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| Joined: | 03-12-2005 |
| Location: | Kingman, Arizona USA |
| Posts: | 532 |
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That said, possibly things with your engine are not optimal and can be improved a bit.
* First, set the ignition timing to 12°BTDC rather than the stock 8°BTDC, with the vacuum line to the distributor disconnected and plugged.
* Second, check your cam timing and verify that the 110 IN mark on the intake cam aligns with the 110 EX mark on the exhaust cam when the engine is at #1 TDC.
* Third, check to see that you have the correct mixture needles in your Strombergs, and that they're in decent shape -- i.e. no bends, no scratches or grooves, and no flat spots.
* Fourth, experiment with damper oils -- based on the symptoms reported, most likely whatever you're using now is a bit too light for your particular conditions.
Current oxygen sensors need to be quite hot to work, therefore I'd expect that yours would have to be installed at the outlet of the Y pipe if you have the stock 4-2-1 system, or at the outlet of the manifold if you have an aftermarket 4-1 header. Normally one welds a suitable fitting to the chosen location. That done, you can attempt to use the sensor to determine the fuel/air mix under various conditions.
Current oxygen sensors report 'way too rich' and 'way too lean' and have an extremely narrow midband that says 'a bit rich', 'just right', or 'a bit lean'. For the midband, they require an accurately calibrated readout device to be usable. For most purposes, asking for direct traceability to the National Bureau of Standards is going overboard, but I would insist on trustworthy assurances about the calibration.
Without a calibrated readout, about all you can determine is whether your damper oil is way too thick or way too thin, and whether or not if your fuel / air mix is way off. With decent calibration, you'll get a reasonable picture of the fuel / air mix your engine sees under various conditions -- sufficient for almost all purposes. And finally, with laboratory-quality accuracy and a lot of data, you can develop a very complete understanding of how the engine is operating -- the sort of thing one does for a brand new engine design but far beyond any realistic hobby-car requirement.
For Strombergs, you would need to correlate the fuel / air mixture information for various conditions with the positions of the carburetors' vacuum valves (sliding piston things) under those same conditions. Next would be a comparison of the profile of the installed mixture needles with those of other (available) needles, hopefully finding one that might improve overall performance. You'd then install a pair of the new needle type, and repeat the tests under the same conditions of temperature, humidity, etc.
As an alternative, you can use a carbon monoxide (CO) sensor. Here, installation is easy -- the sensor probe can generally just be poked into the exhaust pipe from the rear -- but the data received merely indicates how well the engine is burning whatever it's getting, so interpretation is much more difficult.
If you do go to the trouble of installing your oxygen sensor, I'd be quite interested in seeing your data.