K-jet fuel distributor mixture adjustment screw covering bolt issue

I don't know specifically on the Testarossa, but every CIS mixure port I have ever seen has been plugged with a brass plug. This is because it is against emissions laws to have user adjustable mixture. The brass plugs get drilled and removed leaving a smooth hole, which can then be tapped for a bolt or plugged again. I have one car that I put a bolt in the plug, and I just pull it out to adjust, and tap it back in to plug. Another car didn't have the plug so I tapped it and plugged. Finally another car just had a proper size bolt wrapped heavily in teflon tape and "screwed" in.

Proper way to do it is remove the unit like in the picture, tap it, and reinstall. I wouldn't risk tapping it in place, as it would be too hard to catch the shavings. If that aluminum gets stuck on an intake or exhaust valve, the valve will end up burnt.

 

You can carefully cut a M6 mm metric thread (Use a vacuum cleaner while tapping the thread, lubricate with spirit). Then install a M6x10 mm unbrako bolt with a washer and a tight o-ring below the head. Works like a charm and can be removed at any time if adjustment is needed.

Best, Peter

 

take a rubber cone

 

The very first cars with CIS, like the VW Rabbit/Audi Fox had a very nice rubber plug molded around a metal rod with a ring on the end. I use two of these when adjusting the mixture on a TR or one on a 308/328, as you need to plug the hole to keep the unmetered air leak from causing a lean mixture.

I would just put two of these in the airflow meters. They might be hard to find, but here is what they look like:
https://autopartsfair.com/volvo-engine_parts/240-1982-air_intake-b3050_18622bos_2.html

Porsche uses them as well, but they are kind of pricy. I remember when they where $5 each, guess I am getting old.:
https://www.pelicanparts.com/More_Info/91111093401.htm?pn=911-110-934-01-OEM&utm_source=googleppc&utm_term=91111093401&utm_campaign=Shopping+Feed&gclid=CjwKCAjwqdn1BRBREiwAEbZcR1Dw_Y7X3FTaWzzTlPf3sjE4kiBD9uCGVPL-SPQ0-V8Tv2Np59tvOhoCScAQAvD_BwE

 

You leave them in after the tuning. Covers the air leak.

 

such cones are used in the chemical industry. if you have connection to a chemical teacher at school he could help you.

horrible price
so I think getting old also

 

A cat can be skinned in many ways. I admit that cutting a thread seems quite dramatically if you can buy a custom build rubber plug for the same purpose. Anyhow here is a picture from the CIS in my 308QV showing the small "unbrako" plug I installed with the CIS still located in the running car many years ago...Repair time: took 5 minutes, cost: 0.5$, appearance: very discrete, function: "never looked backed", reversibility: you can always add a rubber plug and now the threads will keep the plug tight....-

Best, Peter

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I would not do so. what about the debris when you put in the srew?
if you take out of the car then I not see a problem

 

I don't think a small piece of aluminum is a big problem and with a little creativity and good suction from a vacuum cleaner I think you will be safe. Can you imagine how many aluminium cuttings there were potentially left over in a new engine in 1982 and sucked through the system at first start up?....But if your still worried you can push down the metering plate and put a small cup below the hole while tapping the thread (Soda bottle screw lid could possibly be used).

Best, Peter

 

or you may use an aluminum magnet

it is easy to remove the complete unit and then you are on the save side

 

When I adjust the mixture, I use a silicone plug - I got it by pulling it out of the nozzle of a caulking gun after it had dried. Perfect seal.

 

great idea !

 

I remove the rubber plugs and reinstall the original screws after tuning a TR. Originally the Bosch rubber plugs with the handle were stock on Audis, VWs and Porsches with K-jet. You would remove them, adjust the mixture and then reinstall them. When the EPA and CARB got involved, you were supposed to tap in metal anti-tamper plugs after making a mixture adjustment.

Since the cost of the original rubber Bosch plugs with the handle is so high, I just use nice silicone tapered plugs (from the powder coating industry to plug holes when powder coating) and tap them into the AFM. There is no pressure and little vacuum in the AFM, so if they fit tight, they will not come out.

Brian Brown
San Francisco Motorsports