I’ve got a 1963 Biscayne, swapped a 350sbc into it. Got the block bored to .040” and swapped heads to vortec. RV cam, eldebrock performer intake and edlebrock 600cfm carb. Build the engine our selves, and it runs smooth, but it runs very hot. I swapped the rad for a new 3 core aluminum rad with 2 12” electric puller fans. No thermostat. At idle for 23 minutes, it reached 240F and climbing. Timing is set to 6*. We’ve flushed and flushed with diluted vinegar. Got water running clear. Still hot. Any ideas?

 

Welcome from Florida. I would try putting in a thermostat. With no thermostat the coolant could flow too fast and not effectively cool. it is worth a try.

 

I second that.

 

So I put in a 180* thermostat, still running hot fast. I bought one of those no spill coolant fill funnels to bleed the air out and the air bubbles came up and after 15 minutes of running, a good tap on the upper rad hose every minute or so still brings bubbles to the funnel. I know air can lead to running hot. But it wasn’t stopping the bubbles

 

I take it the electric fans are shrouded? Is the coolent level staying the same?

 

Yes the electric fans are shrouded covering the entire radiator core area. And it was tricky to tell, it went down as it filled back up and then came up as it heated up (I’m assuming it just expanded). But the level wasn’t constantly dropping if that’s the question.

 

Could the radiator cap be the issue, as in not holding a constant pressure?

 

Constant bubbles in the coolant could be a sign of a head gasket leaking exhaust into the cooling system causing bubbles and over heating.

 

I didn't want to go there, but yes. That's why I asked about the coolent level.