My 1969 XKE series 2 OTS has a distributor with a 1968 vacuum adjuster blank.
I have no idea why this would be. I bought the car around December last year and have been upgrading some of the electrical and panel fitting issues.
The car seems to have some carburetor or timing issues that I was investigating prior to dropping it of at a local shop to have the car tuned.
can anybody tell me why the 68’s had no vacuum retard.
Also if I purchase a new vacuum unit would I be able to fit it and splice into the vacuum lines without a lot of other issues showing up.
Bit lost right now, this is not my core expertise

 

Terry

"The 68 & 69 XKE models used a distributor without vacuum advance or vacuum retard. The mechanical advance on this unit was 20 degrees which gave 40 at the crank. Add initial of 5 and you get 45 degrees total advance. The extra advance was necessary as the leaner mixture slowed down the flame propagation so combustion took longer. This required the spark to happen sooner. One has to be careful if converting on of these cars to triple SU carburetors that the proper distributor is also used. To much high speed advance can melt the top out of the pistons with expensive results."
So, you can't just add vacuum advance to an all mechanical advance distributor (even-though the casting may accommodate it). See Distributor curve below. 68-69 could have been #41207

Rgds
David

 

Thank you David,
my car was converted to the triple SU Carbs. I will have to chat with my tune up Guy so he understands all this.
He is not a Jag Mechanic but has vast experience with Classic North American cars. He tunes my 67 Mustang, that’s how I know him.
our local shop British Sports car close down before Christmas, a great loss.

 

Terry
The correct distributor (with vacuum advance) for triple SUs is the P/N 40617A ....(a new Pertronix D171618 - with-vac-advance - distributor, with matching coil would be good alternative)
With the P/N 41207 Mechanical advance curve you are way retarded at 2800 RPM cruise and way advanced at WOT 4400 RPM.
This will negate all the benefits of having 3 SUs. The middle SU should have a vacuum advance nipple just above the throttle butterfly.. it may be capped off, or the fitting threads may be plugged... Internet-sites have instructions on how to drill out plug and install fitting.

One forum member sent his mechanical distributor to a specialty shop in (New England USA) and they added vacuum advance and re-profiled the mechanical advance weights to the correct configuration for his compression, octane and triple SUs.
Rgds
David

 

Thank you David

 

I was researching the distributor, I found the Pertronix D171618 right away. The 40617A escapes me, it does not show up on the CKS site, who is the manufacturer of this unit.
also my front carb seems to have a small plate with a 1/8 brass fitting capped off, I am assuming this is the vacuum line
see photo

 

Terry

The 40617A distributor was for the 1967 XKE S1 with triple SUs.... you would have to find a used one on e-bay, etc; with condition unknown...and its a points distributor, so, many issues if you are trying to stay with original Jaguar parts.
Yes you have found the vacuum source for the Distributor

I think this is the shop that converts mechanical distributors to vacuum advance for the triple SU configuration.
British Vacuum Unit
Canterbury, NH 03224
(603) 731-1788
​For orders or info, use our web "Contact Us" or email us direct at
​bvu@britishvacuumunit.com
Rgds
David

 

Thanks again