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Old April 28th, 2008, 10:32 PM   #1
DodgeitRamit
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Default SBC 400 Blowing Water Pump Gaskets

Did some work on a 71 Chevelle and I have a problem of it keeps blowing out the water pump gaskets. Heres the info on it

This 400 has angle plug heads, victor junior intake, 750 double pumper, 3500 stahl, etc. was running mid 12s in the 1/4 before it was pulled (some ring blow by). Pulled it out, machine shop bored 40 over, new pistons/rings, valve job, etc. Put motor back in and it keeps blowing water pump gaskets.

The funny thing is who built it before didn't have the right head gaskets on it, but the right ones were now installed (With the steam holes). AND he was running no thermostat at all. It ran fine, didn't overheat, and nothing was ever noticed that was unusual about the cooling system. Now it has a 160 thermostat in it. Blew 2 sets of gaskets out of the water pump.

This weekend I am going to pressure test the radiator cap. But this is what I was thinking, if you have any advice or input its appreciated.

- The radiator cap is rated to high and therefore building up to much pressure
- He needs to install an electric pump, I know mechanical pumps aren't meant for racing engines. (But it was fine before? without the stat)
- He needs to take the stat out (I like the previous suggestion better though)
- Possibility of the head gaskets on wrong?
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Old April 28th, 2008, 10:36 PM   #2
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make sure the pumps good
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Old April 28th, 2008, 10:39 PM   #3
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Its the same pump that was on it last year and was fine, and the gaskets seem to blow out when you romp on it a bit.
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Old April 28th, 2008, 11:26 PM   #4
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Are you saying the gaskets between the block and the wp are blowing out?? I have never see that before. What kind of gaskets are you using? Getting them tight? I would put a straight edge across the surfaces and make sure someone didn't get crazy taking old gaskets off and make the surface have a low spot. Don't use any RTV, just put them on clean and dry and get them tight. You should be blowing hoses off before those gaskets go.

Put a T-stat in with a 1/8" hole drilled in it or make sure you use a restricter in place of the t-stat. You need a restriction there for proper cooling system operation.

Other than costing a few HP a mechinal pump is just fine.
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Old April 28th, 2008, 11:51 PM   #5
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I would guess that the pump mounting bolts may be too long or there is some stuff in the bottom of the bolt holes not allowing the bolts to clamp properly.
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Old April 29th, 2008, 09:45 AM   #6
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t-stat in backwards?
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Old April 29th, 2008, 10:16 AM   #7
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Quote:
Originally Posted by Nuggets View Post
I would guess that the pump mounting bolts may be too long or there is some stuff in the bottom of the bolt holes not allowing the bolts to clamp properly.
X2 or your timing chain cover bolts are interfering with the WP/block interface.
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Old April 29th, 2008, 04:48 PM   #8
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T stat is not in backwards, I have used two different type of gaskets (1 felpro I think).

I have read about the drilling 1/8'' holes. But what makes me think about taking it out was apparently they guy who built it (was a shop owner) and obviously knew what he was doin to be runnin as well as it did when it was a bit tired. I think I may make an orifice/restricter plate by just knockin the actual stat part out.

I was going to check the mating surface and run a tap in the holes, but when I did the last set it was definitely pulling tight to the block. Will test it out this weekend.
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Old April 29th, 2008, 09:53 PM   #9
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Quote:
I would guess that the pump mounting bolts may be too long or there is some stuff in the bottom of the bolt holes not allowing the bolts to clamp properly.
It's worth a shot to check.......
I had the same problem when I went to an electric pump last year. The bolts that came with the pump were too long and bottoming out. The pump felt tight, but 1 bolt from each side was loose enough not to seal.
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Old May 5th, 2008, 02:29 AM   #10
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Got her fixed

New water pump, made an orifice for the thermostat housing, made water pump gaskets out of some header gasket material. Surfaces weren't to bad, and bolts were not to long. So far its hasn't done it again. Thanks for the input
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Old May 5th, 2008, 03:22 AM   #11
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was the old pump a reverse flow?
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Old August 14th, 2008, 12:42 PM   #12
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No the old pump was not a reverse flow, its been on the car since he bought it and never had this problem until we rebuilt the engine. It hasn't been back to the drag strip yet, and that the only time its happened . . . . . so we'll find out when we go back
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