Cailiper Method of Carb adjustment.

[exit64]

Has anyone tried the caliper methed outlined in the Carb section of this site? I need to get the mixture set on my 1970 and this seems like a real easy way to do it. Or is this only for setting the idle speed?
Thanks,
Mike

[S Allen]

Trust me it works very well.

Steve

[scotty]

can you direct me to the page? Thanks

[S Allen]

Here is the page link:
http://www.311s.org/tech/engine/su.html

Here is the blurb on using a caliper to set idle adjustment:

"There is another good tip a friend passed on to me regarding the SU carburetors. It is relatively easy and takes the guessing out of setting the initial idle mixture. You will need a caliper to perform this little gem but trust me it is the best way to set them. I will take you through the process step by step.

Step One: Remove air filter housing including backing plate. This will allow easier access to the idler adjusting nuts on the bottom of each carb.

Step Two: Remove the dashpot covers, springs, and plungers with needles from each carburetor. Make note of which one is front and back. Be careful of the needles as they damage easily.

Step Three: Peer down into the center of the opening and you will notice two brass pieces. The center one is the one we are going to set and it should be slightly below the outer brass piece already. You could take the caliper and check the heights before you begin. I did this on mine and they were surprisingly equal-not bad for doing the adjustment by feel.

Step Four: The magic number for the 1600 SUs is 0.087 or 0.09 in. Since you have already checked the settings you should know whether you need to lower or raise the idle mixture adjusting nut. Raise or lower to meet the magic number. Do this to both carburetors until they are both set to the magic number."

Steve

[Conner]

What's the magic number for the 2000 SUs?

[S Allen]

Conner,

I do not have that one but if someone wants to find the sweet spot and let me know I will be glad to add it.

Steve

[exit64]

According to the article the sweet spot on the 2000 is 0.06" Look down the page and it is added in italics. Wish me luck as I am going to set mine up after work today. Perfect weather for getting under the hood in the driveway.
Mike

[S Allen]

Yeah, that was my conclusion but that was on my stroked 1600 with the 2 liter carbs and stock needles. Your mileage/results may vary.

Steve

[Linda]

Stupid Question of the Day:
Any particular type of caliper to use? I've never seen one

Linda
68 1600

[itsa68]

Linda:
They look like this.
The vernier type takes a few seconds to read the scale, so if you get one, go for the dial or digital type.
http://www.archaeologica.org/UsingCalipers.htm

Ray B.

[exit64]

I spent the better part of the evening under the hood with the domes off the carbs. I knew that they were not balanced by the readings from the unisync. Front carb was set at 0.066 while the back was as 0.105. No wonder she was a little fussy without the choke pulled out. First I removed the domes and cleaned the inside of the body and pistons. The was quite a bit of carbon build up that I am guessing is from backfiring. I used Maltby Carb Cleaner and my ex girlfriend's toothbrush for this operation. Nice and clean now. Next I checked the specs and came up with the numbers above. Not good but not the end of the world. After fiddling around with my new digital caliper, $30 at the local parts house, I came up with this method to get a reading. At first I was trying to extend the slide portion into the nozzle to get a reading but would get a different number every time. Too hard to hold the caliper vertical and get a clean reading. Instead I opened the caliper and pushed down onto the nozzle to get my reading. Much easier and more accurate. I set both carbs to 0.0885 as my starting point, put everything back together, filled the dash pots with ATF and fired her up. She cold started with only about 1/4 choke and sounded real smooth right from the get go. I let her warm up for about 5 minutes and then reved up the motor. Very good response through out the throttle range. Unisync read even on both carbs, No backfiring, so at least I didn't scare the hell out of the dog tonight, wich is a good thing. I am going to DMV to get plates tomorrow at lunch so I can give her a good road test and see what still needs to be done. So far, so good.
This is a very easy way to at least get the carbs close to where they need to be for a starting point. Thanks goes out to whoever came up with this method.
Mike

[S Allen]

Sounds like you are getting some good numbers for the 2 liters. I will publish them once you are happy. The guy that gave me the idea was/is a 240Z/510 SCCA race mechanic who has/had a shop at Sear's Point/Infineon Raceway. He has lots of little tricks but is reluctant to share many of them. Enjoy!!

Steve

[Linda]

Now that I know what a calipher is, here is where I found one:
http://www.harborfreight.com/cpi/ctaf/s ... 209&email=

My local Harbor Freight.

Linda
68 1600

[exit64]

Hi Steve,
I guess I should clarify that this is for a 1600. It is stock ecxept that it has been de-smogged. Sorry to get your hopes up for 2 litre data.
Mike

[S Allen]

Whoops, oh well, I am sure someone will step up to the plate!

Steve