[Old Goat 67]

Originally Posted by Formulajones

I've never done any drilling mods of any kind on any Pontiac build and I've never modified any of the water pumps I've used either.

Never had an overheating Pontiac

I just use the stock cooling system parts, clutch fan, shroud, etc... and it just flat works.

Even dad's 571 that makes 724 hp won't get hot, with the stock cooling system parts, stock pulleys etc... There are no fancy water pump tricks or drilled holes. It never gets over 176 degrees with ambient temps at 100 degrees. Even on the hotter days in the desert summer the most I've seen is 185-ish cruising on the highway, and as soon as you take an exit and slow down, it would drop to the 170's pretty quick.

In fact we were just at the track with it Saturday. 96 degrees outside. The RobbMC starter is acting up again so dad decides to just leave it idle in the staging lanes before each run. It's just sitting there for more than 10 minutes and the temp gauge never goes over 176. During the pass it drops to 172, and idling down the return road and in the pits it was already down to 168. We never even bothered to open the hood to cool it down, LOL We could go round robins with this thing and it just doesn't care.

For the OP, I'd go back to the stock fan and shroud setup, verify timing is sufficient, especially at idle, and that vacuum advance is working, and then go from there. If there is still a heating issue then you can start looking at other areas. There is no reason a good working clutch fan and shroud, with a sufficient radiator, won't cool any 400 or 455 out there unless there is something else fundamentally wrong.

Amen to that also.
Only time in 55 years of ownership occurred when I was too dumb to pay attention to the impellor on an aftermarket water pump!

I cringe every time I see someone start praising the virtues of Flowcrapper this or that.