[CWPASADENA]

WOW;

Lots of opinions on how to keep a flathead cool.

I might as well put in my feelings on then subject.

First of all, the exhaust ports run from the top to the engine clear thru the water jackets and out the bottom. This is not the optimum design for a cool running engine. With this design, the Ford Flat Head V-8 makes an excellent water heater. We can not do much about this unless we would want to completely re-configure the exhaust flow thru the engine which is not practical.

Secondly, The water flow thru the engine is not a good design. The early Flat Heads had the water pumps high up on the heads. They pulled hot water from the engine and pushed it up into the top of the radiator. This arrangement lead to cavitation and very inefficent pump operation. The water also entered the engine at the front and exited the engine at the front. There was little to "encourage" the water to circulate back thru the rear of the engine and the rear cylinders would run hotter then the others.

Later, when the pumps were installed on the bottom front of the engine, the pumps worked better and the "Center Outlet" heads did improve the flow thru the block to some degree but the rear of the engine still suffered from inadequate circulation.

When the Hot Rodders started hopping up these engines, they ran hotter and during hot wether or hard usage, the poor circulation to the rear of the block would cause the water around the rear exhaust port to get hot and want to flash to steam. When these "steam pockets" would form some of the coolant was displaced and the car would want to "Boil Over".

On engines where the water pumps are installed on the front of the block, adding restrictors to the outlets on the heads will actually raise the coolant pressure in the block when the engine is running at speed. The smaller the restrictor, the greater the pressure required to flow coolant thru it. This increase in pressure will cause the coolant to boil at a higher temperature and thus delay the forming of steam pockets. Too small of restrictor will not allow enough coolant to flow thru the engine and it will run hot just because of inadequate coolant flow. Too big of a restrictor will not increase the pressure adequately to reduce the formation of steam pockets. Thru experience, it seems a 5/8 to 3/4 in. restriction is just about optimum.

A better way to keep a flat head running cool is to improve the circulation to the back of the block. One of the cleveriest ways to do this I ever saw was a guy with a '37 21 stud engine had the water pumps in the front of the block and put '36 heads on it BACKWARDS so the water exited at the rear of the engine. He custom made water pipes to get the coolant from the back of the head to the upper outlets on the engine. The coolant entered the engine at the front and exited the heads at the rear. This greatly improved circulation thru the engine. There were some aftermarket hanufacturers that made heads with water manifolds that drew water from the head at the front, center and rear. This system worked well.

I have had success by installing a piece of 3/8 in copper tube down thru the center outlet in the head and fishing it back inside the head toward the upper rear corner. I install a disc (restrictor) with two 3/8 in holes in the water outlet in the head, one hole for the copper tube and one for coolant to pass. The copper tube terminates about an inch or so ABOVE the disc. Because of this restriction, at speed, there is a pressure drop across the restrictor due to the higher pressure in the block then the upper radiatror hose. This pressure drop will cause coolant to flow thru the copper tube and thus coolant flow to the rear part of the block is improved. It works out that about 1/3rd of the total coolant flowng thru the engine will flow thru the copper tubes and about 2/3 rds will flow thru the second 3/8 hole in the restrictor. Some additional benifite is obtained by also installing 1/2 in. copper tubes in the from the water pump outlet area in the front of the block thru bottom of the water jackets toward the rear. This also helps promote circulation to the rear of the block.

Some "Racers" do this same type of "Plumbing" on the exterior of the block with good success but I did not want my modifications to show when finished.

The result of doing this on a mildly modified 59AB in a A-V8 Hot Rod, with an original '32 re-cored radiator (no pressure cap) and a stock '32 fan, was the car ran too cool. The car would run at about 140-150 Deg running down the road as long as temps were less then about 90 deg. It may get up to 160 with 100 Deg outside temps. On cool days, it would want to run at about 120 Deg. I finally installed thermostats and the car now runs at 160 deg. almost all the time.

Sorry for being so long winded BUT think about how the water flows thru the engine and the need for increased pressure of the coolant to reduce the formation of steam pockets.

This is what worked for me.

Chris