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Distributor vacuum unit

Distributor Vacuum Unit

The vacuum unit of the distributor does not work (membrane gone). I'm trying to get a new one. I understand that the vacuum cause advanced ignition (and retarded ignition when throttle is fully opened/acceleration, because of loss of vacuum). I can't find it in my Workshop manual, so I hope some of you can answer my question: how many degrees does the vacuum unit operate / do I loose with only the centrifugal system in order? I think a worn vacuum unit might be (the) reason for a "lazy" engine, espesially when accelerating the car? Thank you - Martin Jacobsen, (120 DHC 53)

To all - I've tried different vendors in the UK, asking for a new (exchange) vacuum-unit for my distributor. But no. To day I got a letter from Guy Broad, and he neither had this unit. Does anybody in the group have knowledge about companies who sell or repair this unit? I think somebody of you have some experience what to do? (I think it is impossible/difficult to repair the unit) Thank you - Martin Jacobsen

Martin, You should be able to rebuild the unit yourself. You will need a piece of reinforced neoprene rubber sheet. You can take your unit apart by uncrimping the outer edge. This procedure can be tricky, but it is possible. An easier cheater method is to cut small slices on the crimped edge, with a dremel cut off wheel, then peel the edge back a little at a time until you are able to seperate the two halves. Once open you will reveal the dry rotted old rubber diaphram, use a micrometer and measure its thickness. You should be able to find a local industrial rubber supplier, they will be able to match up a suitable replacement. Use some epoxy to insure a good seal at the edge when you reassemble ( recrimp the diaphram housing. The new diaphram material will be less than a couple of dollars. Good luck! - Regards, Wray Schelin

I got my vacuum unit from Bill Bassett. There is also a specialist who advertizes in every issue of British Marque - M&G Vintage Auto, Tuxedo, NY 914-753-5900 "Distributor vacuum units for all English cars rebuilt or new." - Bruce Cunningham, '53 XK120 OTS

I have several 120 distributors, and might have a good vaccume advance unit. Let me know where you are and if you still need. I'm in Va., USA. CHEERS! - Stefan Roundy

Martin - The Coventry Quarterly product flyer I got last September from XKs Unlimited in San Luis Obispo, California lists new XK-120/140 disributor vacuum advance modules for US $99.95. Their part number is LU-419066. They are on the net at "">XK's Unlimited, Jaguar Specialists. - Glenn C, 53 120FHC

Prologue, I wrote this before reading Wrays' entry. I'll try to add some new stuff to prevent it being just a repeat. Our net is down so this is getting strung out even longer. :-| Ken. Good morning, Actually it isn't that hard to repair the unit. Finding the proper material for the diaphragm is the most difficult part. I happen to be in the engineering biz and called a local die cutting shop. They make gaskets, RFI/EMI parts, various rubber, foam and cork die cut stuff for industry. They have lots of different sheet stock as raw material that they feed into the presses for die cut processing. If you are near an industrial area, the yellow pages under gaskets/die cut materials may have an entry or two. Often the proprietors of such businesss' are car guys, (gals too!!), and will take a bit of time to help out a fellow oil fume junky with a "sample" swatch of material. I did just that, and got a swatch of some really trick kevlar or nomex reinforced flurosilicone stuff about .010" or .015" thick. I carefully peeled the hemed over part of the vacuum bell and from there it was just easy kinda nuttin/ boltin stuff. I did my usual overkill by using 3M 8001 to stick the material to the bell and re-hemmed the bell parts together. SHAZAM!! A rebuilt vaccuum advance unit. Possibly better than new. (I'd bet big bucks the material of the diaphragm is better than new!!) :-) I guess this isn't something for the unmechanically inclined, but care, cleanliness, and patience can net a very nice end result. A little shot of spray paint or cold galvanizing stuff is a nice touch inside the bell to prevent further rust/corrosion. OH!! It just occurred to me a trip to the librarys' reference section should reveal a Thomas Register. A series of about 30 LARGE green books listing about every industrial company known in the U.S. One could no doubt find original suppliers to the die cut houses. Often a phone call (Many times an 800 number) to a sales/marketing person will also net a "sample" swatch. Tell them what you're doing, and that this assembly is now NOT available so you'd REALLY appreciate any help that may be available, you won't hold them responsible if it doesn't work, etc. You need a fiber reinforced fuel proof material, flexible, thin, blah blah. Check it out. - Cheers, Ken Boetzer

Ok, would someone like to volunteer to get a large swatch of this stuff and spread it around like green felt? I could sure use a piece! - Mike Eck, '51 XK120 OTS, '62 3.8 MKII

Thanks to all who responded my question reg. the vacuum Unit. All kind of tips: where to get new ones and how to repair the old Unit. One of the guys on the list offered me a complete Distributor. Hope to get it in a few weeks. The knowledge in the Group still impress me. I hope the Library will be updated. (For my part I use to print good contributions and put them in the Workshop manual). God jul! (Merry Christmas) - Martin Jacobsen

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