Checking Timing

[pdx930]

PrimeMvr,

5 deg ATDC with both lines disconnected sounds a bit too retarded to me. Both the vacuum and boost lines provide retard on the 87 USA distributor. The vacuum line will only provide the retard when the throttle is closed and should go away just off idle. Note that there is also a solenoid valve that blocks vacuum to the distributor for 30 seconds or so after starting to help raise the idle.

If you are seeing no change in timing at idle with the vacuum lines on or off, there is something wrong with the vacuum circuit, either in the lines, the solenoid valve, or the vacuum pot on the dizzy. A hand vacuum pump with a gauge is a must have for verifying proper operation of the dizzy. It's hard to believe that if you have 5 deg ATDC at idle with the lines disconnected, you are getting 26 BTDC at 4k RPM, which is the important value for our cars.

Bob

[PrimeMvr]

Thanks Bob. Do you set yours to 26 at 4k with lines off and ignore the idle timing?

I just bought a vacuum and boost pump with a gauge and will tear into this tomorrow. I have a suspicion something is frozen up in the dizzy because there is definitely vacuum in the line.

[fredmeister]

I had an issue awhile back with my distributor vacuum retard being locked in position because the actuation arm had disconnected and jammed within the body of the distributor. its possible yours is hung up or the diaphragm inside the vacuum canister is ruptured.
Its good to check them with a mityvac and document how far they retard the timing for your own records because each dizzy is different and the spec calls for a tolerance range anyway.
Your original symptoms of doggy power are typical of running the factory spec of 5-10 degrees ATDC at idle with these US engines. I dont know how Porsche released these like this back in the day....until you get some revs I could push the car faster than this.

[PrimeMvr]

I took the dizzy apart tonight and the vac retard side is shot. All of the mechanicals inside are in good working condition except for a broken washer and roll pin, for which I started a new thread.

Dizzy - Mystery washer and nasty powder

Once I figure out the washer and pin, I'm going to cap the vac retard at the TB and set the idle slightly advanced and see where that puts the 4K advance. I'm interested in a programmable MSD (still have stock CDI), so I may get rid of the built in boost retard too.