TheSamba.com :: View topic - Engine Case identification

Sun Aug 17, 2008 11:23 am

I went out today to measure the deck height on an engine I'm building and got a bit of a surprise. First a bit of history. I had originally planned to use another case when building this engine, and had done all of my initial mock up and checking with it. I ended up needing that case for another engine I needed to put together. When I got the current case I checked all the internals and did a mock assembly, but didn't check the cylinder bores because it was a stock engine that had been pulled apart and didn't appear to have been cut so it didn't really cross my mind. The short block went together fine with no surprises. That brings us to today.

I went out today to measure the deck height and the cylinders wouldn't fit into the case. They cylinder was too big to fit into the hole in the engine case. First thing I checked was to make sure it wasn't a 90.5mm cylinder or something I picked up by mistake. Nope, stock 1600cc. Next I looked at my case to make sure it was the case I thought I had used (OK, it was a long shot, but I am an idiot now and then). Yep, same dual relief, large oil passage AS41 case I knew I had built it with. No gremlins or senility there :)

So at this point I've only been awake a bit so I sit down on the Samba to do a bit of checking and make sure I'm not just still asleep. After some searching it looks like there are dual relief 40hp cases out there that were replacement cases. Mine seems to fit the description; it has the recycle symbol, the D, and the X at the end of the engine number. That solves that problem. Sort of.

It seems that every set of pistons and cylinders I can find around my place swim around in the holes in the case like a gold fish in an olympic swimming pool. I have some NOS P & C I was sold as 40HP, but after looking at them today they look more like 1300 ones with the larger wrist pins. THese are way too small for my case it seems. Dug around the shed and found some that were 40HP to the best of my knowledge, and they are small too. I'm going to see if I can find a 40 engine case for comparison, unfortunately most of mine are on the other side of town at the moment.

So the question is, what is the size of the case bore for the cylinder for the following engines?

40HP/1200?
1300?
1500?
1600?

Based on my searches here it sounds like 1500 and 1600 were the same on the case size, and the number I have for that based on a couple of cases is around 90mm. The case in question has holes that are more like 87mm.

So what am I missing here? I currently have a case with a 69mm stock crank and 1600 rods installed. Cam and cam bearings, unlike early 40HP, so I didn't get tipped off there. It sounds like I either need to get some 40HP pistons and cylinders, and 40HP heads, and then swap out the rods, and I'm assuming the crank as well. Alternatively, I've also heard people mention machinging down 1600 cylinders to fit the case. That sounds like an interesting option, but I don't know the feasibility of that from a reliability standpoint, and don't know what else is required as far as other things that are needed for that update.

I'd really like to avoid tearing the case down again, either to replace the crank or to open up the case for the 1600 cylinders*, but don't know what options I have. I'd love to figure out how to make it a stroker 40HP or whatever by leaving the 69mm crank and putting 40 horse cylinders on it, but I know the rods would not work for that setup. Any suggestions or advice?

Thanks,
Richard

*Yeah, I know you should do a dry run and mock up everything together first so you know what machining you need before you put it together, and I did that with the first case, and did that with everything on this case except for the cylinders. Who would have thought what looked to be a standard 1600 case would have been something weird. I certainly will watch out for that next time.[/i]

Sun Aug 17, 2008 2:53 pm

88 machine ins

Sun Aug 17, 2008 3:12 pm

Wouldn't 88mm pistons need a hole in the case larger than 87mm? It is the actual hole in the case that is 87mm, not the piston.

I was actually able to find one 40 HP case in the far back corner of my shop. Best I could tell from measuring it while crawling under the work bench was that it was close enough to convince me that my case is indeed a 40 horse replacement case. That still leaves me with the question of how to proceed with this. I'm curious about the option I saw of machining down the cylinder outer diameter to fit, and also with options for using 40 HP pistons and cylinders in some configuration. Or should I just I just pull the case back apart and start looking for a 40 HP crank and be done with it?

Sun Aug 17, 2008 8:23 pm

I've found a 40 horse crank, rods and pistons, so have decided to do what is probably the right thing and tear the thing back down and start over. Thanks for all the help :)