Before the early 1980's, Toyota 20R and 22R engines had a bulletproof, over-engineered timing chain system. This included a heavy-duty double-row timing chain damped by a thick layer of rubber on a steel backbone.

Around the 1984 model year, presumably to cut costs and squeeze a little more power from the mill, Toyota switched to a single-row timing chain and hard plastic chain guides. These guides frequently break and pieces of them fall into the oil pan. Aftermarket replacement chain guides have until now followed the plastic Toyota design, but have an even worse reputation for breaking.

Once the guides break, the chain begins slapping against the timing chain cover, resulting in the all-too-familiar rattly "diesel" sound you hear from many older Toyota 22R and 22RE engines. At this point, you're living on borrowed time. Uncorrected, one of two really bad things might occur: The first is that it will actually eat through the timing chain cover (typically on the driver's side) and into a cooling passage.

(Click the photo above where you can see where the chain was digging into the cover. Fortunately, the guides is this engine were replaced before massive damage was done.) Suddenly you get a gallon or so of coolant into your oil, which can trash bearings and cause all other types of havoc within, possibly destroying the motor. The other eventuality is that before the timing chain manages to chew through the timing cover, the timing chain gets 'sharpened' by the rubbing, and eats into the tensioner.

Eventually it cuts deep into the tensioner, binds, and breaks. The 22R and 22RE are intereference engines, meaning the valves (when open) take up the same space that the pistons do at TDC. With timing gone, the pistons clobber the valves. Say farewell to the engine! Chain failures of this type are virtually always preceeded by a failure of the guides.

Until now, those with single-row timing chains wanting a more reliable timing chain setup had to retrofit a timing cover, oil pump, water pump, and oil pump drive spline from an early 20R/22R engine, along with a timing kit for the earlier motor. While these are all bolt-on parts, collectively they represent a hefty investment. What was really needed was some tougher chain guides.

DOA Racing Engines of Lakewood, CA, has introduced a solution. They now offer tough metal-backed timing chain guides for single-row 22R and 22RE engines.

My engine had been making the rattly noises recently, after only 25,000 miles on the current timing set. I popped the valve cover and peered into the timing cover and was astonished at what I saw - both the driver's and passenger's-side chain guides were broken.

The driver's side one was barely there at all - the bolts that hold it to the block were holding only a tiny piece of the plastic flange used to mount the plastic guides. The bearing surfaces of the guides themselves had long taken the dive into the oil pan.

Fortunately, I caught this problem before the cooling system was breached, saving myself a much more expensive repair bill. So I called up Tim Jenkins of DOA Racing Engines and asked his opinion. He explained this was very common and was a weakness in the design of the plastic guides. So after a long conversation, I ordered a full timing kit from DOA, including the new guides.

My first reaction when opening the package was "Wow, I won't ever be fishing these guides out of my oil pan." The metal is impressively thick along the entire length of the guides, to which is bonded a generous amount of hard rubber. The rest of the components in the kit were quality Japanese-made Sealed Power/Federal Mogul parts. In addition to the guides, the complete $201 kit includes the sprockets, chain, tensioner, front crank seal, and timing chain cover gaskets.

Installation is no different than any other timing chain job. Its an involved process that can take many hours. For more information on the procedures, check the Toyota 4x4 Mailing List Archives.

Performance

Replacement of the guides has certainly cured my engine of the rattling noises! Timing is much easier to set too - before I replaced the guides, the timing marks would jump around under a timing light. Now the marks are aligning perfectly.

With only a few thousand miles on the set, I can't speak to their ultimate longevity, but since the construction is so much stronger than any other available single-row guides, I am confident they will outlast the rest of the engine. DOA is so sure of it that they offer a guarantee for the life of your motor.

Conclusions:

This is a no-brainer - if you are rebuilding, due for a new timing chain, or your existing guides have broken, I wholeheartedly recommend using these guides to improve your engine's reliability