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Edited May 24, 200818 yr by Sbox

well said mate.

having to larger Venturi will also cause a flat spot too. a lot of people just don't understand carbys have jets idle, progresion, accelerate and power, with the right combination of jets idle and general driving can be the same economical smooth ride, but on full power a little peak can be achieved without flooding the engine with gas all the time.

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Edited May 24, 200818 yr by Sbox

You are quite correct, snapping open a large butterfly causes the air flow to slow and gives you a flat spot. The "venturi" effect lessens and less fuel is drawn in, atomizes and enters the manifold.

So even with the right jets, a larger carburettor is never going to give you the performance increase you seek.

 

a modified standard carby can give great performance , very simple just a slight twink with progresion and the secondarys. and the economy will be great, no flat spots a great daily driver but on the weekends you can have some fun too!! :locked:

I agree. A lot of people tend to get carried away with themselves when it comes to carb selection. The same could be said for too big a cam choice and over the top compression ratios.

 

Ideally you want a well matched overall package suited to your type of driving. Books by A. Graham Bell and David Vizard are the best investment you can make when it comes to tuning a car for performance and economy. :locked:

I guess that rules out the 1.75 SU's on a stock 4k.....

 

:locked:

i have a 32/36 weber on my 4ac and it could really use so proper sized jet in it.

 

i have tuned the mixture screw as best as i can (almost all the way to lean) but its still rich on idel and seems to be lean up in the revs. i think themmain jets (ones that get you going) are fairly close on the primary but the idel jet is too big and so are the jets on the seconady :locked:

 

unfortunatly i really can not afford to have the carb rebuilt (it could probaly use it) and rejetted.

 

something quite intresting was i was reading a 'toyota performance handbook' it had a ta22 with a 20R motor, it said that it was balance, extractors, cam increased cmpression and it only had a 32/36 i thought that this would have been a litle undersized for a worked engine of this capacity.

I found the best carby for a 4K was an early 3K carby with mechanical secondaries rejetted to suit the 4K, it worked far better than a 32/36 and the economy was fantastic aswell as retaining some good power.