John Trindle writes:
My B had this manifold with an HIF6 when I bought it. It seemed to work
OK but was a bit gutless. A single HIF6 has about 3/4 the inlet area of
dual HIF4s, if my math is even close.
I have wondered about how this works, and I guess this is as good a time as
any to leap in with my question.
It's my (limited) understanding that any given intake valve is only drawing
air from one of the two SU's in a dual set up with the stock manifold.
Given the path, down a carb throat, around the bend into the balance pipe,
and around another bend, into the opposite intake port, I can believe this.
That route must flow incredibly poorly. If I had a single, larger, SU on a
well-designed manifold, one where all the intake ports had a reasonably
straight shot to the air cleaner, could I expect to flow more air? Could I
expect higher intake charge velocity, since there are more cc's of air per
minute being sucked through this set-up? Would it fill my cylinders better?
Why is a dual carb set-up favored over a single larger carb?
The experts out there must have opinions on this.
Phil Vanner
Mk1 Midget
I don't plan on giving up my SU's, I'm just curious.
-----Original Message-----
From: John Trindle [SMTP:johnt@tsquare.com]
Sent: Tuesday, March 16, 1999 8:47 AM
To: MG list
Subject: Re: obscure question - austin marina
On Mon, 15 Mar 1999, teds wrote:
> I have surfed around and can't find the answer to this.
>
> I have a intake/exhaust manifold from an austin marina, circa 1974, this
has
> an intake manifold that looks identical to the late model mgb's (same
basic
> engine), and a 1974 no cat, exhaust.
>
> what was the model/size of the SU that was sold with the marina ? I'd
like
> to try one on this manifold and see how it runs.
My B had this manifold with an HIF6 when I bought it. It seemed to work
OK but was a bit gutless. A single HIF6 has about 3/4 the inlet area of
dual HIF4s, if my math is even close.
I can't swear the low power was due to the carb, could have been timing or
compression (engine was nearing rebuild time). It started, idled, and ran
just fine... and less adjustment was needed.
--
John M. Trindle | johnt@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire H Stock | '88 RX-7 C Stock
|