K&B rotor

[William F.]

Has anyone done any kind of independent "scientific" testing to determine if the longer copper tip makes any difference in engine performance compared to most newer rotors that have the shorter tip? Anybody's engine that wouldn't reach redline with shorter rotor tip that did turn up when the only change was going to the longer tip K&B rotor?Anybody test spark voltage at end of plug wire comparing short vs longer tip?

[Larry M.]

Re: K&B rotor

Has anyone done any kind of independent "scientific" testing to determine if the longer copper tip makes any difference in engine performance compared to most newer rotors that have the shorter tip? Anybody's engine that wouldn't reach redline with shorter rotor tip that did turn up when the only change was going to the longer tip K&B rotor?Anybody test spark voltage at end of plug wire comparing short vs longer tip?

Bill Clupper did an article on this subject for the RESTORER about a year or so ago. Check your past issues.

His conclusion(s) were the longer rotor tip did make a difference.

Larry

EDIT: Summer 2009 Issue of the Restorer. Page 16.

[William C.]

Re: K&B rotor

Depends on the engine, but in a SHP engine with advertised 11 to 1 compression, the difference is there with a traditional ignition system. If the system has been upgraded, another matter, but in a restoration with original parts I'd lean toward the longer tip as originally designed by GM.

[William F.]

Re: K&B rotor

I'm very familiar with the article and enjoyed it. But description of differences in the rotors is not the same as controlled experiments as to whether it really makes a difference.-A high performance engine that wouldn't turn up but would with ONLY change being rotore?Anyone?

[William C.]

Re: K&B rotor

That's how I found out about it, real world, real engine, about 30 years ago. Doesn't make much difference in a 10 to 1 compression engine, but certainly did in an 11 to 1 version.

[John D.]

Re: K&B rotor

You know it's getting harder and harder to find a well made rotor at the auto stores anymore. NAPA used to have a heavy duty black one with regular tip and then they had one available with extended tip. All they have now is one with the tip held on with plastic instead of riveted.
Unless you are drag racing like Clupper was the regular rotor with the shorter tip works just fine.
I understand that K&B rotor is one fine rotor with an extended tip and it's definitely affordable.

Ask your local NAPA store if he has any RR1670 laying around. It's extended tip.
Nothing like talking out of both sides of your mouth.
By the way while you are at NAPA pick up a nice set of CS786P points as they will easily go to 7000RPM. JD

[Tim S.]

Re: K&B rotor

By the way while you are at NAPA pick up a nice set of CS786P points as they will easily go to 7000RPM. JD

let'r eat!

[Gene M.]

Re: K&B rotor

William,
I have made my own extended tip rotor. I shoot for .020" clearance with the contacts in the cap I'm going to use. I have found the rotors over the counter are around 1/16" gap. I would assume that the gap wants to be less than the spark plug gap.

The rivet, or drive pin style is the best to modify. I select a plastic heat staked type for a donor brass tip. I file out the "H" notch and drill a new relocated hole for the drive pin to give me .020" gap with cap contacts. Replacing the drive pin with a shallow headed #6 machine screw via taping the hole in the rotor works better than the drive pin.

[William C.]

Re: K&B rotor

I took a slightly easier approach, and just stocked up a few old "goodguys" to tide me over. With only two cars using points and old-style rotors, I think I'm covered.

[George J.]

Re: K&B rotor

I'm very familiar with the article and enjoyed it. But description of differences in the rotors is not the same as controlled experiments as to whether it really makes a difference.-A high performance engine that wouldn't turn up but would with ONLY change being rotore?Anyone?

Bill,
While I have no hard data, I did replace the rotor I was using with the K&B extended tip rotor, and the car seemed to run better. Not greatly, and it may be in my head, but I wouldn't use another, now. My car did reach red line, before the switch, though. It's a '65 fi car.

George

[Timothy B.]

Re: K&B rotor

I think Petronics or MSD makes one with a adjustable tip. How you adjust to a dimension like .020 I ahve no idea. From my memory this rotor is a pretty stout piece..

[John D.]

Re: K&B rotor

Accel made one with extended tip. Don't know if they do or not. Standard made them for quite a while.

[Joe C.]

Re: K&B rotor

It's not very difficult to make a large gap rotor into a small gap rotor. Just apply some heat and re-form the plastic mount.

I currently have a K & B rotor installed in my distributor. A well made and heavy duty piece, and WELL worth the cost!

Some replacement distributor caps are made with a fair amount of slop in the mounting. The alignment tab allows a degree or two of rotation and the base itself allows some lateral movement. When using a small gap rotor it's important to ensure that your cap is centered within a fairly tight dimension, otherwise rotor-to-electrode contact could occur. I currently use a MSD distributor cap which has precision location on the distributor body. It takes some pressure to get it to snap into place and once installed, cannot be either rotated, or wobbled.

There are posts somewhere that I remember reading which explain the principle behind WHY mid seventies and later HEI and other high spark energy systems use a larger rotor to cap electrode gap.

[Clem Z.]

Re: K&B rotor

also if you are looking for max perfromance from you stock type dist. use nylon screws to install the rotor so there is no clear path to ground for the high voltage.

[William F.]

Re: K&B rotor

clem,
Where do I get nylon screws of correct thread and length? Have you actually seen a problem that was caused by voltage gounding to metal screws and corrected by substituting nylon screws?
Thanks