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Barry Eller
07-29-2008, 02:06 PM
I use a crossover system in my 502. I have to drill 6 holes in the outer rim of the thermostat to make the temps constant. On a recent run, the thermostat stuck and my temps climbed to nearly 200 degrees and the alarm went off. I removed the thermostat and all was ok until the rpms got over 3500. then temps would start climbing again. I know without a thermostat this will happen.

So, instead of replacing the thermostat, I am going to try these restrictor plates. they come in 3 sizes, 5/8", 3/4",1" I.D.

The water temps in the Pensacola area are 86 degrees now. Which plate should I try first to keep temps in the 140/160 range?

BlownCrewCab
07-29-2008, 02:26 PM
We used those restrictors with a crossover on race boats and ran 5500rpm for an hour or more at a time, They work.

mrfixxall
07-29-2008, 02:30 PM
I use a crossover system in my 502. I have to drill 6 holes in the outer rim of the thermostat to make the temps constant. On a recent run, the thermostat stuck and my temps climbed to nearly 200 degrees and the alarm went off. I removed the thermostat and all was ok until the rpms got over 3500. then temps would start climbing again. I know without a thermostat this will happen.
So, instead of replacing the thermostat, I am going to try these restrictor plates. they come in 3 sizes, 5/8", 3/4",1" I.D.
The water temps in the Pensacola area are 86 degrees now. Which plate should I try first to keep temps in the 140/160 range?

go wit hthe 5/8,thats what i run and my temps are usually between 130 and 140..Also make sure their ss or they will rust out wit hthe salt water. i made my own out od whols saws and belt sanded them to a smooth finish.

Barry Eller
07-29-2008, 02:33 PM
We used those restrictors with a crossover on race boats and ran 5500rpm for an hour or more at a time, They work.

Yeah, some circle track guys I know use them. They told me about them. I think I will start in the middle with the 3/4" plate. Then I can go up or down as needed and change as the water temps cool in the winter. At least I won't have to worry about another stuck thermostat! T-stat gaskets are cheap!

Barry Eller
07-29-2008, 02:35 PM
go wit hthe 5/8,thats what i run and my temps are usually between 130 and 140..Also make sure their ss or they will rust out wit hthe salt water. i made my own out od whols saws and belt sanded them to a smooth finish.

I think these are made of an alloy of some sort, a magnet doesn't stick to them. They could me SS, they are very thin.

MOP
07-29-2008, 04:19 PM
I ran restrictors in my Ford 60 race car they work great and remove the sweat of a Tstat which were even poorer back then. The passage from the drive is 7/8" and it supplies too much water at speed, the restrictor may help to reduce internal block pressure a little. To be honest I would not run any raw cooled engine with out a pressure relief valve, it is not a matter if just a matter of when you will have head gasket problems. I second the 5/8!

Barry Eller
07-30-2008, 06:06 AM
I ran restrictors in my Ford 60 race car they work great and remove the sweat of a Tstat which were even poorer back then. The passage from the drive is 7/8" and it supplies too much water at speed, the restrictor may help to reduce internal block pressure a little. To be honest I would not run any raw cooled engine with out a pressure relief valve, it is not a matter if just a matter of when you will have head gasket problems. I second the 5/8!
Ok, I'll start with the 5/8" restrictor plate.

Tell me about the pressure relief valve please. I know I have one on my gas hotwater heater...but not on my engine.

onesubdrvr
07-30-2008, 06:19 AM
Just curious,

Do they make them in smaller diameters too?

Seems like in the Gulf, you won't have a problem with the sizes given, but what about in colder water? If the passages are 7/8, and the smallest restrictor is 5/8, seems like you may want a bit smaller on if the water is really cold

Just curious,......
Wayne

Barry Eller
07-30-2008, 06:29 AM
Just curious,

Do they make them in smaller diameters too?

Seems like in the Gulf, you won't have a problem with the sizes given, but what about in colder water? If the passages are 7/8, and the smallest restrictor is 5/8, seems like you may want a bit smaller on if the water is really cold

Just curious,......
Wayne

I don't know, I thought that too. That is why I was going with the 3/4" plate first. But the 5/8" has been recommended. I'll know soon! Right now I'm waiting on a new alternator and MSD Distributor caps and rotors.

The Mr.Gasket product I bought only had the 3 sizes. I have not seen any other restrictor plate producers, I'm sure they are out there.
The Mr.Gasket set was only $7.90

MrFIXALL made his own. You could make them any size you want.

Barry Eller
07-30-2008, 07:28 AM
I ran 5/8 in the X boat.. Temps in colder water (Cumberland) were 130ish, in Biscayne Bay it runs about 160ish..

That settles it...5/8" restrictor plate is going in.:smash:

onesubdrvr
07-30-2008, 07:32 AM
That settles it...5/8" restrictor plate is going in.:smash:

From the information provided, I agree :) :yes:

Wayne

MOP
07-30-2008, 12:33 PM
Barry there has been a problem for many years with over pressure in the raw water system, I am sure many have noticed the rust stained sides of the engine block. That is caused by the head gaskets weeping water out, that is the side you can see. The inner sides also weep right into your lifter valley, usually teh fire rings in the head gaskets have a good enough seal to keep water out of the cylinders. I am F/W cooled but still worry about the high pressure possibly blowing a hose of, would really crush me to fry my mill due to something like that. I have been following discussions on just about every boat site, Merc puts out a pressure relief valve but it is set at 30psi. Some of the posters including me feel that is to high, several of the guys have gotten adjustable ones and have limited the pressure to 20psi. Do a few searches on various hot boat sites there is a wealth of info.

Phil