right on Kirby, rotor to cap PHASING is very important, it took me 2/3 times to get it right!
it may run well starting, but breakup at hi RPM, or start hard but run crappy down low, smooth out at top end!
gotta find that happy medium spot , once set all is well 23yrs.
Could be stainless, I guess. You can usually tell when itâs in your hand. Just how thick is it, anyway? In some of those photos it looks REALLY thin.
While weâre at it, how thick COULD it be? Thereâs presumably a gap in the pickup it has to fit within, and then thereâs the up/down slop in in the distributor shaft. If someone wanted to 3D print a disc/hub out of plastic, how thick could they make the rim?
Itâs 0.020" and definitely not steel. There are different types of aluminum alloy.
Thereâs a metals store near me that sells scrap, and years ago I pick up a length of 1/8" x 1". I often use it to fab little parts, e.g., the shim I use in mounting the optical sensor in the distributor. This aluminum is very soft, making sawing, filing, and drilling very easy. By comparison, the shutter disk is harder for the drill to bite into. And itâs a brand new #25 drill.
The gap in the optical trigger is 1/4".
Sounds like 7075 T6: it requires flood cooling to drill well.
0.020" in a 1/4" gap. Plenty of room. Sounds like you could 3D-print a plastic disk perhaps 1/8" thick and youâd be OK, provided it was located properly within the gap. That, of course, is presuming the âbeamâ is a straight line that doesnât care about the thickness of the disk.
In a Crane/Allison, it is.
My 79 has the Crane system. Might be ibterested in a back-up rotor unless they are available anyhow?
Peter,
I assume youâre talking about the 12-slot shutter disk, rather than the distributor rotor. I donât the former is available since the current maker of the Crane ignition systems, FAST, no longer supports the Jag V-12.
I was just reading an article in Car & Driver about 3D printed parts and how many outfits are springing up to provide hard-to-find parts. I guess someone would have to put together a CAD design for a shutter disk that would enable V12 owners to fit the FAST ignition system.
They mentioned that the 3D printed stuff is primarily for trim. Nothing structural. I dunno how that relates to the shutter disk, since it doesnât hold anything but it does spin at 1/2 engine speed.
I think the 3D printed would work, but given my druthers I think Iâd druther go with a laser-cut metal disk (aluminum or steel) attached to a hub. Interesting question: Would FAST be able to provide the hub? I presume they have an assortment for fitting various cars. If we could find out which car to order the ignition package for, it might come with a usable hub. Just remove the shutter disk that comes on it and install the laser-cut disk with some pop rivets.
Yes the bit of the Crane system that rotates. Trigger wheel, shutter, rotorâŚ
Kirby,
As I recall, there were several shutters in the kit and all but the 12-slot were plastic. There was a plastic hub for the 12-slot aluminum alloy one.
I seriously doubt that FAST will do anything to support the V-12 application. I believe at some point they realized it was a small market segment with far more problems and expected support than from the âpoints replacementâ crowd.
Ed
I was just wondering if the hub from a Ford V6 or some such might happen to fit the Jaguar V12 distributor. All thatâs needed is something that fits the right size shaft and has the right height â and the right height might not even be critical. If the FAST package includes shutter wheels that are 1-piece plastic (the hub and disk are all one part) it STILL might work if the OD of the shutter part is smaller than the V12 disk so you can just rivet the V12 disk down on top of it.
Yesterday I installed a new Crane/FAST LED trigger and tried to install a new disk. The problem I had was, after riveting the wheel to the hub, the plastic hub I.D. was a hair too small and would not go on the shaft. I didnât want to file, sand, or drill it so I just put on the old shutter wheel after polishing it up. Anyone figure out the cost of making one or a run of 10?
Jim,
Interesting that both of us are doing the same job.
Yes, getting the hub & disk back on can be a problem. In my case there were two issues. First, the hub is a tight fit. The trick is to warm it up with a heat gun.
The second problem is the pop rivet holes in the disk and/or the hub sometimes do not correctly center the disk on the hub, so the disk hangs up on the shaft. What I did first (Incorrectly) was to carefully cut away the overlapping edge of the disk using a Dremel up to the key, then a small file. That was a mistake because it can change the angular position of the slots with respect to the rotor/shutter disk key. The best thing to do is drill out the pop rivets and start over. Slip the hub onto the distributor shaft, then the disk. Rotate the hub until the rivet holes line up, and then check how well the disk hole and key align with the shaft. If not very well, rotate the hub 1/3 of a turn and inspect again. The idea is to find best alignment you can. Then, with the disk key in the shaft key slot, use 5-40 machine screws and nuts to securely clamp the disk to the hub at two of the holes . Put a pop rivet in the third hole. The, replace the screws and nuts with pop rivets one at a time. Sounds complicated, but it will ensure the best possible alignment of the shutter and shaft key.
BTW, do I understand correctly that you found a new 12-slot shutter disk and hub? If so, where?
Now for my project, i.e., installing a new optical trigger. I was on the home stretch reassembling everything when disaster struck: I twisted off one of the nylon screws that hold the EFI trigger board to the distributor. Iâm now trying to extract the threaded part. Iâll first try heating a small screwdriver melt a slot in the nylon, then back it out. If that fails Iâll drill it out and re-tap.
Ed Sowell
Success! Got the broken trigger board mounting screw out.
Heat a narrow screwdriver
Nice! We need to archive that fix somehow.
Kirby,
Iâll do a write-up on the project and post it on my Website in the next week or so. And, per youâre earlier suggestion, at some point Iâll talk to the management team about possibly moving my site to J-L.
Ed
Kirby,
Iâm going to look into having some of these shutters made. Do you think it could be done using the scanned image above? It would be a bummer if I spent $100 or whatever to have a dozen or so made only to learn they donât work. 
BTW, I happen to have a spare distributor with the OE nylon disk. When the keys are aligned the slots in the Crane shutter and ferrite (?) rods in the OE disk are aligned.
To me, it seems that all that is required is have the spark occur when the center of the rotor tip is approximately at the center of cap post, where âapproximatelyâ means in comparison with to the width of the rotor tip. If that is correct, an error of 1/2 degree or so in the angle between the slot and the key should not matter. That is, provide the distributor bottom is locked down properly in the first place.
Ed
Remember that the spark moves with the vacuum advance. So, you need to split the difference so that the spark has a small gap to jump both when there is NO vacuum advance and when youâre at MAX vacuum advance. Since youâre at no vacuum advance at static, you generally want the rotor lined up with its retarded corner aligned with the terminal in the cap.
If you base the design of your shutter disk on that scan, I think itâd work fine. I mean, obviously you need 12 equally-spaced slots around a circular disk. The OD is probably not all that particular, and most of the other dimensions are either clear or non-critical.
Thanks.
I was aware of the advance issue, but thanks for reminding me.
Also would like youâre thoughts on my current situation and plans for reassembly and testing the distributor. First, the optical trigger is mounted exactly, or very close, to where the OE magnetic pickup was:
The sheet metal bracket was one of several that came with the kit when I installed it years ago. It has little to no tangential adjustment where it attaches to the bakelite carrier, but since it has been running this way for years it must have been OK. And since I did not remove the distributor and did not change the timing adjuster or the position of the lower part of the housing relative to the engine top plate, Iâm assuming that everything will still be OK. Nonetheless, I want to check it before buttoning it up.
To check it, I plan to put on a cap in which I cut a hole near the 1A contact and connect the coil secondary cable and the 1A cable. Then Iâll:
If Iâve got all this right, I should see the position of the rotor tip relative to the 1A pin in the cap as it cranks.
But, what do I do if the retard corner of the tip is not pointing at the pin center?
Ed
