Distributor Rotor Gap

Maury Novak · #1 (**permalink**) 09-24-2002, 06:49 AM

What would be a minimum/maximun allowable gap between rotor and post? I have just switch from a large Duraspark cap to a small older style Ford cap and rotor. I am running an MSD 6 system and will run either with a Blaster coil or a stock Ford coil.

Thanx for the feedback.

Maury

dalola · #2 (**permalink**) 09-24-2002, 07:33 AM

Hi Maury,

The tightest clearance without actually touching is ideal. Just make sure you get the proper rotor for that particular cap. I've seen many misapplications here, with gaps nearing 1/2"!! Also, as an added measure, drill two opposing small holes(~1/8") in the cap, between the towers, for ventilation. With the smaller caps, the air inside can become charged, and possibly cause a misfire condition.

Hope all is well up north.

Dave

Excaliber · #3 (**permalink**) 09-24-2002, 10:00 AM

I have found that TOO close can also create problems on some cars. I had a heck of a time, years ago, diagnosing a customers Chrysler that was fouling plugs and idling rich etc. Of course I went after the fuel system. Turns out it was the small rotor gap in the distributor causing a weak spark! I use the paper thickness of the "flap" on a pack of matches to gauge (now thats hi tech, lol).

Ernie

W2zero · #4 (**permalink**) 09-24-2002, 10:25 AM

Exca;ibur

Now that statement about the matchbook brought back a memory. My buddy and I used to flog his dad's 63 and a half Galaxie 427 single quad 4spd on the sly. No money and no tools so we used a single thickness of a matchbook for the points and a double thickness for the plugs. Gene could beat the dual quad cars out of the hole but he could only win when they screwed up.

Excaliber · #5 (**permalink**) 09-24-2002, 10:41 AM

Hey, thats how I learned that trick, no money no tools!

When I finally actually started making some money and had some tools, well,,,old habits die hard, HA HA! Here I am in Chrysler DEALERSHIP as a proffesional line mechanic using a friggin match cover to set up a BRAND NEW car!

OK, they drew the line when I got out my ball of wire to "hang" a muffler one day,,,,,,,,,

Ernie (PhD graduate, school of hard knocks)

Thanks for the memories!

427sharpe · #6 (**permalink**) 09-24-2002, 05:34 PM

If you use the small ford style cap, make sure you get one from an electronic ignition car. The later style small caps have small ridges built inside around the inner spark post to shield it from cross travel. Match it to the correct rotor, and you will not have a problem. if I am not mistaken, 1977 was the first year of the large cap, so 1973-1976 should be using the small one. Also, try to use 8mm ign wires. I think the part number of the cap you need is F968 in Wells.