuilt by Eric. I remember another post about spark plugs a couple years back saying I think an NKG was better then the stock AC plugs?

[earntaz]

You may run a 12V "jumper" to the coil and see if if fires off ... this bypasses much of the crank/fire wiring. If it starts immediately, then troubleshoot why there is no 12V during cranking ... TAZ

[Lynn]

You will find wildy varying opinions on spark plugs. I don't know of anyone who has any kind of high tech machine to measure actual spark performance. Mostly based on our own experiences.

My personal preference for an old GM engine is an old AC spark plug. If you can find the "C" plugs, even better, as in a CR43 or a CR43S. They come up on ebay from time to time and are a better plug, normally way cheaper than the "right" plug.

If Eric rebuilt your carb, you can almost eliminate that. Yes, he is human, but not likely an issue. Divorced choke? Again, make sure it is closing.

With no more info than we have to work with, I would suspect the Pertronix.

[Donnie]

put the points back in.