Finally turned the key after my winter projects. Started as a radiator replacement and ended up getting stung by the "While I'm at it Bug".
Here's what I did-
New Dewitt aluminum radiator.
Rebuilt GM waterpump.
All new hoses- radiator and heater.
Drained block at plugs behind those "V" wire shields.Got all the old stuff out.It looked fine, just leaked.
Owners manual says 21 quarts, I got about 17-18 and she don't seem to want any more, even after a few runs.
Before with my old leaky radiator it run a little below the 200 mark, as long as I kept it full.
Now it hovers around 200 and goes higher when driving and back down to 200 when stopped.
Could it be thermostat maybe from sitting all winter?
Could a rebuilt waterpump be not pushing enough?
The fan clutch seems ok but it did leak a little oil when I removed it and let it sit down flat for a while.
The heater works ok, gets pretty hot in the car.
Any Ideas???  Thanks
Jeffm2008-05-18 18:02:19

You could have some crud in the engine that didn't empty out, and you may have an air bubble in the system that needs bled out.  Run the engine with the cap off...let it get to operating temperature and see the coolant rushing past the filler neck.  That should allow air in the system to exit.  Then you can close it up and fill at the overflow tank.

The water pump shouldn't be an issue as long as it's a rebuilt CORVETTE pump...not a standard Chevy pump.  They're not always the same.  Pumps are designed to move coolant at specific volumes in specific engines.  Sometimes a pump that pumps at too high a volume doesn't allow the coolant enough time in the radiator to be cooled properly.

Does the new lower radiator hose have the coiled spring inside it?  If not, it could collapsing under vacuum at higher rpm's and restricting flow.

It seems to me you either have issues with the lower hose not having a spring or air pockets needing bled out as the two places most likely.

Thanks Gunslinger,
It's a replacement Vette hose and has the spring in it.
The pump also came from one of the Vette venders.
I did run it a little with the cap off but it started to run out. I'll try some more.

I forgot about all the seals necessary around the radiator and the spoiler.  Suncountry is absolutely correct.  If those parts aren't in place you'll never get that engine to run at the correct temperatures.

I went through this same problem after a major change, and fluid replacement. You may have an air pocket below the thermostat, causing it not to open properly at temperature. You can drill a small (less than 1/8 ") in the thermostat base, or but a "fail open" one from Checker.

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If you have some air trapped it may help to make sure your heater temp is set to hot to get water to flow through the heater core.