Distributor woes

[antaircooled]

I have a 1978 3.0 motor type 930/03 with a mechanical advance distributor Bosch part number 0 237 303 003.

I have been having overheating problems plus lack of high end punch at the track and after checking the timing found that the advance at 6000 rpm was about 50 degrees. I have pulled the distributor and found about 5mm play in the shaft. I got rid of the play with a washer or two, reassembled and retested the timing - no improvement (still 50 deg advance at 6000 rpm).

A couple of questions - does anyone have the specs on on this type of distributor? What should I do next - start playing with the weights or take it to a professional?

[BURN-BROS]

Getting any more than 20 deg of advance out of that dizzy requires a great deal of work.

#1 Has the dizzy been modified in the past? Has the Vac advance been deleted?

#2 What is your initial setting?

[antaircooled]

Thanks for the reply Aaron.

I have had the car with this engine and Distributor for 5 years and it has not been modified in that time. This timing issue has just started happening. This distributor doesn't have Vacuum Advance and my research tells me the Bosch part number for a '78 distributor should be 0 237 306 001.

[psalt]

What is your initial timing ? The factory spec for the engine is 24-31 BTDC. The original distributor has around 20-25 degrees of mechanical advance and idle timing should be around 5 BTDC. If you cannot rotate the distributor enough to retard the timing, it has been improperly installed and you need to reinstall it at TDC.

[antaircooled]

Hi Paul,

Timing at idle is 5 BTDC. I removed the spark plug from cyl 1 and stuck some welding wire down the hole to find TDC. The Z1 notch lines up with the fan housing notch and the rotor lines up with the notch on the distributor body - that all looks correct to me.

[stlrj]

How did you determine 50 degrees?

[BURN-BROS]

O.K., three pin or 6 pin CD, or points/ solid state?

I do not have distributor #s handy at the moment.

[antaircooled]

The Bosch CDI blew up so I have an MSD 6AL2 - no points just the hall effect thingy inside. I got 50 degrees from a timing light. Stripped and cleaned the distributor then measured timing again. I then took it to a race shop and they got 50 deg advance on their timing gear too.

[pozee]

You need a pro shop to set that up for you. They will replace the springs and index it for you at the desired setting (out of the car).

Good luck and I hope that solves the heating issue. You don't have any restrictions anywhere causing the overheating problem do you? Also, is your gauge accurate? Are you really overheating?

Having stated that, I realize the timing is incorrect at 6k rpm.

[911 tweaks]

caution!!! If in fact you are overheating due to WAY to far advanced timing, you are about to blow HOLES in either the tops of your pistons and or the cyl walls...
If it were me, I would take the dizzy to someone who knows porsche dizzys and have them put it on a sun machine and check it out and repair as needed.
Then, double check the car after re install to see what the timing is at and if still too far advanced, trailer or drive slow to the nearest shop that knows what they are doing.
Best of luck here!!
Bob

[antaircooled]

Thanks Guys for all your input. I have the Distributor out again and have found a shop who know Bosch distributors so will get them to re-index it. I have a big race next weekend so want to get it sorted soon - double points in the handicap races so it counts HEAPS to final placings.

The timing seems to go haywire over 4K rpm so driving around town or to the track is no problem. I have checked the front cooler at the track and it feels very very hot - also when I saw the temp heading into the red I backed off and that made a bit of a difference.

I will post what the results are this week. Thanks again everyone.

[sc_rufctr]

Originally Posted by antaircooled

The Bosch CDI blew up so I have an MSD 6AL2 - no points just the hall effect thingy inside. I got 50 degrees from a timing light. Stripped and cleaned the distributor then measured timing again. I then took it to a race shop and they got 50 deg advance on their timing gear too.

When did you install the 6AL2? That's the new one isn't it?

Assuming you only just installed it you may have to reverse the trigger wires from the magnetic trigger. The're purple and green on my older 6AL. See photo... According to MSD you should wire up the trigger wires to give you the least advance and swap them if needed.

I would guess the 6AL2 would have the same wiring colours but double check the instructions.

When I first installed mine I guessed at the wiring of the trigger. I figured I had a 50 50 chance at getting it right. As it turns out I was wrong and I checked the timing with as light and it was way past the 35 degree mark on my pulley. Once I reversed the wires everything went back to normal.



Note the purple wire at the plug goes to the green wire at the socket! That's how I reversed it...

[antaircooled]

SC RUFCTR - brilliant mate. The overheating issues have happened since the MSD was installed. Unfortunately I didn't install it. I will check it and get back to you.

[sc_rufctr]

Originally Posted by antaircooled

SC RUFCTR - brilliant mate. The overheating issues have happened since the MSD was installed. Unfortunately I didn't install it. I will check it and get back to you.

That now makes sense... It's easy to swap the trigger wires. You can remove the pins easily from the socket side and swap them over.

Hope it works out

[sc_rufctr]

Quote from the MSD site...

Check the polarity of the magnetic pickup wires of the distributor. Reverse the connectors and check the timing again. The correct polarity is whichever connection gives the most retarded timing.

[BURN-BROS]

Originally Posted by sc_rufctr

Quote from the MSD site...

Check the polarity of the magnetic pickup wires of the distributor. Reverse the connectors and check the timing again. The correct polarity is whichever connection gives the most retarded timing.

This should be the solution! Good Luck!

[Gunter]

Originally Posted by antaircooled

Hi Paul,

Timing at idle is 5 BTDC. I removed the spark plug from cyl 1 and stuck some welding wire down the hole to find TDC. The Z1 notch lines up with the fan housing notch and the rotor lines up with the notch on the distributor body - that all looks correct to me.

That could still be wrong.
When the #1 piston comes to TDC with the help of a chopstick or wire, it could be either compression- or exhaust stroke even with the pulley showing Z1 and the rotor pointing to the distributor notch.
I use a chopstick to bring #1 piston to TDC, pulley showing Z1, then I wiggle the intake valve rocker.
It should be loose indicating that the valves are closed for compression/combustion.
Then I install the distributor pointing the rotor to the notch.
If the rocker is tight, it indicates exhaust stroke instead of compression stroke on #1 cyl. requiring another turn of the crank.

However, I hope that your problem is with the MSD trigger wires.

[Gunter]

Originally Posted by antaircooled

Thanks for the reply Aaron.

I have had the car with this engine and Distributor for 5 years and it has not been modified in that time. This timing issue has just started happening. This distributor doesn't have Vacuum Advance and my research tells me the Bosch part number for a '78 distributor should be 0 237 306 001.

Only if it's a US '78-'79 should it be 0 237 306 001. (With vac.)
For RoW SC's 930/03, your distributor is correct: 0 237 303 003

[antaircooled]

Here's my update Guys and thanks for all the great input. My MSD 6al2 does have the Green and Purple wires and they are wired the same as SC_RUFCTR has described. I tried swapping them and the timing was way off still so I have sent the distributor into a shop to be rebuilt.

[T77911S]

50 deg advance? that would sound like a deisel engine when you floor it from all the spark knock, no?

have you checked the font oil cooler to see if it is hot, and what about the T stat in the engine, mine went bad and caused over heating.