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MG MGB Technical - New to US spec MGB's

Hi guys

Need a little help, I'm helping out a mate who has just brought a US import MGB.

I need to know what we can remove from the carb set-up, what needs to stay and what to look for.... or should we just fit UK spec SU's ??


Based in Belgium,

Many thanks Matt

Mid 70's MGB
Matthew Mason

Matt. Much depends on the year of the car. If it is a 1975 or later, it was shipped to North America with a Zenith Stromberg carb and a combined intake/exhaust manifold with a cat installed just below the carb. Not a great set up. It is possible to fit the earlier twin SU carbs, along with the matching exhaust manifold, to such a car. Much information on how to do this in the archives. Be aware that there were two flange thicknesses on the intake/exhaust manifolds (one for the twin HS-4 carbs and one for the twin HIF carbs). Thus, if purchasing an intake and exhaust manifold, make sure they have the same flange thickness.

The conversion to the earlier system would require a new header pipe to mate up with the existing exhaust system. But, it will provide a worthwhile increase in exhaust flow and better performance.

Les
Les Bengtson

Also watch out if fitting twin carbs with a later bulkhead servo as the clearance for the filters is tight and may foul.
mike satur

Thanks guys, I've now seen the car, its a 77 MGB with a single Stromberg.

I propose to stick to a singe carb, SU or weber are there any companies selling complete conversion kits ? The car did run for 1 minute, back fired a few times however looks positive. Still want to remove as much as possible in the way of emissions stuff

Cheers
Matt
Matthew Mason

Matt. John Twist's website used to have a copy of his tech article on desmogging the North American MGB. The webisite is something like www.universitymotorsltd.com but, it that does not work, run a web search for "University Motors Ltd" and you should find it. Lindsay Porter has also reprinted the article in his mgb restoration manual.

The single Z-S can be replaced with a single SU HIF-44 carb or the Z-S can have its water choke replaced with a manual choke. However, in either case, the less efficient intake and exhaust manifolds remain, one of the reasons that version of the car was down on power.

A single Weber DGV can be installed and is a popular conversion. However, the last time I looked into it, the DGV was out of production and prices had doubled on the conversion kits. Do not know whether this is a temporary or long term problem, but, it has been going on for over a year now.

Twin SUs provide better performance than the single Weber DGV. As Mike S. notes, they do require the K&N conical filters be installed so that the filter will clear the brake servo unit. Have a friend who converted from the Z-S to the Weber and liked it very much. He then did a twin SU conversion and likes it better still. This was on a car similar to the one you are working on.

Les
Les Bengtson

This thread was discussed between 19/11/2005 and 20/11/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.