I'm putting in a new water pump and new 4 core radiator (I'm in South Texas, after all).

I pulled off the old water pump and as I expected the gasket was toast (it's been well over 15+ years) but I noticed that whoever owned it before used Permatex with the gasket.

1. I got a new water pump with gasket from Classic Industries, so should I also be using Permatex with this new pump?

2. I noticed a little bit of rusty water (the draining was predominantly all green with just a little bit of rust at the end trickle). Since I pulled off the pump and the radiator, is there a way to flush the motor and heater core before I put on the new components? I may have put the cart before the horse on this one.

3. What are your recommendations on a excellent coolant and has anyone used Royal Purple's Purple Ice in their cars? I'm a bit intrigued with this additive but wanted to know how effective it is.

4. I put in a coolant recovery system in the late 90s and it came with a 17 lbs closed system radiator cap. I am unsure what thermostat is in the car now (it's been in there since before I bought it in 1997). The motor is a 326, and with this info I post here, what degree thermostat should I use with the 4 core radiator and coolant recovery pressure cap?

Thanks for your inputs!

Bill

1. Yes, you need to goop it or it will leak.

2. Heater core can be flushed with a garden hose. Motor can also to some extent...or simply drained via the drains in the side of the block.

3. If you're gonna keep after it and replace every 2 or 3 years, plain ol' green coolant works just fine. Some like to toss a bottle or two of Redline Water Wetter. It's good stuff. If you want a long life alternative to glycol & water, I'm a big believer in Evans: http://www.evanscooling.com/
I know nothing about the Royal Purple product you ask about.

4. I think OE spec for t-stat was 195? Many run cooler than stock these days...like a 180 maybe. Why? I dunno. For some reason people seem to have a hard time accepting that these machines run perfectly fine long lives even if they run at 200 or 210 all the time. Frankly I'm not sure what is "best". Certainly your pressurized system can safely run hotter than the factory open system, so stock 195 is likely perfectly fine. Other school of thought is running a cooler t-stat helps keep underhood temps cooler, allowing cooler intake air and more efficient combustion. Lotsa theories, not sure what's been proven. If it was running good before, you can pull the t-stat out and read it to know what was in there and copy it. The temp rating will be stamped on it.

While your pump is off, pay attention to vane/backer plate clearance and make sure it's nice and close. This does more for cooling system efficiency than anything else you can do on a Pontiac:
http://www.wallaceracing.com/water-pump-mods.php

At this point all you can do is stick a garden hose in the top of the motor somewhere, run it, and let the water run out the bottom to flush. You can pull one of the heater hoses off and run water into it so that it will also flush the heater core.
I would say a 180* T-stat would be a good choice. I personally run a 160 all the time for various reasons. Make sure the new water pump is a cast impeller type and, like crazy's link, make sure you set the correct gap for optimum flow. Make sure you replace any divider plates that are rusted through and replace the rubber collars that mate to the backside of the plates. If it wasn't overheating before I wouldn't mess with it too much, Pontiacs seem to be kind of touchy about their coolant systems.

The following tip is very best in this regard.
While your pump is off, pay attention to vane/backer plate clearance and make sure it's nice and close. This does more for cooling system efficiency than anything else you can do on a Pontiac:

One clarification...I think. Someone correct me if I'm wrong. He's asking about a 326...so it's a 67 I assume?

So the 326 most likely has the 8 bolt water pump, and does not have the 2 sleeves that first came out behind the 11 bolt water pump of many 1969 motors...

Indeed if this is an 11 bolt pump, these sleeves are critical and should certainly be replaced as the rubber fails with age.

I just don't want him confused when he's looking for parts that don't exist on his car...

correct, and definitely change out that 15 year old thermostat!

No RTV needed unless mating surface is imperfect.

True. My initial comment about "goop it or it'll leak" was intended more as a Murphy's law thing. However service manual does not spec it in the procedure. I do feel RTV is cheap and easy insurance against not seeing that one little imperfection that seeps...doing a water pump twice in one day is MUCH less fun than doing it once...

FWIW, I just ran across this very nice video which I hadn't seen before, clearly explaining the divider plate to water pump vane clearance thing...even better than the Wallace page IMO:
http://www.youtube.com/watch?v=UdyAo5546JQ
I'm intrigued that they chose to weld a little round donut of sheet metal on the impeller...that's a new one on me, and seems a little unnecessary if the clearance is already tight...

Thanks all for the excellent inputs so far. They are very helpful and will help with my future 400 build as well.

I have a 326 and the new pump is an 8 bolt cast pump. The two plates behind the pump look to be in real good shape with very little rust.

I was going to start a build up of 68 Pontiac YT block 400 next month. But as always, a priority gets in the way (I found my house's darn roof is leaking). So, back on the shelf it goes.

Crazy,
I think you're right about the 8bolt setup not having two sleeves. I've never had one apart so my tech is limited to the later configurations.

I have a 326 and they are 8 bolt pumps with no sleeves.
craze is right about the type of pump and impeller and make the clearance as close to the impeller without hitting it, I listened to the people here wearj and my flow improved a lot and it stays cooler, I run an 180 deg thermostat.