Updated: Dec 27, 2019
Diagnosis Equipment that Makes a Difference
If you read through the previous post, you may recall this photo below...
This spark plug was removed from cylinder 5 before the carburetor rebuild. Since the idle mixture screws were not responding well to any adjustments, I just assumed that a very dirty carburetor had caused this trouble. When I pulled a few other spark plugs, they were pretty fouled, but nowhere this bad. The best spark plug I pulled from cylinder 8 looked like this one:
All things considered, this spark plug was in much better shape. This dramatic difference should have alerted me to the fact that there more issues than just the carburetor, but on I went to re-install the Edelbrock which was now nice and clean.
I used a brand new kit from a Weber/Carter supplier, and printed off the instructions to place in sheet protectors for safe keeping. You may be wondering about the blue gaskets. These are especially made so that they will not stick to the metal parts or the intake manifold. Essentially, they can be re-used. When one considers tuning a carburetor with different jets, metering rods, etc, this can be a real bonus.
For the time being, I elected to forego the 3rd fuel filter (the inline model that gave much trouble when bits and chunks were in the seat screens) and simply installed a 5/16" line between the fuel pump and the pressure regulator. I do have a full metal fuel filter housing with a re-usable bronze filter on order. The initial settings were checked and the carburetor was re-installed on the intake manifold. While I did hook up the choke cable, I chose not to attach the throttle rod from the accelerator bell crank for the time being. Here is what we got...
Right off the bat, we had an excellent throttle response! Of course the idle was high, the idle mixture screws were allowing the engine to run rich at idle, and I had not yet put a vacuum gauge on it. So, I broke out the vacuum gauge and hooked it to the driver's side port on the carburetor. At the same time, I located my Craftsman brand Engine Analyzer to monitor the rpm's.
Check out the vacuum...
Obviously, with a well-tuned engine, the vacuum gauge needle should not fluctuate but should remain steady. What I saw was the bouncing of the needle about 1 inch of mercury during idle. After some helpful comments from some friends online in a Ford forum, I surmised that cylinder #5 was giving us trouble. When I took a temperature reading with an infrared thermometer we had another anomaly show up.
The only thing left to do was to remove the valve cover and inspect #5 to see why the valves were not seating. Here is a video of the process and what was discovered, but there is also a satisfying end!
Most of this would not have been possible without the proper tools. I cannot stress to you enough the value of a vacuum gauge! While the engine analyzer certainly helps with voltage and rpm readings (it can do more if you have points), nothing beats reading the measurement on engine vacuum. I stumbled across this website www.secondchancegarage.com/public/186.cfm - when you paste this link in your browser just scroll down the page about 1/3rd and you will see an animated display of a vacuum gauge. Just click the different "scenarios" links in that section and it will explain different readings and how they are interpreted.
With the engine about up to snuff it is time to move on to some more projects on this old Ford. There is still some wiring to clean up, a floor and a set of walls to build for the trunk, and on it goes. I sure hope you had a great Easter! Our church performed a brief musical about the resurrection of Christ. Visit https://www.fbcm.org/media-menu/live and click on the Easter service for April 21.
the Hot Rod Reverend