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MG MGB GT V8 Factory Originals Technical - Carter 400 cfm Carb,where to get one?

I want to change my SU HIF 6 carbs into a 4 bbl carb.
Engine is an SD1 , 3,5 l in an MG B GT. What I have is an Offenhauser 360 inlet manifold. Now people told me, best would be a carter 400 cfm carb.
Now my question : Is this carb still available new and where can I buy one? All help and tips are welcome.

Thomas
Thomas Assmann

Thomas'

I have no info on Carter and I would stick to Holley or Eldebrock 500. There is not much between these two carbs on 3.5 but if looking for 0-60 times probably Holley or sophistication and mpg Eldebrock. Real Steel will probably supply either, and may have a Carter 400.

Paul

Paul

Thomas, go with the Carter. You won't regret it. It's the right tool for the job. It's essentially identical in design to the Edelbrock (in fact the Carter is to an Edelbrock what a Buick 215 motor is to a Rover 3.5); just get hold of an Edelbrock owner's manual (available online) to deal with it. They are not available new, but if you are patient and ask around in the US you should easily be able to scare up a used one (they were original equipment on the Chevy 283, if I recall correctly; I don't know what else). Then you should rebuild it or have that done; the rebuild parts are available from Summit Racing. They are very simple devices; it does not take any special skill to rebuild one. You may want to play around with the jets, metering rods and springs; the stock .098" primary jets and 16-283 metering rods may be just a tad rich for your motor (you can get kits of different sizes from Summit as well); the stock red-orange springs should be OK unless you have a real monster of a cam in there.
Harry

Thank you Paul and Harry for your comments.
Paul, do you have an e-mail address from real steel?
Harry, any suggestions where in US i can ask for a Carter 400?
regards
Thomas
Thomas Assmann

Thomas,

Tel 01895 440505
Fax 01895 422047

No email but only deal with Rover Chevy or Ford V8's

Paul
Paul

There is no difference between Carter and Edelbrock carbs. The differeces lies in the jettintg/Calibration (which could be change) finish and the name. The internals are the same on both carbs.
The early Carter AFB(1950 to 70 factory cars) are a bit different in the internal passeges.
Some diffrences are also in the floats material.
Compare both Carbs side by side. For street use the Carter/Edelbrock is a better carb.
Do not exclude the Mitty Holley #8007 390 cfm great carb for small V8's < 350 ci.
Bill Guzman

They are very, very, very similar, but they are in fact not the same. For one thing, the jets and metering rods do not interchange. Edelbrock made a few changes to the Carter design; while you can argue over whether they're improvements, they are in fact subtly different. Note that Carter currently makes an AFB 500 -- that's the correct source of a lot of parts for the 400 because it _is_ identical to the late 400s but for the larger primaries.
Harry

Tank you Paul for the phone number.I will try to talk to them.
Harry, do the bigger primaries in the carter/Edelbrock 500 carbs make a big difference in everydays driving?
Could I take a 500 cfm carb if I don't get a carter 400?
Bill, can I change jetting from 500 to 400 down?
Many questions, It would be nice to get some more Infos from you all.

Thank you all very much
Thomas
Thomas Assmann

Thomas,

For Edelbrock You could try Chris Crane at RPI (check out web site). He will advise on jetting.

Paul
Paul

Thomas, the bigger venturis will just cause a sloppier vacuum signal and attendant throttle response ... bigger definitely isn't always better, as the drag racing guys will tell you immediately. Oversizing just results in lower manifold vacuum for a given throttle opening, almost never a good thing for precise fuel metering. Let's just do the math here:

The old hot-rodders equation is:

carb cfm = (CID * max_rpm)/3456

In our case, he Rover V8 is supposed to have a redline of 5200. But let's call it 6000 just in case you're a pedal masher and/or feel lucky. Using the above equation, and knowing that there are 16.39 ccs in a cubic inch, you find out that for the following engine sizes the following are the theoretical carb sizes:

3.5L - 371cfm
3.9L - 413cfm
4.2L - 445cfm
4.6L - 487cfm
5.0L - 530cfm

However, the above numbers assume the motor is working at 100% volumetric efficiency. Most road cars in good nick operate at about 75-80% VE; a beautifully prepared "fast road" motor, ported, relieved and all that good stuff operates at about 85% VE. So, multiplying the above #s by .85 gives you the practical carb capacities you'd be perfectly justified in utilizing -- meaning, you would be leaving nothing on the table:

3.5L - 315cfm
3.9L - 351cfm
4.2L - 378cfm
4.6L - 414cfm
5.0L - 450cfm

These numbers may seem surprisingly low. I believe the urge to over-carburate is almost as strong as the urge to procreate. But the former offers none of the upside of the latter. As you can see, 400cfm would be appropriate on even a very dialed-up Rover V8, unless you used a lot of trick parts and increased the motor's redline rpm.

You asked about jetting down ... I think you may be confusing the jets with the venturis: apples and oranges. You can change the jets (which regulate the flow of gasoline only), at your pleasure, but the venturis (which regulate the flow of air and are the place where gasoline is introduced into the airstream) are integral to the carb body and aren't change-able. What I have heard commonly done on Rover V8s running Edelbrock 500s (though it never jumped out at _me_ as a swell idea) is to put a restrictor plate under a 500 to take the effective diameter of the primary venturis down to the same size they would be on a 400 (on a 400, the primary venturis are 1-1/8" whereas on a 500 they are 1-3/16"), thus producing an ersatz 400 cfm carb.
Harry

Try Dan Lagrue at D&D Fabrications. He got me a Carter 400. No email, but phone is (810)798-2491 est.

David
David Atherton

Thomas,
The 400cfm is a mid 70s Mopar application. You may be able to trace one down through a Mopar group.
I was lucky enough to find one from a fellow V8 er who changed over to FI. The cost for a used 400 will be about the same as a new 500 but it's the best fit for the 3.5. If you find a rebuilt one, they run about $375 plus a core charge of about $100. (If you had a core you wouldn't need one!)
Let me know if you need any numbers off of my carb.
Good luck with your search.
Kelly
Kelly

This thread was discussed between 29/07/2001 and 04/08/2001

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