Pistons

[Blocker]

Are we talking 253 here Blocker? Original 253's were flat tops and later (HX-VB/HZ) were lumpy tops. Dish tops in a 253 would suit turbo applications or a low compression engine.

Yes mate it is my late 1974 253. I have misplaced my HJ workshop book so thanks for clearing that up.

if you're doing a motor / driveline these will help

ABOUT DISPLACEMENT, VOLUMETRIC (VE) EFFICIENCY, AND CFM
http://www.edelbrock.com/automotive_...disc_cfm.shtml

ABOUT COMPRESSION RATIO
http://www.edelbrock.com/automotive_...mp_ratio.shtml

COMPUTING HP AND TORQUE
http://www.edelbrock.com/automotive_..._disc_hp.shtml

It's no big secret dispite what most mechanics will try to make you believe

Cubes x rpm x compression = X hp (providing the VE is correct)

Just like ETs. If you dont have the correct ratios / tyre size etc 2million hp wont do shit

math is everything

Thanks for the links they will come in handy when I'm talking to mechanics who can rebuild this for me.