RichieP

Hi all,

I sent my 928 block away to have it Nikasil (NiCom) plated and got it back Thursday.

Take a look at a photo of one of the cylinders --> http://home.earthlink.net/~pcar928s4/

Take notice of the crisscrossing marks (like hone marks but deeper) near the bottom of the bore and the solid line near the middle to top of the cylinder. The other 7 cylinders have what I consider to be normal hone marks.

Is this normal/acceptable? I'd like to hear your thoughts especially if you've rebuilt a 928 or other engine.

docmirror

I"ve never rebuilt a 928. I'm in the process right now. The marks you see are what happens when the brittle hone stone breaks on the tool. The end of the stone, or a small bit gets pushed into the bore, and create serious ridges.

It comes from the operator not paying attention when he's honing. A simple mistake that happens all the time. It may seal, but it will never seal correctly. You will have high blowby, poor compression, and very likely oil fouling problems on that cylinder for the rest of it's days.

It happened to me on a boat engine many years ago. The hone comes up out of the bore, or the tip gets tapped on the webbing of the block at the bottom. However it happens it's from the hone breaking, and scoring the bore.

BC

I have seen quite a few 928 bores. I have also seen some nicom bores, but from MUCH farther away.

To ME, and over the internet, of a picture taken in low light and blown up past normal size, it looks WAY deep, and like a mistake.

The normal question in these situation is: Can you catch your fingernail in it?

RichieP

Doc - How do the repair something like this?

Brendan - The line is too thin to catch a finger nail but I can definately feel it as I run my finger over it. This is not the case with the other cylinders. It's hard to judge how extreme it is from the picture but all you need to see is the difference from the rest of the cylinder to know something doesn't look right.

docmirror

Have a custom piston and rings made, bore the cylinder to match.

BC

These bores after the plating process (nikasil) are DIAMOND honed - thats how hard they are. To fix this, it MAY need to be redone. The contractor would need to be contacted. Or you could just run it.

docmirror

Hehe, even worse. A bit of industrial diamond crud got loose and scored it.

hacker-pschorr

Since I have nothing to add, I'm going to ask for additional details of this engine build

Nikasil engine, nice S4 motor in the avatar.......what'cha buildin?

RichieP

Hacker- I'm just doing a simple rebuild if there is such a thing. I tore the engine down to correct a leak down issue and discovered that cylinder 1 was damaged. I sent the block out to get it repaired and Nikasil plated. Now cylinder 1 looks good but # 8 doesn't. I planned on using my stock pistons but UPS destroyed one of them and damaged 3 others in shipment so now I'm without pistons. To be honest I'm ready to throw in the towel. I've been working to get this car restored since 2001 and I keep running into problems like this. Mark Anderson can get me group 0 pistons for a good price but US NiCom refinished the block for the group 1 pistons that were in it and I can't afford to do it over again.

docmirror

Try these guys, they are compassionate about problem engines.

www.egge.com

hacker-pschorr

Before you do that, we need to see what the collective parts bin has available.

Right now you need a set of group 1 pistons, correct?

BC

With the nicom plating, you can now safely use JE pistons, and you can have them made in any compression ratio you would like. Pistons, pins, rings and clips would run less than 950. Maybe even less than 900.

BC

The contractor should really be responsible for this, no?

hacker-pschorr

So where exactly did you send this block?

RichieP

I guess the first step is to figure out what needs to be done with the block and wait to see what UPS will do about the broken/damaged pistons.