SU HS2 needle variation question

[Luke_Healey]

I just could not ever get my carbs adjusted last year on my 1966 Sprite. I couldn't ever get the needles seated properly and the result is that the car runs rich and has no power. I get maybe 20mpg when driving it. I've been into the carbs about 100 times with no success. If you recall, I had two '66 Sprites last year. The rattier one ran like a raped ape, so I definitely know what it's like to have the carbs in proper tune. I did everything I could. I have the carb seating kit, the colortune tool, etc... The needles are not bent, but my seats just WILL NOT align in a manner that the needles don't rub on them. This of course, causes the abovementioned issues.

So, I went to ebay and have now got two complete sets of HS2 carbs from different cars. I figured I'd try manifold back solutions to keep things simple. Here's one set:

These have been prettied up with aftermarket aircleaners and chrome dashpot covers. I'm focused on them at the moment. The pistons were frozen, so I soaked them free with carb cleaner. Last night I took everything apart and gave it a good cleaning piece by piece.

Can any of you recognize what year this setup came from? It varies slightly from my car's carb setup in terms of the emissions portion of the manifold.

Also, the other major difference was in the needles. My needles are fixed into place. These carbs have needles that sit in springs.

My 1966 carbs have needles that look like this:

This other set of carbs have needles with springs on the tops and they look like this:

So, can any of you give me the rundown on the difference between needles? What's the benefit or detriment of the springy needles? How do you even seat them and be sure they're not rubbing on the seats?

I assume the carbs I bought on ebay are off of a newer Sprite with a 1275 engine. Is it going to be a big no-no for me to use these carbs on my 1098 engine?

 

[Pythias]

It's not just the needles that match the engine, but also the springs. 1098 engines take the "BLUE" spring. if you have a CG engine the needles should be "GY" and if you have the CC engine an "AN" needle. assuming a stock engine that is. should be stamped into it somewhere.

 

[blkcorvair]

the needle blank stocks are the same, you can hold the hat part in a vise and tap the center out, this will give you a needle looking like yours accept with a knurled edge. The spring needles work a bit different than the fixed needles your using, they actuallt fit loosly in the carb and lean slightly one one. They have a tiny bit of pressure that actually pushes the needle to one side. These sprung needles always will rub one side of the seat. Over time they will wear wear the valve but SU figured this would stop the hardship of trying to center the needles That you have.

 

[Luke_Healey]

Ok, good to know. I might try them on the car just to see if it runs better.

I can tune it to run rich or lean. I will hunt for the correct needles if it turns out to be an improvement.

I have enother set of carbs off of a 71 Midget that I haven't gotten into yet. Another cheap ebay find.

My carbs are nice, other than the fact the rear carb's seat won't tighten down perfectly in line with the needle.

 

[blkcorvair]

Get it lean and spin the needles down on a drill press with some sand paper. Been spinning down the same needles several times already. Also have some play in the hight of the valve of course youll have to adjust the idle scre to compensate. Mines a bit easier as Im only dealing with one. spinning two needles down to match could be tricky.

 

[jlaird]

I did not know HS2 carbs had fixed needles. HS1 fixed, HS2 not fixed with the springs? Or am I all wet?

 

[spritenut]

HS2s had fixed needles until 1968, the swing needles were part of the pollution system but they are alot easier to work with than the fixed needles and getting the jet centered.
I am working of a couple of sets of carbs now, 1 set will be a door prize at the Missouri meet, but I am doing a tech session on tear down and rebuild.
I have a nasty crusty set that I will take apart at the meet, and a nice glass beaded set that I will assemble at the meet before it goes to the prize room.
1275 HS2s stock, fixed AN needle.
So be there to win a set of fresh carbs.

 

[Hap Waldrop]

You can convert any bias (springed) needle HS carb to the fixed needle with a simple brass bushing that Joe Curto sells, I do it all the time. The AN needle would be a good choice for the 1098 engine, I woud start with the jet about .070" down from the bridge, on the 1275 street engines I use a #3 fixed needle,it's profile is alot like the the stock #AN until you get to the more open throttle positions then it's richer, people seem to like that needle in their 1275. I'm building a set of HS2s now for Tony for his 1098, and will be using the AN needles.

Scott, with the carb you're running you literally have tons of needle to choose from so you don't need to be trying to make a certain profile that already exist. That is a single HS4 on a 1500 right, I seem to remember you saying the engine is basiclly a fast road motor, you may have to play with needles a little bit, but I would suggest using the solid needle and looking at #5, #6 or #7 for the 1500, shoot for 12.5-13.0 for A/F at WOT

 

[Luke_Healey]

All four of the springy needles in these two sets of carbs I have are AAC needles. I notice that Moss motors lists the AN needle as the reccommended one for both the stock 1098 and 1275.

The two sets of carbs I got on ebay look identical and one was mentioned to have come off of a 1971 Midget.

My next question is about the emissions control stuff. As you can see in the photo above, the previous owner used fuel line to bridge two portals that actually have a Y connector on the other set I have.

Can I safely just unbolt my 1966 setup at the heatshield and replace these in without having to worry about any emissions related issues (the car running, not saving the environment.)

My Sprite currently has a little diaphragm puck thing that vents into a canister. Not much else. I assume the 1971 midget had some extra things hooked up to it. I'm wanting to make sure this will even work without causing problems.

Thanks!

 

[ChrisS]

This is a graph of the needle profile to length - Thinner is richer for a given length. AAC is red, AN is green, and #3 is blue.

The biggest issues with swapping carbs / emissions is the vacuum advance for the distributor. Some used manifold vacuum and others used ported (air cleaner side of the butterfly).

 

[Luke_Healey]

I hadn't thought about that. I'll check both setups to see where the vacuum advance gets it's suction from.

 

[Hap Waldrop]

Something else to keep in mind, distributors are set for the type vaccum the factory set it up for, so if your engine like a later model 1275 is set up for manifold vaccum, then so is your distributor. Jeff at Adanced Distributors can set up your distributor for either way. Alot folks like vaccum port off the carb, claims it gives quicker engine repsonse.