SU carb problems on R16

[Slackline]

I adjusted the valves and points, adjusted the timing (it was about 10-15 degrees too advanced), and got the carbs in sync the best I could using a uni-syn. For some reason, my crank pulley has 8 white marks on it. I can't get a good look at it but I went with the assumption that the TDC is the end mark like a regular pulley.

Next, I tried to adjust the mixture.

Front carb mixture was screwed all the way in. I backed it out a couple of turns with very little change to the running condition. When I raise the piston by using the pin, the RPM would drop slightly. Eventually I got to where the carbs were richened up enough to where raising the pin had virtually no effect on the carbs. But then the car would not idle. Lots of shaking and had to keep idle high to keep running. too rich. So I screwed the front all the way in like it was and made sure everything was still in sync.

While it definitely runs better than before, I believe that the carbs need to have parts replaced. Running temps were a little cooler as well, but the weather is also cooler than last time I drove it by about 10 degrees.

I used the carb adjustment procedure on the wiki and they don't seem to behave like the article. Which leads me to believe it could be the nozzle or needle or ??

The PO put Z therapy floats in there but I have no idea what else was done. But when there is hardly a change even if I unscrewed the mixture multiple turns I think there may be a problem...

I have a gunderson clear plug to check the mixture that way, but I just ran out of steam. I thought I could get it close by using the methods in the wiki and then fine tune with the gunderson unit.

[Linda]

What timing setting did you use?
Do you have a smog or non smog distributor?
Does the advance work?
Which method for fuel nozzle setting did you use?
Helpful info needed.
Linda

[Slackline]

non smog
16 degrees before advancing.
yes it works
Fuel nozzle setting? I recently bought it and am trying to work out all of the PO's issues.

Thanks.

[Linda]

The rest of the List knows I am going to suggest the Tech Wiki reference to the “magic number” for a starting point for the nozzles:
http://www.311s.org/pmwiki-311/pmwiki.p ... ion.SuTech
Might want to give it a try and see what you think.
Linda

[Slackline]

Ok. I'll give that a shot.

Thanks.

[The Neck]

I'm in the same boat as you with getting these carbs finely tuned. I don't have anything to add except for stick with it and try again tomorrow. I've gone through the tuning procedure over and over again, redone timing, found vacuum leaks, bad wiring, and a plethora of other things along the way. I'm very close to a decent idle, at least now it's idling under 1k rpm's without dying and drives great.

How long/how many times have you attempted tuning these?

Feel free to DM if you want to chat about it, I'm far from an expert, but have at least narrowed down several contributing factors to it not running very well.

[Linda]

More info on needles, nozzles ( Z Therapy rebuilds them), needle position, needle wear etc affecting running:
viewtopic.php?f=3&t=4927

Linda

[JT68]

You should not need anything other than good condition stock needles/nozzles for a basically stock 1.6.

Random replacement of parts is rarely a good plan for diagnosis- a systematic approach is almost always better, cheaper, more effective.

From your original post it sounds like your method is at fault as well as certainly possible issues with either carb, so the conclusion that parts need to be replaced is probably not correct.

On the pulley, TDC will be the largest, deepest notch (unless someone cocked it up). Timing needs to be correct for all rpms or you are completely wasting your time tinkering with the carbs.

We have helped lots of folks with SU's since we have a roadster test engine- we can bolt them on and quickly determine what's up if you want to send them.

We can repair them (virtually any SU issue), you can repair them after we tell you the issues, or you can send them to ZTherapy etc.

[Slackline]

Thanks.

I used the other article on the wiki which did not go into a magic number. But in my head, I thought there had to be a "starting point" like holleys, etc. i.e. Start at 3 turns out and adjust from there.

I'll try this one. I would like to be able to figure these out.

Unfortunately, the PO is clueless or hiding something. The fact that the bowls have the Z therapy floats means that someone has done work on it. He said his son in law did the resto years ago. He said bought it from his son in law about 7 years ago and had the top done, and replaced the clutch master and slave and the brake master. From the looks of the oil and belt, he has not done much and doesn't seem to know much. They also snuck a thin electric fan in front of the belt driven fan.

I think I got a story. The cylinder walls looked great, engine from 67.5, but the head gasket was upside down (flipped). It seems that a lot was done to it and I find it hard to believe it was done that long ago.

Anyway, I appreciate all of the help. I am trying to get this sorted out step by step.

[Linda]

Well you are still a newbie so don’t put too much pressure on yourself
It’s a learning experience......in patience
Linda

[Slackline]

Yes, all of my experience is on small block chevy. The European cars don't count since they are just reflashes of software.

Anyway,

I set both to the magic number. Front carb was already close (it was the one that used to be screwed all the way up) The rear was up as high as the outer brass ring. Put them both to .087

Started right up. But when I try to adjust them, it seems that the rear carb is doing all the work and the front carb isnt doing anything. Idle mixture screw on top - the car will start to die if I screw it in almost all the way, but other than that, little to no effect. I set it to the same height as the rear carb with no success. I hear the hissing noise from the rear carb and nothing from the front. If I put the unisyn on the front, the car still runs. wont even move the ball. If I put it on the rear, the ball pegs the top and it kills the car immediately.

Needles looked straight, dashpots have oil. Dogbones are equal length.

It appears that I am running or idling on one carb. What next?

[spl310]

Have you balanced the airflow?

[Slackline]

Have you balanced the airflow?

That is what I am trying to do. I thought I had it yesterday, but now it seems to be off after setting the mixture.

Should I set that using the dogbones? The other article said to use those for the higher rpm setting and to use the idle screws on the idle setting.

[spl310]

On an R-16, you need to remove at least one dogbone to adjust the carbs. Remove one, use the idle screws to balance the carbs, then adjust the off dogbone to go back on without altering the airflow.

[Slackline]

Ok. Update.

If I lift the front piston, the rpm initially rises, then drops, runs a bit rough at a lower idle but doesnt die.
If I lift the rear piston, the rpm initially rises, then drops and runs rougher, and wants to die.

I still have a large disparity between the flow at idle on my front vs rear carbs.

I also see that that is just an idle adjustment screw (stopper) on top.

Is the only mixture adjustment through the mixture (nut) on the bottom?