Circulating Pump

four years ago, when I pull the engine for rebuild,I changed the raw water pump,It's pretty easy even some screws were serious rusted. But I found the bump still in goo condition even I thought it's no good,it use brass impeller so not seems will wear.it may hard to change the pump without pull out the engine,may be some body
had experience here could tell you, but worth to diagnose it carefully.

It's not difficult at all. A SBC circulating pump has bolts that are tapped into the block water jacket. You need to coat those bolt threads with a sealer when you put them back in.
I assume the GT40 is the same but I'll defer to others that would know for sure.

Reusing the pulley isn't a problem at all. Like I said, these instructions are what I know based on the SBC. I gotta believe that a SBF is the same or very close to it.

I would pull the block drain plugs first and let the water drain into the bilge. Just less messy that way.

Then remove the pump. Pay attention to what bolts come out of what holes. The SBC has I think three different length bolts they use and they have to go back in the same holes or you'll have sealing problems.

The SBC has two gaskets that need to be installed on the inlet and outlet of the pump where it bolts to the block. Put a thin coat of gasket sealer on those gaskets if you have them before installation.

You should be able to see immediately what bolts (if any) are tapped into the water jacket. Make sure that you wire brush and clean up the bolts good as well as the tapped threads in the block.
Any bolts that are tapped into the water jacket just put a coat of any good silicone thread sealant on them.
If I remember when I get home tonight, I'll look and see what one I have used but I know there are several from Permatex that would work just fine as well as several others.

Put it all back together and leave it sit overnight to make sure the sealant has a chance to cure.
NOTE: I know there are some sealants that are designed so the engine can be put back into service as soon as you put it all back together but I prefer to leave it sit overnight before filling the block with water. Entirely your option if you use that type sealant.

Then you can run it and make sure there are no leaks. Have fun from there.

Also make sure that you replace the old pump with a marine pump. Marine pumps have either brass or stainless impellers that don't corrode.

Keep us updated.

SBF = Small block Ford
SBC = Small block Chevrolet

Gary that's a great idea, I will make sure I do that.
Thanks I will keep posting as I make progress.

I'm betting Gary is right. If you said it leaked or rattled I'd say pump, a squeak is more likely a belt or maybe the raw water pump slightly misaligned or not tensioned enough.

Did you get a chance to check it out?

depending on hours if you go that far maybe change timing chain. Ive heard 1000 hrs but not sure. It wasn't hard on a 1985 351 .2001 just have to get the impact between the ski pole

Good to hear.
Unusual to fail like that. I haven't seen one fail closed but I'm certainly no expert. I guess anything is possible under the right conditions.