crossover pipe chevy big block
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crossover pipe chevy big block

  1. #1
    Senior Member Skydog's Avatar
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    Default crossover pipe chevy big block

    Hey guys I have a crossover set up on my boat and been fighting low water psi and I think volume too. Just for fun I took the center off right were water dead heads and splits to each side of the block. There is a pretty big blockage there that is cast in to the part? That can not help my problems at all, this normal?? The pics dont show how much it blocks it is about 1/2 of the flow block i bet.

    Thank u
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    Last edited by Skydog; 06-05-2013 at 07:46 PM.

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  3. #2
    gn7
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    Whats the big blue nut under the inlet? What does this manifold do that a regulare tube type cross over doesn't do? It looks like it has a function aside from just tying the water ports together. I have to believe the deal in the inler has something to do with why that thing seems more complex that it needs to be.



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    Senior Member Skydog's Avatar
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    That blue nut is on the timming cover hard to tell from pic.Not sure what for?? The crossover has a built in power steering pump mount built in to it. Other than that man this set up was on the boat when I bought it. Just trying to check everything that would cause water problems before it enters the motor. And sure dont like that huge boss right there??
    Ty
    Last edited by Skydog; 06-05-2013 at 08:32 PM.

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  6. #4
    gn7
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    Quote Originally Posted by Skydog View Post
    That blue nut is on the timming cover hard to tell from pic.Not sure what for?? The crossover has a built in power steering pump mount built in to it. Other than that man this set up was on the boat when I bought it. Just trying to check everything that would cause water problems before it enters the motor. And sure dont like that huge boss right there??
    Ty
    Now I understand why its a cast piece. Its serving double duty. I don't think that protrusion is causing you any loss. I think it was somebody's idea to smooth the flow into the manifold as opposed to hitting the back of the manifold. I doubt it works as well as planned, but can't believe its causing a restrction either. Where are you measuring your water pressure?



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    Senior Member Skydog's Avatar
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    Quote Originally Posted by gn7 View Post
    Now I understand why its a cast piece. Its serving double duty. I don't think that protrusion is causing you any loss. I think it was somebody's idea to smooth the flow into the manifold as opposed to hitting the back of the manifold. I doubt it works as well as planned, but can't believe its causing a restrction either. Where are you measuring your water pressure?
    10 4 ty from back of head, big tubes getting hot too. 2 stage pump all feeding that main in with the boss in the middle. Water pick up on bottom of boat.
    Ty!

  8. #6
    gn7
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    Water pressure is a product of flow vs restriction. If I changed my outlet hose from -10 to a 12 the pressure would drop some and the flow would go up.
    I know its a PITA, but it would be nice if you knew the pressure in the inlet pipe compared to the pressure in the back of the head.
    Its the exhaust thats running hot?
    Water enters the engine first then into the exhaust manifolds and out?



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  9. #7
    Senior Member Skydog's Avatar
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    Quote Originally Posted by gn7 View Post
    Water pressure is a product of flow vs restriction. If I changed my outlet hose from -10 to a 12 the pressure would drop some and the flow would go up.
    I know its a PITA, but it would be nice if you knew the pressure in the inlet pipe compared to the pressure in the back of the head.
    Its the exhaust thats running hot?
    Water enters the engine first then into the exhaust manifolds and out?
    Got you buddy, this has kicked my butt from day one with this boat/set up. I have changed lots of stuff and nothing is helping. (added a two stage pump, both stages to block,added pick up in bottom of boat ect ect) Out drive goes to inner cooler and out. Yes headers allways have run hot will burn you fast hot, water temp is not bad 130-150. Added dumps this year on back of intake to help with any air pockets back there.(have lost a few motors) That dump for both lines is like a -4. Water comes in bottom of boat, to sea,oil cooler,power steering cooler, in front of motor,threw intake,out front of intake,to headers and out. The the waster passage in front of intake are only about 5/8" then fitting and hose are 3/4".(go to cmi big tubes) That makes no sense because i would think water psi would be way high then??? But it is not?? Let me kow if you want any pics i have a ton of my water set up.
    I think you are 100% right going to have to get a few water psi readings! Where it goes in to the block... ect ect...... One thing i will check to is line going to water psi gauge for a blockage..

    ty you for any help!!! P.S. My water pickup is so deep i should have tons but from a 1/16" to 1" water psi did not change.....
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    Last edited by Skydog; 06-06-2013 at 08:34 AM.

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    Like to add there is no blackage from pick u to where water line hits cross over. All been checked.. At idle sea strainer full of water and headers will burn your hand ...

    ty
    Last edited by Skydog; 06-06-2013 at 03:33 PM.

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    Where do the -4 dumps go after the rear of the intake manifold? The easiest thing to do is pull the lines going to the headers and see what kind of flow you have. Dead head one side with your palm and see what the other side does. Do this in the water, cold. If you can hit the transom from the front of the header your good. Next would be getting some AN unions and couplers in various sizes with the 1/8" npt presure tap. Start moving these assemblies around to different parts of the cooling system. You will find it!. My guess is the oil cooler. Never liked the double pass. Prefer the one in/out.

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    Quote Originally Posted by MACHINEHEAD1 View Post
    Where do the -4 dumps go after the rear of the intake manifold? The easiest thing to do is pull the lines going to the headers and see what kind of flow you have. Dead head one side with your palm and see what the other side does. Do this in the water, cold. If you can hit the transom from the front of the header your good. Next would be getting some AN unions and couplers in various sizes with the 1/8" npt presure tap. Start moving these assemblies around to different parts of the cooling system. You will find it!. My guess is the oil cooler. Never liked the double pass. Prefer the one in/out.
    The rear intake line go to a tee and dump out the back. Will do, thank u!!! :-) :-)

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    gn7
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    Quote Originally Posted by Skydog View Post
    The rear intake line go to a tee and dump out the back. Will do, thank u!!! :-) :-)
    Shydog, is the line from the intake manifold out going to the exaust in? It appears that way, just confirming. I agree with machinehead. You need to check for restrictions, poissibly in the exhaust. The only thing I can tell you is that I am not a huge fan of pulling water thru anything, like your coolers. The pumps push alot better than they pull, and any restrictiion in inlet of a oopen loop pump cuts its flow. Its not like a closed loop like a car or boat with a closed system, its does mean all that much which side of the pump things are on. Its all just a loop.



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  14. #12
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    X2. Always try to push through stuff. Fuel systems included. I know this isnt always practicle.

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    10 4 guys!
    TY!!!

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