1980 CIS airbox replace/repair questions and writeup - help appreciated

[brian-80SC]

Hi all,

Today I've started a project to repair/replace a blown airbox on my 1980 SC. AS you can see below the screws in the middle of the airbox have pulled out:





My goals for this thread:

1. get feedback on plan
2. help on specific questions
3. identify "while you're in there" jobs I shouldn't pass up
4. document information and resources used, along with my experiences to further help others


I've researched a lot of information over the past few days and am generally basing my plan off this thread and the subsequent writeup here, both from bsimonson.

There are other threads on this topic also, and in them I found a lot of good advice... but it was either too general, leaving me still with a lot of questions, or too far ranging given the differing needs of different model years. Given that my 1980 is in the later year, more difficult category, it's hard to know exactly which suggestions or simpler approaches will be relevant.


After all this reading, I spent some time staring at my installed CIS tonight and have decided on an overall plan to get everything out -- the big challenge is of course accessing the hose clamps and intake nuts to remove the runners. feedback is welcome!!

Plan:

* partial engine drop for better access (space limitations eliminate full drop as option)
* aim to disconnect the runners to help accessing the intake nuts, especially on cyl 5 and 6. Where possible, slides boots onto runners to aid in detachment from airbox.
* after runner removal, cover intake ports to prevent anything falling inside. have telescoping magnet handy
* Left side: remove runners, starting with 1, then 3, then 2. Nuts can be reached for all with socket extensions. #1 looks straightforward. For #3 the hose clamps I think can be reached with a short screwdriver from behind. The hose clamps for #2 are not accessible that I can see -- hopefully I will be able to reach them after removing 1 or 3.
* Right side: start with #4 which is accessible. Hopefully removing #4 will give additional working room to remove runner #5.
* #6 (passenger side, back of engine compartment) is biggest access challenge. Hopefully, with the other runners removed, I'll be able to access the nuts and hose clamps. If needed, try to maneuver airbox slightly for more space.
* when possible, loosen airbox mounts at left-rear (throttle bracket) and right-rear (#6 runner)
* When airbox is loose, remove engine breather hose from underneath
* Throughout the job, label and photograph all wire connectors, hoses, and lines to aid correct reassembly


Parts list for replacement from Peter Zimmermann with numbers (copied from this post):

930 110 197 12 6x intake manifold gaskets
930 110 885 00 6x intake runner/airbox sleeves
999 701 423 40 6x injector o-rings
911 110 886 03 6x injector sleeves
999 701 446 40 6x injector sleeve o-rings
999 707 314 40 1x thermostat o-ring
900 123 101 30 1x oil pressure switch sealing ring (for the idiot light)
914 423 211 00 2x throttle lever (bell crank) bushings for the throttle linkage console on top of the engine
911 110 154 00 2x rubber bushings that secure the airbox brackets to the airbox (at cyl #6 & at the throttle lever console)
999 701 210 4A 1x cold start injector o-ring
999 701 395 50 1x cold start injector spacer o-ring
999 701 124 40 1x throttle body o-ring (updated part number vs 999 701 124 00)
911 110 394 02 1x sensor plate housing gasket


Other things I'm planning "while I'm in there":

* pop off valve
* fuel filter
* throttle linkage bushings (disintegrated)
* engine compartment insulation



Questions I am working on:

* EDIT -- I've decided to go with a new box. Will leave the following, original post text for future reference. Do I repair or replace the airbox? Current plan is to asses the damage before deciding. For repair, I'm considering to use 3M DP 8005 as described in this thread and this thread.

* do the plastic fuel lines need replacement? The outer rubber sleeve is degraded, but the line itself otherwise looks ok...?




* Anything else I should inspect or be concerned about replacing?



Here's what I've done so far (Day 1):

* remove air box cover, air filter
* remove heater hoses on driver's side (2) and blower fan. Leave hose running to right side connected and tucked out of way in front of the alternator fan
* disconnect allen-head set screw in shifter linkage (rear center footwell)
* jack up rear using sump cover, lower onto jack stands under torsion bar covers
* partial engine drop - follow guide here. After lowering the engine about 3-4 inches, rest it on block of wood to support weight and not rely on the jack.
* unbolt AC compressor and set on fender using thick towels to protect paint. tie off to engine cover hinge area to prevent accidental movement.


that's all for today. will update again soon with more information and pictures as needed

[boyt911sc]

These are my only two (2) suggestions:
a). Replace the airbox with a new one. The CIS airbox is now available at a much lower price these days. Rebuilding a cracked CIS airbox takes a lot of time if you value your time.
b). Drop the motor and do the repair properly. You are not saving time by removing and installing the complete CIS unit with the motor installed. It is not how hard you worked but how smart you did the job.

Whatever direction you choose, stay safe. Good luck.

Tony

[brian-80SC]

Hi Tony,

Thank you for your thoughts.

I will definitely consider a new box as you suggest.

If I had space for a full drop I would do this, but unfortunately my work area is very limited so my only current option is a partial drop.

I am not in a hurry so can take the time to get this done.

Brian

[MichaelSJackson]

I've done this without dropping the engine, but I did do a partial drop. It is much easier with the engine out. Getting to or seeing anything forward of the throttle body is tough and hard on the back of your hands.

I used JB-Weld to patch my airbox. Even filled and re-drilled some of the screw holes.

I'd wait until you can see all the damage before committing to a new box?

I have a set of sockets with a universal on each one. Shorter than adding a universal to a socket.
Fits in much tighter spaces. Makes reaching the nuts holding the runners doable.

Take lots of pics while dis-assembling. Always handy when you're trying to remember how things were.

Best of luck!

Michael S. Jackson
'78 SC w/patched and cut-down airbox for BITZ EFI

[theiceman]

i did it with a partial drop and had the cis out in 90 minutes, but i do have all kinds of 1/4 drive tools with universals etc.

definitely replace airbox, its a fair bit of work to not do it right ...

[RDM]

Brian,

I finished this project on my car a few months ago. What I can tell you-

- It is uncomfortable to remove the intake with a partial drop, but definitely do-able. At times I increased the drop to closer to 6 inches (hello # 6) with no noticeable ill effect.

- I have backdated my heat and removed my a/c, so that definitely makes this job easier.

- I can't yet speak to long-term durability, obviously, but the 3M 8005 has worked very well thus far. It has enough body that it can fill some of the space in the joint, even if the tongue and groove aren't exactly matched anymore.

- I used Tony's airbox testing technique, but used my own lungs to provide the air pressure. Plugs for the various openings on the airbox can be bought on eBay for not much money.

- I haven't yet reset the timing and FI as my WUR was also out of spec and has been in Tony's capable hands.

I'm glad to offer what I know as you go. Top advice- don't be in a hurry.

[ClickClickBoom]

I replaced my middie airbox with no drop at all, went quickly.
Here ya go:
https://www.ebay.com/itm/CIS-Air-Box-fits-1974-77-1980-83-Porsche-911-911-S-911-SC-NOS-GENUINE-GERMAN-NEW/254191227076?hash=item3b2efa50c4:g:~x8AAOSw~o5aTsp-

[brian-80SC]

Originally Posted by MichaelSJackson

I've done this without dropping the engine, but I did do a partial drop. It is much easier with the engine out. Getting to or seeing anything forward of the throttle body is tough and hard on the back of your hands.

Thanks for the feedback Michael. I've read a bunch of threads now where people were successful with
a partial drop. I know it will be harder than a full drop, especially with an SC CIS, but I tend to do a lot of research beforehand and I feel like I'm pretty well prepared at this point and have realistic expectations. With the feedback from today I've got some new ideas (e.g. swivel sockets) and have a new, hopefully simpler, plan for removal.

Originally Posted by MichaelSJackson

I used JB-Weld to patch my airbox. Even filled and re-drilled some of the screw holes.

I'd wait until you can see all the damage before committing to a new box?

That's what I was thinking initially, but now after some more research and pricing I think I'm just going to go for a new box for simplicity and reliability. The 8005 is pretty expensive ($50) and I don't have experience with JBWeld. And I don't want to be troubleshooting the box while I'm trying to refresh and tune the rest of the CIS system. Also, it appears I have the old box without the cold start diffuser that helps to reduce backfires, which a new box will have.

Originally Posted by MichaelSJackson

I have a set of sockets with a universal on each one. Shorter than adding a universal to a socket. Fits in much tighter spaces. Makes reaching the nuts holding the runners doable.

This is a great tip and I'm going to pick up a set of swivel sockets right away for this job. I was originally puzzled how folks were accessing the runner nuts with bulky universal adapters... Now that I'm looking I see others have recommended this as well. Thanks!

Originally Posted by MichaelSJackson

Take lots of pics while dis-assembling. Always handy when you're trying to remember how things were.

Definitely will take LOTS of pics!

[brian-80SC]

Originally Posted by theiceman

i did it with a partial drop and had the cis out in 90 minutes, but i do have all kinds of 1/4 drive tools with universals etc.

definitely replace airbox, its a fair bit of work to not do it right ...

Thanks iceman, I'm in agreement with you and Tony now and have decided to go with the new box, and will be picking up some swivel sockets -- hopefully with my various extensions this will be what I need!

[brian-80SC]

Originally Posted by RDM

Brian,

I finished this project on my car a few months ago. What I can tell you-

- It is uncomfortable to remove the intake with a partial drop, but definitely do-able. At times I increased the drop to closer to 6 inches (hello # 6) with no noticeable ill effect.

- I have backdated my heat and removed my a/c, so that definitely makes this job easier.

- I can't yet speak to long-term durability, obviously, but the 3M 8005 has worked very well thus far. It has enough body that it can fill some of the space in the joint, even if the tongue and groove aren't exactly matched anymore.

- I used Tony's airbox testing technique, but used my own lungs to provide the air pressure. Plugs for the various openings on the airbox can be bought on eBay for not much money.

- I haven't yet reset the timing and FI as my WUR was also out of spec and has been in Tony's capable hands.

Hi Dru

So far I've dropped about 3", but I haven't disconnected the fuel and breather lines yet. I was hoping to get to around 6" for better access. Good to know this can work on the '80SC.

I've got the AC compressor hanging off the side now. This job is really tempting me to remove it!

For now I'm going to going with a new box. With all the additional work I have planned around this job I decided to simplify this part so I can focus on getting it all done.

Originally Posted by RDM

'm glad to offer what I know as you go. Top advice- don't be in a hurry.

I'm definitely going to take my time!
Thanks for the offer to advise! I hope to be ordering parts soon and getting started on the teardown this weekend.

[brian-80SC]

Originally Posted by ClickClickBoom

I replaced my middie airbox with no drop at all, went quickly.
Here ya go:
https://www.ebay.com/itm/CIS-Air-Box-fits-1974-77-1980-83-Porsche-911-911-S-911-SC-NOS-GENUINE-GERMAN-NEW/254191227076?hash=item3b2efa50c4:g:~x8AAOSw~o5aTsp-

Lol I saw that same listing earlier today. But looks like new prices aren't too far off so going to go that route.

[brian-80SC]

Ok, my next big question is about old fuel:

The car has been sitting for about 18 months now patiently waiting for me to get this repair done.

Common sense says I should drain the fuel, replace with fresh, and flush any old fuel out of the lines to avoid issues after I get everything cleaned up and put back to together. I'll also be doing the fuel filter at same time, and I'm planning to replace the injectors already. Is it recommended I disassemble and clean any other components? The WUR is on my list but I haven't researched other components yet.

Also, at this age, is it be recommended to flush the fuel lines? If so, is using a cleaning additive a good idea?

Alternatively, I could just drain the tank, fill with fresh fuel, add some Techron, and flush the old fuel out through the the return fuel line and the injectors (before I replace them, and with the old fuel filter too) and before trying to start the engine again.

Or would it be enough to just run some Techron after I'm done?

Thanks!

[30westrob]

18 month fuel should not be a major issue. I would drain and put it in the wife’s car.
Fresh fuel and a short run of your fuel pump and you should be ready to go. Rob

[boyt911sc]

Originally Posted by brian-80SC

Ok, my next big question is about old fuel:

The car has been sitting for about 18 months now patiently waiting for me to get this repair done.

Common sense says I should drain the fuel, replace with fresh, and flush any old fuel out of the lines to avoid issues after I get everything cleaned up and put back to together. I'll also be doing the fuel filter at same time, and I'm planning to replace the injectors already. Is it recommended I disassemble and clean any other components? The WUR is on my list but I haven't researched other components yet.

Also, at this age, is it be recommended to flush the fuel lines? If so, is using a cleaning additive a good idea?

Alternatively, I could just drain the tank, fill with fresh fuel, add some Techron, and flush the old fuel out through the the return fuel line and the injectors (before I replace them, and with the old fuel filter too) and before trying to start the engine again.

Or would it be enough to just run some Techron after I'm done?

Thanks!

Brian,

I will give you an advise which you might not like it or get offended. But I am confident you will thank me after the time had passed by. Spend more time working on the car to gain experience. Stop making a documentation on something you have very little expertise. You will have plenty of time to show off your work. And here is the critical point: select or choose one or two guys in this forum to be your mentor (excluding me). What you are trying to achieve is not something new or a break through procedure. Take as much pictures as you would like and save them for your future documentations.

For every advice you seek, you will get more answers that will confuse you more. So stick to your mentor/s (buddy system). From this thread alone, there are several experienced guys that had done the CIS removal with just a partial drop. Over come your anxiety, a be a natural and versatile DIY’er. Wish you the best.

Tony

[brian-80SC]

Originally Posted by 30westrob

18 month fuel should not be a major issue. I would drain and put it in the wife’s car.
Fresh fuel and a short run of your fuel pump and you should be ready to go. Rob

Ok thanks. Not sure I want to mess with the wife's car right now - if anything happened I'd never hear the end of it

[brian-80SC]

Originally Posted by boyt911sc

Brian,

I will give you an advise which you might not like it or get offended. But I am confident you will thank me after the time had passed by. Spend more time working on the car to gain experience. Stop making a documentation on something you have very little expertise. You will have plenty of time to show off your work. And here is the critical point: select or choose one or two guys in this forum to be your mentor (excluding me). What you are trying to achieve is not something new or a break through procedure. Take as much pictures as you would like and save them for your future documentations.

For every advice you seek, you will get more answers that will confuse you more. So stick to your mentor/s (buddy system). From this thread alone, there are several experienced guys that had done the CIS removal with just a partial drop. Over come your anxiety, a be a natural and versatile DIY’er. Wish you the best.

Tony

Thank you Tony, I appreciate your thoughts. No offense is taken. Perhaps I did not give the right impression in my initial post and/or title. I am not thinking to write a definitive DIY guide on airbox replacement -- what I want is to learn from the excellently intentioned and deeply experienced members on this forum, and use this thread to help organize myself and ask for help as I get deeper into the job. I tend to be thorough and do a lot of research ahead of time. Your suggestion to go ahead and get started is good . I also appreciate your suggestion on mentors and it is great to have such helpful feedback already. Until recently I found the CIS system intimidating, but now that I have spent significant time learning and have begun to appreciate its complexity and grasp its operation I feel ready to tackle the job. And I've finally got the time and tools lined up to start on removal this weekend!

[mhackney]

Where are you in Maine Brian? I'm down in northern MA and thanks to Tony and others know a thing or two about CIS now.

[brian-80SC]

Originally Posted by mhackney

Where are you in Maine Brian? I'm down in northern MA and thanks to Tony and others know a thing or two about CIS now.

Cool! I'm in southern ME, greater Portland area -- not sure how far that is from you but sounds relatively close!

[pmax]

Originally Posted by brian-80SC

Thanks iceman, I'm in agreement with you and Tony now and have decided to go with the new box, and will be picking up some swivel sockets -- hopefully with my various extensions this will be what I need!

Your airbox (small port 39mm OD) should be this one 911-110-904-00 ... odd it's not available from our host.

https://www.pelicanparts.com/catalog/SuperCat/0794/POR_0794_FULINT_pg2.htm#item6

Have fun w/the project.

[mhackney]

I'm in north central east MA. It is a couple hour drive to Portland. I'll be driving up that way next Sunday with a Porsche friend.