Rb26 Piston Bore Clearance

[yogi000]

Hey Guys,

I've just pulled down my engine and found that its running N1 pistons - p/n A2010-AA472 and my piston to bore clearances seem fairly large. On average i'm seeing about 0.113-0.115 clearance.

I know the factory recommendation is 0.035-0.055.

What do you guys usually run on rebuilds? should i be concerned with such large clearances?

Thanks in advance.

[jhjones]

pistons

[89CAL]

Are you talking thou or mm when you are measuring? Because if you are measuring in thou then the nissan spec is most likely mm in which case you are on the lower end of the tolerance

Edited July 21, 2014 by 89CAL

[AngryRB]

Id say your talking mm there, so factory would be 1.5ish to 2ish thou clearance, so in that case you have about 4 1/2thou which is a lot for a cast piston.

Did you have much piston slap and blow by when it was running?

Edited July 21, 2014 by AngryRB

[yogi000]

i'm talking mm.

all measured up with micrometer.

No catch can, only a slight film of oil on the intake pipework when stripped down, never used oil and the engine wasn't loud or out of the ordinary. It was running like this for about 6 years making about 270-290kw

I'm alittle stumped by these measurements.

[scotty nm35]

Pistons aren't round, how were you measuring them?

[AngryRB]

Pistons aren't round, how were you measuring them?

how could they seal if they weren't round?

[scotty nm35]

Pistons don't seal anything, the rings do.

[jiffo]

Pistons aren't round, how were you measuring them?

And where on the piston were you measuring?

Skirt will be different to centre and will be different to top.

Were you right at the top?

[GTSBoy]

What Scotty's saying is they're not round as in they measure different across the pin bore compared to along the pin bore (when cold, in your hand).

[AngryRB]

ah ok, I get it now, different expansion rates due to the piston thickness around the pin etc

Edited July 22, 2014 by AngryRB

[yogi000]

hey guys,

pistons remeasured today at approx. 15mm from bottom of piston and bores measures approx 55mm from top

I'm abit happier with the results today. Clearances of between 0.081 to 0.107. I still thinks she's a pretty lose engine.