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carburetor progressive linkage

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J

JIM NEWMAN

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When I acquired my BN7 it had been seeing service for some 12 years as a vintage racer. Since it had all the "right stuff" I have decided to restore it rally style. The 3 side draft Weber DC0E45 carbs are part of the package I obviously want to maintain. However I want to be able to drive the machine in daily non-rally fashion. Currently at high revs the engine is raucus and quite potent and at low revs, it is quite docile. However, when accelerating (unless very gradually) through the 2200-2500 RPM range, it has a real "flat spot". I can't use vacuum advance to alter the ignition timing and rejetting the carbs has met with only limited success.
I am considering going to a progressive linkage for the carbs and wonder if anyone in LBCland has any experience in this regard. Usually, as I understand it, such linkages are used to improve fuel consumption, and that would be nice, but I'm really more interested in "civilizing" the powerplant and wondered if this might help.
I also don't know that such a linkage is even available for these carbs.
Any help much appreciated.
 
Jim

Are you sure it is not the cam?....

If it has triple Webbers and was used for Racing there is a fair chance it may have a full Race cam. Depending on the cam profile it would only really "come to life" at higher revs.

Can you get any info on this from the previous owner?..

Cheers

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Jim,

You have vastly conflicting requirements. By definition, a racer is not meant to be civilized. Camshaft, port size, carburation, exhaust, possibly flywheel, & compression ratio are all working against civilized operation.

You cannot modify the existing Weber carbs to progressive operation. The Weber manifolds are setup one carb hole to one engine port. Making them progressive would shut off part of the engine's cylinders.

SU carbs, by design, are as close to optimum progressive operation as you can get.

It would probably help a lot to replace the existing chokes (venturis) in your Weber's with smaller chokes to give the effect of smaller carbs. I believe that chokes are available in sizes from 28 to 40 mm. Probably choke tubes of 34 mm would work well. The down side is a lot of trouble getting the new setup working & a possible loss of high rpm power. Webers are not a simple carb for the inexperienced.

Anything that you do to civilize it will reduce power, & if it is tame enough, you are back to a non race engine.

Maybe someone else has some better ideas.

Good luck,
D
 
Thanks for the input gents. Sounds like a lot of trouble to get really "civilized" with this setup. Maybe a little "raucus" ain't so bad.
 
[ QUOTE ]
my engine is comlt.stock very tame,ill swop you straight across! /ubbthreads/images/graemlins/crazyeyes.gif

[/ QUOTE ]

/ubbthreads/images/graemlins/savewave.gif
Don't believe it 59BT7 he will change the rules.---Keoke /ubbthreads/images/graemlins/grin.gif
 
[ QUOTE ]
o.k. keoke,so ill want the transmisson also,big deal!!! /ubbthreads/images/graemlins/crazyeyes.gif

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See! 59BT7 Didn't I tell you.---Keoke- /ubbthreads/images/graemlins/laugh.gif
 
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