safe max to deck the block

[OUTLAW]

I have a spare 74 360 short block sitting here and noticed the pistons sit .080 down the bore at TDC. Since it is a 8.4 compression motor I was wondering if anyone knew the safe max that can be taken off the deck without weakening it and how much it would raise compression

 

[Sanguine]

max: 0.060" to 0.075"

I would look into new pistons with a larger pin height if you want to increase compression, then maybe fine tune it with decking or planing the heads...you dont want to deck anymore than you have to...

When you deck you have to remove some from the intake surface, same as if you were planing the head

you will roughly get .145 point of compression per 0.010" decked on your 360

you will get about 1 pt of compression if you decked it to the max...you could easily get this and more with a set of flat top zero deck pistons

 

[rumblefish360]

Watch out for zero deck pistons and the head you have.
There speced out to be 9.8-1 with open chambered heads and a .039 gasket. Thats a tight quench area. To much gasket and you'll lose the bennifit of the quenched area.

 

[dgc333]

Watch out for zero deck pistons and the head you have.
There speced out to be 9.8-1 with open chambered heads and a .039 gasket. Thats a tight quench area. To much gasket and you'll lose the bennifit of the quenched area.

KB107 pisotns have the highest compression height of off the shelf pistons. These will wind up approximatley 0.015" in the hole on a typical non-decked block. With a typical 70cc open chamber head and a typical Fel-Pro 4.150 x 0.039" head gasket you will get 9.6:1 compression. With this type of piston and an open chamber head you do not get any quench. You would need to get a step/dish piston to provide a quench with open chamber heads.

It would likely be cheaper to change pistons than to deck the block 0.080" and machine the intake to match.

BTW, if your pistons are 0.080" in the hole your compression is more like 7.5:1

 

[rumblefish360]

Dgc, mine came in a zero deck on a '79 engine out of a Doba. I purchsed it off the Son of the orginal owner whom swears it was never apart.