Engine exhaust tempreture

[my65]

I have been chasing an idel problem that I thought was a bad primary carb. The carb in question was moved from right side to the left side, then sent to a shop for rework and after reinstalling it on the left side, the idel came down to 600 rpm but I still had a slight miss. I shot tempretures at the carb base and exhaust pipe before the carbs were switched and after. The run time on these two tests were not the same, hence the lower tempretures.
Before R carb 121 After 129
Before R exhaust. 100. 112

Before. L carb. 140 After 109
Before. L exhaust. 110. 98

It appears to me that a lower temperature is following the one carburetor ( that was reworked )
Is this tempreture variance normal or does it indicate that the cylinders on the lower tempreture side are not firing ???

[Jerry Whitt]

Temperature readings are a very unusual way to troubleshoot on Corvairs.

Engine compression tests, leak down tests, carbon monoxide tests and hydrocarbon tests are more familiar to old car tech people. That the time on the two tests are not the same seems to throw even more confusion into the picture.

Some more basic information would help. What is the dwell reading? What is the initial timing? What is the timing when vacuum is applied to the vacuum advance? What advance do the weights in the distributor add at high speed? Is the vacuum reading at each carburetor choke pull off port the same on each side?
Be glad to help if we can but your input is really unusual.

[my65]

I know that tempreture readings are not "normally" done in diagnosing a 50-year-old automobile, and I am very appreciative of all the help that I have received from this forum!!! I guess the 37 years of gas turbine experience that I have, working on 10,000 HP to 110 MW gas turbines influenced where I could go. With the turbines, if you monitor the exhaust temperatures you can tell if the fuel nozzles are properly set and the rest of the engine is funcationing normally. I didn't know if maybe something similar would work on my Corvair? I tried all the conventional tests and nothing was idenifing my problem. The test results kept coming back within acceptable limits.
I just got off the phone with Clark's and with all the info I gave them, their best guess is my valves are tight......I will adjust next week after my out of town family leave. They also said that a 10 degree spread was nothing to get excited about.

[64powerglide]

How do the plugs look??????? If they are burning clean don't worry.

[wbabst]

Hey Ed, as an aircraft guy planes have an EGT gauge on them. The exhaust gas temperature along with cylinder head temperature indicates your mixture. Too hot means too lean and you richen it, too cold means to rich and you lean it out. If you let the car idle for a given period of time you can then check your temps. It may indicate if one bank is running a little lean or rich. I have never heard of doing it on a car, but theoretically it should work. That said, you indicated a miss? Is it your idle is not perfectly smooth, or is there actual stumbles or it seems like you have a spark plug not firing?
I am not an expert, and am sure some of them will have more to say, but it is my understanding that there were some idle issues with these carb, especially the very early models. Modifications were introduced over the production of the series to help improve that. My 61 carbs had a hole drilled in the butterfly at the base of the carb, that was later soldered closed. It was a mod to let more air in during idle, that apparently didn't work.

[my65]

Thanks wbabst, your reply is what I was hoping for. It is just that the engine is not smooth at 650 rpm ( my miss ) and I have replaced wires, plugs, vacuum hoses, rotor, distributor cap, had carbs rebuilt and adjusted(?) , and replaced after market linkage to original design! My 65 idles is so smooth you could stand a dime on the shroud. I think I will readjust the valves and hopefully I can move on to another item?