I have a rebuilt 70-455 motor..030 over with E heads.The machist took .100 tousandths out of the 10.5 to 1 pistons.The deck and heads have a clean up cut on them.Would anyone know what the compression would be roughly after the machining?

 

I'm confused.....where did the machinist take .100" out of the pistons?

 

Off the face.

 

A few things you'll have to obtain to make a good calculation: Piston to deck height at TDC, Combustion chamber volume, head gasket thickness (crushed), any valve recess or dome in the piston, Although the factory advertised 10.5:1, that was blueprinted specs with a steel shim gasket. Good luck with your engine build.

 

So the pistons are now .135" in the hole instead of .035" stock? What brand pistons are being used? I'm assuming with the information given, it's now a flat top piston?

4.155 bore
4.250 stroke
flat top pistons (now)
77cc combustion chamber
.038 compressed gasket thickness
.135 deck clearance

9.18:1 but 8.9:1 with 80cc combustion chamber which is probably more realistic

 

Speed pro pistons.