Please help me work out my mish mashed - cobbled together CIS

[Adrock]

Can somebody more knowledgable than me help explain my cobbled together engine? Not having a good day today. Decided to take the CIS off the rebuilt engine to replace the intake boots. I wasn't confident they weren't cracked. When I went to install the new ones, I noticed they were too big on one side. Then I took a closer look at the ones I took off there and I noticed somebody had MacGyver'ed them to fit. The intake side appeared to be much smaller than the airbox side.
I decided to google some of the part numbers and discovered that the intake pipes are off a 74-77 car and vacuum valves etc appear to be off a turbo car. I checked the fuel distributor and it appears to be the stock one along with the airbox setup. Ugh. I'd prefer to not have to MacGyver my new intake sleeves to fit. But I also don't want to have to spend thousands on buying the correct parts. Any ideas? I should have noticed all this when I realised I had a turbo WUR that I replaced with a rebuilt one to suit the year.

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[boyt911sc]

Adrock,

I like to help you with your CIS but I have no idea what year and model is your car/engine. And what are you trying to do? Let’s start from the beginning.....

What year is your CIS? ROW? MY?

What is the problem you are having with your CIS?

Do you know the Bosch ID number of the WUR? FD?

How can we extend our assistance to you?

Tony

[timmy2]

Sounds like you may have a large port air box with small port runners.
Year and type of engine would help. Part number of plastic air box as well.

[Adrock]

Originally Posted by boyt911sc

Adrock,



I like to help you with your CIS but I have no idea what year and model is your car/engine. And what are you trying to do? Let’s start from the beginning.....



What year is your CIS? ROW? MY?



What is the problem you are having with your CIS?



Do you know the Bosch ID number of the WUR? FD?



How can we extend our assistance to you?



Tony

Thanks for the message.
Essentially the intake pipes are off a different year car to the rest of the CIS. So the replacement rubber sleeves don't fit. They are too big.
In addition to that the vacuum valve seems to be off a turbo car.


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[Adrock]

Originally Posted by timmy2

Sounds like you may have a large port air box with small port runners.
Year and type of engine would help. Part number of plastic air box as well.

1983 japanese 911 cabriolet. 3.0. Same as USA spec I believe.

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[Adrock]

Here are some measurements.
What would my options be? To sleeve the replacement rubbers like the ones I pulled out? Or replace the intake pipes with larger ones. I believe these are 74-77?

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[timmy2]

The smaller Intake runners are correct for your US/Japan spec engine.
Changing to the correct air box and smaller rubber couplers for your car is the best choice.
The part number for the smaller intake runners was never changed from 74-77. Should show up in the PET for 80-83 US cars as the same

Maybe show pictures of everything you have so Tony and others can offer suggestions as well.

[Adrock]

Here's photos of pretty much everything. From what I can make out there are early intake pipes. A 80-83 airbox with bigger ports. The vacuum valve appears to be off a turbo according to the part number above. WUR is correct have already confirmed that a few months ago.

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[Adrock]

Originally Posted by timmy2

The smaller Intake runners are correct for your US/Japan spec engine.
Changing to the correct air box and smaller rubber couplers for your car is the best choice.
The part number for the smaller intake runners was never changed from 74-77. Should show up in the PET for 80-83 US cars as the same

Maybe show pictures of everything you have so Tony and others can offer suggestions as well.

Thanks Timmy. Is there any benefit to having bigger intake runners or a bigger airbox?
I ordered the sleeves based off the part number from the PET which was actually a number starting with 928 instead of 911.

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[timmy2]

No advantage to large runners on a small intake valve head.
Actually may cause turbulence and make it less efficient.
Best course of action is to get the smaller air box and correct sleeves.
Lucky you, the smaller sleeve air box is almost 1/2 price of the big one!

Airbox link below. It actually lists your car for applications.
https://www.pelicanparts.com/More_Info/91111090401M100.htm?pn=911-110-904-01-M100&bt=Y&fs=0&SVSVSI=911M

Correct 38mm sleeves:
https://www.pelicanparts.com/More_Info/93011088500M260.htm?pn=930-110-885-00-M260&bt=Y&fs=0&SVSVSI=

Search page:
https://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?description=Airbox#

[boyt911sc]

Adrock,

If you check the intake ID (inside diameter) of the CIS air box, you should get approx. 38 mm or 45 mm OD (outside diameter). You have the wrong CIS airbox for your SC. And the intake runners should -2R which I believe you got them already. You will have problem fitting the -2R intake runners that use 34-mm ID air box with the larger 38-mm ID.

This will be your references:
-4R intake runners (larger) match with 38-mm ID CIS airboxes.
-2R intake runners (smaller) match with 34-mm ID CIS air boxes.

The confusion is that the 34-mm ID air box is now called 38-mm OD. Pelican is selling the airbox for -2R intake runners as 38-mm air box. BTW, you got the correct fuel distributor. How about the WUR? What is the number on it?

While you could make the airbox work for now, your problem with unmetered air will soon haunt you. Replace the airbox now while the motor is out. If you think you are saving some money, replacing the airbox in situ is not an easy task. I bet you will regret later.

Tony

[Adrock]

Originally Posted by boyt911sc

Adrock,

If you check the intake ID (inside diameter) of the CIS air box, you should get approx. 38 mm or 45 mm OD (outside diameter). You have the wrong CIS airbox for your SC. And the intake runners should -2R which I believe you got them already. You will have problem fitting the -2R intake runners that use 34-mm ID air box with the larger 38-mm ID.

This will be your references:
-4R intake runners (larger) match with 38-mm ID CIS airboxes.
-2R intake runners (smaller) match with 34-mm ID CIS air boxes.

The confusion is that the 34-mm ID air box is now called 38-mm OD. Pelican is selling the airbox for -2R intake runners as 38-mm air box. BTW, you got the correct fuel distributor. How about the WUR? What is the number on it?

While you could make the airbox work for now, your problem with unmetered air will soon haunt you. Replace the airbox now while the motor is out. If you think you are saving some money, replacing the airbox in situ is not an easy task. I bet you will regret later.

Tony

Thanks so much Tony.

Is there actually a difference in the functionality of the internals of the different sized air boxes, or is the difference primarily the size of the air outlets?

re: WUR - I actually sorted that out with your assistance a few months ago and can confirm it's correct. Thanks again for that!

I am curious about the Turbo Aux Air Valve which is connected to the system. (part number in screen grab in earlier post) What issues could I expect from having the wrong Aux Air Valve? Originally the CIS had a Turbo WUR which I replaced with the stock version. It looks like somebody took bits and pieces they had laying around to make up another CIS. I wonder what happened to the original one that required all of these bits needing replacing.

The car does appear to have had a right hand side rear impact at some point - there is evidence of that - I wonder if the CIS got damaged at that time.

[fred cook]

What Boyt said, you have an early SC airbox with the large runners. You need the later (1980-83) air box with the smaller 34mm runners. If you get the large runners that match the airbox, there will be a major port mismatch between the runner and cylinder head.

[Adrock]

Originally Posted by fred cook

What Boyt said, you have an early SC airbox with the large runners. You need the later (1980-83) air box with the smaller 34mm runners. If you get the large runners that match the airbox, there will be a major port mismatch between the runner and cylinder head.

Thanks - yep - understood. I know I need the air box with the smaller ports if I want to put it back to stock.

More curious now about the Aux Air Valve and also what differences there actually are between the two different airboxes other than port size.

[snbush67]

Just to be safe you may want to measure the intake ports of the heads. I think you mentioned that the motor was rebuilt. It’s possible that the ports may have been ported or non-original heads with larger ports may have been used.

[Adrock]

Originally Posted by snbush67

Just to be safe you may want to measure the intake ports of the heads. I think you mentioned that the motor was rebuilt. It’s possible that the ports may have been ported or non-original heads with larger ports may have been used.

Thanks mate.
Will do. I know they are the correct heads for the engine - but haven't measure the intakes to see if they have been machined. I had the heads rebuilt myself and that wasn't on my list - but not sure if somebody did it before me. Very unlikely is my best guess.

[eastbay]

Originally Posted by snbush67

Just to be safe you may want to measure the intake ports of the heads. I think you mentioned that the motor was rebuilt. It’s possible that the ports may have been ported or non-original heads with larger ports may have been used.

Right on, all the advice here is backwards. Start at the heads, measure the port size and then work the matching size parts back to the airbox.

If the CIS is all mixed up, maybe the rest of the engine is also.

[Adrock]

Does anybody know much about Auxiliary Air Valves?

I'm curious to know what effect (if any) the 'Turbo' AAV will have on my non Turbo engine?
My understanding from my research is that the main differences between the different AAV's is the time that it takes to open, is that right?

If anybody has a good condition AAV to suit a 83 911 SC, I'd be happy to swap for my turbo version.

[boyt911sc]

Originally Posted by Adrock

Does anybody know much about Auxiliary Air Valves?

I'm curious to know what effect (if any) the 'Turbo' AAV will have on my non Turbo engine?
My understanding from my research is that the main differences between the different AAV's is the time that it takes to open, is that right?

If anybody has a good condition AAV to suit a 83 911 SC, I'd be happy to swap for my turbo version.

Adrock,

Could you post a picture of the AAV you have including the last 3 digits of the Bosch ID number? I have a strange feeling you might be referring to the AAR (auxiliary air regulator). In several early reference manuals or books, the AAR as we called today was commonly referred as auxiliary air valve. I believe the discrepancy was in the German translation to English and other languages. This is the reason I am requesting for a picture to make sure we are on the same page. Thanks.

Tony

[Adrock]

Originally Posted by boyt911sc

Adrock,

Could you post a picture of the AAV you have including the last 3 digits of the Bosch ID number? I have a strange feeling you might be referring to the AAR (auxiliary air regulator). In several early reference manuals or books, the AAR as we called today was commonly referred as auxiliary air valve. I believe the discrepancy was in the German translation to English and other languages. This is the reason I am requesting for a picture to make sure we are on the same page. Thanks.

Tony

Thanks Tony, part number and photos from google included in post #4 from myself above. I was only going on the name provided in the google search results.
There's also a photo of my actual part in post #8 - 3rd photo from the top.