The Surprises Continue

- - posted in 1967 Cadillac Sedan Deville, Worklogs | Comments

With things starting to slow down with my work schedule, I was actually able to take this weekend off! I got to relax quite a lot, spend some time with the family, and spend a little time in the garage with the Caddy.

You may remember from my last last update about the Cadillac, that I had a few outstanding mysteries to try to resolve.

Damper BoltsFirst, let’s talk about the “easy” one, the Harmonic Balancer/Dampener. You see, it seemed have been bent or damaged at some point, since one side of it was closer to the engine than the other. This created a situation where it would “wobble” on the crank as the engine was running not cool! As was preparing to remove it, I pulled some of the bolts which hold the crank pulley onto the dampener. What I noticed is that when I removed the first bolt, which happened to be in the spot on the dampener where it was “pushed out”, that the dampener seemed to start returning to it’s original shape. After completely removing the bolts, and using a pry bar the dampener was back to it’s original shape! Turns out that someone before me replaced one of the pulley bolts with a bolt that was nearly twice as long, and it was pushing on the dampener causing the problem I observed!

Now, for the more onerous “clunking” noise. When I first heard it, I thought for sure that it was an issue with the valvetrain, so sure was I in fact that I pulled the passenger side valve cover off expecting to see a bent push-rod, or a broken rocker arm, or some other catastrophic failure. Imagine my surprise when I looked under the valvecover and found no problem what-so-ever! I even pulled the drivers side, thinking I’d misjudged the origin of the noise, no luck there either. At that point I had pretty much decided that the engine was going to come out, and I needed to do a complete inspection to find the source of the issue. I put my tools away and put the project on hold for awhile.

Now, as it just so happens in the meantime I read this little gem, which described another symptom which I’d just sorta ignored. I read down to the 6th post in that thread, and I had a light bulb moment. If my valves were sticking open, it’s possible that the “clunk” I heard was the rocker arm smacking the stem of a still open valve. This would explain why it wasn’t a consistent sound which increased with RPM, since the valve(s) may not stick on ever revolution and increasing RPM probably got the valves moving enough that they did not stick. So, the valve covers came off again, and all the spark plugs came out, and I began turning the engine over by hand, fully anticipating that I’d see one or more valves on the passenger side staying open. Sadly, I was disappointed once again as everything worked exactly as it ought to.

At this point, I was again convinced that the only solution was to yank the engine entirely and do a thorough teardown and inspection. I did a quick compression test which I’d been intending to do for some time. All of the cylinders were within a few PSI of 150, except for the # 5 & 6 cylinders, which were both just north of 170PSI. That’s a fairly good sign that the shortblock is probably in decent shape, and I’ll probably be able to run this thing once I solve the mystery of the “clunk”. So I proceeded to yank the wiring, and everything else I needed to on the top of the motor, then jacked the car up and headed underneath to disconnect everything down there. Once down there, I took a quick peek to see how hard it was going to be to access the engine mount fasteners. Imagine my surprise when I realized that BOTH of the engine mount nuts were missing!

It occurred to me pretty quickly that this could just as easily be the source of my “clunk” sound, the engine slapping against the crossmember when it skips a beat. And even makes more sense that it would be the passenger side since the engine rotates in the opposite direction! At that point I put the car back on the ground, put my tools away, and called a day. Today I am going to go buy some replacement nuts for the motor mounts, and hopefully install them soon to see if that solves the “clunk” mystery. If it doesn’t this time (for sure) I’ll be pulling the motor out to tear it down and inspect it.

The next mystery for me to solve is that the spark plug in the #8 cylinder had absolutely 0 gap! I’m hoping that it was just a mistake while installing it, and not a piston which reached up and slapped it silly (that could cause a clunking noise too), we’ll see soon enough!