My slightly nicer but also terrible Bobcat (742B)

[Scott Cee AKA 2drx4]

Timing belt tensioners:
POST EDITED BECAUSE IT WAS WRONG!

The used one is OEM Bobcat. The new one is a Gates T41055 for the Dodge Colt. In the tracing the black is OEM Bobcat, blue is Dodge Colt. I positioned them as a bit of a guess, but that's basically where the slotted holes intersect at previous tension, and the pulley is in the same place. Pulley diameter is the same, flange is a little different but close enough. This is not as simple as trimming the Colt one and drilling a new hole. It might be easier to drill/grind the pulley standoff so it is freed from the bracket, then install it on the other one with a countersunk bolt or similar. That is a gamble, Bobcat wants $903 for one of these tensioners, and the one I have is a bit rough but I might be able to grease it and have it be okay for a long time. I am undecided on what to do with this.

When I first looked at this I thought "Drill a new hole, trim it, bam", it's a good thing I actually traced it to check. I don't want to add to the massive amounts of absolute garbage "information" that is out there about these engines.

Allegedly the timing belt is the same length, but uses a different profile. I am tempted to order a car one to compare, but in the pictures it looks like it uses the sharper tooth profile versus the more modern rounded pattern that Bobcat used. The belt is available from Bobcat and not as absurdly priced ($88, still absurd, but yeah).

[Scott Cee AKA 2drx4]

I'm still having major issues with parts for this. The machine shop ground the crank before verifying they could get bearings. It's now ground to a size that there is no bearings available in. I ordered sets of both car and forklift bearings, and a set of forklift pistons and rings, and I'm hoping out of that we can make it work and just grind the crank again. Nobody actually knows if the car bearings are the same, and one would assume the forklift parts should be, but we can see how well assumption is going with this. I also hope the pistons I ordered actually exist and aren't an inventory mistake.

I did try to buy another timing belt tensioner and timing belt. Mixed success. These were listed as being for an 1989 Colt DL with the 1.8L, and they do not cross over to the 1981~ with the 1.6L.

Timing belt tensioner is exactly the same as the 1.6L Colt, so it is not correct:

Pictured on the tracing from the other one, with the genuine Bobcat one beside it. So I guess I now have two that I can try to modify. It's interesting that the P/N didn't cross to the 1.6L Colt one, when they are literally the same. This is ITM P/N 60107, and I'll repeat for the random Googlers, it does not work in a Bobcat 4G32.

Timing belt however is the same as the Bobcat part:

It was listed under ITM P/N 4105, but the belt in the box was made by Mitsuboshi. I had to Google that, they're legit, and have been making belts in Japan since 1918 or something. I'm guessing CD93 is their P/N, maybe also the Mitsubishi P/N. The Bobcat P/N is visible on the other belt, 6632772. And yes, I checked to make sure they are the same, both are 120 tooth and use the rounded/sinusoidal cog profile that is pitched the same.

Where the timing belt tensioner comes from is still a bit of a mystery. I do not think it would be likely that they cooked one up just for Bobcat, but maybe they did.

[arse_sidewards]

I would cold email some support rep at some timing components company asking for advice.

Tracking down a dumb mystery like this is a lot more fun than the average mundane bullshit and someone who stares at timing components all day long can probably just tell you what it's for or be damn close just by looking at it.

[Scott Cee AKA 2drx4]

I would cold email some support rep at some timing components company asking for advice.

Tracking down a dumb mystery like this is a lot more fun than the average mundane bullshit and someone who stares at timing components all day long can probably just tell you what it's for or be damn close just by looking at it.

Good point. I did order one more that think might be right, based on the pictures, for a 1989 Colt GT 1.6L Turbo. It also doesn't cross the P/N to any of the other ones, so maybe. If it's wrong I'll probably start emailing all of them to see if anyone knows.

I do have a theory that the industrial engine uses the low compression pistons from the turbo engine. The ones for the N/A version definitely look different, and I have been told that they are not the same. That said, I can't buy pistons for a turbo engine anywhere, and the only N/A pistons in stock were nominal size, so it's pretty irrelevant. I'd love to buy both of them to compare, just so it would be known, but I'm not going to bother to buy a set of nominals knowing I definitely can't use them for anything.

[Scott Cee AKA 2drx4]

Forklift pistons didn't fit at all. Way too small. I don't have a Clark forklift parts manual so I don't have much to go on. The retailer listed them as being for a 4G32 but I don't buy it.

Also, the machine shop may have broken or lost the pistons that were in the engine. When I went there with the forklift pistons to compare them we couldn't find my original pistons. So yeah. Great.

[Scott Cee AKA 2drx4]

I found what the timing belt tensioner is from:

1989 Colt GL with the 1.6L Turbo. I'm not sure on what the right P/N is, but I ordered it off Rockauto under P/N 0241090:8. It was the last one and cost $5. A far cry less than what Bobcat wants. Now, there may be no more from now on, but at least I got one that works and don't have to mod anything up.

This one is not right:

This was for a Clark forklift. P/N was 3779939. The forklift timing belt was also the wrong profile. Now, I am not sure if this means there isn't forklift parts that work or not, looking at the pistons they sent me I believe they are for a 4G33, which is not the same.

[Scott Cee AKA 2drx4]

Finally got the block and head back, along with pistons that probably are good. Yes, from the turbo car, as I speculated.

Bare block:

Crank in:

I forgot to grab ring pliers and a compressor, so didn't put the pistons and rods in yet.

These bearings didn't fit:

Those were the forklift ones, but again I suspect they're for a 4G33, they're real close but the thrust bearing jammed on the crank. They also could just be garbage parts. The 4G33 crank bearings *should* have been the same.

These bearings fit:

ITM P/N 5M1147-020. They were listed as for the 1981 Dodge Colt with the 1.6L.

I got some other stuff together but I'll take more pictures later.

[Scott Cee AKA 2drx4]

Slowly putting crap back on:

Pistons comparison:

We found these pistons by looking for pistons for a turbocharged Colt, but they may or may not show as crossing to that, the box of them lists them as being for the Mirage. The Mirage should be the same, but who knows. They look very much the same, and are correct in the dimensions that are needed. Also, the pins are pressed into the rods on these, so I had the machine shop do that because I'm not sure what you use for a fixture to not mangle them.

P/N of pistons:

P/N is SP-902-3. Lists as for 85-86 Mirage with the 1.6L Turbo. As you can tell, they've been sitting on the shelf for a while. How long this stuff will be available for is debatable.

Rings:

Ring P/N used is 2C675030 (or something like that, 2C675 is the P/N, plus the 030 oversize). These are for the 81 Colt with the N/A engine. This is what the piston supplier spec'd, but it is NOT what the 86 Mirage uses. The Mirage lists as having thinner rings. These rings fit, so I believe they are right, it may be that these pistons are updated with larger rings, or something. I do not know.

Pistons dumped in:

My Amazon special ring compressor tool was garbage. Hopefully nothing broke doing it, getting the oil control rings to go was dicey. But the pistons moved nice after, soooooo.

Head needs some assembly:

[Scott Cee AKA 2drx4]

Other random comments:

-The ring gap with that ring kit was fairly wide, about .021". Spec in the Bobcat OH manual is .016" on the fat side. I don't care, better it's too loose than too tight, but I'm not sure exactly why this is, other than perhaps that is the spec for the turbo engine.
-Certain Mitsubishi Mirage may use the correct timing tensioner too, 1986 with the 1.6L Turbo lists a BECK/ARNLEY P/N 0241090 and SKF P/N TBT75101 that look right. There is no stock on either in RA, and I'm not about to go looking for them right now. All of the other ones listed do not look correct, they appear to be the other style. Perhaps somebody who knows Mitsubishi cars would know why they offered two styles. They also appear to use the same timing belt as the Bobcat, or some of them do.

[Scott Cee AKA 2drx4]

Head back together and on:

I need to strip the paint off the oil pan and get some freeze plugs, otherwise I think I'm set to assemble everything else.


Merry Christmas everyone!

[Scott Cee AKA 2drx4]

Got a little closer to assembled:

I've wasted a ton of time on the paint in the oil pan. Probably won't get this finished tomorrow, so it will wait a week.

[pointsnorth]

the bigger ring gap is for a turbo application for the higher temps it will experience

[Scott Cee AKA 2drx4]

the bigger ring gap is for a turbo application for the higher temps it will experience

Yeah, but these rings are for the N/A Colt engine. The turbo engine lists a different P/N. The only reason we used these rings is it's what the piston supplier said to use (and provided), even though they're not listed as fitting a turbo Colt or Mirage. I think they just started to make one set of rings for the whole family of Colt engines, and I bet if you buy the ones listed for the turbo engine they will be the same but in a different box. That is, with the exception of the actual turbo Mirage rings, which are thinner, and would not fit these pistons that are listed for a turbo Mirage.

My point really is that it's unclear what is going on, but this P/N works. This also might not matter, because that might have been the last set of Mirage pistons in the world anyway.

[Scott Cee AKA 2drx4]

I got all the paint out of the oil pan, and cut the drain hose shorter because it's rotten:

It's a 5/8" banjo barb fitting thing, so if it still leaks I can find some different 5/8 hose or whatever. It's a weird way to do it, but that was factory.

Oil pan gasket didn't fit worth a crap:

I guess it's been sitting on the shelf for a long time. Eh, I'll rip it back apart in a week and just RTV it. It also isn't really right, there *may* be a difference in the oil pan shape with the engines that have counterbalance shafts. Or something.

[Joe_the_ice_man]

I recall a good portion of John Deere lawn and garden equipment has a similar system for remote oil drains, but they use NPT rather than a goofy banjo bolt.

Maybe it's an unpopular opinion, but as long as the oil pickup has a screen, RTV for the pan is fine as long as you dont go crazy. And honestly, the grooves in the pan look like it was made for RTV.