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HS2 Carbs

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TexasSprite

TexasSprite

Jedi Hopeful
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I thought HS2 carbs were HS2 carbs, but I find that there are several variations. One that I picked up off of Ebay has tubes leading to the intake of the carb, which I assume have to do with ventilating the crankcase. Some HS2s have solid needle, some are biased. What the heck is "biased". Could someone clear up what the differences are from HS2s used on early cars vs later? Which ones are more desirable and why?

Thanks!
 
There are a couuple of differences worth mentioning but I if you have multiple carbs to pick from you can probably mix the parts to get what you want.

The biased needles were introduced (as I've been told) to eliminate the need to center the jet. You can compare their appearance to traditional fixed needles in this JPG:
https://www.zparts.com/zptech/articles/mal_land/ml_sucarb2/images4/Fig-3 SU X-Sectn 20030630.gif
and here
https://www.terryhunt.co.uk/mini/pics/tech/picsb/2.jpg

I don't like the basic principal of the spring loaded needles because they intentionally rub the needle against the inside of the jet tube. On a properly set up early HS2 there is no contact between the jet and needle so they don't wear out. Spring loaded needles cost nearly twice as much also.

On the later HS2s there is also the over-run valve on the throttle butterfly. This is probably a more significant (and generally undesirable) addition to the later carbs than the spring loaded needles. The intention was to lean out the mix on deceleration. Most texts on the valve say it is a significant hindrance to air flow. A common practice is to remove the valve and solder up the holes in the butterfly. It's equally common to remove the butterfly plate and replace it with one for an earlier carb. (I've spent 10 minutes online looking for pictures of this valve and can't find ANY. Suffice it to say, the valve is huge and I can see why people remove them).

Were I building a set of HS2s for an A-series I'd use the fixed jet pistons and matched vacuum chambers along with butterflies without the over-run valve. Any intakes for emissions could be plugged or used as you see fit. However, only you can decide whats right for you.
 
Joe Curto sells a bushing that you can install in the biased needle carbs to convert them to the solid needle. I always repalce with the early solid throttle plates, it just make zero sense to pay more for the poppet valve throttle plate. On the crankcase vent tubes on the later HS2s, I ship my carbs of this era out with rubber EDM plugs on the tubes, it give the customer the option of using crankcase venting via the carbs or not.
 
Hap said:
it just make zero sense to pay more for the poppet valve throttle plate.
Click to expand...

'specially when all yer gonna do is solder 'em SHUT anyway! :wink:
 
Some turbulence is a Good Thing, innit? :devilgrin:
 
Well, if it is, I'm sure that thing will give you plenty of it!

As a matter of fact, I suspect that the air molecules will take one look at that thing, say, "you've gotta be kidding!" and turn around and go back the way they came.
 
Man, get that thing out of my carb.
 
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