small diameter HEI, was: 90/91 Vette distributor

[Ward]

On Wed, 19 May 1999 18:54:13 -0700, rr wrote:

> 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
> 
> 

The ProFlo also sets the initial advance at 10 degree to help with rotor to
cap alignment. All GM V8's are limited to about 45 degrees of added
advance.




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