i saw on spec sheet for 408sb it read, steam holes plugged ? for what reason would this be done?
it was for a sreet car, what does doing so achieve?
thanks

 

400 blocks (regardless of overbore) require the steam holes for street use; otherwise, there is a risk of pockets of steam developing under the block deck at those points during periods of extended idling. A block with more than .030" overbore will aggravate the need for the holes.

Having them plugged may increase the deck rigidity slightly, for racing.

It accomplishes nothing for the street. In fact, it is a street-hostile mod.

 

thank you for clearing that up for me i figure people do things for a reason
i didnt understand why until now.
once again thanks.

so if i were to put my afr's off my 355 onto a 400 i would need to drill holes in my heads to match the 400's steam holes right? is this something that i should let my local performance/machine shop do

 

Yes.

No, you can do it yourself, with a hand drill.

6 3/16" holes per head.

Use a 400 head gasket as a template. Mark them with a center punch. Angle the ones on the intake side, toward the exhaust at a 30 - 45° angle, rather than going straight in.

 

cool! thanks again.

 

"13) 400 BLOCKS:
Steam holes are recommended for all 400 block applications. Use a 400
gasket as a template and drill the three holes nearest the spark plug side of the head straight down, the other three which are very near the head bolt holes should be drilled at a 30 degree angle away from the bolt hole. The center hole will intersect water about 1" down and the two outboard holes to a depth of 2 1/4". Use a 1/8 drill. "

 

i never thought to ask about depth but i presume it would be pointless to just drill a shallow colloum out my heads.

if you have plug holes for strength at cost of drivability why not go with a better block or choose another alternative y'know