Block filler probably makes the block stiffer, right? Does it go in the coolant area or what? Does it affect the cooling abilities of the engine? Is it lighter than coolant would be? Just curious. I'm not actually thinking of using it, but was just wondering what the benefits/drawbacks are. Thanks

 

You fill the water jackets in the block with it. It's basically like concrete once it hardens. The point is to stabilize the cylinders in the case.

If you fill it completely, you obviously no longer have a cooling system in the block. Some people fill them partway which lets them still have water circulation to where they can run it on the street. It's mostly for strip-only cars though.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Is there some horsepower or torque level where it becomes advisable to use it?

 

When four bolt splayed/studded main caps and main cap girdles no longer hold the bottom end together, it is advisable to bondo the block of your next replacement engine. A properly prepared SBC will hold together pretty well with 850+ HP coming out the crank at 8,500+ RPM, so unless you're pushing those limits, don't even consider it.

(HINT: NASCAR engines have a complete cooling system.)

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Vader
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another advantage.
the reason for reverse-flow cooling was to cool the heads first and keep the bottom of the bores warmer. The warmer bore stays more round and presents less drag to the piston. Keeping the block stiff and at an even temperature is to your advantage.
For power production, the idea is to keep the oil warm and the coolant cool.

 

yup the engine guy always said hot oil, cold coolant makes a happy motor!