so I listened to what CPR and 67m302 had to say about carb tuning and did it totally different

a) had carb removed so set throttle plates to exaclty where they should be
b) set accellerator pump linkage front and back
c) changed PV to 6.5 which seems about right for my application. will re-measure to see what exactly I need
d) put carb on car and used only the 4 corner idle to set curb idle speed. didn't touch curb idle screw (this way i can keep the throttle plate correctly to the position in transfer slot, which I believe is a good thing)
e) set mixture for highest vacuum
f) most importantly (and thx for the tip) kept the jet spread between front and back. I went down 3 sizes each. Still a bit on the rich side, but _no_ more hesitation anywhere. I'm very very happy. The car idles at 650 no problem (lumpylumplump) and when I press the throttle the car reacts immediately. Easy to drive off a traffic light etc

so for now I'll have to re-measure the A/F on WOT to see about the jetting. But i think my lambda sensor died over the winter ... :-( so it'll have to wait. Will do plugreading instead

Thanks again, I learned a lot

Kalli

 

Very cool...I love carb tuning.
How did you set the front and rear butterfly valves with relation to the transfer slot?
What is your idle AFR?
What is your idle vacuum?

 

i opened the butterfly (with carb off the car and choke off) just so far that the transfer slot becomes a square, so that you can see just as much from the transfer slot as it's wide.
Idle vacuum can't possibly tell as it's fluctuating a lot ... probably because of the low idle and cam. probaly around 10-12. the lowest is just above where the PV would kick in (8) and the highest around 15+.
Unfortunately the sensor of my LM1 died (quite sure). so i'll have to wait til I can get proper values ... (buying replacement sensor, should get it locally as it's Bosch)

 

Don't be afraid to rest the curb idle a little bit. If you bump it up you will uncover a bit more transfer slot, so you may need to rest the idle mixture just a tad. When you get into problems is when ignition timing is too low and you idle it way up, then the transfer slot is way uncovered and you lose control of idle mixture...then you don't have enough transfer slot left to cover the off-idle lean out and so on and so forth.

The initial transfer slot setting is so that when everything else is set right you can adjust the curb idle up or down a tad as needed and not get too far out. And sometimes carb'd setups just want a bunch of timing at idle, and total timing is dictated by the whole combination. I'm running about 16* at idle with mine.

 

That sounds great. I adjusted curb idle by about 1/8 turn max to help with teething problems. It helped the vacuum to steady a bit. But I found that this way to go at it worked very nice. Had her out today for two hours and she made happy. I'm still missing a bit of top end power but most importantly it's no hesitations anymore

 

Top end power loss will be a fuel ratio issue or an ignition issue. Some engines need more top end timing, others need less, you need to figure out what yours needs. And also use the correct plug gap too.

 

That's good to know. What would you suggest for plug gap? I have untouched autolite 25s. 1mm == 0.04 inch? something like that?

 

Depends. .040 is a good starting point, might like more, might like less.

 

clearly I should make use out of the high voltage system (or whatever you migt call it). My coil is running seperate from the 12V system of the car (crane Hi6 and LX92 coil), so there should be plenty of power for that.

I can see that to be an advantage for being able to fire slightly leaner mixtures, so might help with gas mileage if the carb is tuned right. But is there another effect I'm overlooking for high rpm usage (in my case -6500) ?

 

Larger plug gaps are easier to blow out out the flame kernel in higher compression/rpm/boosted applications. You could try a smaller gap and see if it helps or not.