CIS Trouble Shooting

[cooler]

Howdie Ya'all,
I am hopping some of you can help me diagnoes and answer some questions.
I have a fresh '77 2.7 with 964 cams, 9.8:1 CIS J&E pistons (92mm) and back dated exhaust. I am not confident that all vacuum hoses are appropriately connected considering the above modifications. I have done many diagnostic checks (if not all) as per the two Bosch Fuel Injection manuals I have. Fuel pressures and flow rates are now in or near specs.
Engine speed does not drop between shifts. Any suggestions what might be causing this? How much vaccum should I have at the distributor and which source should I use? What should my ignition timing be?
Any help is greatly appreciated.
Thank You
Cooler

[Porsche_monkey]

Is your distributor connected to the vacuum? I think the consesus would be that it should not be used.

[porsche930dude]

how long does it take to drop off to idle after reved up? Perhaps your decel valve is sticking open

[cooler]

The revs do not drop off consistantly. Some times they drop to 2000 right a way then to idle in a few second and other times they stay at the shift point for a few second then drop to idle.
Should I not connect the distributor to vavuum at all?

[Mysterytrain]

I would also check the deceleration valve. Its the pear shaped thing that lives behind the throttle body on the left side. If the vacuum lines are connected incorrectly it will effect the way the rpm's drop..or don't drop. This is a great link with tons of info: http://members.rennlist.com/jimwms/CIS/CIShome.html

[Porsche_monkey]

Originally Posted by cooler

Should I not connect the distributor to vavuum at all?

I think it should be disconnected. Maybe Mr Walker will chime in.

[Paulporsche]

Someone please correct me if this is wrong, but I think the vac line on the 77 dizzy is for a retard @ idle, not an advance. It was used merely as an emission item and is not necessary. Many disconnect it.

@ the top of your decel valve is a nut that surrounds the tube to which the vac line is attached. You can turn the nut CW to shorten the time the revs stay up between shifts and vice versa for lengthening.

Also make sure your dizzy isn't hanging up, keeping revs up.

[Porsche_monkey]

PaulP makes a good point, I think you should pull the dizzy and have a look at it.

[ossiblue]

I had identical symptoms. Check all the hard parts others have suggested. In my case, it turned out to be several air leaks. There are many posts on how to track down leaks, but I found the most effective to be a smoke machine--through my mechanic. He found leaks that didn't show up with shade tree techniques.
Keep at it, and keep asking questions. The more you find out the quicker solutions will come.

[al lkosmal]

The 77 distributor vacuum line is, as has been stated earlier, used to retard @ idle. I disconnected mine and plugged the vac line. If you have checked for vacuum leaks, i suggest that you thorughly clean your distributor. The advance mechanism may be hanging up due to years of crud. It's fairly easy to take the advance assembly apart and clean. i use carb cleaner and cue tips and then lube it up.

[cooler]

I love you guys!
I am over whelmed with the response and am grateful.
I will continue working on your suggestions and will continue responding.

... a smoke machine? is that like a Rastafarian. I am unfamiliar with this techniqe, please elaborate.

[MotoSook]

Start with the Decel Valve.

[porsche930dude]

A smoke machine just puts out smoke and you stick the tube in the intake and plug it off and smoke blows out wherever there is a leak.