Mbam

The 863208A3 mercury valve works so well they doubled the price.

I have a shelf load of them, $281 list, would love to get rid of some for $200 each.

Strip Poker 388

iTrader: (6)

Ratman if ya getting to much presure ? it may be cause of your pickups, they were pretty big looking in your pick and if its from them getting to much water ,it would be slowing ya down also.

Mudball

A fellow on another forum and I experimented with a few styles of relief valves, some very cheap, some not so cheap. Most had 3/4" dumps. The problem with all of these was that they were a linear dump. They even opened a little with 2psi of water pressure. They just increased the bypass as pressure went up.
These all allowed too low a volume and pressure through the system at anything other than WOT.

The Merc unit is what I ended up running. It doesn't dump a drop on mine until it actually hits the 25psi mark. And it can dump a LOT of water. Now, my motor (HP500 carb with EMI crossover) runs a steady 25 psi at about 2.5k rpm and up.
The other good thing about the Merc unit is that it has a 1" dump. Plenty of dump volume.

Yes, they have gotten more expensive, but the price Bam just showed is the best I have ever seen. These things work well.
Kent

ratman

Male x Female

Female x Female
• Set Pressure: See table
• Maximum Temperature: 180° F
An economical choice for low-pressure cold water pump applications. Pressure is factory set and is not adjustable. Body is brass, seat is rubber on brass, and spring is stainless steel. Disc is neoprene for 1/2" through 1 1/4" sizes; Buna-N for 1 1/2" and 2" sizes.
Connections: NPT bottom inlet and side outlet (see table).

looked at this valve @ mcmaster car 1" X 1" 30 lbs 42.00 i think it will do the trick but i do like the merc one but thats a lotta jack!

Mudball

Ratman, that one just might work.
The only way to know is to try it!!
CFM (on the other forum) and I tried only adjustable versions, some bought through McMaster Carr. None would hold pressure until a set trip point. The target was 20-25psi with our experiments.
30psi is pushing it, IMHO.
35+psi can cause gasket failures...
Kent

Mudball

Oh yeah, and less than 15-20 at a good cruise can form steam pockets, I was told...

ROTAX454

I did read most of the posts explaining all of the high and low points of the "non marine" types of pressure relief valve. Like a lot of non-marine stuff, it just simply doesn't work, when and where it is suppose to.

Spend the jack and get the real stuff. Yeah, spending 400 clams on a pair of relief valves sounds like alot, but your cooling system will thank you for it. Sure like those 1 inch dump hoses.

Mudball

Here's a pic of one experimental relief valve.
Note that I have the valve plumbed after the oil cooler, but before the PS cooler, as I wanted it down and out of the way.
Please ignore the dirty bilge!

Mudball

Here's one with the Merc valve...
Again, please ignore the dirt...

Mudball

Here's the dump. It's a 1" SS dump from CP.
I was going to try to dump this onto the drive, but there is not enough room on the transom for this...