speed rII

ok, had some time today and I cleaned up all the engine parts. It's a PITA job, but rebuilding a dirty engine is like shooting ones own leg.

I allso looked at the scrachs in the cyl 5, and noticed that they were not scraches at all. The bearing material had gone between piston and bore and sized there...
So I did the major no no and used a 400grid wetsanding paper and carefully removed the bearingmaterial from the bores...

Before, you can feel the marks with your finger.



After, just slight discolouring in the bore. Can't feel marks with finger.



I think that this worked out real well, or time will tell if I'm wrong.
I will measure the cylinder's next time I work with the engine. I will use this engine anyhow so I will do this just for curious.

I will allso take the pistons to be coated, just in case.

speed rII

Oh, and the bore did not polished at all. I took the last picture after I had cleaned the bore with motoroilled rag..

Flat6 Innovations

The sound of this process scares the **** out of me. I will wait eagerly to see how it works for you. I've never had the ***** to try that!

logray

Holy crap. Wow.

speed rII

You can imagine how long it took to make the decision...

It took long time to finish this and like I said, time will tell if this was mistake

I will have the pistons coated to make the friction on skirts to bore minimum..

But at this point, I had the scraches in the cyl, so I would lose very litle if this method won't work.

And If this would be someone elses engine, I would have fixed it some other way.

speed rII

so, what next? Just discovered that my 1-3 block is new at least not original. Pistons n# 1 to 3 had goetze rings...

So the engine has been opened before.

dcdrechsel

Didn't know you can get aftermarket rings .Wonder if they cost less than 150.00 a hole and hold up ? What rings will you use to reassemble ?

speed rII

I will use the same rings, just took the rings of becouse I have the pistons coated.

Apparently goetze makes rings for 996, the 1-3 cyl rings had "goe" stamped on top side of the top rings.

Well, this previous rebuild could be the reason why the bearing fail now.

dcdrechsel

Thanks .Too bad the rings don't have a part # stamped on them .Last question -I assume you are coating the piston skirts-how did you figure out the piston to cylinder wall clearance ?

speed rII

Piston to bore clearance should remain allmost the same. The method that my friend uses removes litle material from the skirts before coating so the pistons should keep the same measure.

Also the ceramictop reduces the piston expansion.

This method is used.

Techline

dcdrechsel

Interesting and thanks for the link .Anxious to hear how this works out .

speed rII

Part's are here

Rebuild will continue tomorrow. Hope to get the car back on the road at Sunday.

And for the pistoncoating, talked to my friend that does the coating.
He said that the method has been used several times on BMW alusil engines, so I think I'm on the safe water's for that one.

speed rII

Small progress, engine cases are back to gether. Next the 4-6 pistons..
Putting the pistonpins on these is PITA...

Coated piston



I allso measured the bores, bottom of the bores had out of round 0,02mm-0,04mm (0,0008in-0,0016in)
Top ends had 0.05mm to 0.1mm... (0,0019in-0,0039in)

logray

Did you buy a wrist pin installation tool or did you make your own?

Here's what LNE has to say about out of round and tolerances:

"Upon inspection of many high mileage or over-heated engines, the stock engine bores tend to be out of specification, with .002-.006" of ovality, leading to excessive piston clearances, increased ring land and ring wear, and high oil consumption" -from http://www.lnengineering.com/boxster.html

Interesting how your top part of cylinder measurement pretty much falls right into the category that they say is common for ovality and specification.

speed rII

Thanks logray, I had no specs for the measurements just tought that they were on the good side.

I made my own tool for the pistonpins.