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Discussion Starter · #1 ·
Hello all,

I'm in the market for a set of aftermarket pistons to be used on my N/A K20/24 frank motor build-up. I've been looking around but can't seem to find any good, detailed info.

First off, in everyone's opinion, is one brand clearly better than the other? The main piston manufactures I'm looking at are CP and Wiseco, with JE and Supertech as possibilities.

Second, what material makes for a better piston? From what I understand, 2618 makes for a stronger piston while 4032 expands and contracts less - possiblty making it a little more reliable for a street driven motor. Wiseco, CP and JE all use 2618. Supertech and SRP use the 4032 material.

Thrid, what compression ratios are safe on 94 octane pump gas with good tuning on a Kpro? I'm thinking 12.5:1 is the upper limits but I have no real proof or personal experience to back that up.

Finally, what coatings are people using and what kind of success are you having? A moly friction reducing skirt coating is pretty much a must in my mind. Do you agree? What about piston top thermal barriers? In principle they sound good to me but I have the concern that they add weight to the piston, reduce valve-to-piston clearences and lose their effectiveness once the entire engine gets up to operating temperature.

Any info, experience or opinions are welcome.
 

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I use wiseco off the shelf 13.7 pistons in my motor now. But I have a drag cartel custom set of je pistons for another motor. Wiseco is a little heavy they weigh bout 342 grams. If u looking for a 12.5 piston get a cp. They are pretty good from what I hear. I have a few friends who run those wit no complaints. I guess its builder preference on what piston they use.
 

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first off we need to see what engine mods you want or have to further assist you. i Run IPS spec JE pistons because i need deep pocket relief pistons with the cams im running
 

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I like the 12.5 wiseco the pockets are good enough to run any big cam
 

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I'm using a wiseco 13.7 off the shelf piston wit drag cartel cams stage 4. And I'm having no problems. And that's a big cam.
 

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How much is possible to drill stock k20a block, before is have to install Datron etc cylinder pipes? Going to install stroke kit, but piston diameter is now what im have to also think.

also can someone please but me a few link, were is allready made K20A whit stroke kits, need to order also cams etc etc. But nice to look firts difrent kine of project and look what kine of engine works best. Car is coming to steer / track, running pump gas 99+ (102octane).

Thanks
 

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2618 expands more, which generally allows them to take more of a beating, so you have to adjust your clearances accordingly. 4032 has more silicone content which allows you to run tighter clearances since the material expands less than 2618, however, at the expense of being more brittle. I've seen a 4032 piston shatter in a high hp turbo car before. Generally I'd say that 4032 is more suited for all motor applications...2618 is more suited for the abuses of a turbo car. I wonder if anybody runs a 4032 piston for methanol FI setups.

On 94 octane, you could easily run 12.5:1 reliably...just make sure your tuner knows and understands what they're doing.

As for coatings, moly skirts are nice...theoretically...wiseco shelf pistons come with these already. If you're going to coat the piston top, you should coat the chambers as well. Heat will be absorbed through the path of least resistance. Keep it off the piston tops and the head get's to absorb more. Personally, i've never seen any measurable differences. I can see how it could be beneficial, but chances are, if you're at the point where you're counting on coatings to make a difference in the overall picture, you wouldn't be asking.

You can safely go to 88mm on stock sleeves...maybe more...
 

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I'm using a wiseco 13.7 off the shelf piston wit drag cartel cams stage 4. And I'm having no problems. And that's a big cam.
the shelf wiseco 13.7cr (89mm) have valve relief's of .235" int & .170 exh (below Timing Edge ie TE) with the ability to increase that to .265" int & .200" exh. how much clearance is needed to run the ips cams? .290" int???

on a side note you can see some possible characteristics of custom pistons here http://www.cppistons.com/products/custom_pistons/index.html
 

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2618 expands more, which generally allows them to take more of a beating, so you have to adjust your clearances accordingly. 4032 has more silicone content which allows you to run tighter clearances since the material expands less than 2618, however, at the expense of being more brittle. I've seen a 4032 piston shatter in a high hp turbo car before. Generally I'd say that 4032 is more suited for all motor applications...2618 is more suited for the abuses of a turbo car. I wonder if anybody runs a 4032 piston for methanol FI setups.

On 94 octane, you could easily run 12.5:1 reliably...just make sure your tuner knows and understands what they're doing.

As for coatings, moly skirts are nice...theoretically...wiseco shelf pistons come with these already. If you're going to coat the piston top, you should coat the chambers as well. Heat will be absorbed through the path of least resistance. Keep it off the piston tops and the head get's to absorb more. Personally, i've never seen any measurable differences. I can see how it could be beneficial, but chances are, if you're at the point where you're counting on coatings to make a difference in the overall picture, you wouldn't be asking.

You can safely go to 88mm on stock sleeves...maybe more...
I agree with that. 4032 is great for street motors and just about any all motor build. The tighter clearances should pay off with better longevity of the piston itself and the rings (they're less exposed). The Mahle pistons are 4032, have coated skirts, and generally one of the best off the shelf 4032 piston makers out there. That's what I would use if I was going to start a new build today.

2618 can take more abuse b/c it has a higher tensile strength. That means when high HP starts pounding the piston, high revs start to stretch the piston, and high heat starts to soften the piston, 2618 has a greater ability to take the load without falling apart in a catastrophic manner. The downside is that the coefficient of thermal expansion is greater meaning you have less consistent skirt profile as temperature varies. This makes it a little bit more tricky to get daily drivable longevity out of a 2618 piston versus a 4032 piston.
 

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the shelf wiseco 13.7cr (89mm) have valve relief's of .235" int & .170 exh (below Timing Edge ie TE) with the ability to increase that to .265" int & .200" exh. how much clearance is needed to run the ips cams? .290" int???

on a side note you can see some possible characteristics of custom pistons here http://www.cppistons.com/products/custom_pistons/index.html


the amount intake relief really depends on how much VTC you wanna run and of course the lift of that cam. .235 is only enough to run k2s while running 50 degrees of cam angle. With K10s you probably don't wanna run no more than 35 degrees
 

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I agree with that. 4032 is great for street motors and just about any all motor build. The tighter clearances should pay off with better longevity of the piston itself and the rings (they're less exposed). The Mahle pistons are 4032, have coated skirts, and generally one of the best off the shelf 4032 piston makers out there. That's what I would use if I was going to start a new build today.

2618 can take more abuse b/c it has a higher tensile strength. That means when high HP starts pounding the piston, high revs start to stretch the piston, and high heat starts to soften the piston, 2618 has a greater ability to take the load without falling apart in a catastrophic manner. The downside is that the coefficient of thermal expansion is greater meaning you have less consistent skirt profile as temperature varies. This makes it a little bit more tricky to get daily drivable longevity out of a 2618 piston versus a 4032 piston.
would the mahle (4032) piston beable to handle 11.5cr with nitrous on top?

and when you talk about the clearances are you guys referring to the piston rings?...

just tryin to get a better understanding
 

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Im sure it be able to take it
From what I understand the malhe will last longer for the tighter clearance and will be a better dd piston
 

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the amount intake relief really depends on how much VTC you wanna run and of course the lift of that cam. .235 is only enough to run k2s while running 50 degrees of cam angle. With K10s you probably don't wanna run no more than 35 degrees
so how much relief do u need to run the extra 25 degrees?
 

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the only way to tell is to measure it.
I realize this - claying a motor is a must.

Because I can't find out I am trying to sell the pistons in favor of custom ones with .290" int .220" exh but I am just guessing LOL
 

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Discussion Starter · #20 ·
first off we need to see what engine mods you want or have to further assist you. i Run IPS spec JE pistons because i need deep pocket relief pistons with the cams im running
I was purposely keeping things general to benefit anybody reading.

My plans: What I have
K20A2 head
RBC IM
70mm TB
3" intake w/ velocity stack
DTR header
2.5" exhaust - probably gonna upgrade to 3" down the road
KPro
K24A1 block
Carrillo rods

What I still need
Valve train - right now I like the IPS K2's or maybe Toda A3's
Port/polish
pistons

I don't have a hp goal, just planning a well rounded summer daily driver and occational drag/auto cross/road racing.
 
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