Hi guys, so I've got a 1975 Series II XJ6 and I bought an Innovate MTX-L air/fuel ratio gauge and it came with the Bosch Wideband O2 Sensor (LSU4.2). Can anybody give me suggestions on the best place to mount this on the exhaust system?

 

Well fuel injected cars have O2 sensors just below the exhaust manifold as I recall... but why are you installing an O2 sensors if your going to use the original strombergs? One of the reasons people dislike them is because they are notoriously un-adjustable. Your car has about 3 or 4 threads worth of adjustment at the needle. Unless you're gonna really do some experimentation it may not be that worthwhile - interesting but you may not be able to do much with the information the gauges provide -- there's a site online where a guy installed oxygen sensors on a TR6 (same carbs). He also messed around with needle height by making a set of spacers. Don't have the link but it's worth a few minutes of googling to take a look at his findings. Might have been on the buckeye triumphs site possibly...

 

Hi rustfreemike, thank you for responding! I'm just learning about this stuff. I thought the needles were fixed, but when I rebuilt my carbs, that's what I noticed. I have about 2-3 turns of adjustment. Something made me feel that maybe somebody tried changing the needles out to a different profile. In any case, my carbs seem to work properly, but maybe just because they're old, they don't seem to adjust to OEM specification. I originally bought the air/ratio fuel gauge just to help tune it up, but because circumstances changed, I decided to mount the gauge on my dash and permanently install the sensor. I know the carbs won't be perfect, but I was hoping to adjust the air/fuel ratio to the optimum of the most used RPM of the engine. What pushed me in this direction is that when I originally got the car, the carbs were in such bad shape that all the car did was blow out billows of black smoke and the whole air pollution system was totally plugged up with carbon. Parts of the EGR pipe were totally plugged with carbon. So I'm working with this air/fuel ratio gauge to understand quantitatively how the carbs are running.

 

Well at the very least it'll be interesting to see what the gauges tell you under different running conditions. Definitely interested in hearing about what you find.

I believe I mentioned in an early one of your posts that since you got rid of the terrible fixed orifice EGR you should go to the pre- EGR needle profile. There's also another thing you can do (short of grinding your own needles). That's going to the B1E needle. When these cars were new(er) you could get all kindsa needles for strombergs but these days it's pretty much only the stock profile and that's it - makes it hard to experiment. Also they aren't cheap. What's worse is that today's fuel has less available energy than the stuff our cars were designed to run on which contributes to the lean-ness issue.

Strombergs are emissions carbs so they already run lean. Add to that the crappy gas and 40 year old emission systems and you've got a recipe for a poorly running car.

But if you've rebuilt the carbs completely - including replacing the over-run valve, calibrating the temperature compensators and replacing the shaft seals - and you've gotten rid of the gulp valve (probably doesn't work at this point anyhow and only necessary if you have a functioning air pump), and the EGR, there's no reason the car won't run acceptably with the carbs you have. Your car also had a vac retard distributor (also probably doesn't work at this point) which can contribute to lean running at idle because closing down the butterflies to make it idle at the proper speed without the retard functioning is not how the needles were designed... like I said, my 73 idles lean after everything I've done to the carbs.

Enter B1E needles - these were designed for E-types whose only emission systems were strombergs and a secondary manifold plus they had purely mechanical advance distributors - no vac retard to mess with idle. If I were going to keep my strombergs I'd source a set of them but they are a little hard to find. I've heard very good things about going to B1E needles in strombergs.

Oh, one more thing. Your jet's aren't adjustable but they are only pressed in so if you use a brass drift and are very careful about not deforming the hole you can lower them by tapping them down. Something to think about when you get ready to experiment with the carbs while the O2 gauges are operating.

 

Thanks rustfreemike! I'll remember all of that, and probably overhaul the needles at this point.