small diameter HEI, was: 90/91 Vette distributor

[rr]

Tom Sharpe wrote:

>One more thought... My E.ProFlow uses a modified small or large cap HEI (mine
>is large) with the guts replaced and the mechanical (and vacuum) advance locked
>out. Normally the rotor advances with the mechanical weights to keep the rotor
>in phase with the cap. with 45 degrees advance, the effective movement of the
>rotor tip is 1/2 the distance to the next cylinder, possibly causing missfire
>at cruse but not necessarily at WOT. Look at the marks on the cap and rotor..
>if the erosion is on the end(s) of the rotor, maybe you need a wider rotor....
>I silver sodered brass stock to the rotor to make the tip wider to keep it in
>register with the plug wire at 45+ degrees advance. No more missfire.   Tom S
>

Wow, I could write volumes about the problems I had (long ago), before I
understood
this. I used to run points with the Delta Mark 10's or whatever they
were CDI systems.
I'd remove the vac-can and lock the breaker plate to the body. Also R&R
the gear to
shim the shaft to reduce end-play. Used to get the gears on 180 deg out,
not knowing
they are marked for rotor tip alignment, or that it mattered. Also,
didn't do any
phasing between the breaker plate and dist. body, you know, eh, that
looks close enough.

Then the misfire would set in, and just like you said, the rotor tip
only had erosion
on one end. Somethings wrong here...

Finally got a clear distrib. cap, a white line on the rotor, and a
timing light with
the engine running. Phased everything up, and what a difference (moved
the breaker
plate relative to the dist. body).

Back to the present time, after thinking about the max I can run, I'm
not as concerned
as I was. The only time that I'd be running more then 42 deg., is during
a cold
start & light cruise. Once warmed up, the total available is enough.

I did reduce the max allowed timing in the bin, so the cut-out is gone
also.

BobR.


>rr wrote:
>
>> It all has to do with startup spark, coolant comp spark
>> and lots of timing for light cruise. With a max of 42 deg
>> allowed by the software, and six more by the inital, for
>> a total of 48 deg, it cuts out...
>>
>> I've since reduced the max allowed to (42 - 6 = ) 36 degrees,
>> and all is well.
>>
>> BobR.
>>
>> Shannen Durphey wrote:
>> >
>> > rr wrote:
>> > >
>> > > I'm running a small cap now, no firewall clearance. Am trying to figure
>> > > out whether a large cap buys me anything. As far as being able to run
>> > > more advance. I'm thinking that maybe an alum headed vette may be
>> > > different, needing more timing and all.
>> > >
>> > > BobR.
>> > >
>> > Any pros to advancing base timing?  At least for testing purposes, you
>> > could use it to determine max advance.  Why are you looking for more
>> > advance?  No knock at present settings?
>> > Shannen