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Electronic Distributor Experiences?  Rating:  Rating
 Posted: 12-29-2006 04:01 am
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21st Post
Dan Eiland

Joined: 03-18-2005
Location: El Paso, Texas USA
Posts: 159
With all this talk about distributor advance, I'm wondering if I keep my vacuum advance when using dellortos or do I remove it from the distributor? I have read it can't be used with dellortos. Should I purchase another 25D4 without the vacuum advance? From what I read on this subject it sounds like all these distributors are basically the same except for what is on the inside. I don't know why I couldn't just purchase a non-vacuum advance distributor already set up for my engine. All input welcome.


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 Posted: 12-29-2006 08:02 am
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22nd Post

Joined: 03-17-2005
Location: Warmond, Netherlands
Posts: 194
Hi Kurt, that is very interesting. I don't know exactly who the first owner was of my car. All i know is that it was meant to go to the US as it was a stromberg/US set-up. But i was told my car never reached the US but went to Switzerlands instead. I do have information on the previous Swiss owner. It could well be the car did go to the US before it went to Switzerland... My vin is 15175

Dan, you are right; you can't use the vacuum advance with Dellorto's. You need to blank it off. There should be some info on how to do this here on this board. However the cost of having it refurbished and new weights/advance curve is most likely as much as getting a new one.

You can get a NEW dizzy for your JH/Lotus without the vacuum advance part and ready for your high performance 2.2L engine. Check with Delta and ask for the Pertronix Flame Thrower High Performance 45D Distributor for British Engines and discuss a proper advance curve for your car. It comes equipped with a Pertronix Ignitor II. Introductory price is $ 215.95


Last edited on 12-29-2006 08:05 am by Harkes

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 Posted: 12-29-2006 12:21 pm
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23rd Post

Joined: 08-07-2006
Location: Sydney, Australia
Posts: 46
My trusty Jensen Manual shows the following centrifugal advance curves, in crankshaft degrees for the 3 types of distributors.


RPM        Advance
550         0
1250       15 +/- 1
3550       18 +/- 1

25D.4 (early emission engine)
1000         0
1600         6.8
2200         13.6
2500         17 Max

It list idle retard separately for stromberg cars as 3-5 at 6in of Hg and 5-7 at 10 in Hg prior to Eng. No 4803 This is the vacuum capsule on the side. This is vacuum retard NOT vacuum advance


Dellorto (I guess this means the 23D.4 as it list this for non emission engines)

BELOW 1000 No advance
1200             2
1400             4.4
1600             6.8
1800             9
2000             11.4
2200             13.6
2400             16
2500             17
Based on these figures if you were to use a 45D and simply remove the module and lock the base plate you could end up with a far to aggressive advance curve, this could be masked by reducing the static timing but I suggest you would loose performance , I have never tested this on a Dyno so I may be wrong and the engine may accept this, however I strongly suggest having 83% of your advance in by 1250 rpm is not ideal (assuming my trusty manuals figures are correct, it is a old Jensen parts & service book so I have no reason to disbelieve it)

Last edited on 12-29-2006 12:39 pm by normv

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 Posted: 12-29-2006 02:10 pm
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24th Post
Judson Manning

Joined: 03-14-2005
Location: Atlanta, Georgia USA
Posts: 406
The Lucas 45DM with Vacuum advance fits nicely under my Dellorto manifold, and wires directly to my MSD unit.  I got mine off Ebay for about $100.00.

Keep in mind there is no 'right' curve.  At this point, none of our engines are stock, nor are they running the same blend of gasoline used in the 1970s.  Literally ALL of the variables have changed which makes ALL the initial factory settings obsolete.


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