Didnt see the question . Pretty comparable with mine maybe mine is a little leaner at WOT but otherwise similar.
The DRLA book was written by the main US dealer, so if your jetting doesn't behave as expected, it may be because he's talking about the big holes US version, not the European Alfa Sud ones we all have.
One thing that is different thinking more, is that lean cruise on mine extends to slight downhill at 50-55mph where I see the 16-17 AFR, or when I am going downhill and rolling even at 65 it gets back up to 15-16. I think that one feature of my carburettor that is messing me up again is the soft Oilite spindle bushings I fitted have worn out, leading to slop on the spindle again .. So its needle roller bearings this time on the rebuild . I can get gentle back firing at 20mph in 3rd gear when I lift off the gas to go over a speed bump and see 20+ AFR.
I've deffo had blocked jets, and I am still getting popping, I thought I'd cleared them, but I am wondering if one is still blocked.
Back to progression ports. I'm told that (US at least) DRLA36 Carbs also have the bigger ports. Does anyone have European 36s and some jet drills to check? Or maybe just look and you can tell.
The Bus and it has Dells. I cleaned the idles before my France trip, pain of a job with the CB linkage, I did this as the adjustment screws were non functional and that seems like a classic symptom. I also put loads of carb cleaner down the holes. #2 cylinder definitely cleared itself but I am not so sure about #1. I loaned my mates balance tool last time but my new balancer tool arrived at the weekend and I am hoping to find time to twiddle the adjuster screws at lunchtime, or this evening and see if I can get them to balance up.
Recap and results... Type-4, 2.4l, stock cam 8.7:1 Correct original Bosch SVDA for 2l carbed. (S?) Very rich with 55 idles (9-10afr), down the jet sizes one at a time the AFR does lean a little each time. 45 idles afr 14 - 14.5 through progression but these are kind of unreliable, poor starting etc. So... Progression holes 100 - 140 - 140 - 140 - 140 .2 emulsions 5.5mm float 30 vents 47 idles 135 mains 180 airs 14.0 progression 18 max through transition Around 13.5 at 40-50-60mph Around 13 WOT dipping rich at top end revs Now... Progression holes 100 - 140 - 140 - 160 - 160 .2 emulsions 5.5mm float 30 vents 55 idles 135 mains 180 airs 14.0 progression 12.0 transition Low-mid 13s 40-50-60 mph High 12s WOT still dips rich at top revs A combination of slightly enlarging top 2 holes and 47 to 55 idles has turned a lean transition into a rich one and not much else which is more than I hoped for. I'll drive around for little longer to get used to how it drives, but next I'll be upping the vents from 30 to 32 which was the main purpose of the exercise.
For ref.. a 1.2mm syringe needle wont go through the bottom hole but will drop into that slight recess. Assuming that'll be 1mm at the bottom and scaling on CAD gives you next two at 1.6 and top two at 1.8 on 36's Sent from my SM-G930F using Tapatalk
Looks like it. Thanks for checking them out. The bottom holes are like that on mine too. I've been trying the 32 vents and 140 mains. No lean hole, all good driving around casually but any acceleration is 14-15, WOT is 16 sweeping to 12. Disaster! I might quickly try 145 mains but I thinnk I'll be going back to 30 vents and try 52 idles.
Another unexpected change after drilling. I've set the idle mix hundreds of time on these carbs on this engine. I look at the AFR afterwards for interest. It's always 12.9. now it's 13.6. perhaps it burns better with more air in the emulsion - frothier.
I'll have to go and change the vents back while I consider more drilling. @Deefer66 I can't see your throttle plate through the holes?
It's one of the siezed up ones from the diesel bucket.. plates are stuck open but starting to move again.... this one will need a new shaft too prob, little bit missing from the end but might be enough to get a nut on.. Sent from my SM-G930F using Tapatalk
Don't the bigger vents move your torque up the the revs or have you got plenty of torque to play with on that engine Sent from my SM-G930F using Tapatalk
I have goodly amounts of low torque. But I'm back to 30 vents, jetted as before but down an idle size. Now I've lost the rich transition to mains and I'm going to call it good. It's going well.
...but on driving it I found I had that same lean WOT. Doh! I'd backed the pumps right off so I hadn't given the 32's a fair chance. Getting fed up dismantling the carbs in the engine hole but I've got them nicely balanced so I don't want to take them off. That leaner idle afr ... who knows?... I'm back at 12.9.
So..... After sorting the pump squirts and driving around for a while with 32 vents 145 mains 180 airs 57 idles AFR all ok, good for the thrashy end, but I have to finally admit 32 vents are too big. Back to 30 vents 135 mains 180 airs 55 idles Much better, smoother, more torque throughout. Still have better top end from the VS exhaust than stock, the 32's didn't add much to that. Overall I'm pleased My hole drilling has let me use bigger idle jets (much easier cold starting) and for reasons I don't quite understand, one size smaller mains. That's probably it for the hole drilling. Next up, when my Swan gas lighter refil runs out I'll be blocking one on the tailpipes. Sooner if I stumble over something else I can use.
As the idle jets are still active WOT, slightly smaller mains make sense. But mostly the smaller vents make the mains more effective as there is something sucking harder at WOT from the venturi. Might be interesting to put a set of pressure gauges around the carb - one in the manifold, one in the neck of the venturi. As the vent gets smaller, the one in the neck of the venturi will read lower and lower pressure as the air flows faster through the narrow part, for the same RPM . And it will respond sensibly to tuning and be less sensitive to the fuel level. Theres a lot to be said for the elegance of the SU variable venturi...
