Not sure what the issue is but rebuilt 340 is overheating on run stand. Fired up today(2nd time on stand) to dial in timing and it's overheating to approx 110-120*C.
1st fireup was no stat. 2nd fireup I installed 180 stat. Not 100% sure on what timing is at yet, but approx 30* at approx 2300 rpm with va and carb both plugged.
Think it's timing??
Video of 2nd start
Find out what rpm full advance comes in.
But aside from that.. 34 degrees should be enough at the rpm you're breaking it in.
As for the radiator, is it clogged? Do you have a fan on the water pump and is it about an inch or closer to the radiator? Have you tried running a hose off the petcock leaving the cap off and having a hose basically just running into the radiator?
Could be timing, could be clogged rad core, could be cam timing off...check cranking comp test and see what psi yoy have.
Sounds clattery in the video.