Ferrari 400/412 K Jetronic Metering Head Rebuild (Myths and Advice)

I have found this so far, more suggestions welcome.

"After assembly of the fuel system, run the fuel pump and depress the air flow sensor plate for a couple of seconds to bleed air out of the fuel distributor. Remove one injector line from the top of the fuel distributor, and while looking into the injector port in the top of the fuel distributor turn the mixture adjustment screw clockwise until the port just starts to fill with fuel then turn the mixture screw 1/2 turn counter clockwise. Reinstall the injector line, start the engine and adjust mixture when it reaches operating temperature. This is the Bosch recommended procedure for initial mixture setting and adjustment."

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Thanks. Would I not notice a change in the engine "sound" or RPM? I will upload a video.

I think the best will be to get a wide band o2 sensor then,as they have been installed by the previous owner, probably narrow band.

 

Update to his rebuild, I have been chasing down rough running engine, uneven exhaust temperature between left and right bank, and very rich running condition for the last 9 months, in the end the problem turned out to be a defective main rubber diaphragm.

I now have un-metered fuel coming through the ports due to a completely failed diaphragm. I have order a new set from a another supplier and will install it tomorrow.

I should have stuck with my initial suspicion, as the engine ran fantastically right after I installed the new diaphragm and then progressively got worse - this lead me to believe I had vacuum issues, or that the CO adjustment was incorrect - but this was never the case.

To complicate things, I did it timing chain replacement in between which made me second guess other issues like valve timing (which were all correct).

Conclusion: the main diaphragm has completely failed and this was the (only) reason it was running so bad.

 

After replacing the diaphragm and the atomization is vastly different (better).

The problem was undoubtedly the failed diaphragm. (see picture) Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

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