Ferrari 308 gts carburetor version with o2 sensors manifold

Those are probably for the air injection tubes which are part of the emission system of the 78-79 USA carburetor cars

If you want to put an O2 bung in the exhaust header go to an exhaust shop and have them weld one in at the end of the header. This will allow you to measure air/fuel ratio for each bank. Make sure you place it so you can access it with a wrench. They require a lot of force to remove the plug to install the O2 sensor.


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I fitted a Superperformance supplied exhaust system about 3 years ago.

These are not sensor holes at all, they tapped stubs to bolt on the heat shield. Your ones are the same as the old exhaust system I had, they are in a slightly different location on the new system.

I had to braze on 2 lambda probe bungs & plugs on the main pipes just before the silencer. They normally measure the oxygen level in the exhaust, not CO or CO2.

 

Superperformance must have changed from the original Ferrari design. My headers did not have any header shield “tabbed stubs”. They did have threaded holes for the air induction pipes and a threaded fittings for the sampling tubes which were used for tuning. This was for a 78 USA carburetor car.


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FWIW you can install an O2 sensor in the system of a carb engine but there is no way it will ever work. What mechanism will vary the fuel delivery to achieve lambda? Yes those holes are for sampling exhaust temp and exhaust content. Simply leave them blocked.

 

Those ports are for sampling exhaust gas while carb tuning, but a modern O2 sensor won't fit and isn't the correct tool.
Those ports shown are not for mounting the heat shield, those tabs are different.
The air injection ports are in the head not in the exhaust manifold.
Leslie, that tubular thing is supposed to attach to the front header so you can access the ports. Otherwise they would be unreachable. Probably Rifledriver would know if Ferrari supplied an adapter for that to interface with some multi-gas analyzer or not. My guess is the adapter is the easy part, go find yourself a 3+ gas analyzer first.

 

My dynamometer man, who is also a Weber expert, screws a lambda probe into the fittings on the main exhaust pipes, runs the engine up on the rolling road, recording O2 against the revs, and changes the carb jets as readings indicate.

 

Sure, that makes sense but I would not want to be the person standing on the rolling road trying to adjust carbs. Regardless, HE is managing fuel flow rather than an engine management solution. A permanent O2 sensor on a Weber-equipped car is useless without something or someone constantly changing fuel rates.

 

He waits until everything is stopped before changing any jets !

Then gives it another run.

When he is happy, the O2 probes on his machine are removed, and the bungs replaced.

 

The 1-4 header shown in post #1 is for a euro carbed 308, and those studs are for mounting a heat shield (don't know if they are also hollow to serve for exhaust sampling):

https://www.ferrariparts.co.uk/diagram/ferrari/308-gtb-gts-carburetor/012-exhaust-system

A 1-4 header for a US version has a wrapped outer insulation and female threaded fittings on each tube that accept exhaust sampling tubes that have the same double-bubble flare fitting and hex nut fitting like shown in post #5:

https://www.ferrariparts.co.uk/diagram/ferrari/308-gtb-gts-usa/017-exhaust-system

 

When I was fitting the exhaust system to my originally English 1978 308 GTS I thought the stubs might have been drilled through into the branch pipe.

I checked, they were not.