i am taking my block in wed morning to the machine shop for a mild 355 build.how mportant is"ZERO DECKING"? and what are some services that might also be requested or confirmed before $ change hands or i get handed back a substandard shortblock?

 

Zero decking per se is not of much importance. It just refers to cutting the block deck to a predtermined height is order for the piston crown to end up flush ("zero") with the deck surface. A stock SBC has a nominal 9.025" deck height. If you use a 3.480" stock stroke crank, a stock length 5.700" con rod, and an off the shelf piston with a 1.560" compression height, that adds up to exactly 9.000". The block needs to be cut 0.025" for "zero deck". This practice orignated as part of "blueprinting" and was a way to raise CR with stock components. It also makes the deck flat, which helps gasket sealing, and makes it square to the mains, which potentially helps hp by eliminating cylinder to cylinder differences. It also provides a good quench distance when used standard gaskets, which are ~0.040" thick. So, it is common practice but is not necessary except if a max effort motor is being built or the deck is not flat or is markedly off square. It really depends on what other parts you have chosen and what you are building.

BTW: the CR of a 350 that is zero decked versus 0.025" in the hole is substantial, the increase is about 0.5:1. So, you have to be careful in order to get what you are expecting. It may be better to have the piston "down in the hole" to achieve the desired CR. This is often done deliberatly with blower motors.

Rich

 

Good information!

 

Rich,

I can't believe you never went into a full blown discussion to explain quench in that whole great discussion about zero decking. I considered very carefully my quench as the reason for zero deck and my gasket at 0.039.

Bad,

Stop what you are doing right now and order this book: http://www.amazon.com/Rebuild-Small-...1295779&sr=8-1
It will explain everything that you should be asking about at the machine shop.

 

i dropped off block at machine shop this morning and told him "deck block and forget thin gaskets". i am shootong for 10.6-11 to 1 cr with a cc304 cam,stock valvetrain and .030 over

 

Reading comprehension > you

"It also provides a good quench distance when used standard gaskets, which are ~0.040" thick."

Rich

 

Do you know what DCR you are shooting for? Might want to confirm this.

 

i guess dcr is dynamic comp ratio? i would say stock or a tad more-very mild 355 want headaches to a minimum-thanks for great input,LOVE this forum-

 

your running a stock valvetrain with an aftermarket cam and you say you don't want headaches?? Read a little more on cam swaps in the LT1 before you install the cam and valvetrain

 

Completely agree. Valvetrain is the LAST place you should ever skimp on parts.