After a bit more investigation I believe I have finally figured out why I had low compression!
Hot Takes:
- Be careful when using solevents in an ultrasonic cleaner.
- Take your time when removing valve springs.
- Having an Ford Motor Company powertrain test engineer for a father can be really helpful.
- Carb cleaner can clean more than just carbs.
Removing the head it wasn't immediately obvious as to why I might be having compression issues. From the last post you can see that there was no damage to any of the valves, so I knew that timing was fine. The pistons, while dirty didn't seem too have anything inherently wrong with them either. After a bit more massaging with a rubber mallet, I was able to pop the block it self. Once I removed the block and inspected the pistons, I saw something quite peculiar. Upon inspecting the piston rings, I found that the openings in my top two rings were lined up, facing the front of the engine. Taking a look at the service manual they clearly indicate that the openings should be sitting opposite of each other.
Still, the gaps when the pistons are in the bore is fairly small, and lining them up wouldn't kill my compression that much. My dad suggested that I do a crude valve sealing check by back pressurizing the intake and exhaust sides of the valves. With a trip the the hardware store to get some adapters for my air compressor, I was ready. I mixed up a bit of snoop (water and dish soap) as a leak tester and got to work. I pushed a measly 10 psi into the intake sides and saw a bit of bubble growth. The important part was that the bubble growth was identical across all the intake valves. I then removed those valves and they sure were dirty!
The important part was that the wear patterns seemed alright. Everything looked uniform and the thickness of the wear surface was within spec according to the service manual. I decided to throw them in my harbor freight ultrasonic cleaner with a mix of water, Zep 505 degreaser, and some Dawn dish soap. While those were cleaning up I worked on the pistons. I started with some WD-40 and a nylon brush. This wasn't getting me anywhere fast so I tried some carb cleaner, and whoa....what a difference.
I tried a bit of carb cleaner on all the gasket surfaces and it gave me a mirror finish. At this point my intake valves were done in the cleaner and I pulled them out. This was my first major road block. I'm not sure whether it was the solution I had put together or something wrong with the valves themselves, but the cleaner had eaten away at the contact surface. It's hard to see in this picture, but there's a smooth surface to the right and then to the left you can see where the mating surface got eaten away.
This happened with all of my intake valves, so I added those to the list to buy for the rebuild. At this point it was time to pressure check the exhaust valves. I did the same as the intake side, and pressurized the exhaust through a spare manifold with 10 psi. I wish I could post a gif or video of this, but the picture will have to suffice. Cylinder #1 (the one that had 30 psi less of compression) looked like a bubble machine.
After taking the exhaust valves out, it was obvious that E1-1 (exhaust valve, cylinder 1, furthest from cam chain) had a wear pattern way larger than E2-2 (E1-1 on right side).
While my wallet is already yelling at me, I added exhaust valves to the buy list as well.
Looking Forward:
As of yesterday I just received all my valves, gaskets, and other pieces to reassemble my engine. Not wanting to devote too much time to figuring out how to compress valve springs, I broke down and bought a 20 dollar kit on amazon. With that, I also purchased some valve lapping compound and the suction cup tool to do so. From here on out it's putting things back together and hoping it all works!
I hope this thread can offer help to someone in the future who decides to rebuild their engine. I'll be sure to post progress on valve lapping and other reassembly steps!