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View Full Version : Water Pump VS. Crossover?



Air 22
05-21-2004, 02:06 PM
Ok...i have a 1995 454 MAGNUM CARB and might consider removing the water pump. My impeller housing etc is belt driven off the crank and sits on the starboard side. I've been told that b/c my engine is not closed cooling that that sea pump/impeller is all i need? also removing the water pump off the front of engine cleans it up removing the pulley/belt.

I THIS AGOOD IDEA? I'd replace T-Stat and add a Crossover.
Any advantage/disadvantage to this?

Please only respond if you have done this and have the facts. I'm not looking for speed etc...just wanted to clean up the eng.etc..

Thanks... :biggrin:

Forrest
05-21-2004, 02:37 PM
I think a crossover/bypass with a thermostat is a good thing. I did this on my small blocks in my Magnum. The only belts that are needed after the conversion is one for the alternator and one for power steering pump. Beware though that unless holes are drilled into the thermostat, it is possible that the water pressure will become excessive in the block, which may cause internal water leakage through gaskets, especially where the intake manifold meets the cylinder heads. The thermostats supplied by Stainless Marine are already pre-drilled. Always check the water pressure in the engine block while underway after installing a crossover system. Best to keep the pressure under 25 PSI, but pressures to 40 PSI are possible but not at all desirable.

Audiofn
05-22-2004, 06:41 AM
I feel that if you are not running a blower or a very large cube motor that it is not worth it. You can run into water preasure and water distribution problems.

Jon

MOP
05-22-2004, 05:38 PM
Why would the pressure change the sea water pump is not delivering more water you still have the same pressure. I agree with regulating the pressure on any motor, what make pressure build is the ability of the risers to let it out. The cross over eliminate the circ pump and drive belt saving HP. I have only heard the benefits no minuses, I have heard many different claims on HP gain. There is no need for a circ pump on a raw water cooled engine, for many years true marine engines did not have circ pumps. Then they started marinizing car & truck motor thats when circ pumps started showing up in the marine field. There are kits available to eliminate circ pumps on cars. One company touts a 40HP gain on a 5.0 Mustang in the higher RPM ranges. If I were raw water cooling my 383 it would damn sure have a cross over.

BigGrizzly
05-23-2004, 07:38 PM
Fact excess of 25psi on the raw water WILL cause leaks. Guys have you ever seen rust lines on the block just under the head gasket. guess how this happened.There are plus and minuses on the ciec pump vs. the ceoss over. Block temperture are more even with the circ pump providing the bypass isn't closed off. This comes from a thermo engineer who worked for Merc. The cross over has no beltts. However if you have a circ pump it will help when the impeller breaks onthe raw watwr then the circ pump helps --just a little but thayt is beyyyrt then no help at all. Forrest realy is telling the truth. I can and have duplicated the high pressure thing on a dyno. It is especially important on a blower motor. In fact Mercury buys their water pressure releife valves from Grimes Machine for their race stuff. One of rhe reasons I put a closed cooling system on my blown Criterion was to keep an even temp and not having to worry about water pressure anymore. As most of you know I swear by closed cooling systems. I don't want to hear this crap about you can't put a closed cooling system on a blower motor.

Air 22
05-23-2004, 07:47 PM
Randy...should i lose the water pump? or just leave it alone. I have no plans to install a "blower" etc... just want it turn key. Adding a water psi gauge is possible if i delete the water pump and install a cross-over. Will removing the water pump put more of strain on the impeller? ie make it work harder etc?? let me know...Thanks Dwight :D

Cuda
05-23-2004, 07:50 PM
I have crossovers on my 302. I've had no bad experiences with them.

Cuda
05-23-2004, 07:52 PM
[QUOTE=BigGrizzly]Fact excess of 25psi on the raw water WILL cause leaks. QUOTE]

A buddy of mine just bought a water pressure relief valve from Merc, and if I'm not mistaken, it was set at 30 pounds. I'll double check. BTW, he just had to take the heads off AGAIN due to losing a head gasket.

Air 22
05-23-2004, 08:20 PM
Was planning on a new T-Stat from Stainless Marine. Sounds like water psi can be a problem w/ a crossover set up....ie blowing head gaskets etc.. What is the best way to avoid avoids these psi problems... :banghead: Just leave it alone? :smash:

MOP
05-23-2004, 10:05 PM
On any raw water cooled engine pressure is an issue, it does not make any difference with or with out circ pump. The raw water pump is what makes the pressure, a pressure relieve valve is a good idea on any boat run at higher RPM's that is where the pressure is way up on long fast runs. Like Griz says F/W cooling is the way to go, or at least run a relief vavle.