Water PSI fact or myth???
 

OK! Can someone who know 100% for sure tell me whats the max water PSI a engine or head gasket can handle??? For as long as i can remember i've always been under the impression that the head gaskets can only handle about 18-20 psi max water pres. After that you run great risks of blowing gaskets. Does this only hold true for stock applications? Are different gaskets capable of holding more pressure? i.e. copper vs conventional? Please clear this up cause i see some people saying they run with as much as 30psi of water!!! Is that good or bad???

30 psi is WASTED HP!

It takes more power to turn the pump to get 30psi than it does to get 20psi, which translates to less useable torque at the propshaft.

I think the high water pressure (30psi+) people are seeing (myself included) is caused by the stock low water pickup Bravo drive at higher speeds. The pick up has a ram effect which increases the pressure in the system. So I dont think its taking any additional hp to raise the water pressure to 30 psi maybe some additional drag though. In fact I lost an impeller miles away from the landing and on the way back as long as I was on plane I had 20 psi. At idle there was nothing and the impeller was toast but on plane the ram effect of the pickup supplied plenty water pressure.


I read somewhere that some F-1 racers were covering two of the four pick-up holes with no ill effects and a speed increas of 2 mph. Anyone out there tried this?

Ron

energy can not be created nor destroyed....do what you will with it!

Wally,
I ran 35 lbs. for 300 hours with no problems. I guess I'm lucky. I would shoot for 24 max pressure.

Rjcardinal,
Do you have a 502? What is the pressure? The low water pickup does raise the pressure but not to 30+ lbs. Ask the guys who run 500EFI's with low water pickups. I think the high water pressure we have been seeing in the past few years is due to the thermostat housings on the 454's and 502's with the two water hoses going to the exhaust. The four hose systems didn't seem to have these problems.
Dan

I went with the new therm.housing with two outlets with Stainless marine exhaust and have the regular bravo1 pickup and see no more than 18lb at the oil cooler and 15lb in the block at WOT.I allways felt that the book says to test to 20 lb so that is where I draw the line.My .02 for what it's worth.:cool: Ron I thought that they covered the top two holes if they thought that they might be sucking some air instead of water?

FS,
There was a post about gaining 2 mph by plugging two of the four holes of the LWP.
Dan

I'm on the same page now :D thanks

Heres a VERY interesting test result we just did here at work....
We are experimenting with different pump assemblys and Karl and myself decided to see exactly how much these Merc Sea water pumps can pump.

At no head height, and no restiction turning at 3450rpm with a 1.5hp electric motor the pump will do 23gpm and just under 1psi in the line.

From there we went through the spectrum but just to give you guys an idea of the power of this pump thats on our engines.......
we blocked off some of the output line to see how much head hight this thing will do.....boy were we surprised!!! We took it all the way up to 100' and the pump made 43psi in the line!!! And thats only turning it at 3450rpm! This thing has alot more capability in it but we were actually getting acared it might burt the test line we were useing for the water!!!
Think about what this thing is doing in your engine turing at 5000+ rpm and with restricted exhaust risers or sand blockage!! :eek:

Those bleed-off are sounding better all the time! :D