Mark Maras

I'm sure he had a good reason at the time, although I can't explain why. But, if I had to hazard a guess, he may have been trying to compensate for a float setting that left the fuel too low in the nozzle. Let's proceed. Your goal now is to get the fuel level within 1/16" of the top of the hole in the center of the nozzle. (Leave the nozzles at 2 1/2 turns) To achieve the 1 1/6" fuel level, you'll be adjusting (re-bending) the float tangs either up or down. At this point you don't care about the 9/16" float measurement. Ignore it. Don't even go there. After each adjustment, reassemble the carbs, fire it up, run it for a minute, shut it down and pull the domes and pistons. Look again to see the new fuel level. Readjust the floats until the fuel levels are correct. Then we'll go into fine tuning with the mixture screws. Piece of cake.

Clean the pistons and get back to the floats. You'll find out later if the staining was caused by poor tuning. So he's telling you that unless he unscrews the mix. screws to somewhere down near 4 turns (on one carb only) it runs too rich? Someone has something backward. The farther the mix. screws are unscrewed (dropped), the richer it will run. Based on the info from your mechanic, you already know more about your carbs than your mechanic and have the desire to tune the floats yourself. The only thing that's stopping you, is you. Go for it. WE CAN DO IT.

It sounds like you're taking it back to original design. I believe that you're shooting for 23 mm in the front bowl and 21 mm in the rear. Someone, anyone, correct me if I'm wrong. Opinions vary on these measurements. Most seem to like the 21 mm in the rear and if the difference in pivot point height is 2 mm, 23 mm in the front would be a good starting point. BUT you'll never truly know if the floats are correct until you pull the domes, pistons and look at the fuel level in the nozzles, 2 1/2 turns down. Then and only then will you know for sure if they're right.

The second method is one way to double check the accuracy of the 9/16" setting which, as you've discovered, is a very grey area. The other two common ways to double check the float setting (9/16" grey area) are the sight glass and the clear tube. Both screw into the drain plug hole. Now that you've gotten the floats in that grey area they call 9/16", install the newly adjusted floats, start it up, run it for a minute or two, shut it down and pull the domes and pistons. This is the 100% method mentioned above. With the mixture screws 2 1/2 turns down, the fuel in the nozzles should be within 1/16" of the nozzle tops. If the fuel level is either too high or too low, a minor float tang adjustment will be needed. If you find the fuel levels are within the 1/16" of the nozzle tops and you GOT IT on the first try, a celebration is called for and maybe a lottery ticket while your luck is still holding. It wasn't until yesterday that I realized you were working on a spare set of floats. I'm assuming they have the different length pivot ears, are your needles and seats different lengths too?

@siteunseen Cliff, When you shimmed? the needle and seat in one of your carbs, did you have equal length needles and seats in unequal pivot ears? I'm kinda in uncharted territory. My experience is with 4 screw SU's where all things are equal. It seems to me that it would be best to get the different length needles and seats and go back to the stock pivot point. Opinions are needed.

Jalex, I can see that both nozzles are equal distance down. I can't see how far down the fuel is in relation to the top of the nozzle. Is the fuel within 1/16" of the nozzle tops? In the "open another can of worms" paragraph above, he's describing the same thing we're doing here. The setting he didn't know was the 2 1/2 turns down on a 3 and 4 screw.

Stanley, You spoiled the ending of the SU float drama. I was just trying to get Jalex to the 2 1/2 turn intermission before the fine tuning grand finale. Jalex, don't let this scare you. Setting SU floats is like eating an elephant. You can't look at the whole meal. Just take it one bite at a time. You can do it. Even with our help.

A clarification is in order. If the fuel level at the top of the nozzles is too high or too low, a readjustment of the float tang is the next step. The goal is to see the fuel level 1/16" or less below the nozzle tops, mixture screws 2 1/2 turns down. One is actually adjusting the fuel level to the 2 1/2 turn down nozzle height. When that's correct one fine tunes the mixture screws to obtain the proper spark plug color.. (Old school) Jalex, You should take a good look at both needles when you remove the pistons. They should be the same. Hopefully they're visibly ID marked at the base. Compare the lengths too. Frequently, different needles have different lengths. Also. are your new needles and seats the same size or is one longer than the other. Another also, Do you know if the needles and seats that are in the carbs now are different sizes? One more thing, after installing the domes, do the drop test to insure the needles aren't sticking in the nozzles. Got to go back and re-read this thread to see where we're at.

Pink-n-Pull, St Louis, Mo. has an 81 280. parts pricing says that it's under $100.00.

@jalexquijano Don't obsess about getting them perfect. As you're discovering, measuring floats is not easy. Get them as close as you can without driving yourself crazy. Reassemble the carbs, start it up, shut it down, pull the suction chambers, pistons (not the float chamber tops) and see where the fuel level is in relation to the nozzle tops at 2 1/2 turns. Then you'll know IF the floats need to be readjusted or if you got it right them first time. Rest assured that you're experiencing the same frustration that everyone has had at one time or another setting floats. Keep up the good work.

Probably a dumb question but did the old pump have the spacer under it? If it did, I'd have to chalk it up to metal fatigue.

Caig DeOxit is a liquid that one can use on suspect electrical connections to clean oxidation and improve continuity. Great stuff.

I've used Copper Coat Gasket Compound over the years. CRC and Permatex are two brands that I've used. Good stuff, especially on old imperfect surfaces.

Put it back together, start it up to be sure the float chamber has been filled to the new float setting and to see if the float level is now correct see post #54 and #56. Mixture screws 2 1/2 turns down the fuel level in the nozzle should be within 1/16" of the top of the nozzle.

Lower fender bolts, I had to bend the bent flange down to get to mine. Used a Crescent wrench, (adjustable spanner) to get the leverage to bend it down. Cowl screws, copious amounts of penetrating oil, heat, cut a straight slot in the head with a Dremel Tool. Headlight buckets can be removed with the fender. Side trim, heat. I'd try a hair dryer first. If you use a heat gun, take care, the sheet metal is very thin.

Jalex, while you have the pistons out take a close look at the needle bases to be sure the shoulder of the needle is flush with the piston base, NOT flush with the bottom of the recessed section. You should be able to see the fat base of the needle sticking out of the piston.

HS30-H. I'd like to give you a thumbs up for restraint. I expected the saloon fight to start when Series 1 was brought up in the first sentence of post #1. How did you ever let that one slide by? Weren't wearing your outfit yet?

I'm not even asking for something that intimidating. I just want him to remove the suction chambers, pistons and see where the fuel levels are when the mixture screws (nozzles) are 2 1/2 turns down. The mixture screws can be returned to their original setting after the test. Both carbs could be done in under 5 minutes. Then it may be time to move on to resetting floats but not until we're sure they need it.

3 psi-3.2 psi is not the problem. I'm 95% sure that your float levels are incorrect but it seems that you don't want to address this issue. Just because your mechanic has adjusted the floats doesn't mean they're right. And while I'm thinking about it, why are your mixture adjustments getting farther apart the more he works on it? You were about a 1/2 turn difference before, now there's 1 1/2 turn difference. Prove me wrong, Please. All it takes is a screwdriver to remove six screws, a beer and we can move on to fine tuning.

Maybe it would help by not thinking of it as a wild west saloon.

BTW, I see no reason to check the fuel pressure based on the symptoms you've described.

Jalex, Look at post #s 33, 35, 37 and, especially #43 again.

I understand the reasoning for moving the pivot holes. I believe Cliff shimmed a needle and seat to move it down. Keep in mind that they did work with unequal lengths from the factory and they had a reason for doing it, the reason escapes me right now. I believe it was G forces. BUT, as I stated before, the mixture adjustment screws are FINE TUNE ADJUSTMENTS ONLY. The primary mixture adjustment is the float (fuel) level adjustment. Until the float level is very close to the proper setting, the fine tune adjustments (mixture screw) are not going to compensate for float levels that are too high or low. Pull the damned tops off the carbs and tell me where the fuel level is in relation to the tops of the nozzles at 2 1/2 turns down. Until we get that settled, all else is uninformed guess work.

If the float levels are correct, 2 1/2 turns down will be close. Getting the float (fuel) levels properly set is the primary mixture adjustment. The mixture screws are the fine tune adjusters.

I agree with Patcon, . Jalex, IMHO, YOU should be the one tuning these carbs. You don't need no freak'in "expert" or even a "mechanic". You'll be glad you learned how. Let me try to convince you with a trip in my WayBack Machine. 1973, The first thing I worried about when I bought my first Z was the horror stories I'd heard about British cars with SU duel carbs and constantly having to tinker with them. I didn't know anything about them, sooo, I took it to a "sports car garage" for it's first tuneup. $76.00 (a fair amount of money in 1973) later I drove the car home and realized that the tune-up hadn't changed the way it ran, which was good, before and after. I realized that I couldn't afford frequent tune-ups at that price. (Thought it would need them) I bought a Uni-Syn and a repair manual and started cleaning and checking the carbs when I tuned it up. They were always fine. It wasn't until I took a suction chamber off, out of curiosity, that I realized how simple the whole thing was. I already knew about float chambers and had read the tune-up manual. It was the EUREKA MOMENT. There was little to them. Not as complicated as a downdraft carb. To this day I'm amazed at how simple and effective the SU's are and still don't understand where the fear factor came from, unless it was the British aspect. You can do it. Give it a try. All it takes is a balancing gizmo, a screwdriver, a tune-up manual and a beer.