Airbox problems

mike1959 · 02-10-2006, 09:03 PM

I have a '74 911S with CIS that's been sitting around for a while. It backfired on startup and now only starts cold and runs extremely rich. I was told airbox is probably cracked. I pulled the air filter but don't see any cracks. I want to find the crack before I pull the airbox. Is the crack something that can normally be seen without pulling the airbox?

bigchillcar · bigchillcar's Garage

you might try letting the car idle and spraying around the airbox with some carb cleaner..listen for the idle to increase when you find the cracked region. this is a common test for air leaks, but be careful.
ryan

bigchillcar · bigchillcar's Garage

oh, btw..welcome to the forum! you might include your car's year and model in your signature and where you are..helpful for future troubleshooting..plus experienced pelicans might live nearby who could help.

ryan

Dan in Pasadena · Dan in Pasadena's Garage

Mine cracked after a backfire because the previous owner (PO is the abbreviation used here) had done a stupid thing and epoxied the pop off valve shut. Bottomline is that you couldn't really see the cracks until the airbox was removed. It prety much cracks along the assembly joints anyway - at least on mine it did.

You've got to do at least a partial engine drop to get the airbox out of there and then be extra careful about sealing leaks when re-installing a new one. Post a Want To Buy (WTB) thread on the parts board and someone will respond with a good box for sale. I paid $125 and thought I did fairly well. Don't forget you MUST install a popoff valve or why even bother. About $50 here on Pelican. Good luck, Dan

P.S. Ryan is right, it is traditional to post pictures of your car when joining this board and you'll find you need your car year in your signature line or you will be asked about it constantly.

wowzer911 · 02-11-2006, 05:43 AM

Partial engine drop? Is that from experience? I have a stainless steel box I'm intending to install.

jmshepard · 02-11-2006, 05:46 AM

Dan,
I was able to remove my entire 911SC CIS system without a partial engine drop. When I switched over to Megasquirt, I had to remove the system all the way to the heads...all with the engine in the car.
Jim S.

Dan in Pasadena · Dan in Pasadena's Garage

On my car the engine was dropped. My wrench said it is a pain in the butt to try to swap out the airbox without a full engine drop, which is what was done so that I could address a bunch of other "while-I-am-in-therre's". I posted here and it was pretty much a universal consensus that at least a partial is required. Do a search - upper right hand corner, look for the "Search" button.

As for a "stainless steel box"? Not sure what you mean? Some kind of aftermarket replacement for the CIS airbox? Well...., other more knowledgeable guys than I will respond, but I've never heard of that being done...maybe some kind of custom made box or something. I have seen the sorta "custom" CIS airbox tops used for extra "bling" but not a full airbox replacement in metal. Oh well, live and learn. Post a picture of it please.

EDIT - Oops to Wowzer. Thought I was responding to the original poster or I wouldn't have told you how to find the search button. Anyway, what's the deal with this steel airbox?

jmshepard · 02-11-2006, 06:26 AM

Okay, I surrender. I'm not trying to start a fight, just providing my recent experience.
Jim S.

wowzer911 · 02-11-2006, 06:36 AM

They were an aftermarket part, indestructable with a built-in pop off valve, available in aluminum or stainless steel, for 2.7L - 3.0L cars. made by a company in florida I think. no longer available new.

Dan in Pasadena · Dan in Pasadena's Garage

Jim, You won't get a fight from me. I was thinking the airbox COULD be swapped out without ANY engine drop, full or partial. Maybe I was gamed by my mechanic or maybe he just didn't want to hassle it or whatever. I only related what happened to me.

As I said in my original response above...other more knowledgeable guys than me would respond...and so you have! Excellent that you were able to do it, kudos.

I suppose I shouldn't complain that an engine drop was done on my car... I ended up putting in a new clutch package, chain tensioner upgrade and had a bunch of small - soon to be larger? -oil leaks addressed.

I'd love to go to EFI but living in California? I don'tthink it would ever pass smog testing.

sammyg2 · 02-11-2006, 07:35 AM

I just got done removing the CIS from my SC last weekend to replace the air box.
I lowered the engine about 5" and it was still a major PITA getting to some of the fasteners. The inside nut on #6 runner was the worst, I had to remove the AAR and decell valve just to get close to it. I seriously do not believe I could have done it without lowering the engine.
If you can you are a better man than me or you are houdini.
If I had to do it over again I would just pull the engine completely.

bigchillcar · bigchillcar's Garage

interesting..i didn't realize that a partial drop was necessary, but sure sounds like it would require a really good wrench's skill (i.e. 'professional') to do it without the drop. i think i know where i'd fit in that continuum..

ryan

Early_S_Man · 02-11-2006, 08:58 AM

Ryan,

Most pros seem to recommend the partial drop as a necessity ... probably just prudent insurance against the proverbial 'OOPS!' or 'Uh-Oh!'

Scott R · Scott R's Garage

I would do the drop, in fact since I sprung another oil leak the other day I will be doing it that way this time around. When I pulled my CIS last summer with the engine in place I tore up the sounds pad pretty good, and I bent an injector in the process. These mistakes were all do to limited clearance in the engine bay.

Second note, get new injector o-rings, you will probably need them, and be ready to replace all of the other gaskets on the CIS system as a precaution. It's not a bad time to replace the seal under the throttle body, and the one under the fuel distro. I neglected these items and had leaks all over the place when I re-installed it. I think it was just the flexing of the pieces in the end.

A partial drop is a simple matter of disconnecting the shift coupler, and removing the two rear motor mount bolts. About 15min of work, and it will save you some major headaches.

bigchillcar · bigchillcar's Garage

warren..you KNOW that at times our language becomes more 'colorful' than that!

scott..just the two motor mount bolts and not the two tranny bolts as well? i would have guessed that removing the rear bolts would permit the engine to 'tilt', but in a direction that would make cis box access more difficult? intuitively, i would have predicted you'd remove the tranny end motor mounts. no?
ryan

sammyg2 · 02-11-2006, 09:54 AM

Nopers, just disconnect the shift coupling, put a good jack under the engine, and remove the two rear engine mount bolts. Slowly and carefully lower the engine, making darned sure nohing is hanging up like a wire or hose or whatever. Look above and below the engine.
As it gets lower, you now have room above the intake so you have better access to what is behind it.
When done, just jack it back up into place and bolt in in, and hook up the shift coupler.

feelyx · 02-11-2006, 10:27 AM

stainless steel air box pic,

Tim in Sac

bigchillcar · bigchillcar's Garage

sammy..what am i missing? why do i believe that the tranny mounts would prevent this? i keep thinking you'd have to loosen all four. i'm confuzzzed..

ryan

Scott R · Scott R's Garage

Quote:

Originally posted by bigchillcar
sammy..what am i missing? why do i believe that the tranny mounts would prevent this? i keep thinking you'd have to loosen all four. i'm confuzzzed..
ryan

You can loosen the tranny mounts a few turns if wish more clearance, but you don't always need to, the rubber bushings on the tranny mount will allow for anough flex to get it down quite a bit. Try it first, and if it's not enough for you then jack it back up and then take a few turns out of the tranny bolts.

bigchillcar · bigchillcar's Garage

scott..thanks..that clears it up..makes sense to me now.
ryan