So I have my 67 some what on the road, but dealing with overheating.
Engine is a 76-302 and C6 that was in the truck when I got it . I drove it a few miles before I disassembled the truck and had no indication of overheating then either the old radiator
While engine was out I flushed out the block and heads with all freeze plugs out. It was pretty gunned up but was clear when I got done. Installed a new aluminum high flow water pump,Intake and 160 T stat, and new 4 row aluminum rad with dual electric fans that come on with key. Timing is correct, and fans are turning right direction
Water pump recommend a low restriction T stat . I can go about 5 miles with T stat, and 2 without. All the hoses are new with 50/50 coolant
I’m at a loss any ideas

 

I'm no expert as my condenser and fuel system will verify.
I'd guess there is some sort of blockage that is creating the overheat.
Unfortunately it sounds like it might be in the block.

Mike

 

This is a WILD guess only. Is it possible that water pumps for conventional V-belts and those for Serpentine belts turn opposite directions and you don't have the correct one in your New Aluminum Water Pump??

Cap

 

Interesting, You do have the possibility of some kind of mismatch. You can ask online, as I have here and chose this one below. There are more links out there to search.

https://www.ford-trucks.com/forums/1451625-small-block-ford-water-pump-choice.html

Cap

 

I did go back and recheck the water pump info, and it claims stock replacement except for high flow and recommends a low restriction T stat. Nothing about serpentine belts or reverse direction

 

It sounds like some of that gunk you flushed out when you cleaned the block may have come loose elsewhere and now has moved to
a position that is blocking the flow. Can you check whether there is flow into and out of the engine when it is running?
Or as Cap mentioned some sort of mismatch. Something like a head gasket put on in a direction that is blocking water flow.
Perhaps the supplier of the water pump put a "high flow" pump in the box by accident?
I'm just brainstorming ideas.

Mike

 

It sounds like you have tried it without the T-stadt?
If the pump is sucking air, you will have no flow, so run the engine with the rad cap off, and see if your coolant is circulating in the correct direction, and watch it, to see if it stops as the temp rises. A blockage, or incorrect gasket could cause an air pocket to form as it is running. This is only a guess, that's really all we can offer.
I guess a heater hose could allow air to get into the pump, try blocking them?

 

Sorry, I don't know how this Quote thing works, so my way.

You said, "I did go back and recheck the water pump info, and it claims stock replacement except for high flow and recommends a low restriction T stat. Nothing about serpentine belts or reverse direction."

I don't suppose the info that came with your new pump would say anything about serpentine or direction. You can verify that the engine is Definitely a 76, 302?? Casting date on block, heads, water pump housing starting D6=1976 or D5=1975?? Matching of some of the pictures of different Water pump , timing case cover styles?? If you do remove the new water pump, look see of pitch of impeller is same way as your original pump.

Again just throwing some more at you to possibly check if the the suggestion's from Oldie and 1941 don't resolve for you

Cap

 

This forum doesn't allow editing for very long, where I said blocking the heater hoses, I should add bleeding them.
Edit, Another thing I just thought of, have you added a coolant recovery bottle? It will allow the rad to run fuller, removing the 1" or so expansion space we usually leave on older vehicles. The aluminum rad may be designed for this.

 

Yes it held press until it got too hot one time
I plan to try a 180 T stat next
I know it won’t open till 180, but does it also slow down the flow to maintain the temp?

 

Well I put a 180 T stat in this evening and drove more than double the distance I drove without a stat before it got hot again. Temp stayed at 170 -180 on back roads 30-45 mph, then on hwy coming back prob 50-60 temp climes to 190 quickly then on up to 210 before I got home
Guess next step will be pull water pump and make sure a gasket didn’t slip and block a passage

 

have you tried putting a radiator pressure tester on the rad with zero pressure on it, watch to see if it builds up pressure while running, if it jumps fast you could possibly have a bad head gasket or a cracked head ,