How much coolant in a 351W block?

[grybrd123]

I'm changing my coolant, and to calculate the amount of antifreeze I need in my system, I'd like to know how much coolant a 351W block holds. Draining the block is not an option.

Anyone know?

[patrickt]

Originally Posted by grybrd123

I'm changing my coolant, and to calculate the amount of antifreeze I need in my system, I'd like to know how much coolant a 351W block holds. Draining the block is not an option.

Anyone know?

What was in there before? Straight water? Just drain it at the petcock, fill it up with, say, a 50/50 mix of coolant and distilled water that you mixed before pouring it in to the radiator, then run the car to mix it up, and when it cools off check it with a hydrometer. If you live in a really, really cold place, then just up the percentage appropriately. And most Ford small block systems hold less than four gallons, total.

[grybrd123]

After repeated flushes, the block is now filled with distilled water. I know the volume of the rest of the system. If I know how much the block holds, I can calculate the total amount of antifreeze required to make 50%. Filling the radiator and hoses with 50% will result in a less concentrated solution because the water in the block will dilute it.

[patrickt]

You're going to have to check it with a hydrometer anyway, and if the percentage is high or low you just drain a little out and replace it with pure coolant or pure distilled water, depending. I don't think as much stays in the bottom of the block as you think.

[Dwight]

You don't say where you live, but in North Alabama we run 25% max.

Add one gallon of anti-freeze and then fill the system with distilled water. It will be 24% to 30%.

If you drive your Cobra in 32 degree weather you may need 50% antifreeze. But remember distilled water is 20% more efficient in cooling your motor than 50% anti-freeze.
Most of us keep our Cobra in the garage during cold weather.

Dwight