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Re: Distributors...

Subject: Re: Distributors...
Date: Thu, 26 Apr 2001 11:56:49 EDT
In a message dated 26/04/01 7:26:04 AM Pacific Daylight Time, writes:

> Would I be better off rebuilding a 25D or looking at one of the others?

Rebuild your own distributor.

First, the Mallory unit has been marketed for years now as a performance 
option. It isn't. It costs more and it doesn't do the job any better, but as 
most installations involved replacing a thrashed, worn out Lucas with a brand 
new Mallory, of course the purchasers rave about them.

Just buy a new bushing for the body of your distributor, and have it pressed 
in - it will provide years more service and already has the correct advance 
curve, etc.

Be careful about concluding that yours is worn out just because you grab the 
rotor and can wiggle it.

First, the top shaft (held on by the screw under the rotor) is separate and 
intended to move, and second, you often get movement between the rotor and 
the shaft itself, so take the rotor off before evaluating it.

What you don't want is for the top shaft, which includes the cams that open 
the points, to be able to move very much in a side to side direction. If they 
can, it means that it will wobble with the pressure of the rubbing block on 
one side, and will introduce variation in gap and timing. It is usually the 
bushing in the lower part of the distributor body at fault, which can be 
renewed as indicated above.

One final 'point' - if you are not using points, then they can't push the 
shaft and vary the gap/timing, nor is the firing dependent on gap - just the 
passing by of the trigger. It is my feeling that fitting a magnetic trigger 
such as the Pertronix (or an optical one, though I prefer the former for 
reasons I won't bother going into here) will have excellent results even in a 
distributor that has a fair bit of wear, simply because that wear will no 
longer contribute to timing irregularity. If you have a distributor that is 
borderline, you may have good results just by fitting the magnetic trigger 

There is no substitute for properly overhauling the distributor, though. And 
once you have done that, have it checked on a distributor machine for advance 
curve, and adjusted (they change springs) as necessary.

At the moment, I happen to hate distributors - I am rebuilding the ones on my 
Islero - two six cylinder distributors, one for each bank, working 
independently, with truly bizarre and interesting advance mechanisms, 3 lobed 
cams - twin (expensive!) point sets in each, etc. Made like jewellery, 
though, with finely machined surfaces that gleam, and sealed roller bearings 
instead of bushes. It makes me nervous whenever I price parts, as they are 
always Ferrari (they used the same units on the Dino etc.)

I had to make up a template from sheet alloy to locate the pins the weights 
swing from so I could have them welded in place (one side looks like a 
replacement used distributor from an engine that has many more miles than 
mine, and was used hard - the pins were quite loose in the plate).

If anyone needs to do this job on their Ferrari/Lamborghini, I now have the 

At this point things are complicated enough without fitting dual Pertronix 
units and dual MSD boxes, which would be my inclination, so I shall just 
leave it stock for now.............


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