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Hello all new to site
been working on a 1977 Ford F-250 with my son his truck. It has a 400 in it can’t seem to get to run cool 220 plus
have put new heads on as old ones were cracked, new water pump, has 6 blade metal fan with shroud even added a electric fan to help has a 192 thermostat in it seems to heat up very fast. Was told by a friend he think years ago the block was changed to maybe a 351 would do anything for the water pump? Since then alsways ran hot driving me crazy.
Where do you live; Prudhoe Bay or Death Valley? Probably somewhere in between, climatically. There are many things that can cause overheating. It's probably not the water pump unless the impeller has become inoperative in some way. You will just have to check EVERYTHING. Be sure the thermostat is opening properly. If you live in the Northern Hemisphere, summer is coming. It will likely get worse before it gets better.
Last edited by Ozzie H.; Jun 6, 2021 at 05:04 PM.
Reason: More information
Hello all new to site
been working on a 1977 Ford F-250 with my son his truck. It has a 400 in it can’t seem to get to run cool 220 plus
have put new heads on as old ones were cracked, new water pump, has 6 blade metal fan with shroud even added a electric fan to help has a 192 thermostat in it seems to heat up very fast. Was told by a friend he think years ago the block was changed to maybe a 351 would do anything for the water pump? Since then alsways ran hot driving me crazy.
The correct style thermostat is critical. Options.
Find a dealer with a RT-139 still in stock. -Robert Shaw 333-180
I know that some parts people will give you a wrong thermostat for a 351M or 400. These two engines have the bypass cast into the block, it's a passage way directly under the thermostat. It is open to free flow when the thermostat is shut, so coolant flows through it to bypass the radiator since the thermostat is shut still. As the engine warms the coolant, the thermostat starts to open so that coolant can go through the radiator, and as it opens a "hat" looking piece on the bottom of the thermostat "pill" is pushed downward towards the bypass, thus restricting it so that coolant is forced through the radiator.
351C used the same thermostat but it's also got a restrictor that gets pressed in place in the block to work with the "hat". I think it often comes with the ring but the ring will not work in a 351M or 400 block.
If a wrong thermostat, like say a 351w, etc ... is used, the bypass never gets restricted and coolant that is way hot simply gets to bypass the radiator and keeps circulating in the block and heads and the running engine just gets hotter and hotter even with a wide open thermostat. I kept a couple old RS-333-xxx thermostats just to keep the hat available if I ever need to press it on a regular RS-330-xxx thermostat. Those RS 333-192 were great. The Motorcraft RT139 works well too, looks a lot like the highflow Robert Shaw thermostats.
I have in my notes a note about the NAPA THM 197 and the THM 297 working, but I don't know how well they work.
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