HS4 fixed needle or spring loaded? [which is best]

[Guest]

I've got two sets of carbs that need equal amounts of work done to them and I'm trying to figure out which set to build. Both need shafts, SL (spring loaded) needs jets and needles. I'm unsure if the fixed needles need replacing. From wht I've read, the spring loaded type needs the needles replace every 50K or so. That I don't like. I'd rather not have to replace needles if I go to the trouble of tuning them out.

I need to keep a set to convert to injection later on.

Which is the better carb?

 

[spritenut]

I have run both fixed and spring loaded HS2s on a couple of Sprites, swapping them out from time to time on the same Sprite.
The spring loaded ones are a whole lot easier to center the jet. They self center.
The fixed needle type seem to be a bit quicker to respond.
My only answer to that is a shorter needle means less travel so it rises faster in the carb thus making it *feel* faster.
Other than that, there is not a whole lot of difference between the 2.

 

[JPSmit]

On the other hand I can understand your concern that you will ONLY get 50k miles out of the car before you had to replace the spring needles. That sounds like planned obsolescence to me.

(At that rate, I would be about 75 before having to replace the needles)

 

[Guest]

JP, I already have over 5K on my redneck rebuild.

 

[JPSmit]

still 10 years - I don't think the engine itself was designed to last 50k - yours surely isn't

 

[Guest]

Yeah, so I don't want to have to build carbs againtoo.

 

[Hap Waldrop]

I have run both fixed and spring loaded HS2s on a couple of Sprites, swapping them out from time to time on the same Sprite.
The spring loaded ones are a whole lot easier to center the jet. They self center.
The fixed needle type seem to be a bit quicker to respond.
My only answer to that is a shorter needle means less travel so it rises faster in the carb thus making it *feel* faster.
Other than that, there is not a whole lot of difference between the 2.

I think that was well stated, the only real reason racers use solid needles most of the time is there were more richer needle choices. No real reason a street car to change the type of needle in almost all cases.

 

[Guest]

Hap wouldn't the fixed ones last longer w/o attention being needed?

 

[Hap Waldrop]

I don't see alot of evidence of any of the needles wearing ecessively, and look at a lot of them Isave needle, and of course buy the richer one for racing, I probably have a couple hundred needles, and measure them frequently at differet station heights and see no real change in their posted measurements. However I often see, where people have filed flat at the top staion to improve idle mixture, that trick has been around forever.

 

[Guest]

However I often see, where people have filed flat at the top staion to improve idle mixture, that trick has been around forever.

Never heard of that, please do explain.

 

[jlaird]

LOL, when the engine is at idle the top of the needle valve is deap into the valve thus the top' big end of the needle is controling the fuel. If you file a bit of a flat there you richen the fuel at idle.

 

[Guest]

That I understand, but why flat?

 

[davester]

...because it's hard to find circular files.

 

[Guest]

...because it's hard to find circular files.

If you spin it in a drill chuck and hit it w/ sandpaper, it'll still be round. From what I've read, that's the best method for changing needle profiles. I was wondering if a flat surface had better emultion properties or something other than most files being flat.

 

[jlaird]

I don't care what you use or even the shape of the idle portion of the needle. The carb will never know. What ever works for you, file, sandpaper, lathe, what ever.

 

[Hap Waldrop]

...because it's hard to find circular files.

:lol: