Distributor timing

[JFairman]

I've heard people say a 911 motor will run with the distributor installed 180 degrees out on the wrong stroke.
I've never witnessed this and was wondering how the motor runs?

[Steam Driver]

I don't see how it could work timed to the wrong stroke. But the distributor itself doesn't care how it's oriented, as long as the wires do to the correct plugs in the firing order. You could arbitrarily pick any given cylinder and plug wire location on the cap as "#1," as long as you continued in sequence of the firing order after that. But I can't think of a reason why anyone would want to confuse the issue by doing that!

[JFairman]

I'm just trying to get a positive answer to my question to maybe help diagnose a rough running problem before pulling things apart again.

I've never installed the distributor on the wrong stroke on purpose and the only way I can think of checking if I did is remove the left side rocker cover and feel if both #1 rocker arms have a little slack meaning both valves are closed while the pulley TDC mark is at TDC on the fan housing mark.
If they both have .004" clearance and can be wiggled then #1 is on TDC of the compression stroke and the distributor rotor should point at or close to the #1 hash mark in the distributor housing under the cap.

I can go out and remove the intercooler and do all that but I just wanted to ask here first because it's really hot outside in the S. Florida sun right now.

So, if anyone has an answer to my original question I'd appreciate hearing it.

[H2odiesel]

I can tell you I tried to start my 85 3.2 with the ignition timing 180 out for several hours with no success. It turned out my cap was wired 180 out when I bought the car and when I disassembled for a rebuild I labeled the plug ends and left the wires on the cap. It never came close to firing not even a sneeze. When I pulled the distributor and relocated the rotor 180 around it fired off instantly and ran great.

[JFairman]

OK thanks. I didn't think it would run with the distributer installed with the rotor pointing180 degrees away from where it should be when #1 is at TDC on the compression stroke.
One person told me it would but not well and I've never tried it intentionally and I doubt that's the misfire problem I'm dealing with right now.

I think I may have a CIS injector problem on #2. This is on an '87 911 turbo.
An hour ago I pointed an infrared thermometer with a lazer pointer at the B&B header primary tubes where they attach to the heads while the motor is idleing and number 2 was around 200 degrees cooler than the rest of them. Pulling the spark plug cap off #2 while it's idleing doesn't change the misfire as much as doing that to any of the others.

It's cooling off right now.
Tomorrow I'll take off the intercooler and do a CIS injector flow test comparison into empty plastic water bottles between #2 and some of the others. It could be a CIS injector causing this.

Only other thing I can think of trying is reversing the polarity of the green and violet
magnetic trigger wires going from the green coaxial distributor wire to the MSD digital 6AL ignition box that's in the car. I can easily switch them back if that doesn't help.
I have the center wire in the green coax wire from the distributor connected to the green wire going to the MSD and the outer sheild wire of the green coax wire connected to the violet wire going to the MSD.
I think thats correct and the MSD fires when the square wave from the distributer magnetic trigger drops. Reversing the polarity of those wires fires the igntition when the square wave rises and that advances the timing around 20 degrees and also makes the timing unstable.
That's how I understand it anyway and I may be wrong.

Thanks for any help with this...

[Flat6pac]

Remember, in a turbo, the pressure lines are not vacuum so they push the advance, not vacuuming it,
bruce

[JFairman]

Originally Posted by Flat6pac

Remember, in a turbo, the pressure lines are not vacuum so they push the advance, not vacuuming it,
bruce

On an '87 USA turbo. That year distributor has vacuum advance which turns into boost retard under boost on the outer side of the vacuum pot and vacuum retard on inner side of the vacuum pot that only gets vacuum from the throttle body from idle up to around 1500 rpms.
Above that the throttle butterfly goes past the little hole in the side of the throttle body throat and vacuum retard goes away and does nothing.
There is vacuum advance on this distributor. The centrifical advance mechanism in the bottom of the distributor is maxed out by 4000 rpms.

I've removed the lambda system timed vacuum switch that blocked vacuum advance to the distributor pot during cold starts to keep timing retarded a little and heat up the catalytic converter faster. The catalytic converter was removed decades ago before I bought the car. I'm in Florida where there is no emission testing.

I've checked all this vacuum pot stuff on my '87 with a mighty vac and watched the plate move inside the distributor while it's off the car and also with a timing light on the pulley while the motor is running.
Different years and countries the cars were sold in have different distributor vacuum pots and advance curves so the cars could pass emission testing and still have some performance.

[Eagledriver]

Originally Posted by JFairman

Only other thing I can think of trying is reversing the polarity of the green and violet
magnetic trigger wires going from the green coaxial distributor wire to the MSD digital 6AL ignition box that's in the car. I can easily switch them back if that doesn't help.
I have the center wire in the green coax wire from the distributor connected to the green wire going to the MSD and the outer sheild wire of the green coax wire connected to the violet wire going to the MSD.
I think thats correct and the MSD fires when the square wave from the distributer magnetic trigger drops. Reversing the polarity of those wires fires the igntition when the square wave rises and that advances the timing around 20 degrees and also makes the timing unstable.
That's how I understand it anyway and I may be wrong.

You have that all correct. The distributor doesn't put out a square wave though. It has a slow ramp up and then a sharp ramp down as the magnetic pick up gets passed by the "star wheel". The slow ramp up is too early for a trigger and because it's a shallow ramp the trigger isn't consistant. It's unstable and way too early as you state.

-Andy

[porschetub]

Its easy enough to do ,my motor was purchased with the dizzy lifted out off mesh and not @ TDC,its a cr#pshoot because it can be reset @ 2 cylinder TDC setting,sorry can remember but maybe #1 or #4 (someone correct me please),without the valve covers off thats the only way???
Maybe my crazy way works ?,took my air cleaner off put low tack masking tape over the velocity stacks and turned the motor,found TDC that way by looking how the tape sucked in and blew out ,found #1 or am I dreaming with this idea?????.
Can't find my Haynes manual so maybe just guessing.

[JFairman]

It's all fine now The misfire was the #2 CIS injector not spraying. I took it out and blew carb cleaner through it with the little straw from the can inserted into it and then blew compressed air through it from my compressor. The spray pattern is a nice conical mist.
Then I switched the #2 injector with the #5 injector on the right side that is easy to get at so I wouldn't have to remove the intercooler and CIS intake pipes going down to the turbo inlet if I needed to remove that injector again.
Anyway, it started right up! and it runs perfect again Timing is right on where it was.
Thanks for all the responses.

[porschetub]

Originally Posted by JFairman

It's all fine now The misfire was the #2 CIS injector not spraying. I took it out and blew carb cleaner through it with the little straw from the can inserted into it and then blew compressed air through it from my compressor. The spray pattern is a nice conical mist.
Then I switched the #2 injector with the #5 injector on the right side that is easy to get at so I wouldn't have to remove the intercooler and CIS intake pipes going down to the turbo inlet if I needed to remove that injector again.
Anyway, it started right up! and it runs perfect again Timing is right on where it was.
Thanks for all the responses.

Pleased to hear that,mechanical injectors are easy to clean like that ,if they get clean fuel the pintle (needle) wears @ a very slow rate and if you are keen you could pull them all and have them ultrasonically cleaned and a leak down test done for a modest price @ a good fuel shop.

[toddu]

btw- I believe you were remembering the car will run (like crap) with the cams 180 off.

Todd