Instructions for SU Conversion?

Hello all,

Long time reader, first time poster here. A complete newbie to the world of auto rebuild/repair and MGs.

I own a 76 roadster that I bought in August of 2009 and i love it! I am having the time of my life learning and driving, driving and learning. It has been a family affair and the community of MGB folks have been helpful, insightful, and very generous with their knowledge and time.

The big area i am struggling with is fuel consumption. I know one does not buy an MG for the gas mileage, but i am averaging 18 mpg and that is not endearing the car or myself to my better half. I have decided that the problem lies in my Stromberg and a friend is selling me a pair of HIF4s with linkage, heat shield and intake manifold.

My question is--are there step-by-step instructions for this kind of conversion? My B has all the smog equipment and i know that will have to come off and plugged up in certain places. Is that right? I have checked all my local laws and I think i am good to remove the smogger as well as the cat. Everything is stock on the car so far. Outside of the clutch master and slave work, this will be the first major work I do.

Any suggestions? I tried searching the archives and have come up with some great information (new engine mounts at the same time as well as issues w/ air filter and brake booster housing). Anything else I am missing? Anything else I should consider to improve my gas consumption? I read an interesting thread on exhaust manifold v. a new header and i think the manifold has won (doesn't look as exciting but behind the heat shield, what does?). I like fast and performance but efficient would be great right about now. Would like to get the four kids through college instead of putting it in the gas tank....

Thanks all!

Todd R .

one common problem with the Strombergs is the diaphragm gets torn. Which causes the car to run rich. which is the issue you are having. Running rich also causes the cat converter to run hot, in extreme cases this can sometimes ignite the car on fire!

The B should get about 25 mpg. If it is not, then a less-hassle thing to do would be to fix what you have.

Welcome to the MGE forum Todd. I'm sure you'll find some local Ohio help as well.
There are soooo many things to consider so I'll mention a few to start the ball rolling.
Intake manifold needs to be same thickness as exhaust. You can use spacers under the nuts if they dont match.
After removing cat convert, you'll need a downpipe that matches remainder of exhaust.
Smog equip., if operating correctly can remain. If you think GREEN, it should. The HIFs were used in '73 too and it had alot of smog equip. Sorry I dont know the difference to a '76.
You'll need a different throttle cable and do you get the cable bracket w/your intake?
You'll need a manual choke cable routed to the dash or below it.
With the manifolds off, the may as wells start to figure in. Mounts like you said and side covers? Are they seeping?
That will do for now, I'll think of more and others will chime in.
RS

Mac is absolutely right and I was thinking the same thing as I typed but dual SU set up is better.
And I figured you had your mind made up.
RS

You might want to read "carb swap day 1 & 2" on the Chicagoland web site.

http://www.chicagolandmgclub.com/techtips/mgb/mgbtips.html#fuel

As Mac noted, it probably makes sense to sort out what you have before making big changes, unless the ZS is hopeless, I know nothing about them. A Weber is another common option.

In the SU change over you will also need to consider exhaust manifold/header setup. An early manifold and double downpipe would be a good solution. Someone needs to chime in if you will encounter clearance issues between the rear-carb air-filter and the brake booster, this was a 1975 issue, not sure about 76.

Go ahead and update your profile with your car's year so you won't forget.

Oh yeah, WELCOME ABOARD!

You all are awesome--Thanks so much!

I don't know for sure but i think the ZS is hopeless. it was rebuilt about 2 yrs. before i bought it. i think i can get into the SUs fairly inexpensively and i sure do get that "cool factor" that all ya'll chrome bumper B owners enjoy (I feel a little like Steve Martin in that old SNL skit where he is sitting in a chair at Christmas, "If i could have just one wish at Christmas, it would be for all the children in the world to enjoy peace and happiness. If i could have two wishes, the first would be the kids, but the second would be for all the money in the world to be deposited in my bank account. If i could have three wishes...." If i could have just one wish for my B it would be good mpg. if I could have two wishes, it would be for the mpg but it would also to have those really cool looking chrome air filters on my SU carbs....)

I thought for sure i would have to remove my smog equipment. i will see what i need to do to keep it. The ZS was converted to manual choke way back when so i have a place on the dash for that. I will check on the throttle equipment as well.

I took a part my clutch master cylinder and there is a small section of the inside that is worn away. The general consensus is get a new one--can you get the OE looking lockheeds still or am i relegated to a plastic one?

Thanks again everyone. Very helpful stuff....

Here's my 2 cents on the down draght "weber" conversion. Every import parts dealer wants to sell you one as a fixall for your carb problems. This is not the weber of Grand Prix and Le Mans racing fame. It has more in common with a Pinto or Vega carb of the 70s. I don't know much about the ZS but the SU carbs are really slick. They take a bit of time to set up, but it's not that tough.

I would definitely make the switch to dual carbs. I can't promise they will give you any better mileage, but you will at least enjoy the 18 MPG a lot more! :)

Are you talking 18 MPG city or highway?

for clutch MC contact Basil Adams here on the board.

Sounds like you're going ahead and there's lots of good advice here. It certainly does get beyond just a carb swap as there are exhaust impacts and also some plumbing aspects with no water choke and alternative route between lower rad hose T and the heater box needed.

If you do go ahead with this and no longer want the CAT Conv can you e-mail or PM me as I would be interested in buying that from you. I have a very original 77 but the CAT self destructed and is now hollowed out. If yours is complete with Honeycomb and in good condition I'd like to have a CAT to keep up my originality trip ;)

Good luck.

Simon

Thanks all. Unfortunately, thems is mostly highway miles. Ugh! Am going to order my rebuild kit this week and start wading in as soon as possible. Simon, I'll let you know how it looks as soon as I bust a few knuckles!

Thanks again!

Todd R.