79 midget carb question

[maddy]

I was told that with a modification to my manifold that a HIS-6 SU carb would work well on my 1979 midget. The carb has a 4 hole mount with 1 3/4" outlet. My manifold is setup for 2 hole mount with a 1 1/2" inlet. I will ream the inlet to match the new carb and mount with 2 holes. Has anyone done this mod? Did it work? Is $200 to much to pay for it? Would a weber down draft be better?
Thanks,
Mark

 

[Hairyone]

The carb you have sounds like a Rover Metro carb. Not sure you had the little crap UK car over there, but this is the manifold you need:
https://www.minispares.com/Product.aspx?ty=pb&pid=34220
1 3/4" carb sounds a little big. the single 1 1/2" is good for just over 100hp.

 

[blkcorvair]

I got a simple MGB 1 1/2" SU on my race car. Just have to enlongate the carb mounting holes with a file. Works outstanding!
Way better performance than the weber I yanked off.

 

[maddy]

WOW! Thanks guys. I'll try to find a good 1 1/2 SU. BLCOVAIR your engine bay is outstanding!

 

[blkcorvair]

Thanks! Thats an old pic. I actually wrapped the header and installed a heat shield between the carb and manifold.

 

[maddy]

Do you know where I can find a 1 1/2' SU in good working order?

 

[bigjones]

I got a simple MGB 1 1/2" SU on my race car. Just have to enlongate the carb mounting holes with a file.

Scott,

How did you manage to do that? Even elongating the holes, I would think you would have the SU at mounted 45 degrees.

The 1500 manifold has a square interface for the ZS to bolt onto, with the two bolt holes in opposite corners.

The SU carb has bolt holes horizontal.

I can see you have done it - but how??

Cheers,
Adrian

 

[JPSmit]

pretty sure you can get SUs with different flange angles

 

[maddy]

The duals have opposite angles, I NEED one just like in the picture above.

 

[blkcorvair]

The SU from the MGB has a 45 deg angle maounting flange as well. I beleive the sprites and midgets were straight. I believe the carb you see in the pic is a rear carb from a 71 MGB. I run a wide band O2 sensor so I was able to put the needle and shave it down on a drill press a few times til I got the mixture perfect. Runs great from take off to 6000.

 

[aeronca65t]

Yes, the 1-1/2 MGB carb will fit easily.

I had this setup on my 1500 racer years ago. As Scott says, just slot the carb holes a bit and it'll fit.

At one point I had a 1-1/2 SU from an old Volvo on a 1500. That works fine too, but the float chamber is at a slight angle (because the carb was made to match the Volvo's angled manifold). It's easy to remove the float chamber and modify the locating tab so that the float chamber will fit "level".
I don't think you have to do this on the MGB carb, but it's been a while so I can't exactly recall.

 

[bigjones]

Thanks for putting me straight on that.

I suppose the next thing to consider for non-racer types is the choke mechanism. For example, if Maddy and I were to split a set of twin carbs from a MGB, could we fabricate the mechanism for the choke?

This has me very interested - I thought the only alternative to the ZS was getting a SU manifold (1975 onward) from the UK and fitting twin carbs.

The ZS on my 1975 1500 is working just fine but I'm disappointed with the 22 mpg.

Many thanks for the posts.

Adrian