Damaged piston crown

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Comment by Dave Price on June 13, 2011 at 22:12

I had rotated the piston to find the greatest gap, the greatest gap was .002.  The piston I used was a low mileage piston from another engine (standard size).  Quickly checked another bore tonight (had to be quick should have been washing the caravan), with the piston ring gap.  That bore showed .0025 wear.  This was one of the middle cylinders, I am sure that I had read somewhere that the Essex engine shows wear first / most in the middle bores.  So if the most wear I have is .0025" then this engine should have some life left in it.  Not bad considering the engine and 'box only cost £50.

Comment by Dave Price on June 8, 2011 at 21:27

Stephen, I followed your advice. 

1) Piston ring gap.  Top of bore gap 1.30mm, bottom of the sweep path 1.45mm.  So 0.15mm increase in bore circumference.  Rough conversion to diameter equates (3.14 etc Pi) to 0.05mm (I think that is 2 thou)

2) Piston gap.  Easier said than done trying to measure the gap when the piston is upside down in the bore.  This appeared to show an increase in gap of 0.05mm (Again I think this 2 thou)

Had to measure in milimeters as my imperial feeler gauge is too rusty to read the numbers on the blades.

I would be grateful if somebody could confirm my conversion to imperial thou'.  I would assume that wear of 2 thou is acceptable, is that correct?

Comment by Dave Price on June 1, 2011 at 21:41

I recall reading some where you can check bore wear by placing new rings in the bore and checking the gap in the rings will a feeler gauge.  Then move the rings down with a piston and check the gap lower down the bore.  I can't find where I read this.  Anybody able to have a guess at the size of gap I should be recording?  Or how else to roughly check bore wear?