1800: 1800E Distributor

[ACESRR]

My 1970 1800E has a 123 electronic distributor fitted by a previous owner. I have noticed the distributor has an outlet for a vacuum connection but there is no pipe connecting it to the engine. So my two questions are:

1. Would the original distributor have had a vacuum connection to the engine?

2. If the distributor did have a vacuum connection, where on the engine would it have connected to?

Many thanks for any help with these questions.

Andy

[volvobysea]

Hi Andy

I have an 1800es fitted with a 123 distributor and I have left the original vacuum tube in place. So in answer to your first question there would have been a small rubber tube connected to the original Bosch distributor.
The connection on the inlet manifold is located just past the cold start injector and the air intake connection, also behind the throttle linkage.

It may be your has been removed and blanked off.

I hope this helps

Cheers

Gavin

[ACESRR]

Gavin,

Thank you for your reply. On my car the connection on the inlet manifold has had a blanking plug screwed into it. I did wonder if this was meant to do something else and now I know.

I will have to make up a connection and connect the 123 vacuum outlet to it.

As a matter of interest which 123 curve setting did you use?

Kind regards,

Andy

[volvobysea]

Hi Andy

It was such a while ago when I set up the distributor I cant remember the setting I used I think it was the most basic setting as I wasn't interested in tuning the car using the different advance curves.
I just set up the timing in the normal way at 10BTC at 1000 Rpm vac unit disconnected.

Cheers

Gavin

[ACESRR]

OK, many thanks for that.

Andy

[Rustinmotion]

Originally Posted by ACESRR

Gavin,

Thank you for your reply. On my car the connection on the inlet manifold has had a blanking plug screwed into it. I did wonder if this was meant to do something else and now I know.

I will have to make up a connection and connect the 123 vacuum outlet to it.

As a matter of interest which 123 curve setting did you use?

Kind regards,

Andy

It depends where the PO bought it from, if it came from Amazon cars tune 3 is optimised for unleaded otherwise not much in it between 0 and 1

[ACESRR]

According to the receipts that came with the car, yes, the 123 came from Amazon Cars. However, there is nothing to suggest the head has been modified for unleaded petrol.

When I get the opportunity I will see if I can check with setting it is on, it's just the the distributor is not the easiest thing to see, being tucked inbetween the engine and the brake servo.

hanks,

Andy

[142 Guy]

As noted, in the original application the B20E and B20F had a servo signal on the distributor from the intake manifold. Notable items are that in the original application the servo is set up to retard ignition as vacuum increases and the signal is not a pure manifold vacuum signal. The manifold signal is taken from a port on the top of the intake manifold just in front of the throttle plate. The port location is shown circled in red on the attached diagram.

The signal is a 'ported manifold signal' which means that it is a blend of atmospheric and manifold pressure that changes with throttle position, not a pure manifold pressure signal. This is the correct nipple 943513 for that top port.
https://www.skandix.de/en/spare-part...ifold/1035418/

Having the correct nipple may or may not be important. Flow through the nipple should be close to zero so the hole diameter should not influence the signal. However, the part is still available from Volvo so I would be less inclined to screw around if you are going to try and replicate the original application. What is important is that if you want to try and stick to 'factory' you cannot use just any tap point on the intake manifold. It must be a ported vacuum signal.

The B20E / F engine will run fine without the manifold signal. If you apply the vacuum retard signal you will have to go through the idle speed and ignition timing set up as described in the service manual for the B20E because the vacuum signal will alter the idle conditions. The ported vacuum retard signal was an early bodge to try and make the B20E / F compliant with emission standards. Running without a vacuum signal will not affect maximum output (wide open throttle) performance. It will alter part throttle performance. You get to be the judge of whether the change is + or - or undetectable.

A final comment about an advance curve being for 'unleaded fuel'. Leaded versus unleaded is irrelevant. Octane rating is what matters. Tetra ethyl lead was just the dirt cheap solution to high octane. When TEL was banned or restricted octane ratings fell until the chemical engineers were able to figure out suitable fuel reformulations. So, ignition curves to accommodate low octane fuels became synonymous with unleaded fuels. Generally, these days you can purchase unleaded high octane fuel. It just a matter of how much you want to spend. Since the distributor came from Amazon cars, I suggest you email them and ask them what curve you should use. The relevant information would be:
- 1970 B20E (with stock compression ratio?)
- what octane fuel do you want to burn
- do they recommend that you run with or without the vacuum signal and does this alter the curve that should be selected.

[Ron Kwas]

Forum;

Great info from 142guy, as usual! The key is: ...not just manifold vacuum, but ported manifold signal (which varies as a function of Throttle position because of the port location)!

I'd love to see someone do some dyne/exhaust gas analysis test with and without the vac connected to the Distrib...but until I see some quantitative info, I'll keep going by the wise words of Phil Singher: "...vac retard is a performance killer" (paraphrased), and forego it.

It also does seem quite strange to me that these questions continue and repeatedly come up with 123Ign Distrib users...if this manufacturer had any sense of product support and wanting to grow their customer base, why would they not have this and all the other installation and adjustment questions competently and completely answered, and simply available?!?

Cheers

[Rustinmotion]

Originally Posted by Ron Kwas

Forum;

Great info from 142guy, as usual! The key is: ...not just manifold vacuum, but ported manifold signal (which varies as a function of Throttle position because of the port location)!

I'd love to see someone do some dyne/exhaust gas analysis test with and without the vac connected to the Distrib...but until I see some quantitative info, I'll keep going by the wise words of Phil Singher: "...vac retard is a performance killer" (paraphrased), and forego it.

It also does seem quite strange to me that these questions continue and repeatedly come up with 123Ign Distrib users...if this manufacturer had any sense of product support and wanting to grow their customer base, why would they not have this and all the other installation and adjustment questions competently and completely answered, and simply available?!?

Cheers

If it’s an Amazon cars distributer give them a call, they are very knowledgeable and friendly , I’d not so easily write off curve 3 it’s been developed on the RR and rally circuits, it’s not necessarily just unleaded but the modern fuel that it’s optimised for




NB: Curve3 is not as stated in the printed literature, read on!
 Or you can choose Curve3, developed by us for…
◦ modern unleaded 95RON fuel
◦ sports engines running on 98RON unleaded.

Curve3
The optimum setting can be ascertained by a trip to your favourite rolling road dynamometer, however we have found that the following initial set up has given excellent results…
• Set to 17° BTDC static/idle
• Which will give you 32° max advance at 3500rpm

NB: if it doesn’t state “AMAZON” on the label, then it doesn’t have our special curve – you can only get this Curve3 from Amazon Cars