elementary manifold vacuum question

[Stowe, Ted-SEA]

Andy, I believe that you are correct about the Weber being a fair to poor
choice. I can see that the secondary only come in on the last 20% or less, I
think less, of the throttle range. I mean they only start opening at nearly
full throttle. on the plus side it is very easy to set up. having spent
years with LBC's I really don't want to switch back to the stromberg nor the
twin su's. even though the su's were fine when intact. thus my quest for
TBI. I am beginning to wonder if a system like the bosch LH Jetronic would
be a better idea, something that would just measure air flow and not MAP
like the gm TBI. I need to find a way to put a vacuum line into the base of
the carb to see what is happening there, those pulses would confuse the gm
ECU.

thanks. Ted Stowe

-----Original Message-----
From: am018 [mailto:am018 at post.almac.co.uk]
Sent: Tuesday, November 10, 1998 7:13 AM
To: diy_efi at efi332.eng.ohio-state.edu
Subject: Re: elementary manifold vacuum question


I suspect you are seeing  a particularly strong 2 cylinder pressure  pulse
due
to the combination of  the port design  and the  design of the manifold.

It may not be relevant but in the UK magazine Car and Car Conversions  it
has
been  stated  that Weber progressive carbs don't  work well on manifolds
designed for ones on which the butterflies open together and vice versa.

About 130 psi  compression pressure is  fine for standard B series engine.

With siamesed inlets the standard tuning procedure is to open out the inlet
port
as far as possible to partly reduce interference between cylinders


Andy Mcf