Ok so, running some numbers, ot looks as if the P2W clearance is "built in" to CP pistons. If I did my math right, the bore comes out to 75.998 with the measurement at the guage point. This is piston measurement plus the clearance.
measurements are: piston 75.908/clearance of .09mm (converted from .0035") totalling 75.998mm. Piston "marked" as 76mm. So again, if my math is right, 76 should cover it?
Any concern about the .002mm over what it would require or would that be ok?

 

might sound like a dumb question, but what is the room temperature of the room you're in when measuring? because the standard is 68-74 degreesF, ideally 72*F. Temperature difference can cause the pistons to be bigger or smaller, and same for the micrometer you're using. Micrometer calibration is to be done at 72*. Meaning temp alone could be the variance in your measurements.
CP usually builds their piston sizes to fit an exact bore, which as you presumed means a 76mm piston is made to fit a bore that is exactly 76mm, with the proper clearance built into the piston size.

if temps are within the range I mentioned above, and your measurements are accurate, you'll have a P2W clearance of 0.0036", which is well within spec of the recommended 0.0035". Clearance also depends on power goals too, fuel type, how aggressive your timing is, how hot your oil will get, ambient temps, and so much more. Pistons that recommend 0.0035" P2W can often ideally run anything from 0.0028"-0.0050" P2W depending on many variables such as the ones I mentioned.

 

Thank you! The info was taken from the spec sheet itself. I like to plan ahead. I have not personally measured the pistons as they are not in hand just yet. Rest assured, they will be measured and any potential reconfiguring done. Funny enough, I keep my house temp at 72° lol
Fuel used is 93 pump, timing is fairly conservative; actual timing as read in Neptune at 17psi, WOT at 6k is around 15°
With this piston setup, I'm looking to go from 347 to as close to 400 as my little little and current setup will go. Which, and again, if I am correct, should be 370-390. I'll be down about 1.5 points in compression with the new pistons, so I should be able to squeeze out the last 5 psi the turbo offers. Oil temps.. That's a tough one. Not sure what those run and I'm just gonna throw it out there, I don't wanna find out with my bare hands.

 

0.09mm is fine for cp..0.08mm sucks..i recommend 0.09mm to 0.12mm on cp, wiseco, je.

 

Thinking about it, the measurement of the piston plus recommended clearance came out to 75.998. I didn't account for the cylinder hone, which could take up the last .002mm?

 

keep in mind 0.002mm = 0.00008"
you have nothing to worry about. Even a REALLY quick finish hone will take out more than double that.

 

Pistons should be here tomorrow!

 

Should I be worried about this scratch? I can feel it with my fingertip and my fingernail catches when dragged across..
Brand new set of CPs..

 

no. but if it was mine, I'd hit it with some emery cloth

 

I wouldn't worry about it, you will get enough carbon build up on that you wont see it after your first drive. I would however recommend coating the pistons if you have the cash. It goes a long way and works well.

 

Coating the piston with what?

 

They can anodize, ceramic coat, moly coat.. Skirts, crown, whole piston. There are quite a few options offered by CP.

 

Thanks! None of the edges catch a Kleenex, so that's a plus. I've got some 2k grit wet/dry stuff around if need be.

 

Txdragon beat me to

it but yes lots of options and it makes a difference. Here is mine.

 

Gotcha. How much is it to have a set sent back and coated?

 

That depends on the type of coating, it ranges in price, the rule of thumb is the higher the price the more protection against detonation for a longer period of time.

 

Check this out but they offer more options too

https://www.cp-carrillo.com/p-32904-coatings.html

 

When I was looking at the coating options, you're showing an example of what I considered. Lol! The moly skirt and ceramic crown. What'd that set you back, if I may ask?

 

To be honest with you I couldn't tell you off my head, i got these years ago, i can look up the receipt but I'm sure the prices have changed since. Your best bet would be to contact your dealer or CP direct to get the latest pricing. I do recall it wasn't egregious in terms of cost and the for the insurance and added benefit it was well worth it. If i recall there was one other option that provided even further protection but that cost an additional couple hundred that I opted to skip on. It had to do with the hardness of the coating but don't quote me on that. Best to call them direct to see what they offer. I'm going to send them an email and see what they respond with and I'll post the answer her if you can wait.

cheers

 

I'm patient. Lol! I wouldn't think it'd be all THAT much. I'm curious though how something like the ceramic coating does with the piston expansion as it heats up and shrinkage when it cools down.

 

I sent them an email, it works very well even with the expansion, i took my motor apart and rebuild it over the past few months and the coating was still present, I'll dig up the pics. You have to keep in mind when it expands and contracts it is minimal and not enough to flake off the coating. If you observe metal under a high powered stereo scope or microscope it is very pores and the coating penetrates these pores, metallurgy is a very interesting field. In an case it is well worth the added protection, my guess your looking at $2-600 for a complete coating depending on what you pick but I'll know more when they respond as i requested pricing too.

 

I used to do thermal spray coatings on turbine engine components. If the coatings were good enough for those parts, I imagine they'd be good enough for car engines...granted we were coating non-rotating components. However, I'll probably roll with uncoated pistons for this build. I've got to draw the line somewhere, or else I'll just keep hemorrhaging money.

 

Buddy, if that isn't the truth, I don't know what is. Lol! For about 2 weeks after the build was completed and running, I was checking and tightening and adjusting and replacing various bolts, brackets, and hoses. Lol! It's the little things that get you frustrated.

 

You know the saying, you have to pay to play. Most people don't realize what it costs to build a "reliable" high hp car. Reliability does not come cheap. A lot of factors of course and how you spend your money should account for some length of longevity unless you have money to burn for rebuilds.

CP got back to me fairly quick.

"In regards to our features and options, I attached a copy of our catalog pages that contain this information. Below is pricing for some of our more popular options. If there is anything specific you are looking for (price) that I may have missed just let me know and I can provide. Pricing is per piston.
-Skirt Coat $32.50
-Ceramic Coat $30.00
-Anodize $30.00
-Anodize Top Ring Groove Only $50.00
-X-Style Forging $10.00
-Box Style Forging $20.00
-Shelf Mill $12.00
-CNC Underhead Milling $57.50

 

The prices for the coating is actually reasonable. Thanks for that! As far as the pay to play rule, the weakest link in my block build, the NPR pistons, is what forced me to get the CP now. I planned on revamping the build anyways but didn't plan on anything breaking first. Lol