M20b25 piston ring end gap

[nickphine]

Hi there, does anyone have any practical experience of ring end gaps. The manual says .2 to .5 mm but then goes on to say 1mm is not excessive. Mine are approx 1.5 mm which on the face of it sounds rubbish, but is it one of those where someone who builds m20's all the time says actually that's fine...

Any info would be appreciated

[HairyScreech]

well it wont do any harm, but its not great, ill have a think and a dig and come back on that one, i havent looked at the rings too closely thus far.

[CHR1S1990]

not great IMO as youre probably aware some of your precious cylinder pressure will be leaking into the crankcase losing you free power - however though I dont think its worth pulling it apart to change them! What is your CR?

1.5mm however is ideal for a forced induction/nitrous motors with increased heat and cylinder pressures if that is of any comfort

[CHR1S1990]

just found an example in one of my books:

350ci Chevrolet

reducing ring gap from 0.6096mm by 0.2302mm to 0.4064mm gained 30 horses!