I have very little experience when it comes to these inline engines. Do the head bolts run through a water jacket or is it something worse?
it's too dark and cold to go out to the barn and check...but I would not be surprised, since the same vintage Chevy V8s have all the head bolts threaded into water.
I can check tomorrow morning. I have a bare block in the corner of the shop. I think @squirrel is right . Is it in the middle?
I'll check my book when I get home, but I think the answer is yes. If I remember right, even the front head bolt on the driver's side actually threads into the opening for the thermostat housing at the front of the head.
@GearSlammer, Here is a picture of the 230 Chevy block in my shop. All the head bolts clearly hit water, as you can see if my picture is good enough. I also stuck a drill bit into them all to verify. I can't answer your question on sealing it with any authority, but I would take the chance on getting it out, sealing it with thread sealant, and retorquing the single bolt. If you were a bit more cautious, you could take them all out one at a time, apply thread sealant, and then torque in proper sequence. No need to remove the head or break the seal on the gasket. Someone please correct me if I'm wrong. Hope this helps. Take care.
what he said ^^. Drain the coolant system so when you pull the bolt it doesn't siphon out anyway & make a mess. Then pull the one bolt & reseal it. Or if you want to make sure find the torque sequence for the head bolts. Pull them out one at a time, reseal them IN ORDER so not to warp the head gasket seal. IT should be fine.
On a new build with everything clean, I use Loctite Head Bolt & Water Jacket Sealant. To re-seal one on a used engine, I've used Teflon tape.
We use Teflon tape on steam pipes. Pipe thread is tapered. Bolts are straight thread so it doesn't take a very thick layer. It acts as both a lubricant and sealer.
I use pipe thread sealer with teflon...seems to work ok. I'll have to look around for the special loctite head bolt stuff.