Airbox crack - did I just find the reason for my 2500 rpm cold idle speed?

[pampadori]

My 83 has had a few odd running characteristics. For one, when i cold start it i get an idle speed around 2200-2500 rpm before it settles down to 950 (idle adjustment all the way in).

It also pops a lot out the muffler when i let off the throttle. Running lean, right?

I removed the CIS this week and found a handful of things. found a vacuum source capped on the bottom. noticed a cracked hose on the pipe that connects just behind cyl 3 intake runner. And then I found these cracks in the intake box. Is this consistent with what others have seen as far as airbox cracks? Does this appear to be a considerable vacuum leak that might be the cause of some of my odd running, high idle issues?


Here is the capped off vacuum source. What does it usually go to?


And in closing, 100th post! Woohoo!!

[al lkosmal]

I'd say that you found the source of your problems....the crack. The capped off port is not vacuum but a drain that connects by hose, to a drain tube mounted to the front of the engine.

regards,
al

[Reiver]

You have a cold start valve that kicks up the rpm on dead cold start when the block is below a certain temp....but you are also prob correct about the leak effecting your lean operation thru out the spectrum.

[john walker's workshop]

Hell yes. New airbox time. Don't try to glue it, nothing sticks to that type of plastic worth a crap.

[pampadori]

Originally Posted by al lkosmal

The capped off port is not vacuum but a drain that connects by hose, to a drain tube mounted to the front of the engine.

regards,
al

I've never noticed a drain tube mounted to the front of the engine. Are we talking pulley end or transmission end?

Instead of replacing the airbox, i'm seriously considering going carbs or ITBs and megasquirt. Decisions...Decisions...

[al lkosmal]

tranny end....... the gizmo highlighted in yellow is a drain tube and the hose from the underside of the airbox connects to it.






if you decide to go EFI.................I have been known to dabble in that a bit....

X-Faktory - Home

regards,
al

[boyt911sc]

Originally Posted by pampadori

I've never noticed a drain tube mounted to the front of the engine. Are we talking pulley end or transmission end?

Instead of replacing the airbox, i'm seriously considering going carbs or ITBs and megasquirt. Decisions...Decisions...

Pompadori,

Al is correct about that tube as a drain tube. The earliest CIS engines have oil drain tube connected to the air box. This was eliminated in the mid year CIS engines and so on. The cap shown in your picture is just to prevent unfiltered or dirt from getting inside the air box (before air filter). Removing this plug will have no effect to your fuel mixture because this area is unmetered region of the system.

So switching to another system is something you could only decide. CIS is simple to maintain if you know and understand how the system works. It has been 20 years since I have done or replaced a CIS component in my '78 Targa. The WUR was replaced in 1995 and have no touched my engine since then.

Tony

[al lkosmal]

When CIS is n good shape and tuned properly....it works very well.

[Nux]

Just changed the airbox on my '78 (blown from backfire). Car had the exact same symptoms (high cold idle, popping, varm start issues, surging varm idle, and uneven acceleration).

After change: Completely different engine. All is smooth and runs incredibly nice. 500$ and a few hours with a wrench.

Still thinking about that EFI though......

[jason2guy]

just did the same thing. i actually purchased some 3m 2part adhesive but i guess i stored it improperly because when i went to use it, it globbed up into a mess. so i used jb weld and used screws and nuts to hold it all together where the original screws were and its holding up well. that crack will not create a high idle condition, it will create a lean condition. for the idle to increase the air leak has to be in the METERED air system. your super high startup idle is because the AAR is too far open when cold

[diy83sc]

+1 - the next time you start it cold, give the AAR several light taps with the handle of a hammer to cause the open AAR to close. It should come down in RPM.

Originally Posted by jason2guy

... your super high startup idle is because the AAR is too far open when cold

[gazzerr]

That crack in your airbox is the classic spot. Mine was the same. Just age. Probably multiple backfires .

My cold start valve phenolic block had a huge crack in it too. It came apart in my hands when I removed it from the old airbox.

[jason2guy]

youll probably have to open the AAR up and adjust the position of the heating element. its really easy

[pampadori]

i brought the AAR home with me and did some "testing" with the freezer and toaster oven. Should this thing be fairly open at 75 degrees? ANd should it close all the way around 200 degrees? Probably a little sticky but again...ITBs won't care.

[pampadori]

look what I received in the mail this week!



No plan yet how to mount them to the heads. Maybe PMO manifold and X-faktory adaptors? Maybe weld up some custom runners to go between the ITBs and the heads. That might be the cheapest solution since I have a tig in the garage and sorta know how to use it.

[al lkosmal]

Featured Products

http://www.x-faktory.com/

regards,
al

[pampadori]

Been ordering some parts and thought i'd document some of it here in this thread.

Crank and cam sensor - The AEM EPS and Rasant adapter
I ordered this nifty adapter from Rasant to use the AEM Engine Position Module with my factory distributor housing. Nicely machined, tight fit, quality part! Unfortunately it didn't include instructions so i used my best guess to figure it out. Set the engine to TDC and removed the distributor. Took the insides out, which wasn't exactly easy. I finally found the 3 little hidden allen bolts and then struggled again to remove the vacuum advance. Finally the insides came out!
The Rasant adapter appeared to fit well until i went to secure the two bolts on the sides to hold it to the housing. THey wouldn't line up with the holes in the housing and appeared to be about 4mm too high. I ended up drilling two new holes in the housing and got it together.
I called Andrew at Rasant and apparently there are a few variations in the distributor housings. Mine was bosch part number 0237302045 which is for a 930 I think.

Turns out my motor is from a 930 as well, albeit without the turbo bits. So i guess the distributor might have been from the same donor. She turns clockwise as it turns out...

Pics showing the new holes i had to drill for the securing hardware to line up:

[pampadori]

For my fuel setup, i had decided to ditch the accumulator and factory filter and run right off the hard lines that run into the engine bay. These hard lines have a large 17mm female tube nut on a 45 deg flare on the end of the tube. THe threads are m14x1.5 and had the hardest time finding an adapter to put either -6 AN/JIC or barb fittings on the end of them. I could find male 14x1.5 threads, but not with a 45 deg convex flare like what i needed. Most everything was 37 deg which might would work but isn't ideal. Flares must mate and 37 and 45 don't do that.
Finally after searching everywhere i tracked down a fitting made by Goodridge. I ordered two of these from Pegasus Racing and waited to receive them.

More disappointment when they arrived. They were as described but unfortunately the threads weren't long enough and the fitting bottomed out in the tube nut before making a seal at the flare. I ended up scavenging the fittings from the factory fuel lines. Once you cut the clamp off and remove the hose, they are basically exactly what I was looking for all along. I just need to remove the serrated barb with a file or grinder so i can use my clamps instead. Below you can see the blue fittings i got from Pegasus that didn't work because the thread was too short, as well as the two fittings i removed from the factory lines (one has already had the serrated barbs in the middle ground off) that I will end up using with my flex fuel line and clamps.


I should have my flex fuel line, clamps, and clamp pliers here this week and get started there.

I also ordered the items needed to build my custom throttle cable. I'm going with a 1 into two cable that will actuate both racks of Triumph throttle bodies. I sourced all of these parts t Flanders Cables for Mechanical Control, throttle cables, brake cables, automation control cables, custom robotic control cables which was a bit painful since their site doesn't look like its had any update since 1996 and you have to key in all the part numbers and prices you want on a form hosted by some other company. I treated myself to a beer after I finished placing the order because I wasn't sure that I was gonna have the patience for that process!

[pampadori]

Found a cheap alternative to the AEM wideband to use with my Infinity EMS.
Subaru fitted a bosch wideband to some of their cars and it happens to share the same harness plug with the model AEM requires.

Ended up getting it for $45 shipped from Advanceautoparts.com by using a coupon code.

Part number: 17018

['76 911S 3.0]

Originally Posted by pampadori

Found a cheap alternative to the AEM wideband to use with my Infinity EMS.
Subaru fitted a bosch wideband to some of their cars and it happens to share the same harness plug with the model AEM requires.

Ended up getting it for $45 shipped from Advanceautoparts.com by using a coupon code.

Part number: 17018

The same plug does not necessarily mean it is the correct sensor...you need to verify that this sensor reads correctly via the Infinity. I would hate to see incorrect sensor data and an improperly tuned/running engine over $50 for a critical sensor.