Thermostat bypass hoses

[bakerfreak]

I've seen pictures of some motors on this site that have tubes going from the thermostat housing down thru the lower pan.

Is this a race-only mod, or should you do it on a weekend ski racer?How do you set this up? Do you just remove the thermostats and drill and tap the housing for a hose barb? What size would be appropriate? I'm assuming you want some restriction to keep the water pump pressure up.

Any help would be appreciated.

[vnemous]

They use a washer with different diameter holes in them to keep water in the block. Unless its a hp race engine I would suggest sticking with the thermostats. JMO

[WATERWINGS]

Unless I misundersand you, you can still run the dump hoses thru the pan even still using the thermostats?

[laglass69]

What motor?

[HStream1]

You replace the T-stats with 1/8" fender washers (Stainless Steel) and for a two piece plate you fine tune the pressure by changing hose sizes on the poppet dump. Only use 1/8" fender washers as they have a 3/16" hole. When done correctly you will see 0 psi at idle and between 15 and 20 psi at WOT.

It's primarly a Racing/HP mod but some do it becauuse of the waters they have to run in. The T-stats can become trash magnets. Below is a procedure that John Marles wrote on doing the mod. But it's for a one piece adapter. The procedure is similar for a two piece.



<TBODY>

From John Marles (These are for one piece mid plates, not two piece)You MUST throw away the popet and thermostats. You can not run them with a one-piece plate , they will never open thus never pee. The water temp has to reach 140 to open the stat. It not going to happen, reading cylinder head temp. is where you get the 140 degree number. The water temp is 100 degrees when the heads are at 140. If you have a 2.5 exhaust plate and not a 2.4 you will need to plug the dump holes in it and re drill two 19/64 holes, install two 1/8 fender washers in the heads and run a 5/16 hose off the popet for a Nicasil block and no hose for a steel sleeve motor. The cylinder head temp will be about 140 All the mods I am talking about are for a 260 as well as a steel sleeve motor, With a one-piece plate the popet valve does nothing. If it runs too cold just plug the popet hose to get more heat, Merc 2.5 plates dump way too much water. There are four holes in the Merc plate totaling a larger surface area than the L and S plate and 2.4 plate. Calculate the surface area with 3.14 time the radius squared and you will see what I mean Water must come from the thermostat housing when at an idle or the top of the motor will overheat. Only run 1/8 fender washers in the heads, they have a 3/16 hole
Just remember if you rebuild it, to open all cylinders to .008 clearance Wisecos and .007 for Mercury pistons. With the one-piece exhaust plate you don’t have a choice to run a popet and thermostats you are stuck with the low pressure and cold motor.
Set you idle up to 1100 in neutral. Put in diverters The one-piece plate should run 15 lbs. at WOT and 0 lbs. at Idle. Some mercury one piece plates come with dump holes that are too big to accomplish the 15 lbs. minimum to cool the motor at WOT. Yes they are adjustable. I like to plug the stock dump hole in the one piece and redrill 2 new holes that are 19/64. Then run 1/8 fender washers in the heads and fine tune the water pressure with the popet dump hoes size. The 0 lbs. pressure at idle is normal as long as the block stays full of water and continuously dump from the heads. This type of modification is terrible for a motor that turns 6500-RPM or less because it will run way too cold. Unfortunately this is the only way to cool a HIGH RPM motor. The blocks are all the same it is the exhaust plate that has the different water passages in it. The one-piece plate allows water to flow in to both sides of the popet of it rendering it completely useless With a one-piece plate the thermostats will not affect the running temp much. Too much water has to dump through the plate to cool the block at high RPM. I only get 5 or 6 lbs at 6800 I have water temperature gages in the top of the heads and I run 100 degrees at 6800 Nothing does more damage that running a motor ice cold. I do every thing I can to talk people out of converting their stock motors to 260 cooling. Unfortunately an 8000-RPM motor needs the 260 cooling on the top. I would rather see the stockers just fix the stock cooling systems so the motors can develop some heat while running and have the motors last for a few years. I think converting to a 260 cooling system to fix a overheating 200 in not a good thing to do.



</TBODY>