Determining correct jet size

[johnbilt]

The only thing with those air/fuel gauges is that they connect to an O2 sensor, and if you don't have an O2 sensor in your exhaust system already, then you have to install one.

True - I welded in a sensor mount in the exhaust pipe close to the exhaust manifold for a good reading. I used a spark plug insert I bought at an auto parts store. The threads fits one the standard O2 sensors (SG-1) and makes an easy weld-in mount. I can tell instantly what is happening with the fuel mixture. Pretty valuable for finding the right jets, accelerator pump, power valve, secondary spring settings, etc....I solved my carb problems right away once I had the right info.

 

[elwood blues]

Cool, did you take pics? I'd like to see your set-up.

 

[johnbilt]

I'll try to get some pics of the jeep this week. Here is a photo of the spark plug insert (anti-fouling) doohickey.. They are used to space the plug out of the cylinder for certain applications (not sure what). Anyway, they are conveniently sized and threaded for the SG-1 O2 sensor. I cut the end off in my application rather than drill it out. I measured the overall depth and trimmed it to get the sensor into the main exhaust stream to get a reliable reading. The I drilled a hole in the exhaust tube and welded in the insert. The O2 sensor threads right in and I routed the wire away from the exhaust and up to the dash.

Can't get the photo to load... Will try later

You can check out this link:
O2 Sensor modification using spark plug non-foulers

 

[johnbilt]

Here is a photo of the spark plug insert. I figured out how to load a photo on the advanced menu..

 

[johnbilt]

Here is a link to Gerard Forgnone's website about holley tuning that includes info about mounting the O2 sensor. Excellent information. There is a lot of reading here, but about 3/4 down the page is the part about the O2 sensor specifically.

Carburetor Tuning the Scientific Way