What is a good a/f gauge for a old car? All I found say hook to pcm. I have no electronics on my car.
You would need a wideband O2 sensor in the exhaust. There are a lot of different options. Check summit racing.
I don't know what you're looking at. You need a wideband gauge. There are plenty that don't connect to a PCM. https://www.summitracing.com/search/part-type/gauges?N=gauge-type:air-fuel-ratio-wideband
https://www.amazon.com/wideband-o2-sensor-kit/s?k=wideband+o2+sensor+kit Not a big A fan, but they do allow quick comparison shopping and lots of results. There are more high end companies that don't market there. It's your budget, but don't go too low end.
I run the Innovate dual kit. One in each pipe. Great guide for getting you very close but have to remember that like mine with one in each pipe I'm sampling 4 cylinders, so while it's got me very close I've made the last little tweaks by how it actually drives. o2 placement in the pipe is critical for longevity. One other thing is if like me using silicone to mount headers, let it cure fully, as silicone will kill the sensor quickly.
I have the Autometer, just needs 12 volts and an oxygen sensor, which it comes with. I've welded a bung in all 3 of my carbureted cars. Takes about 20 minutes to swap from one car to the other. Makes plug reading obsolete.
that should work The Autometer costs another hundred bucks, they have one that actually looks like a gauge... https://www.summitracing.com/parts/atm-3370 Just remember that "it's only a number", the engine has to run good and not be crazy rich or lean under typical operating conditions.
O2 sensor requires placement that has no leaks, it must be up to temperature, and is susceptible to contamination. Basic stuff, but pay attention. Do not shrink wrap the wiring/ sensor. It needs to compare outside air to tip gases. If your car has that parking lot lope at idle, it's going to mess with the readings. If your exhaust is short and you have a big cam, it may push/pull at low RPM. Hold a piece of paper over the end of the pipe(s). It should be pushed back steadily. If it is pushed, then sucked tight, there is reversion and this can dilute the gases and mess with the readings. It will give accurate readings at higher RPM, but not when the gases are pulsing.
I have the AEM gauge and mine came with the Bosch sensor, been very reliable for the last 7 years and I even run slight mix of leaded fuel. I only set it up for idle and wide open throttle with the Dominator carb I’m experimenting with. I have the sensor mounted in the header collector and it’s pretty accurate with a full exhaust on the car.
I run a SpeedHut stand-alone gauge in my truck. https://speedhut.com/gauge-applicat...alog-out-o2-gauge-8-5-18/?dd-link=0ldtcryzj5b You can choose the dial color, font, needle, face plate, etc... Mine has worked flawlessly since installing it. I thought the O2s was acting up so I called and talked with the tech guy about purchasing a new one, nope, he sent one straight out no charge, didn't want the old one and said to call back if I still had issues. Great customer service. Turned out to be the fuel I was running. I run a 1970's 250 inline six, with a home made dual carb intake, twin Carter W-1 carburetors from the '40s, and HEi ignition. I installed a FlowMaster catalytic converter I found on sale for $20 at a Holley blowout sale. The exhaust smells cleaner then my late model, theres no more garage smells coming into the house, no fuel smells, and a heck of a lot better fuel mileage, and I thought it ran good before the gauge install.
I have one in my car, but I have a header leak in the middle of the collector, hard to fix now so I know my reading are off a bit. They work well, just don't have any header leaks.
Since your avatar picture has a blower on it, you might want to consider having 2 sensors. Innovate sells one that has a guage with 2 readouts so you only need one guage on your dash(?). Naturally they are more expensive since they come with 2 sensors. Innovate is a quality set up. There may be others that offer the same option. With the blower there is more chance of differences in readings between each bank. Also, mounting location should be with a slight downward angle so moisture (etc.) drains away rather than settles on the sensor when the engine isn't running.
I prefer an analog gauge to a digital for AFR. It changes rapidly enough that reading a digital gauge can be a little distracting. I get a better “sense” of what’s going on with an analog.
This is going on a friends 67 coronet. It has a 340 in it with full exhaust out the back. Thanks for the help. I will let him decide which one.
I enjoy reading plugs and learning the old ways, actually. It's not as easy to solve problems, but when I do, I fricken earned it.
Reading plugs is still part of the program if you use O2 sensor. Being able to read individual cylinders lean/rich conditions are important, with an O2 sensor you are reading an average of multiple cylinders. The O2 sensor is a great tool as is a vacuum gage and a spark plug wrench.
@oldiron 440 ,How do you adjust the air/fuel mixture to individual cylinders, based on plug readings, on a carbureted rod?
Depends. If you have a sensibly built multi carb setup where each cylinder draws air only from one carb you'll know which carb to adjust when you see a cylinder running rich. If different cylinders fed from the same carb get different amounts of fuel grinding channels in the bottom of the manifold to lead liquid fuel on the bottom to a lean cylinder or adding "dams" preventing fuel from going towards a rich cylinder may solve the imbalance. If you have a horrible setup where multiple carbs feed a common intake that all cylinders draw from you throw sh*t att he wall and see what sticks. Yeah, there are plenty of reasons why I call that type horrible - they sure run, but fine tuning an engine isn't their strong point. If you can't tell what carb feeds which cylinder tuning anything well will be a nightmare.
Usually it’s the intake manifold causing the problem and if it’s drastic enough you change it. I’ve had a new intake that fuel distribution was so bad in half the cylinders that I couldn’t with a clear conscious sell it at a swap meet. There was 80 horse power difference between the one I removed and the new one, it was junk. Sometimes you can make small adjustments with spacers, a 1” open hole spacer on a two plane intake will sometimes fix fuel distribution issues. I will add that a four hole 1” spacer can help a single plane intake fuel distribution issue.
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