What can cause that ?

[jonask]

Hi, I was looking at my pistons.

One of them (#6, the nearest one from the firewall) is cracked


is this caused by :
- Overheat ?
- Bad oil ?
- ... ?

I want to know so I don't repeat myself

Thank you,

[99_SI]

Cylinder 6 running lean causing high heat

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[jonask]

is there a way to prevent that other than heat itself (oil cooler big FMIC) ?

[bobbo]

Is your car completely stock?
If I'm running my car hard I add fuel (1.5% if memory serves) to #6 for better cooling. Apparetnly because of the intake manifold design #6 can run leaner risking detonation on unmodifed RB.

[jonask]

the rb20 pulled exactly 304 wtq and 306 whp on a mustang dyno with stock internals, car is mainly for drifting and track.

I wonder how you do the trick to add 1.5% of fuel in #6, do you have an aftermarket ecu ?
what modification should be done to the engine to prevent that ?

I'm swapping an rb25 neo in the chassis, hope this kind of problem won't happen...

[99_SI]

Stock rb20 shouldn't have that since you have an equal length intake manifold. I would look at the fuel rail and injectors.

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[jonask]

injectors were new (sard 550cc from rhdjapan) however fuel rail was oem, maybe this was the problem ? should I check for aftermarket fuel rails ?