A bit of an unusual one to ask but does anyone know the coolant capacity of just the block and head? My spare engine has some internal rust so I plan on filling it up with Evapo-rust, leaving it for a day or so and flush it out a few times. At about £35 per gallon I don't want to over buy the stuff but also want to have enough to get everywhere in the coolant passages.

Thanks

 

I did the same thing with my latest build. I used Krud Kutter but in a spray bottle. I sprayed it into the coolant passages, let it sit overnight and went in with a small chimney brush attached to a drill (through the freeze plug holes/ thermostat & water pump holes). I'm pretty sure evaporust and krud kutter both use phosphoric acid as the active rust converter. When you do this, it's important to physically brush the coolant passages after treatment. Phosphoric acid chemically reacts with iron oxide, turning it into iron phosphate. Everything will be coated with iron phosphate and prevent proper heat dissipation unless you scrub it away. Also, be careful to keep the acid away from sealing and bearing surfaces. The acid can eat it's way into those crucial surfaces if left too long. I only used about a quart of acid but that's with a spray bottle. If you want to actually fill the block and head, 1 gallon should be sufficient.

 

Krud Kutter doesn't look like a product really available over here. Doing more research into it I have found a product called Evapo-Rust Thermocure which is designed to go in the cooling system, run it for a few days then drain out and flush thoroughly. Although I cannot run this engine as it is out of the car, looking at some videos of the stuff I feel it looks to do a good job. You get 1 quart and add water to it at a set dilution. I couldn't replicate the heat of an operating system, but could get the water pump to spin to get a flow through the system. I still have the radiator and hoses so can close the system back up.

Thanks for the tips on brushing everything after treatment. The core plugs are coming out and being replaced so I will have access as best you can get to brush inside.