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MG MGB Technical - HS4 to HS6 manifold conversion

Has anyone fitted twin HS6 SUs by fitting a conversion plate on the standard HS4 manifold?
Graham Gilmore

Yes a HS6 will bolt up to a HS4 intake, as you know the HS6s carburators have 4 mounting holes, but 2 of the 4 match up to the HS4 intake, the next issue is you need to realy port out the HS4 intake to justify putting the HS6s on it. I think the purpose built intakes for the twin HS6s on the MGB, the aluminum one over the steel maniflow is the way to go.
Hap Waldrop

Fitting HS6 carbs to an otherwise standard engine is not likely to increase performance at all, so unless your engine has had significant porting and head work done, probably with a different camshaft, putting them on may be a waste of money. You may even see a drop in performance and almost certainly it will use more fuel.
Mike Howlett

Don't do it Graham, you will lose some of the low to mid rpm torque, unless you have a very modified engine and are using it above 4500 rpm most of the time, i.e. track days, sprinting or racing.
Had HS6's on our std B, complete waste of time and money, lost that lovely low end grunt that makes the B so nice to drive. Changed back to HS4's and also back to cast iron manifold, much better now.

Hope you are both well
Regards
Graham & Cynthia
G Cherry

The car has a Peter Burgess Rally head, 285 cam and is currently running a long manifold 45DCOE with 45D vacuum less dist. and uses lots of fuel. Peter Baldwin recommended HS6s last time he had it on the rolling road when it was giving 115BHP at 5,200. Picked up a pair of HS6s for a good price but now need manifold, air fiters etc.

Both good at the moment, enjoyed the Marathon.
Graham Gilmore

Graham,

For better fuel mileage, you should consider getting a distributor WITH vacuum advance. The one with no vac is more appropriate for competition where your foot is usually planted on the floor or on the brake, and nothing in between.

Charley
C R Huff

The car is used for rallying Charley.
Graham Gilmore

Understand the need for HS6's now Graham, sounds like a bit of a beasty.

Regards
Graham & Cynth
G Cherry

This thread was discussed between 30/07/2009 and 05/08/2009

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