Hot Rods Cooling problems

I have a 302 with an aluminum radiator and new water pump. I recently did a cooling system flush and had the water clear before sealing the system again and refilling with 50/50. Engine continued running hot so that's when I changed the water pump, hoses, and new thermostat(not all at once but over time while chassing the problem). Before all of that I was finding these tiny pieces of ferrous material stuck in the top of the radiator. So I would stick a magnet in, get as much out as possible, refill with water, run up to temp and repeat the process until I was getting no more out.
Cut to now where all in the cooling system is new and the engine started running hot again (215-220). Let it cool off and in with the magnet again to find it covered in ferrous material.
Car ran great while system was initially clean but obviously can't cool itself with a clogged radiator. Where is this ferrous material coming from? There is no water in the oil or white smoke. I'm at a loss where this material is coming from or how to stop it. Anyone seen anything like this?

 

Looks like rust from the water jackets .

Tommy

 

While I can't say for sure, the bottom of the engine in the coolant passages. Depending on how you drained it, block plug removal or just dropping the rad hose, you may or may not be cleaning it out when you flush before the fill.

 

I only dropped the radiator hoses.

 

My first thought debris from boring. There is a block plug on both sides, on my 289 anyways. So flush with plugs removed but not sure how much crap you going to get out? Removing freeze pugs and flushing with garden hose would be great but access wouldn't be fun. How about going to the Box store and getting a piece of brass drain pipe in 1-1/2 " dia and remove a section of upper hose and use brass pipe as connector with a couple magnets glued inside? Pretty sure there are filters to go in upper hose if you search.

 

I've got to go with crud that got broken loose from the nooks and crannies of the block but didn't get flushed out of the cooling system.
I'd drain the cooling system. pull the radiator off and turn it upside down and flush it with a hose to see if I couldn't break that stuff loose and flush it out. If that doesn't work a radiator shop should be able to flush it.
After you get that taken care of and before you get your undies in too big of a knot over the temp it wants to run at do some homework and see what temp those engines actually ran at in the donor car it came out of. 215/225 isn't actually hot in most post mid 70's production cars. Put the same engine that ran fine in the donor with a 195 thermostat in it in an old car and the owner looses his mind because the engine wants to run at the same temp it always ran at.

 

You might be surprised then at what gets wash out next time when you do. I myself would drain some of the mix out, dump in a couple gallons of cheap white vinegar, bring it up to temp , let cool, do this a couple three times then drain the system. Both side plugs, thermostat, pull the rad to reverse flush. flush out the block. The crap seems to collect at the base of the water jacket and around the cylinders, as mentioned, rust, scale and sand.

 

Might also consider one of these https://ganofilters.com/

 

The only way to get the block really clean is to pull all the core plugs and dig around in the water jackets to get all the crud loose and then flush the block. You will be amazed at what will come out then.

 

I recall on the FordBarn, a member did several runs/changes with evapo-rust. Unsure of the mix though. I wonder if a Citric acid mix would would to dissolve stuff?

 

This actually all started from using Thermocure to clean the system. I'm on the tail end of getting the cooling issue resolved and am just chasing this last little bit of crud in the tank.
I've actually had this system drained and opened too many times to count now so the last thing I want to do is drain and open it once more. So today I opened an old hard drive and robbed it of its heavy duty magnet and setup a semi redneck operation of fishing out the last bits of crud. I did let the thermostat open and then let the car idle for close to 40min while I fished out particles. Hoping now to have most of it out now. Thanks for all of the replies and suggestions.