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Re: ZS to HIF

To: MonteMorris <mmorris@nemr.net>
Subject: Re: ZS to HIF
From: "Henry D. Reynolds" <hdr@halsoft.com>
Date: Thu, 16 Oct 2003 13:26:03 -0500
i am sure other will disagree with me but...

I would set the timing based on the total mechanical advance at
somewhere just past 30-ish degrees. At the very least set the timing
according to the specs for that dist. and then make sure that you
overall mechanical advance does exceed (it will probably be far
short of that figure) that by very much or you may have some souvenir
pistons to show for it.
(ask me about my souvenir pistons)

  unless you distributer is brand new it is going to have more than a
  little slack in the springs and elsewhere. and you will find that
  when set to factory specs you run out of advance early.

PS I just read the Classic Motorsports article "Supercharging your
MGB" in by Carl Heideman. In there he says,

     "The ported head and improved camshaft would take more (than
     32 degrees of total) advance without detonation, but still
     made peak power at 32 degrees."

This pretty much agrees with my experience although i have had none on
a dyno.

I had the opportunity to speak to Carl at length at the MG2003 in St Louis
and he seemed to be of the opinion that connecting to ported versus manifold
vacuum made little practical difference.

PPS not connecting vacuum to your dist even if it is not the correct
site (ported versus manifold) will severely reduce your MPG. I did an
experiment in June on the way back from MG2003 and without vacuum got
about 19 mpg on the highway and with vacuum about 29 mpg. the car was
my 1978 MGB with (2*)HIF4 carbs and a 41288 D25 dist. with the vacuum
advance connected to the intake manifold and NO TCSA. It was driven
between 70 and 80 most of the way home. It seems that this dist is
intended for "ported" vacuum but it is connected to the manifold


MonteMorris wrote:
> I got the HIF's mostly all connected and plumbed tonight, but of course have
> more questions:-):
> (HIF's and all related hardware off  a 74 parts car. They are going onto a
> desmogged 79B)
> 
> 1. the 74's instruction plate by the radiator says: time to 11 degrees BTDC
> at 1500 RPM and gap plugs at .025. The 79 is timed about 18-20 degrees BTDC,
> .035 plug gaps, and has a points dizzy in it. What settings should I try now
> and should I use the dizzy out of the parts car, or keep the one that's in
> the 79 (45D, I believe).
> 2. I rerouted the heater hose (with metal tube) downward between the
> manifold and the heat shield. Will this cause any problems, or should I put
> it back up by the valve cover?
> 3. On the Chicagoland MG site,  I read to use the old alloy back plates off
> the 74's air cleaners to put inside the oval foam air cleaners (#223-220,
> pp. 7) so you can use the Unisyn easily without removing the air cleaners. I
> can see you must bore out the mounting holes on the back plate so the bolt
> heads will be flush, but what type of mounting bolt (head) would you use?
> Thanks,
> Monte
>           79B, Carmine
>           67B, BRG
>           74 1/2 Rust, parts car
-- 
"Alle Menschen werden Bruder"

  Henry D. Reynolds - System Administrator
     mail: hdr@pobox.com - phone: 512.448.3617 - cell: 512.699.8658




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