911 SC air box replacement

[Jacob Odgaard]

Hi,

My air box has now blown for a second time, this time terminally.
I have got a new air box with a pop off valve installed, but I am struggling with how to attack the replacement. So far I have removed the intake rubber boot on top of the engine and the heater blower and hoses.

My goal is to remove as few things as possible, as everything else was working fine. My main challenge is how to free the air box from the intake runners. I think that the people who have fitted these have either had special tools to reach or have strange looking hands.

I have found a lot of threads about diagnosing a blown air box, but none about its replacement.

Can anybody give me advice on how to remove the old air box?

[Vin-barrett]

If it' a 1980-1983 SC, the engine needs to come out, or at the very least partially dropped out of the car as you cant reach the nuts on the right side intake runners with the added emission tube and equipment.
I believe anything earlier than this can be done with the engine in the car.

I can't imagine getting the box free of the intake runners if they are still attached to the heads. No special tools or funny hands, it's just that the CIS assembly needs to come off in one piece

[psalt]

Hello Jacob,

You can remove the airbox without dropping the engine, I have done it several times. You need to unbolt the intake runners at the heads, not the boots.

[OldTee]

I have done this on a 78-79 a couple of times.

Hints. Jack the car up and remove the rear wheels. Lower the engine about 6 to 12 inches first disconnecting the fuel lines, electrical stuff, hoses at the oil filler. Then remove the popes hat. Remove the nuts from the runners (intake pipes). The rear #6 can be tricky. I used 1/4" universal sockets for this. Then remove the entire set from the car. Don't forget the stand off on the throttle pad. Don't drop anything into the open engine ports, cover immediately. Then swap the stuff from the old box to the new one. Take pictures of the whole process.

Note the position of the rubber tube clamp screws. Tightening them can be a pain. When removing remove the left side first leaving the right side assembled. Install the same way with the right side more or left assembled.

Use new intake gaskets. Torque to spec. Take your time, wear a hat to reduce head knocks.

[Daviboy]

+1 on what Paul says, no need to drop. I did my 82SC airbox without dropping as said need to unbolt intake runners at the heads. It is sore on the back and knuckles but very possible. Check these threads
Dived right in

or go join Rennlist forum and look at this thread by the iceman very good info

http://forums.rennlist.com/rennforums/911-forum/432772-air-box-replacement-guide.html

[JohnJL]

Done it too.

I have a complete, spare CIS intake if you do decide to switch. By the way, why do you say everything else was working fine? Airbox-exploding backfires doesnt sound like everything else was indeed OK.

[Scott R]

I've done it in car a few times now, very easy. Remove the cruise control bracket and the air boot. Next remove all of the 12mm intake runner bolts except the nasty one on the #6 intake runner. Now that everything is lose pop all the injectors out (so they don't get bent on removal.) Last step is to remove the #4 intake runner, loosen the rubber coupler and pull the runner up and away. After that you can hit the nuts on the #6 intake runner easily.

Last tip is to get the airbox lifted a bit and put a brace under it, this way you can disconnect the crank case breather hose easily. Then it's up, up and away!

[Gunter]

To get to the nuts on the intake runners, a long 3/8-drive extention and a 13mm? swivel-socket really works.
A partial drop does help unless one has very good mechanical skills.

[Scott R]

Originally Posted by Gunter

To get to the nuts on the intake runners, a long 3/8-drive extention and a 13mm? swivel-socket really works.
A partial drop does help unless one has very good mechanical skills.

If it's the original barrel nuts they 12mm.

[Peter Zimmermann]

I love this thread, and reading about how replacing an SC airbox with the engine in the car is "easy." Funny, back in the mid-'90s one of my master mechanics (911 specialist) asked if he could do an airbox replacement with the engine in the car (we had been dropping all CIS engines, except '73.5 - '75 models, since the beginning). I said sure, have at it. But if you need stitches I won't call Workman's Comp! Well, about 12 hours later my mechanic finished the car. Keep in mind that this guy could R&I an engine and replace an airbox blindfolded - and have every piece of hardware, the head of every clamp, every support bracket, exactly as the factory had done it.

When the job was done my guy admitted that that was probably the single stupidest idea he'd had for at least ten years - and he had been working on 911s every day for 15+ YEARS!!!

Go ahead, do the airbox with the engine in the car. It's "easy."

[Scott R]

Originally Posted by Peter Zimmermann

I love this thread, and reading about how replacing an SC airbox with the engine in the car is "easy." Funny, back in the mid-'90s one of my master mechanics (911 specialist) asked if he could do an airbox replacement with the engine in the car (we had been dropping all CIS engines, except '73.5 - '75 models, since the beginning). I said sure, have at it. But if you need stitches I won't call Workman's Comp! Well, about 12 hours later my mechanic finished the car. Keep in mind that this guy could R&I an engine and replace an airbox blindfolded - and have every piece of hardware, the head of every clamp, every support bracket, exactly as the factory had done it.

When the job was done my guy admitted that that was probably the single stupidest idea he'd had for at least ten years - and he had been working on 911s every day for 15+ YEARS!!!

Go ahead, do the airbox with the engine in the car. It's "easy."

It takes 45 mins to pull it, an hour to swap out the plastic then another 45 mins in. After that off course the mixture reset work. Normally I would pull the engine, which is like an hour for me, but then I've just added 14 quarts of Brad Penn to the shopping list. Then I may as well adjust the valves.....and sop on.

[Paulporsche]

Peter Z,

The Porsche_Monkey and I recently re/re'd the airbox and runners on my car in about 6hrs total w/o a drop, and we didn't have a clue WTF we were doing. At least I didn't! All it took was some thought, some prayer and some foul language. The foul language probably helped the most! And no Workmen's Comp claims either!

I'm sure the next one (!) will go a lot faster.

Scott R's description sounds pretty accurate.

[Gunter]

Originally Posted by Scott R

If it's the original barrel nuts they 12mm.

Hmm............the only barrel-nuts on a 3.0 are on the heads, on the exhaust studs, a few on the cam towers and one on the starter.

The nuts on the intakes are Nyloc 13 mm hex, not barrel-type.

Some like under #6 cyl. are harder to reach but I found that a 13 mm swivel-socket with a 10" extention (3/8"drive) worked fine.

Whenever someone asks about a particular job, one has to recognize that not everybody has good mechanical skills.

Bragging about how fast it can be done doesn't help at all; the issue is not speed.

It's obvious that replacing the airbox is easiest with the engine out. Next best is a partial drop especially when someone has limited mechanical experience.

To do it in situ is pretty frustrating and difficult; why make it harder than necessary? Besides, doing it the hard way will invite mistakes and more problems.

[Scott R]

Originally Posted by Gunter

Hmm............the only barrel-nuts on a 3.0 are on the heads, on the exhaust studs, a few on the cam towers and one on the starter.

The nuts on the intakes are Nyloc 13 mm hex, not barrel-type.

Some like under #6 cyl. are harder to reach but I found that a 13 mm swivel-socket with a 10" extention (3/8"drive) worked fine.

Whenever someone asks about a particular job, one has to recognize that not everybody has good mechanical skills.

Bragging about how fast it can be done doesn't help at all; the issue is not speed.

It's obvious that replacing the airbox is easiest with the engine out. Next best is a partial drop especially when someone has limited mechanical experience.

To do it in situ is pretty frustrating and difficult; why make it harder than necessary? Besides, doing it the hard way will invite mistakes and more problems.

I'm not bragging at all, that's exactly what it takes. In situ is not problem at all.

[stevemfr]

Originally Posted by Peter Zimmermann

I love this thread, and reading about how replacing an SC airbox with the engine in the car is "easy." Funny, back in the mid-'90s one of my master mechanics (911 specialist) asked if he could do an airbox replacement with the engine in the car (we had been dropping all CIS engines, except '73.5 - '75 models, since the beginning). I said sure, have at it. But if you need stitches I won't call Workman's Comp! Well, about 12 hours later my mechanic finished the car. Keep in mind that this guy could R&I an engine and replace an airbox blindfolded - and have every piece of hardware, the head of every clamp, every support bracket, exactly as the factory had done it.

When the job was done my guy admitted that that was probably the single stupidest idea he'd had for at least ten years - and he had been working on 911s every day for 15+ YEARS!!!

Go ahead, do the airbox with the engine in the car. It's "easy."

When I was wrenching my way through school in Munich, I did a number of CIS removals w/the engine in place at the Porsche shop I worked at. I wanted to drop the motor the first time and the shop owner came storming out of the office yelling at me to quit being stupid...

It's been a while, so exact figures are tough, but I'm going to say I could have done at least 3 cars in 12 hours in and out (and I really don't mean this to sound like bragging or whatever. Just stating the facts). It really is not difficult. As Gunther said, a swivel socket is key (and varying extentions). It's def more comfortable on a lift at slightly less than waist height rather than on the ground, too.

[Jacob Odgaard]

Thank you for all the hints and directions. The most important one was probably the one that made me realize that I have to remove the intake runners.

I am working my way through it now and looks like I will get there without an engine drop.
The fact that the air box split right through has made at least the dismantling job easier.

What has stopped me temporarily is one nut on cylinder #2 which is very hard to get at with the tools I have available. All the other ones have come off fairly easy with a socket an a 1/2" knuckle extension. The nuts are actually 12 mm, so maybe they are not original. I will see what other tools I can get from the store to remove the last hindrance.

I have stripped a couple of knuckles and used a couple of swear words, but no more than expected. Should probably keep the worst ones for the assembly part.

Couldn't help posting a picture of the car in rare norwegian sunshine.

[JohnJL]

Very nice.

You probably thought of this but put a rag or some tape over the intakes as soon as possible. They attract washers and nuts.

[Paulporsche]

My point in relating how long it took "me & the monK" was to try to establish a timeline. We had a couple of false sarts due to inexperience on this procedure.

By comparison, how long could the same re/re take, again w/o experience, if the engine were partially dropped?

Anyone have any knowledge/opinion?

[Gunter]

Nice picture.
Narrow space is always an issue with these engines.
1/2" drive is too bulky, try a 3/8" drive extensions with metric swivel-sockets.
Swivel-sockets have the "knuckle" already built in.

Inspect the rubber sleeves and gaskets on the runners and replace if necessary.
Install a pop-off valve in the new airbox.

[Peter Zimmermann]

Originally Posted by Scott R

It takes 45 mins to pull it, an hour to swap out the plastic then another 45 mins in. After that off course the mixture reset work. Normally I would pull the engine, which is like an hour for me, but then I've just added 14 quarts of Brad Penn to the shopping list. Then I may as well adjust the valves.....and sop on.

Well, I'd comment but I'm laughing too hard.

To clarify my above comments regarding engine removal, I'm talking about 911s built from 1976 - 1983. '76-79 cars still have their smog pump system intact, all models have their cold start system intact, '80-83 cars have Lambda, and all are fitted with the original heater blower. The finished product must be technically correct and done to a master mechanic level.