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I have the heat riser wired closed (as in don't heat the intake) right now. I have pulled one wire at a time and it didn't seem to make any difference in the noise.

I did notice that even with insulated pliers and new silicone boots on the plug wires, i still got some tingling and shocks taking them off while it was running.

Place stethescope at timeing cover to determine if noise is more pronounced.

If the car accelerates ok but looses power at about 40 mph (a sustained cruising speed of 40 mph) then it is likely that one of the ex. valves has some crud built up directly at the point where the stem is even with the top of valve guide and is allowing the ex valve to hang open ever so slightly. I've experienced this recently of 2 different engines.

Also note that if the oil pump has a FLOATING screen then it is possible that the screen dogs are bent or broken and the float is hitting the crank counterweight. Try draining about 1 qt or more of engine oil to lower float) OR raise rear or front or side of car real high with jack or some steep hill and/or off camber terrain to see if noise goes away.

First check timing chain cover for noise.

With this exhaust valve hanging issue, would you expect to hear/have you heard the knocking?

I'll try draining the oil a quart or so also, i hadn't thought of that, although it's a hard knock, i don't know if hitting the oil pickup would sound that "deep". Also, when i had the pan off and the engine on the stand, nothing seemed amiss. It'd be nice if that was it.

I have a new timing chain/gear set on, i would hope it wouldn't be wore and slapping already. The noise is up front in that area, but seems to be around cylinders 1 and 2, based on some quick stethoscope testing.

I saw someone recommended putting MMO down the spark plug holes and letting it sit for a bit to help that clean some valves, although i'm not sure that's it.

Also, when i was running the sea-foam spray through it the knocking was steady at the rpm i used (in the midrange) and then when i started spraying the knocking went away for about half the time i did the treatment. If it was something like a rod, i wouldn't think that would make a difference at all??

I feel like i'm missing something simple that would make a lot of sense.

Ok took it outside and got it good and warmed up, and did some stethoscope checking and found it's not related to the timing cover in anyway and it's not the fuel pump but is louder down in that area than the top.

After getting it totally up to operating temps and running it about 1000rpms where you here it the most at idle, i did the spark plugs one by one and found that when you remove the number 2 that a) it gets noticeably quieter and b)even if you have welding gloves on you can feel it shocking you if you pull the boots off.

Taking off numbers 1 and 3 made no difference, which makes me feel like it's not main related, and most likely a rod bearing?

Again, when putting it away, put it in park, gave it lots of gas to get over the drain bump in the driveway and pulled it in the garage and no noises. You really don't hear it under heavier loads, just at idle like i've described and when at cruising RPMS.

Wonder if that one bearing got some debris in it and the others haven't made their wear noticed yet? I wouldn't think the rod is bent or anything like that since it runs fine with no noise most of the time.
Can you drop the pan while the engine is in the car in a bathtub?

I'm wondering if i shouldn't just drop the pan and do new bearings and get away with it. If it doesn't work, that's $250 in bearings wasted but then again small price to pay to avoid having the engine out and professionally redone.

Comments anyone?

Have you thought about trying a dose of STP?

I hadn't heard anything good about doing that, maybe i'm misinformed? That would just mask the problem to come back later?

Cheap to try i guess, but if it masks the problem, more damage might be done to where i can't just sneak bearings in to solve it?

Anyone have luck with STP and the like in a failing rod bearing situation?

Yes, you can get the pan off. Remove the lower bell housing, drop the idler arm, and she will just go. As I wandered through your post I kinda thought rod. You will need to jack your crankshaft gently upward in order to use plastigage on the mains, but it will be worth your time to know the whole story. Check all the rods too. Rod noises are usually worse under no load or on the overrun as there is little compression pressure to hold the piston and rod down. If you just need a couple of shells to tighten her up let me know and I'll send them you. When I do rebuilds where I'm installing new bearings, I always sort through the old ones and save those which are still perfect(that is not scratched and less than .0003 thinner than new)--and use them in my own cars. I have a whole box of em.

Ross...thank you for the offer. When it comes to machining and things of a finer nature, the less i do the better. I was thinking since the oil pressure was great, i may just do rods, starting with that one to see how bad it is. Depending on how confident i am, i may do mains also.

I wasn't feeling rod because it wasn't happening as much, and before i couldn't isolate it pulling plug wires. As much as a rod bearing sucks, especially if just a new bearing won't fix it, it's great to have finally found the issue.

When you say jack the crank up to use plastigauge, is that because it drops some when you remove just one cap or because you can't get into the mains above the cross member?

I may do the rods (again, more than number 2 if i'm feeling confident.) and be done with it for a year or so to hit the show in warren, and save doing everything for a motor out refresher total rebuild in a couple winters.

I'll let you know if i need one bearing, first order is tearing it down to see if it's factory sized or if the crank has been ground under.