castle nuts between cylinders 2&3

[classicnvintage1]

Hello,

I'd appreciate a bit of advice please. There are two castle nuts in the space between cylinders 2 & 3. Before stripping down to get at them, I thought I'd ask your help!. It looks like the one on the inlet manifold side is leaking oil. I can't see a split pin in place, but I presume there should be one. Will I be able to get at it from the side to tighten it up? Any idea on size?

Len

[Dan Hatch]

Main bearing bolt sounds like to me. If so not tighten up can you unless hold the bolt in bottom. Dan

[Norman Kling]

The head of the bolt is on the center main bearing cap. You should have an inspection cover under the engine. Remove that to find the head of the bolt. By the way, if that bolt is loose, you might have a main bearing knock. And if it is tight, your leak could be coming from the hole in the center of the block where the fuel rod goes through. There will be some oil in the valve chamber and if you have blow by, some of that oil could be coming through there. I don't know of any way to fix that unless the drain holes inside the valve chamber are full of sludge, which could cause the level of oil to rise inside. To find out whether that is the case, you will need to remove the plate on the side of the engine below the manifolds. The other bolt which holds the main cap is inside the valve chamber. If you take off that cover, check for a cotter pin there also.
Norm

[classicnvintage1]

Thank you guys, very helpful.

Len

[TonyB]

Some early blocks were missing the two drain holes in the valve tappet area. If that’s the case as it was one one my customers 1914 car, they can be drilled thru the bottom with the inspection pan removed.

[classicnvintage1]

Thank you again. I'm now ready to tighten these nuts up. It turns out both are very loose, probably because they weren't fixed with a pin. As I tend to be a bit of a klutz, I thought I'd better just check about possible overtightening on the main bearing! Any advice there would be welcome.
Len

[speedytinc]

They really dont loosen on their own if properly torqued. Some folks replace with modern hardware & just torque. Maybe someone left them loose instead of proper shim & fitting. I have seen a situation where assembler FORGOT to tighten. Made for some frightening noises on start up.