TR4/4A Hs6 carb rebuilding

[charleyf]

While rebuilding a set of HS6 carbs I discovered that the air hole in the lid of the float chamber has been plugged. I am assuming that that air hole needs to be open to allow the proper function of the float and fuel system. In the past I have had one needle valve stick open and allowed fuel to squirt out that opening. So I can imagine a previous owner not wanting that hole left open. But logic says to me that it needs to be there and open to prevent any pressure or vacuum to build up.

Am I correct?
Charley

 

[TR3driver]

Yes, there has to be a vent. Otherwise the mixture will be changed drastically as the air volume in the top of the bowl warms up, etc.

However, look for an added vent tube. Sometimes it is desirable to have a tube rather than a simple hole; and someone might have been adding the tube.

 

[charleyf]

Thanks Randall. I had not thought of the heating up possability. But these HS6 carbs do not have any tube. There is a small removable aluminum cover over the exit hole. That allows the fuel to drip out instead of shooting out in case of a stuck valve in the float chamber. I am guessing that it is also to keep anything from entering into the hole. A tube would have been a better way to go , like the HS carbs.
Charley

 

[titanic]

I am using the same variation of HS6 carbs (from a Volvo) on my TR6 and have wondered if the small hole and cover/deflector was for ventilation or overflow. I would prefer overflow tubes that did not dump gas near the starter or manifold, like Jaguar used. I suppose another tubing fitting could be added to the float lid.
Berry
,

 

[TR3driver]

I can't seem to find the information at the moment, but there are lids available that have a fitting for the vent tube. However, most people seem to just modify the stock lids with JB Weld and small tubing.

This is a photo from a friend of mine. Hopefully he won't mind me posting it here.


PS, the most important function is vent. Unfortunately, if a vent will pass air, it will also pass fuel, so the overflow function is a bonus

 

[TexasKnucklehead]

I also have a set of HS6 that were not originally from a TR4A -I don't know what they are from (other than ebay). I thought mine had no vent either, but after reading this, I went out and saw the little metal cover under the feed line. I removed the lid, and can see that it is vented under that cover.

Is there a procedure to set the float height in these?

 

[TR4nut]

Is there a procedure to set the float height in these?

Yup. 1/8" from top of float to lid https://www.britishcarforum.com/bcf...needle-adjustment-on-SU-HS6-slightly-OT/page2

 

[charleyf]

I also have a set of HS6 that were not originally from a TR4A -I don't know what they are from (other than ebay). I thought mine had no vent either, but after reading this, I went out and saw the little metal cover under the feed line. I removed the lid, and can see that it is vented under that cover.

Is there a procedure to set the float height in these?

The instructions with the kit I received says to use 3/16 ". The easy way to do this is to use a 3/16" drill bit to measure between the float lid and the float. Different floats have different ways to adjust to that measurement. Some have a metal connector to the float and some have none. In the case of none you can possibly use a thicker or thinnner or no gasket under the valve.
Charley

 

[titanic]

Both are right about the float level-1/8" to 3/16".
Berry