Piston and cylinder question

[stlrj]

I'm starting to round up parts for my 86 3.2 engine rebuild and came across a set that the owner says had 10K, "still have the factory's cross-hatching on the cylinders - to show just how low the milage was. The carbon never even had a chance to build up and the rings are not fully broke-in."

My question is, did the factory hone new cylinders with a cross-hatch pattern? I read somewhere that the factory cylinders were chemically etched and not honed.

If that's the case, then these p/c's may have been reworked and not original?

What's the story here? Should I be concerned?

Cheers,

Joe

[cnavarro]

No need to worry about the cross-hatch on those. They probably have nikasil cylinders (or alusils that have been replated). Only the alusil cylinders were etched. What kind of sealing surface did the cylinders have? If they were flat (i.e. without a sealing ring), they are definately nikasils. Only the alusil cylinders had a ce ring groove.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[stlrj]

Thanks for your quick reply. After reading posts here on reusing p/c's, I'll wait until I see if i can reuse of my old p/c's before getting another used set.

Joe

[Jeff Alton]

I do not think any 3.2 cylinders had sealing rings.

Jeff

[cnavarro]

Jeff, you're absolutely correct. No 3.2 cylinders had sealing rings; instead, Porsche used a taper on the sealing surface (spec reads .0015-.003" taper) that creates a gradient in the clamping loads over the sealing surface, helping to form a carbon seal. Works good enough that I use the same specification on all my billet cylinders regardless of application (unless otherwise desired by the customer or a ni-rist or gas filled o-ring is used, which requires a flat and true surface).

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[snowman]

All cylinders have cross hatches on them when they are new. Its the result of the honing, which all cylinders undergo when new. No matter what the treatment, the new cylinder was made round by a honing process. Not having a cross hatch is bad, ie cylinder is badly worn.

A cylinder is good if it measures like new and has no defects in it, and has cross hatch pattern present. If so its good, as good as new if dimensions are like new.

[KobaltBlau]

I'm not sure that alusils have cross hatching when new. I thought this was discussed in the honing alusils thread.

[snowman]

ALL cylinders have cross hatching when new, period. If they did not they would not properly lube the rings, and it would wear out pronto. The cross hatch is a result of the final machine step that makes the cylinders perfactly round the cross hatch is also NECESSARY for proper lube of the rings as the cross hatch acts as the resavour (sp?) for oil. Without it there is no lube for the rings and the the result will be early engine failure.. Whatever treatment is applied to the cylinders after the cross hatch is generated is whatever it is, but to make round cylinders it is NECESSARY to first HONE the cylinders. Honing is done either before or after the cylinder treatment, but it is ALWAYS done.

NO Cylinder can be ROUND without honing.

[David]

You can get your cylinders replated and honed for under $800.