I needed to replace the water pump and the lifters on my Jeep TJ. The lifters are quite involved, since you have to remove the head from the engine. I decided to do this job in the winter, since I don’t typically drive the Jeep in the winter and it wouldn’t matter how long it was torn apart. Boy am I glad I did.
While the engine was torn down, I decided to replace a bunch of other maintenance items: radiator, radiator hoses, heater hoses, and the timing set (chain and gears). I had ordered some of the parts back in the summer, so that I knew I would have what I needed on-hand. This summer when I replaced the oil pan gasket, I could access the timing chain and I noticed it had quite a lot of slop in it. They are known to last upwards of 300k miles in this engine, but it was easy enough to replace it while I had everything else torn apart. Or so I thought.
My good friend Joel was a valuable second set of hands for the entire project. We encountered some minor difficulties with the other items on the list. For instance, I could not get the lifters out with a magnet because they were stuck in their bores. I scrambled and bought a tool to get them out, but the tool was garbage. Thankfully, my neighbor had a much better version of the tool and let me use it. We got the head reinstalled and were making great progress. I decided to tackle the timing set last, as I expected it to be fairly straightforward. After all, it is just two gears and a chain.
The old timing set came off without incident. I grabbed the new set and slid the small sprocket on the crankshaft. It got stuck and would not slide on.
You can see in this photo that the crankshaft has two keys on it. The outermost key is for the harmonic balancer, and the inner key is for the timing gear. The new gear was binding on the inner key and would not slide back against the engine block. I took the gear off and inspected it. No burrs or other crud in the keyway that would prevent it from fitting. I inspected the key on the crankshaft with the same result. I took the old gear and slid it right back on the crankshaft without any resistance. I compared the two gears and they looked nearly identical, but clearly the keyway on the new gear was narrower. I grabbed a set of digital calipers and measured the keyways. This was more difficult than I thought, because the shape/size of the keyway makes it very difficult to get calipers inside for measurement.
The original gear keyway measured about 0.1890″.
The new keyway measured about 0.1850″.
The crankshaft key measured 0.1880″.
The new gear was clearly too small. I called Cloyes (the manufacturer of the timing set). They were able to give me the spec for that keyway, which was 0.1885 – 0.1910″. I grabbed a file and tried to open up the keyway a bit. The gear appeared very hard, and the file didn’t seem to have any effect, so I stopped. I called Cloyes back and let them know that my gear was out of spec. The tech had someone measure the gears they had on-hand and they were all also undersized and out of spec. They didn’t have one gear that was within spec to ship to me. Since I bought this timing set back in August, there was no way I could return it now (January). I decided to try to file it again.
Out of the arsenal of files I have in the toolbox, only about 5 of them fit inside the keyway and were aggressive enough to attempt to remove any of the steel. I spent about an hour with the gear in a vice, putting a lot of weight on the files trying to remove any material at all. I managed to get the keyway to open up to about 0.1855 or 0.1860″, but that was not enough. Frustrated, I began my search for a replacement.
I wanted to find another brand, to try to avoid getting another out of spec gear. I called every local auto parts store, and all of them only carried Cloyes timing parts for the Jeep. I went on Rock Auto and ordered a Melling timing set, and another Cloyes sprocket (just the sprocket was pretty cheap) just to see if I could get lucky. If the new sprocket fit, I could return the Melling set and save some money. They arrived a couple days later. The Cloyes sprocket was identical to what I had, and measured the same, so it did not fit. No surprise there. I opened the Melling set, and to my surprise there was a Cloyes set inside the box. Apparently Melling just rebrands Cloyes products in this case. This gear was also out of spec and did not fit. For those keeping score at home, I now have 3 identical Cloyes timing gears, and none of them fit.
Frustrated, I began another online search for alternative brands of timing sets for this engine. Most of the sets I could find were for the earlier model of this engine with a different type of camshaft sprocket (the larger sprocket). You are supposed to install these as a set, and not mix and match new and old gears or gears from different sets, as the gears and chain wear together. I eventually located a Comp Cams timing set on Summit Racing, and ordered it. I paid for overnight shipping because I just want to be done with it at this point.
The Comp Cams timing set arrived the next morning, and I could not resist a quick test fit. The gear slid right on the crankshaft, with virtually no resistance. Victory!
The Comp Cams sprockets are cast instead of milled like the Cloyes unit. They definitely aren’t as nice, but they fit and I’m rolling with it!