Just a quick one, does anyone run these pistons as ive just bought a set and supplied by my engine builder, ive just rebuilt the whole engine to find out the pistons are touching the ridge of the combustion chamber, the piston comp is 7:5:1, just wondering as the standard pistons are tappered around the top and these are not, so they must need the crown re machining am I right on this, buy the way theres plenty left on the head and im using a standard ford gasket, not a spacer, any help appreciated.
Tel

 

are they totally flat topped?

How much do they stick out of the block at TDC? If they are sticking out more than 1mm, they are not at 7.5:1. Mine is 7.4:1 and deck height is 0.41mm. Most forged flat topped pistons need machining down to the required compression. E.G. My cosworth racing needed over 2mm taking off.

 

Also what head are you fitting, Hemi or lean burn?

has the head or block been skimmed?

And what block, crank and rods are you using?