Bus Engine Rebuild – Part 2

This weekend I started putting the engine back together, and I’ve decided to replace a number of parts:

  • Camshaft – A few of the lobes were worn down, limiting valve lift. Replaced with a very mildly modified cam that will provide more power to go along with the new higher transmission ratios.
  • Lifters – Lifters had worn slightly concave rather than the correct slightly convex.
  • Connecting Rods – All rods weighed the same but were not balanced end-to-end and there was not enough material left to grind off and correct the problem.
  • Bearings – The bearings were OK but it’s easy enough to replace these while the case is open.
  • Pushrod Tubes – These could have been reused but were a little beat up and now is an easy time to replace, ensuring no leaks.
  • Oil Cooler – The old cooler was made in 1971, no telling how much build-up there was inside preventing heat transfer. Replaced with a larger cooler from a later engine style.

It’s mostly reassembled now, including shimming the crank/flywheel for proper end play and verifying with a dial indicator to 0.001″ (end play is critical on aircooled VW’s). I also modified the fan shroud to accept the bigger oil cooler and also re-built the thermostat. The thermostat is a sealed copper accordion that expands when heated. For some reason mine had expanded permanently; these are no longer made and becoming increasingly rare, so I had to fix it. Luckily I was able to find information about others who have had the same problem and I was able to fix it in the same way; the fix consisted of unsoldering the end plate, compressing the accordion, dropping in a bit of rubbing alcohol, and resoldering the plate before it had a chance to evaporate. The thermostat is now completely contracted at room temp and begins to expand around 80°C, allowing it to push on a linkage that opens cooling flaps in the fan shroud.

The new bearings are “structurally guaranted[sic]”, hopefully that’s just a typo and not a clever way to dodge claims – “they weren’t guaranteed, they were guaranted

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