Bluish cylinders

General engine tech -- Drag Racing to Circle Track

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joe 90
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Re: Bluish cylinders

Post by joe 90 » Wed Sep 06, 2017 1:39 am

The pistons got too hot, too big, too tight.
Aluminium pistons +too much heat = aluminium oxide.
It's abrasive.

You see this exact same damage very often with diesels which have leaking injectors.
Caused by pre ignition.


If you measure the diameter of the skirt(s) you might find that it's shrunk.
That's compared to the specs you had when it was built.


One of the most common mistakes made by the ricer crowd is to fit the biggest fuel pump they can get, fit a low quality FPR and then either refuse to measure the fuel pressure......OR.......if they do measure it, they've got no idea what they're looking at on the gauge.
That's a universal problem with ricers and turbos.


Then when they pull the plugs, they're sooty around the outside and white in the middle.




Oh but it must work...........everyone else does the exact same mods?

Matt80
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Re: Bluish cylinders

Post by Matt80 » Sat Sep 09, 2017 2:35 am

So aren't the mains a bit short on clearance?

And what about this wear? Nothing to worry about?

Image

About the fuel wash/map issue, I read somewhere that rpm limiter with ignition cut only could have caused that wear on pistons/cylinders: do you agree? Thanks

naukkis79
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Re: Bluish cylinders

Post by naukkis79 » Sat Sep 09, 2017 4:55 am

Matt80 wrote:So aren't the mains a bit short on clearance?
Nope, just about right.
And what about this wear? Nothing to worry about?
Image
That spot might have had some debris under bearing shell.

Block has lightly warped after line boring, totally normal and harmless. You can line hone main bearing line and get rid of those marks - but will get bigger main bearing clearances in that trade - not better situation than what you have now. Line boring to bigger bearing will fix things - but will need bigger outer surface bearings. You have not problem with current situation so better to keep it that way.

About the fuel wash/map issue, I read somewhere that rpm limiter with ignition cut only could have caused that wear on pistons/cylinders: do you agree? Thanks
Yes, unburned fuel will cool piston and cylinder and fuel will be condensed everywhere. Man should always cut fuel together with ignition when hitting hard limiter.

Matt80
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Re: Bluish cylinders

Post by Matt80 » Tue Oct 17, 2017 9:41 am

This is the back of those main bearings:

Image


And these are the conrod ones:

Image
Image
Image

even here there are some marks and discolourations

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