MY 66 Chevy Cooling system flush questions

[66K10383]

Now that I got my truck running time to do some maintenance. Ive had it around 2 years and the only thing Ive done to the cooling system was change a sticky thermostat with a new NAPA thermostat that still stuck just as bad.

There is no rust that I know of in the antifreeze its self, mainly just mineral deposits.
Id assume it is from someone using a garden hose for the water source.

What would you recomend for a system flush?The petcock is froze up on the radiator so I will probably pull the lower hose to drain it.
I would like to flush the radiator and the block, so could I just pull the upper and lower hoses, stuff a garden hose in the upper hose and blast it?
Could I do the same in the thermostat housing in the intake?
While Im at it I might as well change the thermostat again, What is the best temperature to run?
How many gallons of anti freeze will it take?
Im sure the radiator is the original Harrison rad. cooling a 350 block stroked out
I have 4 gallons of Prestone 50/50 mix and Im hoping it willl be enough.

Thanks

Thanks

[61_FL_Apache]

I just did this to my daughters 99 Camaro last week. I added a Peak heavy duty rad flush. It said you can run it 6-9 hrs total run time. I left it in there for a week. That was probably 4-5 hrs total run time.

To flush:
I removed the T-stat and put the hose back on.
Ran the engine with the petcock wide open, garden hose in the rad cap opening with the hose running.
Keep an eye on the temp but it should stay cool with fresh water coming in.
Wait till water was clear.
Drained the system.
Refilled with one gal of coolant and water to top off.

Notes:
her car recommends a 195 stat, so I replaced with the same.

In my truck im running a 160 stat with no issues at all. You can run a 180 and be fine too.

These systems dont hold that much so you have plenty. With a drained system, I start with 1 gal of coolant then top off with water.

[LostMy65]

I read recently in these forums to not use tap or well water with your coolant, but rather distilled.

[Slow Build]

I have one of those Prestone flush T's on the heater hose for mine. I usually run some flush that stays in for a while like 61_FL_Apache said. Then connect hose to tee remove cap, shove in exit tube and flush with engine running, heater on until it runs clear. Drain (you'll have to pull lower hose) and start filling with the cap off of the T until the clear water is displaced by the 50/50 antifreeze (until it goes from clear to green), replace the T's cap, fill and burp. Works for me.

[Captainfab]

There are a couple of ways to go about this. One is to use the Prestone flush kit as Slow Build mentioned. Just follow the directions with the kit. The other is to remove both hoses from the radiator and flush it out with a garden hose. You can do the same with the engine by removing the thermostat, and also the 2 pipe plugs on either side of the block just above the oil pan rail. Those 2 holes are typically plugged with sediment, but you can open them up with a small screwdriver. Then just reassemble and fill with a 50/50 mix of antifreeze. Just how much depends on what size of radiator you have, but 4 gals should be enough. And yes it is better to use distilled H2O, but not everyone does.