http://www.elprototypes.com/Scion.htm

What does a Block Guard Do that is on this site.

 

Looks like it's a device used to extract money from suckers.

 

:? It looks to me as if it slips down into the water jacket of the block, perhaps to strengthen it. That might be why there are all of those little holes in it- so the coolant can still pass. I agree with the guy above, I don't believe that I'll ever need one.

Unless I enter my xB in Top Fuel or somethin'.

 

it is inyended to stabilize the upper part of the cylinder sleves. they can float and lose sealing and loss of power.
the holes are for the water to flow through.

 

That actually sounds like a good idea. How effective do you think this piece is?

 

i think it might be more useful when used in boosted motors

 

it is designed to help high reving motors. so boosted or not should benefit (good idea for boosted thou...)

 

This is something that has been used on Hondas for a long time. Our engine blocks use "floating" sleeves, meaning that the top of the cylinder sleeves are not connected to the top of the block. During boost, preassure levels inside the combustion chambers can rise suddenly and can cause the sleeves to move. The block gard is designed to support the top of the cylinders and keep them in place.
There are a few problems with them..
1. The differences in material and their corresponding different expansion rates can cause distortion. You could end up with sleeves that are narrower in diameter at the top. it takes a while for this to happen and it also depends greatly on how well the engine is tunned.
2. Poor installation. If these are installed crooked, they will distort the cylinders' spacing.
3. Cooling problems when the holes for coolant to flow don't align well with either the head gasket or the passages in the cylinder head.

I would not use them unless it's a race car where tearing the engine down is done on a regular basis.