Distributor Help

CraigD · 12-06-2001, 10:21 AM

I need the boards help. I think I finally figured out why my car runs poorly at high RPM. I checked the timing, it is set ok but has ~2 degrees of advance/retard movement at high RPM. I checked the dwell...set at exactly 39 at idle, however, drops about 8 degrees as I increase engine RPM. I increased the dwell to 42 and the car would rev up better but still felt missing/hesitation above 5500 RPM. I checked shaft play and I think that is the problem as there is visible movement at the shaft. I unfortunately have the original Marelli distributor.

Do I need to shell out $800 for a new Bosch unit to replace the aging Marelli? Anyone have leads for best price?

If possible, what used Bosch units can I purchase and refurbish?

What do you recommend?

Money is an issue but don't want to save on a used distributor to end up having it cost more by the time it is refurbished.

RoninLB · 12-06-2001, 01:00 PM

I assume you checked Dwell properly. You can do it wrong on CDI. A good inexpensive Bosh dizzy is the 2.7 Carrera dizzy. Pelican should have it for around $275.

911pcars · 12-06-2001, 02:16 PM

CraigD,
You should show about 35 degrees of advance with your timing light, not 2. Sounds like you have a problem with the centrifugal weights hanging up, possibly due to lack of lube and/or wear.

The dwell change might be happening because of vertical play in the dist. shaft. As rpm increases, the shaft rises which causes a different (unworn) area of the dist. cam to contact the points.

If your dist. is beyond repair, I'd look around for a used or rebuilt unit. Many convert to a Bosch because parts are difficult/impossible to find for the Marelli. Email the various used parts sources. BTW, I have a Marelli off of my '69T. I took it off years ago (about '75) so it's in pretty good shape. Let me know if you're interested @ $150.

Sherwood Lee
http://members.rennlist.org/911pcars

Superman · 12-06-2001, 02:43 PM

Yes, dwell crawl is caused by worn distributor shaft bushings.

CraigD · 12-06-2001, 08:07 PM

RoninLB,

Yes, checked dwell correctly black to ground red to distributor. Thanks for the info regarding the 2.7 Carrera distributor

Sherwood,

Maybe I wasn't clear the total advance is 35 but there is about 2-3 degrees of flutter while holding the RPM steady.

Everyone,

Any other dizzy's that will work in a 71 911T? Anyone have one of these they have sitting in their garage that they would be willing to sell for a fair price?

grant lyon · grant lyon's Garage

I have a '76 and the distr centr weights used to hang. There is a little metal cover on the body portion of the distributor below the advance plate. Pop the cover off and you can oil the Centrifugal advance weight pivot points. You can also put a dab of grease on the ball clip assy that hold the advance plate. Lastly, some oil on the felt pad in the hollow distr shaft (under the rotor) helps. My distributor is not new, but a little attention to these points (i.e. oil) can make a major difference.
Good luck

Olivier 3.0 · 02:10 AM

my question is: I took off my dist, and check everything: cent.advance weights seem to be OK, I clean and oil everything, and have no horizontal play at all, but there is a vertical play in the shaft.
I thought it was normal, in order to insert the dist. pignion, but what Sherwood says seems to tell me I'm wrong. There should not have any vertical play at all ??
If there is some (about .5 cm for mine), what is the cause?bearings?
I didn't succeed in taking out the axis which retains the dist. pignion... Do I have to use a press, and is this axis re-usable?

thanks

911pcars · 12-07-2001, 12:17 AM

Olivier 3.0,
.5 cm (5 mm/0.020"). I couldn't find the specs. If Mr. Walker happens to tune in, I'm sure he would know.

If the shaft is lifting and causing the dwell (and point gap) to change, you could remove the pinion gear and insert a spacer on the shaft to take up the unwanted play. The net affect of this dwell change is that the ignition timing is advancing a like amount.

If the dwell is fluttering 2-3 degrees, this is an indication the distributor cam lobes are worn unevenly, thus the opening ramp on each of the 6 lobes (one for each cylinder) is not symmetrical.

If your vertical play is within spec, I would suggest changing to an optical breaker system to replace the contact points. These kits don't require a good cam lobe for proper operation, and adjusting points is a maintenance item of the past. Look at Crane's XR700 or Pertronix points replacement units as they're the most cost effective alternative to buying a new/used distributor (typically <$100).

Sherwood Lee

Olivier 3.0 · 12-07-2001, 01:51 AM

thanks a lot, Sherwood

... In fact, I do want to change the ignition system, and for that I bought an Ignitor kit... But I met some trouble and I'm trying to solve this issue with Pertronix

.

Anyway, I don't think my dist.cam is worn, but with the former points, in order to prevent backfires and holes, I had to hardly reduce the points gap (largely less than specifications)... what can be responsible for that?

I can't test anything until this week-end, because I'm detailing my engine, and the distributor, injectors,coil, Cd box, fan housing and Fan are off the car

....

Early_S_Man · 12-07-2001, 08:17 AM

Olivier,

The vertical play shouldn't be more than approx. 0.1 mm!

You probably ought to disassemble and clean your distributor and replace the shims and washers, and probably the oilite/bronze bushings as well. Check this thread:

http://www.pelicanparts.com/ultimate/Forum3/HTML/009677.html

There are fiber washers and shims and ither steel washers in the stack, but all must have worn thru or come apart for you to have that much play! See if this generic exploded diagram helps any:

Roland Kunz · 12-07-2001, 09:11 PM

Hello

The 911 T will not like to work with a 911 S or carrera distributor.

Just use any other 911 T or standard 911 CIS distributor from Bosch to replace the weak & cheap made italian piece from ferrari quality and pricelevel

If you search the archives you will find a long thread from Early S man.

Grüsse

Olivier 3.0 · 12-09-2001, 10:09 AM

thanks Warren for your answer, and as a matter of fact, my play is really huge

! I tried this morning to reinstall the Ignitor kit on my cleaned and reassembled distributor (but still with the same play), following the instructions of Bill Hoge from PerTronix...
Halleluia! my car runs for 5/10 seconds, then died... and no way to start again...
Disappointed, I tried several other times, but with no success... So I reinstalled my points

.

I've already read all your threads, Monsieur Warren, but this is my problem:
-erratic run at 2200 RPM on constant idle, and some very little "holes" above, though my car climbs very well to the redline
- no possibility to respect the specs about point gap, without lot of backfires and erratic run; the only it runs correctly is to reduce the point gap to a very thin gap, but the erratic behaviour still remains at 2200 RPM when you stay at this level.
I tried another coil, changed points, plugs, cap, rotor, and wires are one year old...

I agree with you , Warren , when you say that points can be as reliable as electronic ignition when everything is in good shape, but I can't find what is the mess... The only lasting issue may be to change the distributor, but I want to be sure it's the responsible fot all of that...

Merci

CraigD · 12-09-2001, 10:32 AM

Roland stated "Just use any other 911 T or standard 911 CIS distributor from Bosch ".

Roland, can you or anyone else tell me what years or what part numbers I should be looking for? I have called around and found dist for anywhere from $350-750 but all except one of these so called replacements are "S" distributors and based on Rolands response the "S" dist really isn't appropriate. I searched the archives and there seems to be conflicting info re:Carrera 2.7, RS 2.7, "S" dist use in a 2.2T.

I tore the Marelli down and will look into replacing the worn bronze bushing at local bearing distributors next week. I suppose if I can replace the bushing I can get a few more years use out of the Marelli while looking for a good reasonably priced used replacement.

On a side note does anyone know a part number to replace the Marelli points with Bosch points?

RoninLB · 12-09-2001, 01:07 PM

Sorry I can't give you specific info. I hate to see a grown man confused. I have a 2.7 CIS that I will install a 2.7 Carrera dizzy on soon. Have been told by big people that it "should" be OK. I figure the worst situation is that I change advance weights and springs from old dizzy to new dizzy. I don't have any experience with any fuel injection dizzys, only carb. dizzys. It's a carb eat carb fuel world in my opnion.

Roland Kunz · 12-09-2001, 11:34 PM

Hello

2.0 & 2.2 Marelli are NLA including the finger and the cap as spare part. The distributor is still avaiable 2.4 Marelli are still maintancable but not a distributor aviable.
Porsche also used Bosch units in all T cars.
The Marelli deal had to be done to fullfill the contract.
( Porsche used Marellis for race cars )

Porsche replaced all 911T distributors by the 911 2,7 CIS unit as they have nearly the similar specs. This is to handle spare part storage easier.
So all sparepartnumbers are NLA and the said distributor is the direct replacment.

Sorry I don´t have all Porsche # in my mind.
Identifing the distributor is done by the Bosch ' witch is not identical to the Porsche '

The Distributors are in various stages the early units had been JFD 6 types then came the 159, 169 and the 184 series.
The number behind the typenumber is relatet to the specific version. Warren S had a list with the most used distributors in a recent thread ( 5-8 months back )

However smog equipment or other stuff my force to add advance/retard canister to the base distributor. I´m in germany and not sure about the US versions. They where even not covered in german shop manualls and books as Porsche tried to avoid gray market sales.

Porsche has the same price for 2,7CIS and for 2,7MFI distributors, they look similar and have only other curves.

In Germany most try to sale the S/RS distributors more expensive as people think they can tune the car to S-specs and will gain the "missing" power.

I would recomend to order the part aat a company who knows what they sale and will assist if problems show up.
You also can rebuild the Marelli unit but like said they are dead end as no serviceparts are aviable and the last NOS make a complete new Bosch unit look like a bargain.

keep in in the box if you think about return the car to a showpiece. The judges will rate originalty and cleanyness over function and if they ask why the engine runs so bad then smile and tell them becourse it has the original marelli and this is the original wear

I think those are the interessting threads:

http://www.pelicanparts.com/ultimate/Forum3/HTML/009677.html http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=32442

CraigD · 12-10-2001, 10:04 PM

Roland,

Thanks for the clarification and for the links. Not sure how, but I missed seeing the second reference in my search. I feel more comfortable about what to look for to replace the Marelli. The car is running great now, see below, so I will take a little time to find a reasonably priced Bosch replacement.

I reassembled my Marelli distributor after a good cleaning and lube. Set the dwell and timing and got in about an hour of driving. The dist shaft seems to have ever so slightly less play, probably the wheel bearing grease I used on the shaft rather that a permanent fix. Not really sure why but the dwell is virtually motionless now. Car accelerates well and reaches redline while still pulling. I came up with 2 possibilities though I am sure there are plenty of explanations. 1) I didn't really check the points before I took them apart and cleaned them up. Is it possible the points were hanging up and were the cause of the wandering dwell? 2) I replaced the slotted screws for holding the points with new longer phillips screws. I was just loosening up things to clean and inspect, I suppose its possible one or both of the screws wasn't tightened down sufficiently. Probably should have checked these things out first but I was convinced there was too much shaft play.

Olivier 3.0 · 12-11-2001, 12:02 AM

Roland,

The Bosch number resembles this: 0-231-000-000, and mine is :0231 184 006 , which doesn't seem to be a part known in USA (Pertronix cannot find this part number in their Bosch books); it makes your "grey market theory" very credible. It is installed on a Carrera 3.0, which is not supposed to have been regulary imported in the USA, even though there are some specimens overseas...

has anyone a clue , about my upper question (why do I have to reduce the points gap?)

?

Oldporsche · 06:30 AM

Wear in the upper bearing of the distributor allows the distributor cam swing in a larger radius. This reduces the amount of time your points are closed thus reducing your dwel time. You can compensate for this by closing up the point gap slightly.

I have been around this distributor thing a few times myself. As Roland says, Ferrari price level, cheap quality. I have seriously persued using a billet MSD distributor from an even-fire V6 motor as a replacement distributor for the 911. (Good quality, cheap price) This would be a drop in and could be recurved for any camshaft.

As Roland says, use any Bosch distributor that has the appropriate advance/retard mechanisms. Rebuild it to take the play out of it. Get the advance curve specs for your motor/camshaft from the spec book or shop manuals and take the distributor to your local hot rod shop that recurves distributors. They can verify the curve or match your curve to the appropriate curve for your motor/camshaft.

Good luck,
David Duffield

Roland Kunz · 12-11-2001, 08:40 AM

Hello

Seems to be my error while past & cut.

However from the IE history those are the possible links:

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=8720&highlight=distributor+marelli+bosch
http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=29928&highlight=911+t+distributor+conversion+bosch+marel li
http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=28885&highlight=911+t+distributor+bosch+marelli
http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=32442&highlight=distributor+marelli+bosch

Now the marellis are a bit strange and need more attention then the Bosch units.
I never do change the contact on the car, I allways pull the unit complete and work on the bench. Well we ( to company ) have the bench becourse we sevice F-cars as well and you need a bench for Dinoplex or V12 engines. Will safe time.
Ok woun´t blame on marelli the 547 Carrera distributors are also needing a bench.

You always have to grease & oil them when you change the contacts and I worked to often on 914/6 with marellis. Its just inneffective trying to do that in a 914/6 engineroom..

The marellis are just a old design when mechanics where used to oil the distributor every 5000 km.

Now there are some aftermarked contacts around who have a to soft spring. Those will not work on higher rev rates.
Adjusting them is allways a bit close to trail & error sometimes new contacts will "set" after a tesdrive and you have to begin again. A part from the problem is that the little plasticslider runing on the cam will waer in at the first miles.

Not sure about the screws, needed clamp force isn´t that high.

Like said on the long run you will need a Bosch unit as caps and finger for the marellis are nla and even the contact runs into 30$ regions. Now I´m not sure about your car but if you still have a early non CDI unit a petronix, lumetition or similar upgrade will pay back.

Grüsse

CraigD · 12-12-2001, 12:15 PM

Ok,

I have found a distributor...I think. It is a Bosch unit 0231-169-008
jfud 6. It is out of state so I can't look at it but I am told it is in good overall condition. It is supposed to be out of a 70 or 71 911 T. Can anyone confirm that this is a 911 T distributor and from what year 911?

Thanks