Today, I tuned the engine. I’ve been pretty nervous to start messing with the engine and all of its parts. It runs, and I don’t want to do anything to stop that. I also apologize in advance for the techiness of this entry; If you don’t know what I’m talking about, just skim it and be impressed with my massive mechanical knowledge. If you happen to be a VW nut, keep me honest and tell me all about how I am doing everything wrong. As I mentioned earlier, I ran the engine for about 10 – 15 minutes the other day, and didn’t really like the way it sounded. It also seemed to get pretty hot. So now I’m going to tune it up and make sure everything is set correctly!
I started the day on a shopping spree: Auto Zone, Menards, NAPA, other Auto Zone, back to NAPA. I have been researching the steps needed to tune an air-cooled VW engine via the Muir book, internet resources, and many You Tube videos. What I planned to accomplish today was 1) Replace fan belt, 2) Adjust timing, 3) Adjust rocker valve gaps, 4) Change oil, 5) Check compression, 6) Start up bus and drive off into the sunset.
I found the belt I needed at NAPA; they had the exact 10x905mm size I needed, Yay! However, when I loosened the generator pully, I noticed that, of course, my engine only has 6 shims instead of the 10 that it should have. More shims means wider pully gap, which allows for a smaller belt. I would have needed at least 8 shims to handle the new belt, so instead I kept the old one and removed some shims to tighten it. Its not perfect, but is definitely not as loose as it was before.
Adjusting the timing was actually very easy, and didn’t really need done. I found the notch in the crankshaft pully indicating top dead center (TDC). Because I have a 009 centrifugal distributor, I know that 7.5 degrees before TDC is when cylinder #1 is in firing position. I made a pencil mark at this point, and when I flipped the key in the ignition, the test light light up bright – the engine appears to be properly timed – a good start to this tune up!
I then started adjusting the rocker valves. There are two sets (one for intake, one for exhaust) for each of the 4 cylinders. At a point in the crankshaft’s rotation (TDC for cylinder #1), each respective valve set is fully extended. A tiny gap should exist between the rocker arm and the intake/exhaust valve. The gap needs to be .006 inches, and its my job to turn the adjusting screw and locking nut until this gap is right. To much gap and the rocker arm will slap against the valve head, causing a tickty-tock sound and eventually damage to the valve assembly. Not enough gap, and the valves could stick, potentially causing massive internal engine damage.
My valves didn’t have any gap… at all… they were essentially fused directly to the valve heads – this is not good, and it makes me wonder if the previous owner knew what he was doing. I’m worried now that the inside of the engine is somehow messed up, or burnt out. I spent money for a bus with an engine that actually works; if i wanted a rolling shell I would have bought that instead, and paid a lot less – I guess I’m learning more than just mechanical lessons today! Ok, enough of my ranting – I adjusted each valve set to the proper .006″ gap (it took me all afternoon!).
At this point, I’m ready to change the oil, but need to warm the engine up first. Small problem, it doesn’t start! It turns over a few times, but then dies off. As my frustration built, I kept trying the ignition. Finally, I turned the key and had almost immediate ignition. Success! My newly tuned engine seems to run well; it does sound different now that the valves are adjusted, and the tighter fan belt seems to be helping. My generator light is still on though, and when I revved the engine for a while, it died as I released the gas. I also noticed that the crankshaft pully has significant resistance as it rotates cylinder #3 and #4. I’m thinking this is why it wouldn’t start, and could be really bad. Sounds like I have more issues to research! I’m planning on changing the oil, and performing the compression test tomorrow. I’ll probably check the valves again too.
Overall I’m glad the day went well. I’ve never so much as looked at a car engine before this, and today I went in head first, got my hands dirty, and had a great time fiddling with the bus. It’s not road ready yet, but at this rate it will be soon!
