I recently finished rebuilding my engine. I have a 1.7l case. I have had a fairly significant oil leak. If I run the engine for about 10 minutes, I will get about a 10cm puddle of oil on the passenger side of the case. It was pretty easy trace where the oil was coming from. I ruled out all the routine leaks, pushrod seals, etc. I was able to see that a decent amount of oil was coming from the bolt hole in the case where the engine tin attaches (hard to explain so I took a picture, it was an old picture of my carbs). I am pretty sure it is from that hole however since the tin is in place I cannot be 100% sure. Apparently, the PO stripped the hole and tapped it with a large size because the normal size tin screw is too small. The bolt fits fairly snuggly. I even put a small amount of RTV on to seal the hole however I am still getting a decent amount of oil seeping from around the hole. It seems like an odd location for an oil leak.

I really don't want to take the tin off to see if the the leak is actually coming from somewhere else in the area. Is there anything else in the area that might leak? I really think it is seepage from around the bolt in the picture. Any ideas on how to fix the problem, why I am having this, etc.

You're going to have to take the tin off to find out.

Yep, take off the tin and see. It shouldn't go all the way thru the case but if it does due to the PO retapping it then you'll have to seal it after cleaning it good.

The reason that I didn't want to take the tin off was because I have been working on my car for 3 years and my goal was to have it ready for an upcoming car show. Oh well, I guess I gotta do it.

Is it easy to take off the mentioned tin piece with the engine in the car? I have always done it with the engine removed. If I can do it with the engine in, then I can probably still make the car show.

yeah not hard to do, specially sinced you dont have the stock manifold runners to remove. you probably need to remove the carb manifold, other wise the top tin is easy to remvoe even with engine in the car. you might be amazed at how much junk gets sucked by the fan and clogs up the cylinder / head cooling fins.

also check for leaks at the cylinder/case interface.

there is a UV light glowable dye that can be safely added to the oil to help find leaks with a balck light. consider that before you tear the tin up, cuase you'd want to run the engine a bit after adding the dye, then shut down and inspect with a black light

That's a blind hole. At least it was when the engine was built. In the 1.8 case it's a 10 x 1 mm thread, in the others it's a 6 x 1 mm. Even if it were drilled through, any oil reaching it would have to be thrown against it by the movement of the crankshaft. I suggest you pull the screw/bolt and take a look in there before removing any tin. If indeed it goes all the way through, You could slightly lift the tin and carefully enlarge the hole in the tin, then drill and tap the hole in the case to one easily filled with a new bolt. Use a greased drill bit and tap in order to collect the shavings. Clean the hole well and seal the new bolt threads with a good plumber's sealant or blue Loctite.

The Cap'n