Timing marks and dizzy caps

[Fetta GTV]

Have been scratching my head trying to help a mate get his sud TI going.


I have always thought it strange that the cap is wrong. Mine has 4 on the cap where no 1 plug lead is. It runs fine but it is just enoying.
I have 3 timing marks
T top dead centre
I This is where my timing is set when checked with timing light
II this I thought was the 2000rpm timing mark but at 2000 rpm I am not getting that much advance
III in the manual says 4500 rpm timing mark, I can't find this one.

My car revs smooth and idles perfectly at these settings

I had not really looked at this until We tried nutting out what is happening with the advance on the sud.
The sud is idling perfect but has no gut until about 4000rpm.
Checking with the timing light shows that it is not advancing until 4000rpm.

Would be great to hear what marks everyone else has there boxer set to.
Who has just mechanical advance, and who has mechanical and vacuum? Mine has both.

[ricky ricardo]

Hehe! Cylinder 1 is at No.4 on the cap because the oil pump is installed backwards. I did the same assembling my engine, it messes me around when I take the distributor and leads out. I use the timing light as a guide but end up tweeking where it feels right to me.

[Fetta GTV]

The rotor button is in the correct position, pointing towards the drivers side of the car where the number one lead goes to. It's just that the cap has number 4 moulded onto it at that lead and you cannot rotate just the cap.

[ricky ricardo]

My car already confuses my this'll only make it worse. My rotor points to the passenger side headlight and the notch on the distributor.

[Spacenut]

OK. The distributor cap is keyed onto the body, so cannot move relative to it. However, by moving the distributor body through 90 degrees, you can time the engine up to the next lead, if you see what I mean.

When I repositioned the engine In my bespoke chassis, the vacuum advance on the distributor fouled the gearbox top mounting (a more substantial "bridge" assembly that also carries the rear suspension turrets and roll hoop bracing bars), so I needed to move it round 90 degrees to provide clearance.

But as Ricky says, if your rotor arm is pointing in the correct direction for #1 TDC then the oil pump has been replaced incorrectly.

Some engines only have TDC, 8 degrees BTDC and the full mechanical advance timing marks (my 1980 engine has only these markings). If the mechanical and vacuum advance are in good order (sometimes the bob weights can sieze up, or the vacuum advance can suffer from leaks), timing at idle, vacuum plugged and 8 degrees BTDC should give smooth performance throughout the rev range, as the advance characteristics are fixed during manufacture of the distributor.

As far as I know, all Alfasud distributors have both vacuum and mechanical advance. If nothing it happening below 4,000 rpm, I would suggest a vacuum leak - vacuum advance kicks in earlier than the mechanical. You should be getting 32-36 degrees of advance at WOT (vacuum can take this up to 50 degrees, but only on light throttle openings).

Very similar Bosch units were used on some models of VW Beetle, which sometimes use mechanical advance only. Vacuum advance is used for fuel economy at part-throttle, so for racing is usually disabled.

Lauren

[Fetta GTV]

Thanks for the replies, this has been very helpful, car is now running.
Now another question, do any of you guys have or know much about the twin pickup distributors. This one has no vacuum advance and 2 pickups. I have read that the second pickup is activated by a temp sensor.
Any info would be greatly appreciated.

[buzzed]

Thanks Fetta,

I am said mate. Here's a pic of my dizzy. Not sure if you guys got these or not in the uK, but in Aus, I have two such examples where no vac advance is installed. whilst it is now running it still refuses to advance at 2000-4000rpm. The car is not smooth revving in this rev range, and seems to find its life again at 4000+. Pretty keen to get it sorted, either by sourcing a replacement bosch dizzy or fixing this one. Anyone got a wiring diagram for said model/dizzy?

[Spacenut]

Thanks for the replies, this has been very helpful, car is now running.
Now another question, do any of you guys have or know much about the twin pickup distributors. This one has no vacuum advance and 2 pickups. I have read that the second pickup is activated by a temp sensor.
Any info would be greatly appreciated.

Hi Fetta - I have heard read about these distributors on emissions-controlled cars. The second pickup acts in the same way as an advance mechanism, allowing the distributor to switch between normal and advance running modes. I seem to recall that for the US-spec systems at least, a microswitch on the throttle pedal was used to detect WOT and retard the ignition accordingly. I think the mechanical advance was still fitted though; the twin pickups were used to replace the vacuum advance.

I wouldn't be surprised if temperature came into the equation as well!

Lauren

[PETROLHEAD]

And the lower octane fuel too I shouldnt wonder.

I know in the states, regular pump gas used to be as low as about 83/85 Ron wasn't it Lauren?

that is a huge difference in timing terms I would guess too.

I used to deal with a lot of early/mid nineties Vortec engined yanks, and over here they ran 100% better with a timing set up more typical of our 95+ Ron fuel suiting.


Are these dizzys a left over from a similar era in Aus possibly?

[KevJTD]

i've seen those rotor arms before on other cars, a mechanical rev limiter built in, sprung loaded. they play up.........

[buzzed]

Remember when comparing US fuel to UK fuel that there is a difference between MON and RON. MON being the lower of the two. Whilst both are determined on a special single piston test bed, the MON is done at 900rpm instead fo 600rpm for RON, and has its timing adjusted to further load the fuel. The MON is a better measure of how the fuel will perform underload...eg up a hill.

Back to my point....US fuel numbers are based on MON, which for example, on 95 octane RON fuel is about 85 MON. when people talk about crap fuel in the US, perhaps they are refering to the availability of 95-98 RON fuel. It's a big country and I am sure they struggled in some locations to get much more than 91-92 MON...so then perhaps Auto companies adjusted timing accordingly. same as in Aus...they say it's too hot, so timing gets retarded on all our cars....when the tight arses could simply add another callibration in the compture to only retard based on external temp...then for most of the year we would get our full serve of Hp...how hard?...

[AlfaCorseChris]

Mate, dont change to bosch dizzy !!! Its rubbish !!!

Keep your Marelli !
I've taken my working bosch distributor and placed it neatly in the trash can

Marelli FOR THE WIN

Tell me what it is exactly that you need...

First of all, have you checked that the cable underneath the rotor arm hasnt perished and is causing shorts ?

[ricky ricardo]

I just cleaned up a Marelli distributor but the wiring was totally rotted out. The Marelli in my car works fine but still ordered a new cap and rotor.

[Spacenut]

RON or MON, US fuel is rubbish. Perhaps it is the high ethanol content, or the fact that it is "re-processed", its horrible.

The factory manual for the '71 Baccaruda advised ignition timing of 0 degrees BTDC to run on contemporary fuel. I tried it over here on super unleaded and it ran like a dog. By trial and error, I found the optimum timing was 14 degrees BTDC! Made a BIG difference to the fuel economy - I was getting 18 mpg

Unlike Chris, I can't say that I have ever had a problem with the Bosch distributor. In fact, the one on the Green Machine came off my 1978 donor car, so is now 36 years old! I don't think any of the 1970s emissions control solutions (dual pickup, EGR, PCV, carbon filters etc.) were ever really effective, so it may be worth ditching the dual-pickup distributor in favour of a mechanical/vacuum unit. Stick to Marelli if you like, just bin the emissions dizzy.

Or, if your consience is keeping you awake at night, you could always convert to EFI

[Fetta GTV]

When all you guys convert to your no dizz systems let us know, should be lots of marelli single pickup dizzy's available for sale

[AlfaCorseChris]

hahahaha

I'll take your Marellis as well

[PETROLHEAD]

Suits me, you can have whatever i've got spare when it hapens.


but as Chris knows Fetta, sadly these things won't be rushed! ha ha!

[AlfaCorseChris]

...truth be told...

I think I'll be going into hibernation and wake up in a few years