What would happen if your Distributor was off by 1 Tooth?

[IAN]

I did the oil fed chain tensioner update and had to take off my distributor.

I painted a line on the case onto the distributor so it would be easy to line back up without having to re-time the car.

When I removed the distributor the engine was at TDS for cylinder 1, and the rotor was pointed to the notch on the distributor.

What would have happened if I put the distibrutor back in place, lined up the paint marks, but had accidently turned the rotor a tooth??

Thanks.

[911pcars]

To make up for the slight error, you might try to rotate the distributor housing further (CW or CCW depending upon what tooth direction you're off) in an attempt to line up the rotor (or start the engine) so it points to the no. 1 spark plug wire in the dist. cap as it fires. Insofar as you can rotate the distributor housing and get them both aligned, you can do this. In reality, you may run out of rotation room which will prevent you from setting the proper ignition timing.

The distributor drive gear is a helical shape. This means the distributor shaft will rotate slightly as it meshes with the intermediate shaft drive gear. You must compensate a little before it meshes so the rotor points in the same position as it came out.

Hope this helps,
Sherwood Lee
http://members.rennlist.org/911pcars

[dean]

It would run like crap and you couldn't time it

[makaio]

You don't say what year car it is, but since you're concerned about timing I'm going to assume it's pre 84+. Even when marking a line on the distributor body and case you will have to re-set the timing.

[Oldporsche]

Off which way?

You have different results depending upon which way your distributor is off.

Good luck,
David Duffield

[Bill Jennings]

Hi All,

I have a issue that may be caused by my distributor being one tooth out.

Distributor has not been removed since I bought the car two years ago but may have been removed by PO.

According to the little Porsche Technical Specifications book my idle should be set at 5 degrees ATDC.

When checking timing at idle on my C3 I find I cannot get to 5 degrees ATDC because I cannot turn the distributor far enough to get it there. On my car I have turned the distributor clockwise as far as it will go and I can only get to TDC (Z1) at idle.

This may be related to the fact my car will not idle reliably below 950-1000 rpm without stalling.

If being out one tooth is the cause which way do I need to turn it to put me into the adjustment range?

Cheers
Bill

[Flat6pac]

From the look of the distributor setting you need to advance the distributor one cog.
There is 12teeth on the bottom of the distributor so each tooth represents 60 degrees of the 720 in firing order..
Weather your dist rotates clockwise or ccw you want the rotor approaching the mark on the distributor body.
Bruce

[Bill Jennings]

Flat6pac,

Looking at my picture I'm thinking turning it one tooth anti clockwise will give me more adjustment clockwise which is the direction I need.

I am just looking for another 5 degrees of timing at idle will the 60 degrees take it too far?

Cheers
Billj

[mreid]

On your car, nothing unless you run out of room in the adjustment slot and can't time it. In that case, set the crank at TDC cylinder 1, pull it out, turn the rotor about 45 degrees, drop it back in and rotate the housing to approximately the correct position. Start it and set the timing correctly.

[kach22i]

Back in 2006 my distributor was cocked all the way the other direction, and I too had to reindex.

Might be some good information in this old post, look for Walter_Middie's valued input.

JWalker + 35Deg + 3.5CO = HP


911pcars's post in this thread is spot on.

[911pcars]

The distributor rotates CC (early is Clockwise). If you've run out room to rotate the housing to set timing, it's probably off a tooth.

You could rotate the distributor rotor and shaft so it meshes the equivalent of one tooth from it's current position so you'll have more room to rotate the housing for timing.

However, while fully functional, I'd suggest reinstalling the distributor so it sits in the factory position (refer to factory photos from various sources):

1) Rotate crank so #1 piston is at TDC, engine ready to fire (end of compression stroke, both valves closed). Sounds like your engine is close but not exact.
2) Install/reinstall distributor so rotor points to notch on housing. Be aware that the distributor drive gear is helical shaped (it will rotate slightly during gear engagement), thus you may have to compensate a bit so the rotor ends up pointing at the notch).

Leave the housing loose enough to rotate to set the ign. timing. You should have plenty of room to rotate the distributor housing to advance or retard the ign. timing.

There are more accurate methods to "dead time" a static engine, but that's a "nice-to-know" procedure.

Sherwood

[Bill Jennings]

Sherwood,

Many thanks for the information.

I wonder how long this engine has been running like this as it is unchanged from when I bought it two years ago.

Do you know what difference it will make to how it runs after I move the distributor?

Currently I cannot get the car to run reliably with a idle less than 1000rpm, I get 19 MPG and I think I have less power than my old 79 SC which had 25 less ponies when it was new.

Currently my timing range is TDC at idle to about 30 Degrees BTDC at high revs.

Cheers
Bill

[Bob Kontak]

Originally Posted by Bill Jennings

I am just looking for another 5 degrees of timing at idle will the 60 degrees take it too far?

60 degrees of two spins of the crankshaft not of the rotor itself.

Rotor spins at half the speed of the crank so one tooth of the dist gear is 30 degrees of rotation relative to a 360 spin of the rotor.

Six plugs on the distributor - 60 degrees apart - 12 teeth on the rotor gear 30 degrees apart. One tooth off puts you between two of the plugs when on TDC and dist body is positioned correctly.

Depends what circle you are looking at.

[911pcars]

The ignition timing is the result of the relative position of the distributor housing with the occurrence of the spark for reference cylinder #1. Therefore, it doesn't matter if the distributor is off one tooth as long as the housing can rotate far enough to maintain the correct relative position with the rotor position/spark occurrence. However, for most vehicles, the housing can only physically rotate a limited no. of degrees, especially with distributors that have a vacuum diaphragm protruding from the housing.

Sherwood

[Bill Jennings]

In my case it's not the vacuum housing that is in the way I am at the limit of the groove the dizzy turns in.
I know I should have posted a picture because we all like pictures in here but it was late and I had a couple of Crown Royals in me at the time!

Bob & Tim,
Many thanks for the instructions on moving one tooth over.
Will report back probably tomorrow as life has gotten in the way of my Porsche habit this afternoon.
In this picture I am at TDC but still need 5 more degrees to get to idle timing!
Cheers
Bill