RV "Tune-Up" Update
The Toyota Sunrader RV is now back on the road, running better than ever, but it sure took a lot of long hours and midnight oil to get it there! The original problems were two-fold, a top end rattle, and it wouldn't run below 1/4 throttle. I decided that ,even though it was a lot more work and expense, to pull the engine and go through it from the crank up. That way, I would know exactly what I had, and I should be able to rely on it for a long time without any major problems. After pulling it apart, other things needing attention were also discovered, including a clutch disk and pressure plate nearing "End of Life".
The rattle, which sounded a lot like a collapsed lifter, except with the Toyota overhead cam and rocker arms, there aren't any hydraulic lifters. The rattle turned out to be a piece broken out of one of the cam chain guides allowing the cam chain to hit a bolt head nearby. Curing the lack of idle took a very thorough rebuilding of the carburetor, including cold tanking the major castings and compressed air. The front main seal was just starting to leak a bit, so both main seals were replaced. I ported the cylinder head a bit, but nothing major, basically just matching the head and manifolds to the gasket. I also cleaned up a bit under the valves, and took out a bit of casting roughness here and there. One of the things that took quite a bit of time was to individually wire brush and clean every single bolt and nut, and then use anti-sieze compound on all the threads when re-assembling. I learned a long time ago that whenever you throw something back together dirty assuming you will never have to take it apart again, you will truly regret not taking the time to clean the bolts and threads. You WILL have to take it apart!
I replaced all of the rod and main bearings, and the crankshaft looked better than a new one as it's journals were polished like chrome, and not a single score to be seen. The cylinders had absolutely no ridge at all, and a ball hone made them look like brand new. I used Perfect Circle chrome rings, so compression should stay up there for years and years.
In a comment to the previous post, Phil suggests the Weber carburetor conversion, and that is definitely on the list for future upgrades. Headers would be nice, but the stock exhaust doesn't look that bad, although it's pretty heavy, being cast iron. It looks like Toyota did some dyno work on the stock headers, as it goes from four to two, then the two don't merge into one for another foot or so.
To finish off the job, the stock rusty brown engine block was cleaned and degreased, then given a nice coat of medium gray paint. It's now much easier to keep clean, and it looks pretty good, too.
I've now put about 150 miles on the engine, changed the oil, and re-adjusted the valves. It runs like a sewing machine, but I'll feel a whole lot better once I get 500 miles or so on the clock. Saturday morning we head to Sherwood, Oregon, just South of Portland, for the big Man of Steel match, so keep your fingers crossed for us!