Help identify this ditributor?

rsrmike · 11-20-2008, 02:23 PM

Can someone help me identify this ignition distributor? It is a counter clockwise rotation. The Bosch number inprinted in the side is

0 237 301 004

It has a single vacumm hose connection. I initially thought it was from my old 79 SC, but I did a search and only one thread came back w/ this bosch # in it. Claiming it was for a turbo.

Bosch part numbers test

The vacuum actuator only responds to vacuum, boost pressure seems to have no effect. However, w/ vacuum, the trigger "tines" turn counter clockwise as well. Wouldn't that be "vacuum retard"? Seems weird, or am I the one who is retarded?

Anyways, I offered it to another Pelicanite w/ turbo-SC engine troubles and he asked if it was boost retard. When I got out the "mity-vac" the confusion ensued...

Can anyone w/ an 86-89 turbo apart look at their dizzy and help out?

Thanks!

Please help!

patkeefe · 11-20-2008, 04:03 PM

Mike:
I found this. I'll look some more.
Distributor query

rsrmike · 11-20-2008, 05:29 PM

Thanks, I'm starting to think mine is not a US 86-89 dizzy. I think I remember them all having a larger 2 port cannister, w/ red and blue vacuum hoses originally

Mine has a smaller single port, which did not respond to pressure from my mityvac but moves the trigger CCW w/ vacuum

I still don't understand why the vacuum appears to retard the trigger?? Did they ever have vacuum retard?

356-930 · 356-930's Garage

Quote:

Originally Posted by rsrmike

. . . I still don't understand why the vacuum appears to retard the trigger?? Did they ever have vacuum retard?

The term, "vacuum advance" is a misnomer. To be gramatically and descriptively correct, the device should be referred to as a "vacuum retard."
Engine manifold vacuum acting on a gasoline engine distributor's "vacuum pot" does indeed retard timing. Distributor timing is advanced by loss of vacuum on the vacuum port.
Easy to observe/verify action of the vac pot using a timing light. At idle, check timing, crimp the vac line, pull it off the vac pot and timing will advance aprox. 18-deg.

rsrmike · 11-20-2008, 06:25 PM

AH HA, that makes perfect sense. I wish the dizzy was still in the car for me to test. I was thinking of the timing being advanced more under light load as it is in the newer fuel injected cars.

I guess the vacuum retard function of a mechnical dizzy was there to have reasonable idle timing, improve off idle throttle response, and still have the proper advance at higher RPM?

Just another reason EFI cars run smoother, make more power, and have cleaner emmisions??

It's easy to get confused if you didn't learn the fundamentals on older cars and try to apply modern logic to older mechanical systems huh?

voitureltd · 01:16 PM

[QUOTE=rsrmike;4315550]Can someone help me identify this ignition distributor? It is a counter clockwise rotation. The Bosch number inprinted in the side is

For a turbo it ran clockwise ( 1 year ) . I had to have Supertech make up a special twin plugged distributer for me as mine went bad inside. Quite a project as they had never done one before. Other years they may have done this in race cars. Why Porsche did this I never found out. This car has lots of real 934 or 935 stuff on it including the small spark plug heads. My distributer was so bad my race shop tried to get a donor . As I remember there was a 911SC year that turned the same in a certain year( maybe 1979? ). Supertech made one up reusing my original distributer drive gear to mesch with my engines innards.Anyone Know why Porsche did the clock wise scenario as i can see no benifit?.

billjam · billjam's Garage

For the record, this is what a US 1986 dizzy looks like ...

rsrmike · 11-21-2008, 05:54 AM

Thanks Bill that is what I have in my memory, The thread I found must be wrong.

Chris, thanks for the remedial clarification about the advance, it's been so long since I've serviced anything with a distributor!! Late model Porsche/Audi/VW's just don't have them anymore- doh

rsrmike · 11-21-2008, 11:31 AM

Here are some pics, Finally got a new charger for the digi cam, Obviously I need some practice, or some intruction...

NathanUK · NathanUK's Garage

Mike, I think you had the camera too close. Next time try having the camera further away and using the optical zoom to get closer. Focusing is much easier this way.
If that doesn't work then try using the little button that looks like a flower for close up pictures, the macro feature.
You need to hold the camera very still as you shoot!

rsrmike · 11-26-2008, 01:46 PM

Thanks Nathan,

I keep meaning to take better pics. It's not a huge rush obviously.

I'll try to do better and maybe get a trophy for "most improved", then I can have flashbacks to my "little league" days...

cole930 · 04:43 PM

Mike,

I have the same distributor in my car. It is the stock unit for an 80 ROW 930.

counter clockwise rotation and single vacume port.

Cole

rsrmike · 12-01-2008, 05:13 PM

Thanks Cole.

I take it the single port means it doesn't have "boost retard"? When I apply vacuum to the port, the trigger turns counter clockwise as well. So it appears boost will have no effect on the ignition timing?

cole930 · 06:03 PM

Mike,

You might have to work with me here I trying to post a scan. You might want to
try saving it as a pic and printing it out. Hope it sheds a little light on the boost retard.

Cole

patkeefe · 12-02-2008, 12:11 AM

Cole:
What does the factory prescribe for timing settings on your model?
Pat

cole930 · 12-02-2008, 11:57 AM

Guys,

Save these as pictures and keep them in your files.

Cole

lucittm · lucittm's Garage

I just want to point out that the information in those scanned documents is perishable because my 3.3L turbo factory distributor does turn CW. The way the text is written, "A left-turning distributor is installed on 3.3 liter turbocharged engines." was true in 1979. But not universally true today.

I don't know why they changed direction, maybe someone can enlighten us on this thread.

Thanks,
Mark

voitureltd · 10:45 AM

Quote:

Originally Posted by lucittm

I just want to point out that the information in those scanned documents is perishable because my 3.3L turbo factory distributor does turn CW. The way the text is written, "A left-turning distributor is installed on 3.3 liter turbocharged engines." was true in 1979. But not universally true today.

I don't know why they changed direction, maybe someone can enlighten us on this thread.

Thanks,
Mark

On my post#6, I had the one year distributer that needed rebuild. To multiply the problem it was a 12 lead one that was only used one year on a 930 and one year for the 911SC. Supertech did the work after exhaustive research along with my race shop . Neither ever came up with a reason for this one year reverse ( clockwise ) spin. Needless to say it was a problem to internally build a new one. I believe they used V12 BMW electrical innards and reused the bottom drive gear to mesch. Works great now. My 930 was a 1977 however it was built from who knows what. I believe the 911 SC year of clockwise rotation was 1979? ( its been awhile ) that Supertech wanted as a donor before they tried to rebuild mine. There must have been a reason for Porsche to go to all of that trouble.