Engine Vibration 3k RPM

Engine Vibration 3k RPM

If the rotating assy wasn’t balanced, it really should be.[/QUOTE]

dadsbee said
Sounds like a fuel delivery stumble and not an engine vibration to me, why I questioned it in my first post.

512Stroker said
Lets do the easy things first.
Check the torque converter bolts make sure they a tight and loctite has been applied.
Remove all the drive belts from the front of the engine, water pump, alternator, etc with the car in park check for your vibration you may have a fan or pump that's going south. Make dam sure you do not overheat the engine doing this, start with a cold engine.
Post some close up pictures of the spark plugs so we can see the timing mark on the ground strap.

I removed and re loctited and torqued the converter bolts, no change. I will add taking the belt off to my list of things to check this weekend. As well as add pics of plugs to this post.

PRH said
KB flat tops for a 340 are over 150g lighter than factory pistons...... each.

If the rotating assy wasn’t balanced, it really should be.

That is the bummer part - it was a long time ago and my first build. I was/am young, and I though balancing was only really needed in a high hp build. I wish the machine shop would have suggested it. Looking back, I bought the motor complete and it was already .030 over. So I thought I could just re ring and bearing it, but there was too much clearance in the cylinders. So it had to moved to .040 and get new pistons, went ahead with a full rebuild.

512Stroker said
"nonsense" hold on there partner, we/I are only giving the OP suggestions to check for it is up to the OP which path to follow. I agree that the rotating assembly could be the issue, but I would try everything else before I take the engine apart.

I appreciate it. I want to be sure that I am not mis diagnosing it, either.