[bnorris_74]

Originally Posted by baron_

A clog somewhere?
I'm on my way to stick the garden hose in the top of the motor for a few minutes and flush things out

I think you're on to something there. From the looks of the rusty water stains on the outside of the radiator and valve covers, I'd bet you've got some serious flushing to do.

[baron_]

all good ideas


I'm pretty sure it isn't just the sending unit tho
Its splurging out some nasty looking stuff when it overheats


I've been flushing it out for the last hour
Some really nasty red stuff coming out. And keeps coming out
I fill up the system, warm it up....and can get another load of nasty red stuff

[steve]

it was running ok prior to this ?

[baron_]

Just had a cam put in the engine
Its a stock motor, more or less that I got second hand...
New gaskets, new heads (6x) that I had rebuilt



Overheated again
I tried a new radiator (aluminum) and different radiator hoses (the type with metal wire in them, to make sure they weren't collapsing)


The only things I haven't touched (yet) are the crank pulley (recently painted, but i cleaned it up with sandpaper - so i don't think its slipping and those AN cooling lines plumbed to the back of the heads


Its still full of red crap. I've flushed it about 7 times now...

[bnorris_74]

Its splurging out some nasty looking stuff when it overheats

I think you'll need a recovery tank for the radiator, at least from what I can tell from looking at your cap. (after you get it flushed real well).

You might try removing those fittings at the back of the heads and run water through the block that way with the lower radiator hose disconnected.

[steve]

i think it sat a long time and has serious build-up in there. i flushed mine by removing the t stat and putting the hose in the inlet of the rad and letting the water drain out the disconnected hose from the top of the rad while running until it runs clear, but you may need a pro flush and rad clean after this ! you might not be able to get it all with a hose ! i guess you could go crazy and try to remove the water jacket plugs but i have never done that....you would need a second opinion.....

[baron_]

I'm at about 9 flushings now. Still a stock motor (stock bottom end), so yea...40 years of buildup.
But would that really make it overheat? I guess if its got a clog or blockage somewhere in it...

I can put the hose in various spots (radiator inlet, outlet) and flush it for about 3 minutes, until it finally turns clear


Then I run the car for about 3 minutes....and its dirty enough that you can't even tell i flushed it the first time - and need to repeat water hose in outlet, then inlet, etc...


I've been thinking about those little plugs on the side of the block....rather scared I'll break one, though
Tomorrow the AN hoses to the rear of the heads get plugged and see if that does anything

[GOAT8U2]

RMI 25 will seriously clean out a clogged rad of rust and build up. It also reduces temps better than Water Wetter.

What is your timing setup like, manifold vacuum, vacuum advance etc?
With vacuum advance, if you can get it to idle around 22 degrees that would help lower egts.

[chiphead]

If your water jackets have that much rust and scale, then your radiator is plugged up. There's no flushing it, all the scale compacts in the radiator tubes and wont budge. You'll have to take it to a radiator shop and have it rodded out. A P350 in my car did the same thing, and my radiator hasn't been the same since.

[steve]

Originally Posted by chiphead

If your water jackets have that much rust and scale, then your radiator is plugged up. There's no flushing it, all the scale compacts in the radiator tubes and wont budge. You'll have to take it to a radiator shop and have it rodded out. A P350 in my car did the same thing, and my radiator hasn't been the same since.

i agree !

[baron_]

Just tried two radiators (so that might not be good, if both are now clogged)
Second one overheated pretty quickly too
Theres not really any rust chunks or anything - just lots of really really little stuff
Almost looks like mud (but who knows otherwise)
Seems to be good flow going through


I have it at about 14 initial
35 total (or so)
6x heads on a 389, so low compression...
ported vacuum at the moment (because it was easy - port on carb)
I have been intending to switch to manifold, but never got that far with the overheating issues


Would timing be that big of a deal? I figure i'm close enough that it shouldn't be overheating
Maybe if i was way off...

[lust4speed]

I've never had any problems removing any of the 1/8" NPT side plugs on the block. If they are original, they will be pretty eaten out on their bottoms. Pick up two new brass plugs before removing the old ones so you won't have to put the old stuff back in.

I'll probably get some "heat" for this, but if you analyze the water flow on a Pontiac engine, the water comes in the block with most of the coolant flowing to the rear, and then circulates up to the heads and finally out to the radiator. Heads are the main heat producing area of an engine; and when you bypass a large percentage of cooling water out the rear of the head, I can't see anything good coming of it. The argument is whether Pontiac knew what they were doing, or has someone come up with a better idea? My thought is that having a large percentage of water exit at the rear, the front cylinders might not be getting enough coolant flow. Has anyone taken temp readings to see if the average cylinder head temps remain even? Water temp at the cross-over won't tell you this, and in fact might read lower because more heat is being retained in the engine. Just food for thought.

Retarded timing equals more heat, and running manifold vacuum will help at idle; but as soon as you crack the throttle, ported vacuum will equal manifold vacuum so there should be no difference when you're cruising along. Vacuum advance does help the engine run cooler and increase your mileage.

I did testing to see if lowering the water pump speed (and therefore fan speed) would really make that much difference in running temps. What I found was simply that the faster you turned the water pump and fan, the cooler the engine would run. Nothing worked as good as the 8" bottom pulley and 6-1/2" top pulley. This was with the 19-1/2" fan with the severe duty Hayden clutch fan, and the matching fan shroud.

[GOAT8U2]

How much advance do you have, at least 12 degrees?
There isn't a point in running ported vacuum unless you're concerned about emissions. Manifold vacuum with vac advance will idle smoother on big cams, have better mpg and minor acceleration. Watch how much the idle goes up after adding the advance.

You'll notice some difference in cooling since idling is an easy way to heat up the cooling system.

[GoatDr]

I don't see where you have changed the t-stat. I put a high flow in and it lowered my temps from 210 to 185. Regular t-stat was restricting the flow.

[baron_]

Here's the crap that's coming out of it...

I've already flushed it like 9 times (maybe more)


I let it run for a few minutes and its nasty as hell
I can flush with the hose for 2 minutes or so and it'll be clear - can't get anything else out


But i start the motor, let it run....and flush again...and it looks like this


Rust, no?
Oil looks clean. Stock motor...40 years old...
Its not chunky at all, just looks like mud

Heads were rebuilt...and cleaned
So this has to be water jacket stuff?

Should i take the water pump off and try flushing in that manner?

[george kujanski]

You still have the heater core hooked up?

George

[baron_]

Nope.
Timing cover nipple blocked

Both rear nipples on the head routed to the crossover (routed to the same spot)

Done for the night. I'm sure the neighbors hate me
Tomorrow I'll unhook and block those nipples on the back of the heads

[GOAT8U2]

That's a crazy amount of crude in there, I'd ditch that rad for a Summit aluminum and flush out the block and start over. Damn that's the worse tomato soup I've seen out of any rad, especially on it's 9th flush.

[bnorris_74]

Back in the day, I worked at a gas station/garage that had a nozzle that screwed onto a garden hose and another place to plug in an air hose. If I remember correctly, we would remove a heater hose and put the the end of the nozzle in it. We also disconnected the bottom radiator hose. Then turn on the water and give it a shot of air. After a minute or so the air would be the only thing coming out of the radiator hose. We would turn off the air and let the water fill the block and then hit it with the air again.
The bad news is that after a week or so, the cars with the really cruddy systems would be back in for soft plugs.

[ctgross]

Clay, are you using any type flush additive or just water? A couple of heaping tablespoons of dishwasher granuals(I use Cascade) will greatly help break that stuff loose. I've used it several times on my goat and an old Bronco I had. Its a good cheap flush.