Re: Ken's 1937 120 Touring Sedan

Posted by Ken_P On 2020/7/13 7:28:59

Gents, thanks for all the thoughts.

I suspect I know what is wrong, but I'm just going to go through the entire tune-up procedure, to try and get everything perfect.

When I recently replaced the intake manifold to fix some exhaust leaks, it also inexplicably fixed my rich running problem - no smoke once warmed up. I think that my rich running was caused by an un-diagnosed vacuum leak, causing the carb to demand more fuel. Now that the excess fuel condition is gone, it is actually running a bit lean, and thus hot.

I've been busy, so haven't done much, but I did pull the plugs, confirmed lean in addition to hot. Did a compression test. I was very surprised by the results. Spec on my car is 118 psi. Last summer, I did a test with the carb off and got 130-132 psi on all cylinders. This time, with throttle plate and choke blocked open, I was at 116-119 psi on cylinders 1-6. Hooray! But, I was down 10 and 15 psi on #7 & 8 respectively.

I ran some marvel mystery oil in my last tank of fuel, and a little diesel in the previous tank, to clear carbon out of the combustion chambers. That appears to have worked. I'm hoping my lower compression on two cylinders is due to an issue with my recent valve adjustment and not burnt valves!

Next up - I'll finish changing the points out (saw some minor pitting). I was going to install a new condenser, but the existing one is a NOS Autolite with an integral distributor wire (not sure of the title, the one that goes from the points to the distributor body, eventually to the coil). The NOS one is in spec for capacitance, the new one (from NAPA) is not.

I also checked the spark plug wires for resistance, just for fun. All were good, less than 0.3 ohms, but I did find two slightly loose terminal ends.

I also have a new cap coming, and need to order a new rotor.

Once the ignition work is done, I'll do a cylinder leak down test, verify timing, and then tune the carb with a vacuum gauge.

I'll report back once I get some more done.