BUT... without reading through all that you wrote or knowing all that is entailed in HIS engine or HIS purpose... What say you on the removal of the vacuum actuator?
My thoughts are if he is not going to multiple carbs and using it for the street... he should reinstall it and tune around it as well.
All's good Papa Tony, I was never good at trying to be funny even my old dad jokes get massive groans.
Time in the bell bottoms drilled into my skull that there is so much RF interference going on around us that as SteveC informed us Army chose optical, avoid RF. Anything you can do to get a nice solid reference signal and then amplify from there is prefereable to filtering/conditioning.
Hard for me to answer your question on the vaccum module, Won't that depend on the type of vacuum capsule you have. An 'advance' type has no vacuum at idle, this is the type where the vacuum tap is on the carburetor. The vacuum tap on the carb will have no vacuum until the throttle is opened (isn't this called 'ported' vacuum?). A 'retard' type has vacuum all the time, this type will conect directly to the intake manifold. I'm a noob WRT carbs so useless to answer the question definitively. This dizzy looks like it has two types of advance; vacuum and mechanical. Willy only disabled one system which from the skim read of the Crane PDF I found said remove the vacuum advance mechanism and block the vacuum ports. The Crane box would in all probability have advance curves built into it, as to if it is enough to compensate for WOT with dual carb's on low RPM I don't have enough data to answer that. This unit has no MAP sensor so can't see inlet vaccum. But for you I am happy to go and ask the Dyno tuning guy I use if you need an answer for one of your applications. I humbly submit that in the mid 80's when I saw results of a rough Frankenstein EFI hack I was involved with, adapting a 1835cc VW carb motor to a 1800 EFI system off a GM 'J' platform motor. A seminal moment that blew me away as to how much better it was over the expensive/fiddly IDF carbs we were used to running. So a carb guy I am not, from the little I remember if the carbs are mechanical or vacuum and how the secondaries on the carb is brought in has a lot to do with it. But I see the reasoning in the curiosity of your question.
If Willy has a vac carb maybe replacing it with a mechanical secondary carb is going to address a flat spot, things like that for me are a little easier as with programmable EFI I just plug in a laptop and change a few numbers after looking at some data sets. I find carbs are harder and changing software maps easy peasy, so sue me I am lazy. "Cheating" with split injector pulses is a pretty cool weapon to have in your kit bag and has saved my bacon in these low port velocity scenarios. From the back locker of the brain here's how to check for the type you have, you will need a vacuum pump, a helper and a timing light. Hook the vacuum pump to the advance unit, then fingers clear start the engine and aim the timing light at the timing marks. Now have your helper work the vacuum pump. With an engine that turns clockwise, don't laugh some Euro stuff spins backwards. If the timing mark moves counterclockwise with vacuum, then it's an advance type which needs to be connected to ported vacuum. If the mark moves clockwise, it's a retard type and needs to be connected to manifold vacuum. I don't even know what kind of Vac pots are on the Fiat dizzy's. But to add weight to your point I run a Bosch Motronic in one car and when the diaphragm went in the Vac capsule it was a dog off idle until it built some speed. Replaced it and it was 'eager' off idle again.
Rob has already commented on the bracket that Butch installed and perhaps the reason I have reservations with 'one size fit all kits' like the Crane ignitions (and I do like them performance-wise) is that the mounting brackets are well...flimsy. There is the potential for harmonic vibration, and if the optical sensor oscillates enough on the end of that bracket it can strike the spinning rotor and wipe the rotor/IR LED out, much sadness all round. The use of loctite on all securing fasteners, and the addition of an additional tailored 'L' bracket to stabilize that optical trigger is all I can offer. After that... I can't see why it won't be dead reliable to 9000+ rpms.
The #1 problem is the pickup needs to be properly 'phased'. Not difficult, just a little tedious. 'Phasing' means that the rotor points to the contact in the cap at the same time that the shutter wheel slit is centered in the pickup. The pickup has to be slid on the mounting bracket to set this and it might take a few goes to get it right. Without this step the ignition timing will be impossible to set properly. I like Rob's idea of cutting an old cap to set the phasing, the old Beetle dizzy had a kewl ( but gimmiky ) see through ditributor cap available and thats what our bunch used to check this step when we were 'mucking around' you could use a timing light to look at the rotor while it operated and check to see if it was phased correctly. I wonder if that cap fits the Fiat dizzy, its still a 4 cyl so for low speed tests it might just work. Odd parts cross matches occur perhaps . . . . . if it was a Bosch unit. Wait a second. :confuse2: Since the XR3000 has the optical sensor in this instance if you have one of the clear distributor caps won't it screw things up when you pull the trigger on the timing light?
This is all just conjecture but messing with the static advance at X degrees (as per spec) might be a bit flat off idle he might find it actually runs faster around XYZ degrees but could get a hesitation into that engines power curve. Maybey sacrifice a slightly rough idle for smooth, quick acceleration, there's so many variables with an old dissy. At least lubricate and move the mechaical advance mechanisim by hand before refitting. If the advance doesn't change with rpm then the mechanical advance is stuck. If it is just 'slow' re fitt with small lighter weight dizzy springs if available. That may create a dizzy with a good mechanical advance curve and no vac advance troubles. I haven't seen a distributor dynograph machine in a very long time , this sort of finite tuning is a dying skill that the newer generation of computer Plug in Tech mechanics used to repair by replacement will have a vacuous look on their faces if you dare ask.
One thing is for sure Willy has done such a admirable job on his Blog that others who follow will find things eassier. There are some really knowledgeable NA / carb aficionados on this board that understand the intricacies for each carb. My old Webber books are in the bottom of a archive box with plastic boxes of jets etc, my dusty knowledge is probably there too. Seeing Rob has fessed up and made us aware that he has done this three times I would offer that he is better positioned to judge. The question I think you are asking is are the gizmos in the 'black box' of the Crane effective in emulating the behavior of a dizzy vaccum module. Perhaps point the query at Rob. I would lean to the affirmative position but I have never had a Crane 3000 in my hands, that it has no MAP sensor is a weakness but it is not a terminal weakness. Those that own one are better placed to answer that, but the answer needs to come with what carb / dizzy did they use etc.
One thing we can be can be sure of is that Willy is better off without the points/condenser and there my dear friend we sing from the same sheet music. The throaty sound of a pair of carbs behind your head is darn cool, especially when the Lampredi SOHC engine is screaming at 9,000 RPM - Musica per l'anima
