[TR] Is My Distributor Worn Out?

[Randall]

> How do you know if your distributor needs to be replaced or 
> rebuilt? I have a Lucas 25D installed.

Hook up a timing light, start the engine, shine the light on the timing mark.  If it jumps around, the distributor is worn.  Slowly
rev the engine up while watching the mark.  It should move gradually and evenly until it's roughly 3/4" or 1" away from the pointer
at roughly 2500 rpm.  Again if it jumps around, or doesn't move, or immediately flops over to full advance, there is a problem
inside the distributor (eg bad or missing springs).

IMO this is a good test to run at every major tune-up.

Vacuum advance is much less important, it is mostly a fuel economy device.  To test it, you'll need to be able to hook up a vacuum
source (like a MityVac) to the advance module.  I don't know the TR4A specs offhand, but if it doesn't leak and you can get the mark
to move by at least 1/8" or so, the advance module is probably OK.  I usually don't bother to test this unless I suspect there is a
problem (engine seems sluggish at part throttle).  It only changes fuel economy a little bit, maybe 4 or 5 mpg at most, and mine
varies more than that just depending on where and how I've been driving.

For a more accurate test, take the distributor to an old time "Auto electric" shop that has the magic machine.  I bought one on
eBay, but haven't restored it to operation yet.  (Just got the on-car wheel balancer put back together, hope to try it out
tomorrow.)

-- Randall