ack5252

Hey guys, this is my first engine build and I'm trying hard not to screw it up and have a question here. If I'm just an idiot feel free to let me know.

I got my completed/built bottom end back yesterday and upon inspection this morning have some serious concerns. The first is a complete lack of cross-hatching. I'm trying to figure out how to attach a pic and will do that ASAP.

Through research and talking to the guy I got the pistons from (Mahle 87.25), I was aware that the honing process is different/more involved on FRM cylinder walls. I brought this up with my shop and the guy said he was familiar and had done several porsche blocks with similarly high silicon content cylinder walls, he even said he had called his Sunnen rep to confirm the proper procedure. He did mention something about how the honing would be different than standard cross hatching and I didnt think anything of that at the time because he seemed quite confident in what he was doing and he was recommended to me by a few other people.

All that said, I'm looking at the cylinder walls and there is zero visible cross hatching. In addition, there are some knicks/scratches on the pistons and cylinder walls that concern me, not sure if those would be an issue though.

I'm trying to figure out how to upload pics and will do so ASAP. Any input you guys can provide would be immensely helpful.

s2kt3

cross hatching is there for several reasons im sure,

first and id say most important, is those "cross hatching marks" are little grooves that are put into the cylinder walls so that when oil gets onto the cylinder walls the valleys of the cross hatching hold oil and help it stay on the wall vs a completely smooth surface having the oil run off easily,

anyone else want to chime in on this...

blueosprey90

Boy, I don't think so. Don't know nuthin' about modern engines, including S2000, but my old school understanding is that cross hatching is supposed to help break in the piston rings. And I don't believe it has anything to do with oil. My old "Blue Smoker" had oil in the combustion chamber, but that isn't something you necessarily want on a new engine. One of the rings should be an oil ring, which is supposed to scrape the oil off of the piston bore.

chris_barry

The honing for the Mahle pistons required polishing/plateau stones be used to finish off the surface.The surface ends up looking very smooth. If you cannot see any cross hatching it means they didn't go too hard on the rougher grades.

Just make sure not to baby the motor in the first few hours of operation. Get it under full throttle below VTEC in lots of short burst so make sure the rings bed in. Also, don't flood the bores with oil as this hinders the bedding in process. Wipe off any excess oil above the piston before you put the head on. Turn the engine over and wipe any oil that come out from between the pistons/bores.

ack5252

Thanks for the input chris_barry, that really puts my mind at ease. He did talk about using the plateau stones, I just didnt realize it would leave a smoothish finish. Thanks for the tip on the break in as well, that was my next question. I had been told to break it in hard similar to what you suggested. How long/how many miles before I can start revving up above vtec and to 9k?

chris_barry

I run my race engines in on a dedicated running in oil ( Penrite 20w40) for approx 1 hour of running time. ( after this drain, new filter and swap to normal oil). I try to get the car started and cooling system bled ASAP, then hit the road or dyno. Keep below vtec but get onto full throttle in short bursts, even with your left toe on the brakes a little. When the engine is under load the cylinder pressure goes down between the piston/bore and onto the top/inwards facing surface of the ring. This pressure provides the force to push the rings onto the bore. You have to make sure that this area isn't flooded with oil. The aim during the break in process is to get the edge of the ring that is touching the bore worn slightly so it seals properly. You dont want to keep the engine under heavy load as any high spots on the pistons skirts can expand from the friction and start to gaul. Give the engine time to cool down after 5-10 second bursts at full throttle. After the first 15 minutes you can start to hold load for longer.

When I assemble race motors, I only use CRC on the bore/rings/pistons during installation of the pistons. Once the engine is together I squirt some oil on the bores from the underside so the skirt and oil scaper ring have an oil film on them. The aim is to get the rings to their normally running lubrication film as soon as possible. I've seen some engines where the engine builder has flooded the ring area with assembly lube and the rings have glazed the bore during running in.

B0neSt0ck

My old school understanding must be different. I have always understood the cross hatching is partially for ring seating and mostly to hold an oil film for the rings. A very thin film,but it is there.If the cross hatching was not there,that is what you would call a glazed cylinder wall,which usually results in a smoker.

http://www.hastingsmfg.com/ServiceTi...efinishing.htm

As for the s2000 block,I have not rebuilt one yet,but I did rebuild an H22A prelude motor once before. The cross hatching is barely visible,but it should be there. I actually couldn't use the block because the shop overbored the block too much. I ended up resleeving it.

blueosprey90

Touche'. Two points.

s2kt3

My old school understanding must be different. I have always understood the cross hatching is partially for ring seating and mostly to hold an oil film for the rings. A very thin film,but it is there.If the cross hatching was not there,that is what you would call a glazed cylinder wall,which usually results in a smoker.

http://www.hastingsmfg.com/ServiceTi...efinishing.htm

As for the s2000 block,I have not rebuilt one yet,but I did rebuild an H22A prelude motor once before. The cross hatching is barely visible,but it should be there. I actually couldn't use the block because the shop overbored the block too much. I ended up resleeving it.
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Yup same thing I thought........

w00t692

The part of the process that really sets those rings in good is when you're engine braking after flooring it. Vaccuming the rings to the piston walls getting them broken in.