bilwilli

I have a 1987 928 S4 block which a small scratch in one cylinder.. if the block is Alusil ( which I am not sure of ) would it be less expensive to fix it with that process or go with Nickasil which has to strip all the Alusil off...This car is for normal driving...so I would like to do the job for as reasonable as possible..
Thanks for any input,
Bill

Kevin in Atlanta

did you get a lower compression on that cylinder?

bilwilli

This was discovered after engine was taken apart..piston was dirtiest of the group

G8RB8

Might not be worth worrying about. Post a pic.

bilwilli

I will post a pic this Friday...

Fabio421

You cannot "scrape off" the Alusil. The block is made from it, not coated with it. You can send the block out to be Nicasil'd if you think it's no good in it's current state.

jeff spahn

Bilwilli. I had a lot of large scratches in one of my cylinders. I just left them in and put in new rings when I put in a new piston. Something got in, beat the crap out of my piston, but not the valves. Talked to a few well known 928 repair guys here on Rennlist and they basically said "Are you going to race it". "NO?" "Then put new rings in it and put it back together." Best advice I have been given in a long time. Car runs great. Has good compression and leaks/burns no oil.
You could easily feel the scratches in mine with your fingernails.

bilwilli

Hope this pic helps....this one is the worst of the group....Can these cylinders be honed?
Thanks, Bill

Mrmerlin

clean the head gasket surface,
install new rings and run it,
the scratch is negligible

BC

It is quite easy to relapp the cylinders for new rings, essentially preparing the surface for bedding in the rings.

It involves a paste, and some felt pads on a expanding hone or some form of one.

http://www.goodson.com/AN-30-Silicon...und_for_Honing

http://www.goodson.com/MM33-FO5_-_Fe..._Alloy_Blocks/

Last time I did this it was over 500 dollars for the block, but I think that involved hot tanking. This time I bought this stuff and will do it myself.

G8RB8

+1
Not that Stan needs it.

GlenL

Ignore the scratch. Use some solvent to clean the bores. Don't scrape. Don't hone them!

Tails

+1 to Stan's post #9. The dirty piston is probably from the small amount of oil passing the ring and burning in the combustion chamber.

mark kibort

if you had the block in a position to get it re-pasted, i would do it. but , it probably will be fine.

depami

Do not hone. Those scratches are minimal, just ignore them.

And by all means, get that chevy symbol away from your engine.

Chevy mentality has no place near a 928....