I’m rebuilding my Escort Cosworth engine, and after installing the pistons, I noticed that they protrude ever so slightly out the top of the block. I expected them to be flush with the top of the block. Is this normal? (I hope so ) These are new pistons, and the block has been bored etc.

Cheers
John

 

if the block has been skimmed this may explain why - how much are we talking, less than half a millimetre, this may be ok if fitting a slightly thicker gead gasket like the cometic one.

 

Yes, the block has been refaced, and I will be fitting a 4 layer WRC head gasket. It’s probably only just protruding, I’d say less than 1mm. I’ll measure it tonight, and post my findings tomorrow.

Cheers
John

 

hi john,std deck height on cosssy yb is+ 0.45-0.5mm,any more may cause pistons to clip head under full load as rods stretch and as bearing and pin clearances add up.WRC gasket is normally 1.15mm compressed so you should run at least 30 thou or 0.75mm clearance between piston crowns ane head face.1.15mm(check each gasket though)-0.75mm=0.4mm max safe deck height-regards PJ

 

OK, I measured my piston crown to block height last night. It was protruding by .59mm, and the WRC gasket measured 1.25mm. I measured the gasket by the little brass rivets, but I’m sure the actual gasket when installed will compress a little further. So if the gasket does compress to 1.15mm as per PJ-Msports post above, that will leave me with a clearance of 1.15mm - .59mm = .56mm from the piston crown to bottom of the head.

Cheers
John