Help Identifying CIS Airbox

[69 Soft Targa]

How do I determine what year an Airbox is from?

I didn't see a part # only a 5 digit #.

[jcc911]

I think you have to measure the ID of the intake runner ports. Dont recall the size of the 78-79, Euro airboxes. 38mm?

[nineball]

correct. the larger, 84mm, is for 78-79 and euro 78-83. the smaller, 38mm, is for 74-77 and 80-83.

[db_cooper]

Are the screws inside the box pulled? Might be a blown box? (sorry off topic)

[69 Soft Targa]

Thanks.

The ports measure 38mm.

Re: Blown box

There are only 5 screws in it currently and one is stripped. May be from overtightening?

Pictures show the only damage. Is this a problem?

I found these numbers 51.0538 and 51.0462

[69 Soft Targa]

[nineball]

if it is stripped and you can't make the airtight seal then you need a new one. sorry mate.

[69 Soft Targa]

I see others have sealed the seam with good results per old posts.

I think this box is a good candidate for repair.

rebuilding the airbox

[Jim Williams]

Originally Posted by nineball

correct. the larger, 84mm, is for 78-79 and euro 78-83. the smaller, 38mm, is for 74-77 and 80-83.

The correct numbers for the port sizes of the airboxes (internal diameters) are 34 mm for the US '74 - '77 and US '80 - '83, and 38 mm for the US '78 - '79, and the
Euro '78 - '83. Just for completeness, the '73.5 airbox had 30 mm ports.

[nineball]

well then i stand corrected, and i had a typo that should have read 44mm not 84mm. i got my info from our host's listings.

CIS Air Box (44mm Intake Port), 911 (1978-79), 911 Euro (1978-83)
Brand: Genuine Porsche [More Info]

CIS Air Box (38mm Intake Port), 911 (1974-77), 911 (1980-83)
Brand: Genuine Porsche [More Info]

[Jim Williams]

I spoke with someone at Pelican a year or so ago and told them that common and less confusing way to describe the airbox port sizes is to use the internal diameter of the ports, as that is the internal diameter of the aluminum runners, and also of the intake ports of the heads that match, but I see they didn't take my suggestion.

I think it is common practice to measure a "port" using the diameter of the hole, and not the OD of the boss, or casting, that surrounds the hole.

But I could be wrong...

[carrera turbo]

Agreed JIM

most everything that flows something I.E. pipe, hose, ducting, etc. uses inside diameter I.D. as this is the area that move the product weather it be fluid or air. now if you where to buy the rubber booty's for the box to runners then you maybe could use the outside diameter of the sealing surface of the connections, when you get into tubing and such then you start using o.d.

it does get confusing at times.

cheers ed

[davihun911]

I have a customers car in my garage. its a 911 SC. the airbox has the 44mm intake ports but the manifold pipes are the 38 mm.
Has anyone come across this before. 3 of the connection sleeves are split and I'm having a hell of a time trying to track down replacements. any help would be gratefully appreciated

[Jim Williams]

First you have to state which convention you are using to measure. The proper convention is the inside diameter on the ports. The large diameter ports are 38 mm and the small ones are 34. The 38 mm ports were used on the US 78 - 79, and the Euro 78 - 83. All the others with the aluminum cast runners are 34 mm.

There are no air boxes or runners with 44 mm inside diameter ports.

[allaircooled]

Just to add to the confusion, I have what I believe is a #2 intake runner from a '74. The ID of this port is about 32mm with the same OD of the 34 mm runners. Notice in the pic how thick the wall is. I'm not sure if this is a '74 only runner or what application it was used on.

[Jim Williams]

OK, here's more detail from measurements I've made in the past - Check these numbers out.

For the '74 and '75 2.7 Non-S runners: 31 mm
Casting numbers end in 0R.

For the '74 2.7 S and '80 -'83 3.0 runners: 34.5 mm
Casting numbers end in 2R

'78 - '79 3.0 US runners: 38 mm
Casting numbers end in 4R

[allaircooled]

Thanks, that's good info.