#1 plug question
 

I'm assembling my 30 Std Coupe with a recently rebuilt engine. It starts immediately yet runs a bit rough. I placed a sensor on all four Champion plugs and found the #1 plug does not fire consistently like 2, 3 and 4. I changed the #1 plug but the same problem continued. Is the problem a relationship between the #1 distributor cap contact point and the rotor or what? I'd appreciate any help. I enjoy the forum. Thank you.

Re: #1 plug question
 

What does the plug look like? Fouling? What is the gap between the rotor and body when it's at the #1 plug? Is it different than the rest? What is the point gap? Was the distributor rebuilt with the engine? If not how much side play is in the shaft?


As you can tell, there are a lot of things that could affect the plug firing, most of them are in the distributor. Was the sensor you were using an inline spark tester?

Re: #1 plug question
 

If it's consistently #1 then distribuotr body ( like ryan suggests above )would be my first check. side- play in distribuotr shaft? And we recently across a cam that was so worn down on one particular lobe that it was insufficient to open the points for #3 plug!!

Re: #1 plug question
 

Like the other said, but start with easiest first to rule out. Swap plug wires with one of the other cylinders. Inspect the Number one contact carefully. Play in the distributor shaft etc would seem to me be more erratic and not give you consistent results. I could be wrong as my experience with Model A's is limited.

Re: #1 plug question
 

Probably a stupid question but, what's the best way to check for side to side play in distributor? Use a tool to pry and watch for movement? Grab the shaft with your hand and move back and forth?

Re: #1 plug question
 

Check compression, check for vacuum leak. Swap plug with another cylinder.

Re: #1 plug question
 

I just grabbed the cam and checked how much it moved back and forth. I would say any discernible movement would be cause to change the bushings. Like Humperhill said, that kind of play would probably show up as more of an erratic spark problem.

Re: #1 plug question
 

You need to be concerned with the hi-voltage components of the distributor that are the body and the rotor. Modify a distributor cap so you can see what is going on as the rotor passes the #1 contact in the body. There is a transparent cap you can use instead, but I do not know if it is available from suppliers.

Re: #1 plug question
 

The gap between the rotor tip and the contact in the distributor cap has been advertised to be twenty five thousands . The gap should be the same at all four contacts in the distributor cap . More gap to a certain point can increase the intensity of the spark , less gap decreases the spark intensity . This is why that the gap needs to be the same on all four cylinders . I use a gap of thirty five thousands for hotter spark . This isn't a recommendation but just what I do for hotter spark at the spark plug . I also prefer the hotter Champion W-18 spark plugs .

Re: #1 plug question
 

Gentlemen, I appreciate all of your responses. The entire distributor has been completely rebuilt and there is no play in the shaft. I believe the issue may be w/the contact points in the new cap. Is it a matter of "extending" the rotor contact and then filing the cap's contact points so they are all the same distance from the rotor?

I'd also appreciate any candid comments on your experience with two systems from FSI - their electronic ignition system retrofit to be installed in my distributor body or the Zipper Distributor. Thanks again!

Re: #1 plug question
 

Usually the gaps are too small . I have only had to file the contacts in the distributor cap body . I suppose if the gaps are too large , soldering and filing the contacts may help . It looks to me like there would be a risk of melting the cap if soldering was performed .

Re: #1 plug question
 

I do remember the new distributor body I got having between 0-0.005 clearance to the rotor. Fixed by filing the contacts on the body.

Re: #1 plug question
 

My distributor body to rotor shows .025 on 3 cylinders, with .045 on number one. It does not seem to make a real difference.
I think you need to check how much gap you have between the distributor body and rotor for each cylinder. If anything is over 0.50, I would suspect that maybe the problem.
You can check the gap between the dist body and rotor by simple turning the engine over with a crank and using a feeler gauge.
My other concern if your gaps are within tolerance, would be either compression on that cylinder, or, possibly a valve hanging up.
Tom L.

Re: #1 plug question
 

It might be a valve sticking too. The spark is weak with a cylinder that's not pumping good compression.

Re: #1 plug question
 

If you have no mileage on that engine the rings in # 1 cylinder might not be seated,a compression check will give you some answers,60 lbs is good with a stock head.If no 1 is low shoot some oil in the cylinder and see if the pressure comes up,I had 35 lbs in a recently rebuilt engine in #1 cylinder,it turned out to be an intake valve not seating.