A couple questions on 2 holes in 83 SC CIS

2jmotorsports · 2jmotorsports's Garage

Dear CIS Experts,

I am currently buttoning up a rebuild of my 83 CIS injection system.

Does this little hole in the air flow sensor remain open? If not what is supposed to go in there? Thinking of plugging it with a little plastic plug or squirting a bit of gasket maker urethane in there. Technically this is not a source of unmetered air because it is not in the path of the air flow sensor. The rubber boot flange buts up against it. However it is a source of unfiltered air. Air with dust or crud could get sucked through there bypassing the filter and going through the air flow sensor. It looks like it might be threaded but not sure. I could also thread it and put a tiny set screw in there with loctite. Cant really put a bolt in there because the head would prevent the boot from fully seating over the air sensor flange.

Secondly, this little fitting on the front of the throttle body is a fairly precise slip fit. It connects to the vacuum circuit that goes to the brake booster. Is there supposed to be some kind of sealant in there or just a dry slip fit like this? This would be a source of unmetered air if it leaked.

Thanks in advance.

proporsche · proporsche's Garage

The first is for adjusting you fuel mixture with 3mm Allen wrench T like tool , do not plug it you will not be able to adjust it.
The second is common problem Use JB Weld and attach the pipe back...
Ivan

on the pic is a 930 just the tool is the same

Walt Fricke · 03-30-2019, 02:47 PM

The first hole is there to allow you to adjust the air/fuel mixture. The mixture setting screw (it has an Allen head, so you use that kind of wrench to adjust it)is directly below this hole, so this is how you set the relationship between the air metering plate (which pushes the fuel distribution plunger in the fuel distributor up, feeding more and more fuel into the six injector lines as it moves up)and the plunger. It is how you set your engine to have the proper CO in the exhaust to pass emissions, if need be, or to change your air fuel ratio to richer for a bit more power or leaner for better mileage.

The car came with a plug - listed as a shear bolt, which we owners were supposed to leave alone. But they get removed. And no one I know ever replaces them. You need access to adjust things, and you can't count on a sort of set and forget forever approach, as things change. You might be able to make a rod with a rubber tip, so you could get the tip into the hole with the engine in the car and the rubber boot and everything in place after adjusting, and still be able to pull it out when adjustment is needed. The space there is tight in an in situ engine, and getting your long hex into the hole is a bit tricky, and getting it to slip into the inhex you can't see is even trickier, none of it being helped by the fact that your hand is so close to the sound deadening right above that area.

Looking at the parts book, P/N 911 110 934 00 might be a screw thread plug with an extension on it. But why?

As to the brake booster fitting, I don't think that is supposed to separate - it certainly isn't listed as a separate part. Someone who has lots of throttle bodies on their shelf like Tony might have a better feel for this, but I'd use green Loctite sleeve retainer on it before pushing it in and call it good.

Walt Fricke · 03-30-2019, 02:51 PM

Proporsche - I wish the 911 CIS had that extension tube the 930 (which is an 8 cylinder model Porsche/Bosch adapted for use for just six cylinders)part in your picture has. Should make getting the tool inserted and straight for engagement easier.

boyt911sc · boyt911sc's Garage

Jose,

The first picture shows the access hole to the fuel mixture set screw. Find a golf tee and use it to plug the hole. With regards to the loose metal tube to the throttle body apply some Loctite thread lock to secure it in place. The engine looks great.

Tony

2jmotorsports · 2jmotorsports's Garage

Ah yes the mixture adjustment screw! I dont know why I thought that would be on the fuel distributor itself. Ok now that I know what it does Ill find some kind of easy to remove temp plug.

Ill seal the metal tube on the throttle body with loctite once I get my those hard fuel lines in the periphery tightened down.

Thanks for the quick feedback!

proporsche · proporsche's Garage

Walt, yup it would be much easier to adjust...

Jose, here is the tool From Stahlwille i have and the original plug which is supposed to be there..

Ivan

2jmotorsports · 2jmotorsports's Garage

Quote:

Originally Posted by proporsche

Walt, yup it would be much easier to adjust...

Jose, here is the tool From Stahlwille i have and the original plug which is supposed to be there..

Ivan

Ooh good to know. Now I must find one of those plugs!

Thanks Ivan!

proporsche · proporsche's Garage

U r welcome Jose...i do have more then one plug but i am a little too far from you..4 time zones;-)
Stahlwille has a dealer-truck i think in LA...

Ivan

boyt911sc · boyt911sc's Garage

Jose,

Below is the picture of the flow rates calibration for your FD. I needed three (3) consecutive reproducible test runs to pass QC.

When are you doing your start up? Can’t wait to see your motor runs. Keep us posted.

Tony

2jmotorsports · 2jmotorsports's Garage

Thanks Tony. I am super excited to see how a 100% fresh CIS rebuild behaves.

Should be back in the car within the next 2 weeks. Got a couple of seals to replace on the gearbox and everything goes back together. I am taking the week of 4/15-4/19 off to work on the car and fire it up, break in, and hopefully get it dialed in.