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Talking to an expert on the 351 Cleveland who asked if I had the right thermostat in my engine. (me: "huh?").
So I did some research. My engine is using a PRW water pump:

And has a Balkamp BK 8251007 thermostat.

My question is: Is that the right thermostat? And should I be running a brass bypass?


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The brass bypass plate is more or less permanently pressed into the engine block and it is doubtful that it has been removed. Easy to check, however

to determine if your current thermostat is correct go to the link you provided for flow cooler. They depict the correct high flow thermostat which must have the “hat” on the movable plunger that indexes with the bypass plate

note there are standard flow and high flow thermostats, the high flow is what is pictured at flow cooler.

The correct thermostat for our Cleveland engines is a high flow with the hat. Any other choices will most likely cause you cooling issues


the "hat" needs to be the correct diameter to fit into the brass plate's hole

when cold the hole for bypass is open and no coolant to radiator

when warm, the hat will start throttling the coolant and reduce bypass

when hot the hat has the hole nearly plugged so virtuatlly no bypass

when real hot the body of the thremosat contacts the plate

the 333 (correct dimensions)

the 330 has a hat BUT its the wrong dimensions

and would not throttle allowing more bypass (and less to radiator)


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The Cleveland is the only Ford small block with an internal coolant bypass. All other Ford small blocks have an external bypass hose. That hose is always in play, never blocked.

my understanding is the hat on a Cleveland thermostat is not intended to completely seal the bypass opening, but allows a similar amount of permanent bypass as found in the other Ford small blocks


AAAAAAAAAABrass Plates.jpg2                                        AAAAAAAAAABrass PlatesAAAAAAAAAABrass Plates.jpg1                  ...Listen to the facts! NO 'Skirts'! You Have Two of the Wrong Thermostat! I'am going to say this once more...  has the correct RS Thermostats. With 'Hats', understand That!

...Take it from someone who has modified well over 640, (Quality Controlled and Documented) of the 330 RS Stats. All for the good of the 351 Cleveland.



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Last edited by marlinjack

875ABD8A-3F23-4BB6-B45C-CD8FA79C99B7Marlin is a machinist who arguably has unsurpassed knowledge on our Cleveland thermostats and the block off plate.

he is correct that neither of the thermostats pictured is designed for a Cleveland engine. Neither of them appear to have the hat that is designed to properly index with the block off plate opening.

as Forest pointed out earlier, the part number does not reference to a Cleveland engine.

you are not the first to go down this road but until you install a thermostat with a hat you have not fixed your thermostat problem

Go online and order one from Tim Meyer and all will be good.



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Last edited by lf-tp2511

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