A couple of months ago, I pulled apart the Comet's 250 to repair a blown head gasket. I didn't want to pull the whole engine so I left the block in and only pulled the head and had it machined and new values and springs installed. I replaced the gaskets and a few odds and ends along the way (worn rockers, corroded water pump, misc. bolts, etc.) Once back together and after some carb tuning, everything was running great. Until this past week. After a 20 min cruise, I started hearing a lot of knocking from the engine. It sounds like it is coming from the rear of the engine but I can't figure out what it might be or why it has suddenly appeared. I uploaded a video to YouTube of the engine idling incase anyone can help identify where I should start based on the sound. One other thing to note, the carb has a high pitched whine since the rebuild that wasn't there before. Not sure what the cause of that is either or if it is related.
Not sure, but it doesn't sound good. Sounds too deep for a lifter, but to me it doesn't really sound like a rod knock either. I think I'd do 3 things first: 1) Check all around the back of the engine and bellhousing area to see if something has come loose and is hitting it. 2) Pull the valve cover just to see if there's something going on under there. 3) Drain the oil to check for metal. Does the sound vary at different rpm, with speed, or load? Oh, and check on your friends.
It's one of whatever it is, maybe a damaged rocker arm. If it changes pitch when disconnecting spark plugs one at time, probably not valve related. I'd definitely pull valve cover, start it up if valve it'll be obvious.
I popped the value cover, everything there seems good. I am going to pull the oil pan this weekend and see if anything obvious shows there.
