Proper Needle Sizes for SU HS-4 Carbs. on Detoxed MGB et. al.

Thread View: net.auto.tech

4 messages

[T] Back to Threads [V] Tree View [G] Group Articles

4 total messages Started by K.DELBENE Tue, 29 Oct 1985 14:03

#503

Author: K.DELBENE
Date: Tue, 29 Oct 1985 14:03

25 lines
1808 bytes

A year or so ago, I detoxed my '79 MGB, removing the catlytic
converter and Zenith carb in favor of dual SU HS-4s and  a 
stainless exaust system.  Not wanting to go overboard, I left then
valve train in tact.  Well, last night I got to wondering about
the carbs' applicability with the stock pollution-control-influenced
valve train.  The question I have is whether the size 6 needles that
I put in are perhaps a bit too rich for the valve timing in the later model
Bs. I thought perhaps I'd try a number 21 instead.
Has anyone had experience with this modification?  Any recommendation
on needle sizes.  

While you're thinking about that one, try this one on for size: 
Sometimes when I accelerate hard off the line, I get a sharp knock
from the passenger side rear.  I've checked the brakes and spring shackles,
but nothing seems amiss.  I've had the problem since I bought the car 2 years
ago, but never experienced it on any other B's I've owned.  Having 
just had the car repainted 6 months ago, I told them to check for any frame
cancer, but the prognosis came back negative.  Anyone ever experienced such
a problem?

Any help  is much appreciated.  

					Kurt D. Del Bene
					Bell Labs - WB
					...!ihnp4!homxa!delbene

Re: MGB rear end noises

#513

Author: Hank Cohen
Date: Wed, 30 Oct 1985 21:10

21 lines
1781 bytes

In article <1154@homxa.UUCP> delbene@homxa.UUCP (K.DELBENE) writes:
>
>Sometimes when I accelerate hard off the line, I get a sharp knock
>from the passenger side rear.  I've checked the brakes and spring shackles,
>but nothing seems amiss.  I've had the problem since I bought the car 2 years
>ago, but never experienced it on any other B's I've owned.  Having 
>just had the car repainted 6 months ago, I told them to check for any frame
>cancer, but the prognosis came back negative.  Anyone ever experienced such
>a problem?
>
Your knock may be due to a bad rubber bushing on some suspension component
that flexes under hard accelleration.
I would like to mention that burning rubber off the starting line in an
MG or Triumph is a very dangerous game.  The first gear in those British
transmissions used to be straight cut instead of helical cut like all of 
the others.  This means that all of the load is carried by one gear tooth
and you can strip off a tooth or two trying to drag race in those cars.
My experience is a few years old so they may have fixed the problem but
there are a lot of MG's around that go clunk clunk clunk in first gear.
		Iligitimi non carborundum
			Hank Cohen

Re: Proper Needle Sizes for SU HS-4 Carbs. on Detoxed MGB et. al.

#399

Author: GERARD MAYER
Date: Fri, 01 Nov 1985 13:47

10 lines
1126 bytes

On my '71 MGB with dual SU carb I can easily test if the mixture is too
rich by lifting the manual piston rod slightly while the engine is at idle.
If it is too rich the engine slows and does not return to the same idle 
speed. When it is just right the engine speed stays the same as I lift the
piston rod. I have found this to be a sensitive method with a little
practice. Noise: I had the same problem and in my car it turned out to
be the vapor collection canister in the trunk was loose enough to hit when
I took OFF!!!
						Gerry Mayer
						uucp  linus!raybed2!gxm

Re: MGB rear end noises

#398

Author: Douglas Eshelman
Date: Fri, 01 Nov 1985 21:07

9 lines
1214 bytes

If you have wire wheels, it is possible that the splines are worn
(as they are on all my wheels, which go clunk on acceleration and
braking -- unless I get real excited with my spanner and hammer).
Ie, tighten your wheels.  It is also possible that your shock bolts
may be loose.  The offside, rear wheel splines tend to wear first,
since it receives most of the torque on accelaration.  The problem
is aggravated by improper care and tightening of the wheels ( I'll
take Reagan's stand and blame the previous owners ).

Thread Navigation

This is a paginated view of messages in the thread with full content displayed inline.

Messages are displayed in chronological order, with the original post highlighted in green.

Use pagination controls to navigate through all messages in large threads.

Back to All Threads