Building a zero-hour F engine
If you’re only going to rebuild an engine every 20 years or so, you might as well do a thorough job. That’s been the guiding principle for both me and my master Toyota mechanic and friend Bill Lee, as he disassembled and inspected the six-cylinder F engine and transmission of my FJ40 (see this post for background). Actually it wouldn’t have mattered whether or not it was my guiding principle—Bill would have refused to do it any other way.
The engine had been showing distinct signs of power loss, although oil consumption was not unusual. Teardown revealed one certain cause: the camshaft was badly worn, and on a couple cylinders was clearly not producing much lift on the intake valves. Bill’s explanation for this was illuminating. Apparently on start-up of an F engine, the cam is the last part to receive oil from the pump. Generally this is no problem as residual oil provides plenty of lubrication—unless the vehicle is parked for long periods, in which case the oil will drain away from the cam lobes. The cam will then be without oil for the first 10 or 15 seconds after starting. And—surprise—for several years my FJ40 has seen long periods of idleness while we were traveling overseas, using the Tacoma and Four Wheel Camper for journeys in North America, and putting miles on various long-term review vehicles. Shame on me. (Bill suggested changing to an oil from Joe Gibbs Racing that displays cling properties superior to standard oils. And driving it more.)
Once Bill had the engine disassembled entirely, he called and we had a chat. The cylinders were in excellent condition, still within specs, even still showing factory cross-hatch honing marks. The pistons came right out, Bill reported—no wear ridge at all.
However. The bores showed vertical scoring, and Bill and I were pretty sure where this originated, as I’d discovered a surgical-strike rodent intrusion in the air cleaner last year, the cleaner itself chewed through and remnants of comfortable rodent accommodations in the housing. I cleaned everything out, but it’s likely some debris had been sucked into the engine in the meantime. (Mystery: After the incident I put hardware cloth over the opening, but Bill found the air cleaner chewed again. Either one got in during the day or two before I installed the screen—likely—or I had the Harry Houdini of mice.)
The consensus from the machine shop was that the scoring could not be completely honed out while keeping the bore stock, so we decided to bore the cylinders and install new pistons, Japanese-made units from ITM (Toyota pistons are no longer available for the F engine).
The main bearings were in good shape, but given the need for machine-shop work anyway we decided to turn the crank and install one size over bearings. Bill also suggested balancing the components—not a huge deal given the inherent primary balance and even firing order of an inline six-cylinder engine, but every bit helps. The machine shop matched the weight of all the connecting rods to the lightest one by judiciously grinding away material on the caps. (Hey! Less weight means more horsepower!)
Meanwhile, the head has been given a valve job, and equipped with new OEM valve guides and springs—which Bill had to source piece by piece from several dealers around the country. Factory parts such as these are becoming more and more rare. The replacement cam is an aftermarket item; however, it’s a brand Bill has used before with good results. The lifters as well are aftermarket Japanese manufacture. (The last few new OEM F cam/lifter sets sold for near $1,000; this set totalled about $400.)
What else? Bill wisely recommended replacing the oil pump, even though it was working fine. Toyota no longer makes the F oil pump, but the (improved) model from the 2F is still available—however, installing it requires a 2F oil pan as well, so that is in hand. New OEM timing gears will ensure precise cam timing.
Once everything is put back together (with a one-of-few-remaining factory gasket kit), we’ll have an essentially zero-hour engine. It should in fact be better nick than when I bought the vehicle from its original owner in 1978, with 24,000 miles on it.
The header was in good shape, and so ceramic-coated for re-installation.
Next up for attention will be the H41 transmission and transfer case.
