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SU Carb "Hiss"

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Scott McK

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SU Carb "Hiss"

Hello all, I'm trying to tune my twin SU6s on a TR4. The number 2 carb has a strong hiss at the intake, however, the #1 has no hiss at all. How do I balance the hiss if I dont have it on one side? The car idles ok a little high 1100-1300 RPM. I've read all the manuals and I think I have it set up correctly. Any ideas. Thanks Scott
 
Re: SU Carb "Hiss"

Scott: with the air cleaners off try bringing your palm up close to the carb inlets. I suspect you can put it right over the one that is not hissing without much change in the engine but trying it on the other carb will cause the engine to stall. It's a bit too complicated to explain here but any good manual will give a fairly complete procedure on synchronization of the carbs. Basically you have to lossen the linkage tying the carbs together so you can adjust them separately for draw (hiss) once the mixtures are equalized. Bob
 
Re: SU Carb "Hiss"

Hi Scott: Bob is right on. There is a great tool out there called I believe the Uni-Sync. It is a carb synchronizer and will allow you to balance your carbs. I always check my balance before I make mixture adjustments. It is available almost anywhere and certainly from any of the TR parts suppliers. (Moss etc.) Short of that, if you have a good ear and a short piece of garden hose, about 1 foot, you can balance by hiss. As Bob said, loosen linkage between carbs and adjust the throttle shaft stops on left side(facing carbs) of each carb. Make sure your stops are bottomed out, sometimes they hang up. Screwing in will increase hiss, backing off will reduce the hiss and of course your revs. Once you have balance, tighten the linkage between carbs. 11 - 1300 rpm is a bit on the high side, I try and shoot for 700rpm Good Luck.
 
Re: SU Carb "Hiss"

Scott,

What part of Oklahoma are you from? If you aren't too far maybe I could take a peek at them and help you get them in synch.

Cheers,
thirsty.gif
driving.gif

Walter
 
Re: SU Carb "Hiss"

Scott, if there is no hiss, there is no vaccumn, this generaly means NO gas in the carb and the 2 cylinders it feeds are just getting what the cross over pipe lets through. Check the float bowl it will likely be empty, or full of something that aint gas!!!
MD(mad dog)
 
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