The 'E' Type Forum

Hi all, this is my first post on the forum and have decided to kick it off with a hot potato topic. My USA import series 2 4.2 manual has arrived this week (built early October 1969). I've ordered a 123 tune plus (bluetooth) dizzy and trying to fathom the minefield of vacuum sources.

i think i've understood that:-

1) If i was fitting a uk spec vac advance dizzy, i'd need to put ported(carb side) vac takeoff on the front carb

2) if i'm fitting a 123 programmable dizzy i could use a manifold vac source (as the 123 has the capability to deal with the constant manifold vacuum).

I've taken some pics of the current set up which is puzzling as the front carb has a ported vac take off already., using a brass nipple vis the pre tapped boss. i pulled the pipe and is open.

Is this standard for my car - does it suggest the dizzy has been changed or is the dizzy the USA spec vac retard ones?

Given that the front carb has a ported vac takeoff already done, should i just use that, or is a manifold source better for the 123tuneplus

You have a distributor with vacuum retard which was standard fit for some US cars at that time.

Replacing it with a distributor with vacuum advance like the 123 is definitely the way to go. I would use the ported vacuum take off you have already fitted. You can connect straight to it now and then experiment with ported or non ported vacuum at your leisure later if you wish.

There's plenty of debate on here around ported versus non ported vacuum take off which you can read and decide on but all E types and subsequent XK engined cars produced by Jaguar used ported vacuum take off.

Whatever you must also wire open the secondary throttle set on your inlet manifold - again details on the forum.

The combination of new distributor and wired open manifold will give your car the fantastic performance it deserves

Thanks John, i'll go with the ported take off for now. I've read up on the secondaries, just trying to find some photos of how to wedge the quadrant. I'm assuming the secondary is open in its rested state so its a case of disconnecting and wedging so it doesn't move.

i'm also planning to do the bypass (burp) valve block and lock down the temperature compensators. longer term is the adjustable needle conversion.

Hi Matt....this thread may help and see the link with in it...Steve http://forum.etypeuk.com/viewtopic.php? ... 4a#p115047

mgcjag wrote: ↑

Thu Dec 03, 2020 11:05 am

Hi Matt....this thread may help and see the link with in it...Steve http://forum.etypeuk.com/viewtopic.php? ... 4a#p115047

I've read all those....no pics anywhere. A simple photo would explain how to rig the butterflies open.

Hi Matt....i mentioned to look at the link......within the linked thread i posted .......its linked to Jag Lovers......plenty of detailed photos. ....Steve

It`s quite easy to remove the secondary throttle plates and spindles completely and block off the ends to stop air getting in .Makes a huge difference to the driveability .

mgcjag wrote: ↑

Thu Dec 03, 2020 12:01 pm

Hi Matt....i mentioned to look at the link......within the linked thread i posted .......its linked to Jag Lovers......plenty of detailed photos. ....Steve

Got it now thanks - had to log in to that forum to see the photos.

Thanks
Matt