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MG MGB Technical - who has the best price on quality weber conversion kits

Limited budget for a conversion for my 78 MGB. Wondering if any one has knowledge of quality kit at a fair price? Thanks in advance. Ed Johnson
edward johnson

Performance Parts Warehouse in NY is the distributor and usually has the best prices but little tech support (usually not needed anyway). They have a website. Brit-Tek is a good place for all B parts and offer very good support. Their prices aren't much higher than P.P.W. www.brittek.com Also check Carbs Unlimited, www.weber-carburetors.com Lots of good info. I believe everyone sells the same kit- DGAV or DGEV with Pierce manifold and K&N air filter.
Terry

Here's a stink grenade to roll into the middle of the room.

For people with later RB's (1977 and later, particularly those with CID ignition - 1980 and those retrofitted) - did you really get a performance bump with the Weber?

As reported in the MGB General Thread "Rubber Bumper Performance", I had found out by checking my Road & Track road test compilation on MG that the rubber bumper's 0 to 60 time improved from the 18.3 seconds recorded in two test reports from 1976 to 13.5 seconds in 1980 for an LE.

(When new, the chrome bumper B recorded 12.5 secs in 1962 or 3, and 12.8 secs was recorded for a Brown and Gammons Heritage version tested in 1991. The heavy, tall 1980 RB is ALMOST as quick as a CB.)

It turns out that MG recovered about 4 horsepower, but more importantly, 22 lb.ft of torque from the early RB to the latest. (CB's had about 110 lb/ft, the first RB's dipped to 72, the last ones recovered to 94 lb/ft).

The changes were a slight change to the ZS, a metering needle change, and a change from the points and condenser 45D distributor to electronic ignition. I believe that MG retuned the advance curve to recover the horsepower and torque.

I believe that the Weber does not quite equal the CFM of the dual SU set up (could be wrong, of course - which is why I'm posting) - which means you won't get the 110 lb/ft, and probably only get close to the 94 or so that you already have.

So - the question is, in comparison to a late RB with a good ZS setup (maintained, tuned, etc.) will a Weber downdraft really help?? OR is this analogous to people tossing out their old, worn out front lever shocks and then reporting that their conversions are so good, after never really driving the car with properly operating lever shocks?

Of course, all bets are off if the conversion is part of a comprehensive engine upgrade, etc. I'm just wondering if the expense and trouble of a straight Weber for ZS swap is worth it?
John Z

John. I had purchased a 79 LE for my younger daughter. It was basically stock with a very strong engine. Unfortunately, the Z-S could not be made to meet emissions standards and still have the engine run well enought to be able to drive it in for testing. A Weber 32/36 DGV solved the problem, allowing the car to both perform well and meet emissions standards. I do believe that the twin HS/HIF-4 carbs with two 1 1/2" openings (venturis) perform better, closer to a 38mm bore than a 36 or, especially a 32 mm. The SUs would also open in a simultaneous manner rather than the progressive manner that most Webers use. I noticed no significant peformance gain by switching to the 32/36 DGV over the Z-S 175CD carb. A rebuild kit and a manual choke conversion for the Z-S may be less expensive than the cost of a full Weber conversion (which requires replacing the intake manifold with the one for the Weber, then using some other form of exhaust manifold, or cutting the intake loose from the old exhaust and plugging one hole, and may require a new exhaust system to complement any switch to headers.) If money is tight, and the Z-S can be rebuilt, that is the way to go. Les
Les Bengtson

My thought was that the Weber would not noticeably outperform a properly set up later Z-S. A dual SU set up, particularly restoring the head and camshaft profile of the CB car, would probably provide a useful bump.

It looks like your evidence supports that theory.

For earlier (74 1/2 through 76) RB's, I believe they'd need the later metering needle and an ignition change to get the benefit of the added torque of the later set up. Would the use of an earlier 25D distributor restore the necessary advance (if that's what's required)? Can the 45D be remapped? Would they have to install a newer distributor, or what about an aftermarket?

I know next to nothing about the sparking bits, if anyone could help with that . . .

PS - The Vicki Brit catalog lists an SU single replacement carb for the ZS - I wonder how that would "emissionize". Strangely, this one carb (with air filter and manual choke kit) retails for the same $500 as the Weber DGV carb, but it's probably more of a bolt-on replacement for the ZS.
John Z

This thread was discussed on 16/05/2002

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