First hand experience is always the best. I would not trade any slight improvement vs the reliability, simplicity of the SU carbs.
If I had a set of triple Webers intended for an XK engine, and nothing were fitted yet, then I too would make the attempt to fit them. Even if I had a set of triple SU’s on hand.
As a hobby car I would be under no deadline to get the car perfected by a certain time, so as long as I found the process interesting I’d keep after it. Seems like the closer your engine is to stock, the better the chances of being able to use an established set of parameters and components as others have determined.
Best wishes! It certainly can be done, so it would be great to see you accomplish it!
Dave
Webers increase the PAR, the Performance Appearance Ratio!
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Yep! My experience with triple Webers on my Austin Healey 3000 was the initial “launch” from a stop light. Always a stumble. Race cars run the race at mid to high RPM, and the Webers are great up there!
The SU dash pots give you a constant velocity over the jets. They rise as vacuum increases, and the engine vacuum doesn’t fall off when you suddenly open the throttle. SU’s are much better for driving around town, or entering the freeway!
(JC in Seattle)
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Bigger pump jets and or stroke?
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If they stumbled from the beginning, they weren’t set up properly: Webers don’t have that problem normally.
Ok! Good to know! I have a line on a complete Weber conversion kit for my 4.2L Jag, at a very good price. I’ve been hesitant to go for it though because of all these problems I hear everyone having.
I do want to replace the current twin strombergs.
The triple SU conversion kits seem to be super expensive!!
Well… Here’s my two cents, based on a lot of experience: unless you do a lot of other modifications the engine, you’re going to spend a large amount of money for not a large amount of performance increase.
The dual Stromberg’s, with the ‘five minute strangleberg fix,’ and a different distributor, will gain you very nearly as much performance for a lot less money than the triple Weber’s.
Both the Weber and the triple SU carburetors certainly look pretty and do make a bit more power than the duals, but it’s not as much as you might think.
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Can you tell me about " the ‘five minute strangleberg fix,’ and a different distributor"
Would that be like a Pertronix distributor with the optical pick-off? And what’s the “fix” on the ‘stranglebergs’?
There are those who insist that this will cause running problems: I did it on a number of cars, as have others here, and coupled with the backdated non-emission control distributor it works it works fine: it will not cause running problems.
There’s a secondary throttle that you either wedge open or remove altogether. I did that on mine and it made all the difference in the world.
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Thanks for the tip.