Big hp numbers and a well loaded pump,  I can see it happening.

Kind of like twisting an axle

This picture doesn't make sense to me with the post under it. Maybe I missed something here. How does putting a magnet on a metal shaft tell you if it is magnetic and good? Does twisting it make it non-magnetic?


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Just wanted to know if any one has seen this happen?   Crazy to see this but to me I think something locked up in a high RPM.  Nothing to do with HP but could be wrong.  Saw this and had to share because I can't be leave a shaft twisting like that. What are your thoughts???😏

That shaft is probably from a boat that jumped or the pump somehow took a big gulp air and the driver didn't lift before the pump loaded up again.

The splines usually roll over from exceeding the HP limit of the shaft rather than twisting.

If the yoke doesn't slide, easily, all the way to the snap ring, the shaft and/or yoke is damaged and needs to be replaced.

When the pump builds pressure, the impeller is pushed forward.  If the yoke binds on the shaft, the drive line and crankshaft are also pushed forward, putting excessive load on the engine's thrust bearing.

Just for curiosity's sake, I ran some numbers.  Assuming an A cut impeller producing 100PSI of bowl pressure and the equation Force = Pressure × Area:

A 9" diameter A cut impeller has an area of 63.6173 square inches.

100PSI × 63.6173 = 6,317.3 pounds of force pushing on the crankshaft.

A healthy little big block is capable of two to three times that and a quick race boat can produce over 400PSI of bowl pressure.

With all of that said, think of the power that your engine produces.  All that power is being stopped by the pump.  Now imagine the pump unloading and the engine is free to rev uncontrolled followed by the pump taking a big gulp of water and momentarily looking.  That is a lot of impact force that the antiquated square splines and the 1.147" diameter shaft are asked to withstand.

This brings me too another question that I have been meaning to ask...

I don't have a pressure relief valve in the line that feeds water from my JE to my engine. Does that mean I will be feeding water to my engine at 100psi? Is there any way to control the pressure without the relief valve?


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Sort of,  yes,  pressure is a function of limited flow.

If there is some type of restriction BEFORE the outlet,  the pressure will be much lower.

The restriction could be anything,  washers in the fitting at the pump,  a gate valve (advantage is it's adjustable) a pressure relief etc.

As long as the outlet, or dump line is larger than that,  the pressure will be lower. You also have to keep in mind how small or large all the other fittings are.

But if the outlet is restricted or just too small,  yes,  it is very possible to over pressurize the block.

GT

Thank you GT, as always, I appreciate your help. I have a 1/4 turn valve in it now, and I will make do with that until I can get a pressure relief valve in.


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The problem with a ball valve is the chance it could be bumped.

As stupid as it sounds,  you could replace the ball valve with a 3/4" gate valve and a tie wrap and be good to go. It gives you pressure control and limited temperature adjustment with a $20 valve.

The pressure relief is not bulletproof and does the same basic job but costs 5 times more.

I would rather see you invest in a pressure gauge and a gate valve. Money better spent, in my personal honest opinion.

The gauge just has to be installed in such a place it can be seen temporarily,  not on the dash.

GT

I have a standard shaft in my compjet. 750hp motor....and shock loading the pump every chance it could.

Maybe I've just been lucky.

The problem with a ball valve is the chance it could be bumped.

As stupid as it sounds,  you could replace the ball valve with a 3/4" gate valve and a tie wrap and be good to go. It gives you pressure control and limited temperature adjustment with a $20 valve.

The pressure relief is not bulletproof and does the same basic job but costs 5 times more.

I would rather see you invest in a pressure gauge and a gate valve. Money better spent, in my personal honest opinion.

The gauge just has to be installed in such a place it can be seen temporarily,  not on the dash.

GT

My 1/4 turn valve is hidden away in the bottom of my engine bay, lol. I am hoping I'm good there.


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So,  valves 101.

Here is a cutaway view of each type of valves involved in the discussion,  as you can see from the pictures, the gate makes a funny looking,  very obstructive and clumsy crescent shape opening,  flows quite well with low pressure drops and gets worse as the pressure increases, actually hydrodynamically pinching itself down.

The Ball valve on the other hand is quite smooth and sort of eye shaped,  this will allow a linear flow rate from idle to the upper rpm ranges (exact opposite of what your engine needs).


Just food for thought.

Do what tickles the pickle.

GT

Thanks guys, I'll start the hunt for a gate valve. It makes sense to my now.


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