tjacobson01
Member
- Joined
- Jun 23, 2013
- Messages
- 13
My experience putting automotive 4G32/G32B engine in 742B. I recently purchased a nice 742B with 1400 hours for cheap, where the 4G32 Mitsubishi engine had spun a big end bearing (a fairly common problem I understand) and the No. 1 rod went through the block. (BTW, it still ran! The No. 1 piston was stuck at the top of the cyl, we ran it to load it on the trailer… LOL. ;-) Since a refurbished 4G32 engine with no core to trade in (my core and crank was ruined) runs upward of $3.5K to 4K, I decided to try to use an automotive block. Here is what I learned during this project. It looks to me like the 4G32 industrial engine used in 90's vintage Bobcats (642B/742B) is based on the late 70's early 80's timing belt version of the RWD 4G32 automotive engine, also called the G32B in some versions (Note pre 1977/8 versions had a gear drive cam shaft, that wont work). There are two major versions of the 4G32/G32B engine, one with "balance shafts" and one without, and it also comes in a FWD transverse version that has different mounts and would not work. I used a the RWD balance shaft version of the G32B engine typically used in a early 80's Dodge Arrow/Challenger/Colt. and had to go through all sorts of monkey business to do it, as outlined below. It is worth your while to find a 4G32/G32B block that does not have the modified casting to support the balance shafts and uses the same oil pump as the industrial 4G32 in the Bobcat. (Note: some rebuilders remove the shafts and call it a non-balance shaft version, you need the one without the casting changes to the block.) - Had to move the starter about an inch further around to clear the balance shaft housing. Did this by using a jig saw to cut out a half moon in the existing hole and welding it to the other side of the hole and grinding flat. Use a dial-indicator to get it exactly right, and check bendix gear clearance at flywheel with some .020 wire, as if the bendix jams, you will burn up your starter and battery as it will hold the solenoid on…. - Had to move one of the counterweight plates under the oil pan forward a bit by drilling new 1/2 in holes in it to clear the oil pan. - Automotive oil pan uses different thread, so could not use the drain hose. - Governor bolts right up. - Had to cut one or two small ¼ in. notches out of other engine mount plates due to small differences in casting, but all major bolts were otherwise in alignment and same size. Flywheel area engine mounts were exactly the same, and flywheel flange was the same. - Had to reuse my original Bobcat head, as the automotive head has goofy MCA valves, higher compression, probably different cam shaft grind, and also older timing belt tooth shape (square vs rounded tooth on newer belts). - Balance shaft version uses different oil pump, so had to find different oil pump sprocket with newer style teeth for timing belt, and use timing belt for newer style balance shaft engine that has two more teeth and new style tooth shape. (Contact me for the Mitsubishi p/n for the belt and sprocket if anyone is foolish to use a balance shaft version of this engine like I did) - Reuse the Bobcat crankshaft timing sprocket and spacer. - Had to make a little 1 in. bracket for the alternator casting as one bolt is different. - Had to cut the timing belt cover plastic a bit. If you rebuild an automotive engine for your Bobcat 642B/742B, suggest you try to use the industrial engine pistons, they are a bit lower compression (not too much different, but once you mill the head, it all adds up). Anyway, using the non-balance shaft block is the way to go, and s/b a direct fit and almost identical to the industrial engine block. Not sure how many of the non-balance shaft versions were made/sold in the US. Suspect they may have been used in compact pickups, but that most auto versions had the balance shafts, which are, a big pain. (The balance shaft idea is patented by Mitsubishi, and the only other manufacturer to use it is Porsche!) If I had to do this over again, I think I would look into using a modern replacement crate engine that has an electronic governor, s/b fairly easy to figure out the drive coupler and cooling connections I would think, and worth the effort. T.
