Distributor advance springs

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[quote="stovekjj"]my old workshop manual (i've got a federal S3) states:
"on no account should the vacuum mechanism on the 25D distributors be connected"Page L14 / Manual 26T327quote]

Hi stovekjj, I have seen that in the old manual and is why I was surprised when Frank said he had an advance vac unit on his Elan as I know the Federal cars had a retard unit, I think the reference "on no account should the vacuum mechanism on the 25D distributors be connected" is referring to the very early 1500cc cars which were recalled, I think Lotus fitted the Cortina distributor (with vac advance) at the start of production but just did not connect it up, the later cars had no vac unit until emission laws forced them to fit the retard unit on Federal cars.

[69S4]

a good start for static timing would be 18 BTDC

I'd be a bit worried about that. Even without wondering where it ended up on full advance you must be getting close to the "kickback" zone when trying to start the engine.

Stuart

[stovekjj]

This manual ( saying don't hook up the vacuum on 25D ) is 'S2' vintage, but for 1600 TC motors
with either 25D or 23D(no vacuum) distributors...

Hmmm, my bad,
the 18 BTDC is for idle ( 800-1000 rpm),
the static is 7 for 25D, 14 for 23D per this manual.

[Frank Howard]

Frank, I thought Federal cars were fitted with a retard vacuum unit and not vacuum advance, does your Europa have a vac advance or retard?
Here is an artical that mentions the Europa's retard device.
http://webspace.webring.com/people/q3/3 ... inCam.html

Brian,

Sorry to take so long to respond but I had other projects on my plate like changing out our 32 year old furnace just in time for the northern hemisphere winter! Today, we are in the middle of our first big snowstorm so I canceled my insurance on the Lotuses. Before putting them away, I thought I'd go out and check so that I could answer your question before next spring.

As you predicted, both my S4 and my Europa Special have vacuum retard mechanisms i.e. the distributors are mirror images of what the MG distributors look like. I tried to make the points base rotate by sucking on the vacuum tube but was unsuccessful. Either the mechanism is not working properly or contray to what others may say about me, it turns out that I don't suck. Not really sure. I did attempt to rotate the points base by hand and while I was able to rotate it counter clockwise, I was not able to rotate it clockwise at all.

Paddy, you were quite right when you questioned whether or not twin cams came with vacuum advance mechanisms. I stand corrected. Brian, I want to thank you for enlightening me with the information that in addition to mechanical advance mechanisms, apparently both of my cars are equipped with vacuum retard mechanisms. Enjoy your summer.

[Tonyw]

Gent's,

I have had this discussion many times before with my vintage car colleagues. The vacuum unit on any distributor can be either vacuum advance or vacuum retard, with vacuum retard there is usually vacuum at idle and at cruise so that when you put your boot into the accelerator pedal the ignition retards due to low or no vacuum, this of course reverts to advancing the ignition when you ease of your foot and at cruise or light throttle.

Vacuum advance usually uses a "progressive vacuum port which is usually found on the carb and allows the vacuum to increase gradually at light throttle, planting your foot will automatically retard the ignition back to a static position or where the mechanical advance is situated. Distributors that have no vacuum advance usually have more mechanical advance than those with vacuum advance.

Tonyw