vacuum for distributor...where?

[RogerFrench]

Bob,
The US Federal Stromberg manifold has internal passages that connect the two main inlet passages, providing some degree of balance pipe function.

I have recently bought a Pertronix distributor for my Elan, from RD Enterprises. It has no vacuum advance or retard. I've seen the advertisements on eBay and do not trust them, I think the Pertronix tech is pulling your leg.

[rdssdi]

I am developing an opinion of Pertronix which is not suitable to be written here.

On page 46 of Pertronix' 2012 catalog "Performance Distributors for British Engines" it says "tailored advance curve for optimal performance and drivability" . I assume that the vacuum advance distributor cataloged on that page is covered by that claim also.

The link posted by CBUE1771 for the tech article on vacuum advance was a great read. It appears to me that advance at idle and low throttle will result in a better running and cooler engine. That seems to be what the Pertronix catalog claim is saying.

I cannot understand why Pertronix tech support is so evasive. I cannot get an answer about the suitability of their "LOTUS" distributor with vacuum advance. I spoke with several engine builders and they agreed that 20 degrees additional advance when the vacuum is present is excessive. They all said they would be happy with a 10 degree advance. Pertronix tech said that you cannot modify the distributor by limiting the plate travel as it would ruin the vacuum pot. Or something like that. The tech guy said I should get a Lucas vacuum advance and attach that. I am baffled. I requested that an application engineer at Pertronix contact me. I doubt that will ever happen. I cannot get them to even state that the distributor I purchased which is described in their catalog as written above is suited for the Lotus TC engine. Rather frustrating.

I will pursue this as long as I am alive! I have reached my limit with companies who are all hype and no substance. Either they know what the static timing, total advance and suitability of their product for my specific application or all they are peddling is crap. I will post more as I continue on my quest of a better running engine and a distributor that offers that.

Bob

[RogerFrench]

OK< I've now read the Pertronix catalog and it's pretty clear they don't differentiate between the Ford pushrod engine and the Lotus TC - they sell the same distributor for both, and specify vacuum advance for the road-going distributor.

This is a load of horse-manure. As previously noted, the TC was never fitted with vacuum advance, and should not be. I think the distributor shown as track-only, without vacuum, is the right one for our cars when the emission stuff has been removed. It's also clear they don't supply a distributor for the emissions-controlled engine with vacuum retard.

[CBUEB1771]

As previously noted, the TC was never fitted with vacuum advance, and should not be.

My federal +2S with Strombergs most assuredly came with a vacuum advance distributor. I believe your assertion applies to pre-1968 US market cars with Webers and non-US market cars with Webers or Dellortos.

[types26/36]

Here is an other thread where the vacuum advance/retard was discussed.
elan-f14/distributor-advance-springs-t19584-15.html

[rdssdi]

Whether or not some TC engines came equipped with a vacuum advance is academic.

Pertronix, a self proclaimed leader in distributors and ignition, offers a vacuum advance unit which has a "tailored advance curve for optimal performance and drivability". Therefore I do not consider it a difficult request to supply me with the centrifugal advance curve and the amount of advance added with the vacuum advance in use. They should also be able to defend the "tailored advance curve" suitability with the TC engine.

I would also like proof that the vacuum unit without the vacuum advance connected is identical to the non vacuum advance centrifugal advance only unit.

I just got off the phone with the Pertronix tech support voice mail. Again, I do not expect an answer. Their policy seems to be be vague and when pressed do not respond.

I will search for the company directory and possible get the extension number of an application engineer.

Bob

[rdssdi]

I called Pertronix main number and asked for Roger Wilkinson their Director of Engineering.

I left a message on his voice mail requesting the advance curve built into their distributor as well as my doubts about an additional 20 degrees of vacuum advance for the TC engine.

Further I reported that this information was not available after several calls to their tech line.

I hope this will yield some response. Now we can see what their vacuum advance unit really is and whether or not they actually tested it on a TC engine.

Bob

[CBUEB1771]

Bob,
I am sure I have my original distributor with vacuum advance in a box in my garage. I'll try to get the Lucas number from that and then we may determine what the advance v. inlet manifold depression curve was intended to be.

[rdssdi]

I received a call from Mr. Wilkinson. He said he understood my questions and would get me the answers and get back to me either today or tomorrow morning.

I was pleasantly surprised. I will report the information when I get it.

Bob

[Chancer]

If there is a reliable way of getting a reasonably constant unmodulated vacuum signal then any vacuum advance even if of unknown characteristics can only be a good thing for fuel economy.

With a couple of proviso's, that the engine doesnt pink on partial throttle openings, and that the vacuum signal is not damped, that is to say that when the throttle is whacked open the vacuum advance is released immediately and the engine doesnt pink.

Most engine builders would not have any experience of just how much advance can be tolerated, indeed should be encouraged on part throttle openings, they are concerned with power, wide open throttle and minimising timing flutter which a vacuum baseplate aint good for.

I should have also added the proviso that the engine doesnt overheat.

I would be very keen to have a modern electronic dizzy with the benefits of vacuum advance.

[RogerFrench]

As previously noted, the TC was never fitted with vacuum advance, and should not be.

My federal +2S with Strombergs most assuredly came with a vacuum advance distributor. I believe your assertion applies to pre-1968 US market cars with Webers and non-US market cars with Webers or Dellortos.

I'll bet it came with a vacuum retard, not advance. If not, it's unique.

[rdssdi]

It appears that on the emissions cars Lotus took the vacuum for their vacuum distributor (retard or advance) from the idle retard device which took vacuum from the #4 manifold port which on my car is powering the brake boosters.

If I ever get this Pertronix vacuum debate settled, I will tee off the #4 to supply the distributor with vacuum. I should be able to use a timing light to see if the vacuum advance goes away above idle and when it actuates when throttle is reduced.

Bob

[CBUEB1771]

Bob,
Unfortunately the distributor I have under my work bench is centrifugal advance only, one I bought when I first converted to a Weber head. It is possible I no longer have the original vacuum "modulated" distributor.

[RogerFrench]

May I suggest yuo read the following? http://www.lotus-europa.com/manuals/tcwork/l/index.htm

I know it's Europa, but believe me, they're the same carbs, ignition etc., and I don't know where there's an Elan equivalent to point you towards.

It's your car, persist if you will with vacuum advance, but I'd suggest you just leave the vacuum on your distributor disconnected, or if that's untidy, remove it altogether.

[rdssdi]

I heard from Roger Wilkinson at Pertronix. He reports:

Mechanical advance
Start 1100 RPM
All In by 3000 - 3100 RPM
Advance: 20 degree crank angle (10 degrees distributor)

Vacuum advance
Begins at 5 inches Hg
All in at 17 inches Hg
advance: 22 degrees crank angle (11 degrees distributor)

That would agree with what I saw with my timing light. With 10 degrees initial timing I saw 30 degrees max with mechanical advance only and 30 degrees at idle with the vacuum attached.

The question is whether or not 22 degrees vacuum advance is excessive. Mr. Wilkinson said they have not had any problems reported and believes
the TC engine will work well with the distributor as supplied.

I will get a tee and use #4 manifold port for vacuum supply and report what happens.

Bob