MMWS (Cross Performance) 066/660 Cylinders

[Brewz]

Are we talking the little sunken ring between the plated cylinder wall and the squish band?

 

[Mastermind]

Are we talking the little sunken ring between the plated cylinder wall and the squish band?

Yep. The aftermarket have a bad habit of overboring the top when they cut the intersection between the bore and band.

 

[Brewz]

Ahhhh OK

thanks for the warning folks
I will measure it first

 

[jmssaws]

It would have to have a giant death ring to get a ring in it lowering it 030.
020 squish it's over .100 to the ring and if it that big stake the top ring down or loose it.

 

[Moparmyway]

Yup.

They don't call it "The ring of death" for nothing.

Take a clay imprint and measure where your top ring will land.

I found, what I think, is the easiest way. Treemonkey has a video showing that he uses a sharp pencil to mark the piston while its at TDC. Measure the mark to the top ring, then measure the port you drew it from to the line above the plating & done

 

[Moparmyway]

It would have to have a giant death ring to get a ring in it lowering it 030.
020 squish it's over .100 to the ring and if it that big stake the top ring down or loose it.

Did you measure a stock cylinder or CP cylinder ?

 

[jmssaws]

Did you measure a stock cylinder or CP cylinder ?

I didn't measure a cylinder
If squish is 020 then it's over .100 to the top of the first.
I'm guessing at the distance but I think just from the crown to the ring is over .100 and then the ring thickness so the death ring would have to be huge to hang a ring in it.
I've never had one that was even close but I haven't ported many am cylinders.

 

[Moparmyway]

Gotcha Jason !
The ring on mine is pretty tall, I'll have some measurements of mine after work

 

[jmssaws]

I just measured a KS 660 piston
With a 020 squish it's .163 to the top ring.

 

[wcorey]

It scratches just like the chamberView attachment 44741

You can clearly see where the plating ends just over the edge partway into the combustion chamber.
I'd bet if you scratch from the band down into the chamber you'll be able to feel the transition from nicasil to aluminum.
I was playing around with the band cutter last night on my undercut cylinder with the wonky squish band and it's certainly plated, tough as hell to cut through even with carbide.

I've since found that on my better looking cylinder that's much like yours, the dark band is the undercut, so doesn't much matter if it's plated or not (I believe it is). Looks to be about .10" so top of ring to top of piston is about .120" plus .020" squish clearance equals about a mm to play with.

 

[Moparmyway]

You can clearly see where the plating ends just over the edge partway into the combustion chamber.
I'd bet if you scratch from the band down into the chamber you'll be able to feel the transition from nicasil to aluminum.

I did exactely that, it felt and sounded the same, that scratch is visible in the picture

I was playing around with the band cutter last night on my undercut cylinder with the wonky squish band and it's certainly plated, tough as hell to cut through even with carbide.

I've since found that on my better looking cylinder that's much like yours, the dark band is the undercut, so doesn't much matter if it's plated or not (I believe it is). Looks to be about .10" so top of ring to top of piston is about .120" plus .020" squish clearance equals about a mm to play with.

I'll be playing on the lathe with it tomorrow morning, if I can get home early enough to get some sleep

 

[Tomo6400]

I've seen three, and they were all pretty damn good. The Chinese never seem to be consistent with QC.

Is it ok to run them straight out of the box randy the exhaust port roof does look a little flat but it’s a nice cylinder thanks for your time.

 

[huskyboy]

Is it ok to run them straight out of the box randy the exhaust port roof does look a little flat but it’s a nice cylinder thanks for your time.

Arch the exhaust roof a little and bevel the the port thoroughly. The one I had was pretty flat on the bottom as well.

 

[Spladle160]

I have one on a FT660 that is just about straight out of the box. I did do my best to go over over the port edges and make sure nothing was sure to catch but that's about it. Only a couple hours on it but it's a good runner with just the basic mods of timing advance, no base gasket, and muffler mod.

 

[MustangMike]

I ALWAYS check the bevels, especially the ones you can not see, like the lower side of the exhaust port.

They often need beveling.

I would only recommend arching a roof if it is absolutely flat, and / or you want to change the cylinder timing.

If you bevel properly, you don't need a lot of arch, and I think you will often run stronger with less of it.

 

[wcorey]

It's usually the exhaust floor that's somewhat flat on these.
And check for debris stuck in the dark corners of the transfers...