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Old 01-24-2019, 04:15 PM   #1
mini612
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CXracing 130mm M20 rods in M50?

Has anyone compared 130mm Cxracing H-beam rods for the m20 to the 135mm M50 H-beam? Yes, I'm aware of the mix reviews on these rods and yes, I am aware that these are 130mm and not 135mm. And yes, i'm aware that these are only rated for 600hp.

Since some OEM rods and pistons are interchangeable, I would like to assume that these 130mm will mate well with the m50.

I'm building a turbo M50nv with M54b30 crank, CXracing 130mm rods with OEM M52b28 or M50b25tu pistons. If my calculation is correct and please someone may double check for me, is/will be around 9.2:1 with b28 pistons and around 9.8:1 with b25tu pistons. That is with 1.75mm headgasket.

Thanks!
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Old 01-24-2019, 04:21 PM   #2
digger
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Have you compared the stack height of
- rod
- piston compression height
- crank throw
Vs the block deck height ?

Can you get a full m54 rotating assembly and jamb it in ? It will have the shorter compression height for the longer rod so you don't need to use garbage ones.

People have put m54 gizzards into the regular m50 before surely with NV it's fine to
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Old 01-24-2019, 04:28 PM   #3
mini612
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Quote:
Originally Posted by digger View Post
Have you compared the stack height of
- rod
- piston compression height
- crank throw
Vs the block deck height ?
Yes, last night/early morning around 1AM. so my numbers can diffidently be wrong. i'll have to find my scribbles and post them on here.

I based deck height at 210mm. And used "stroke/2 + rod + piston comp height = n. Then I take 210 - n = distant from deck to piston (flat top)

Then I use this distant for the formula on http://www.csgnetwork.com/compcalc.html
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Old 01-24-2019, 04:37 PM   #4
digger
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The problem will likely be short rod and piston smashing into crank at bdc
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Old 01-24-2019, 04:59 PM   #5
mini612
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Quote:
Originally Posted by digger View Post
The problem will likely be short rod and piston smashing into crank at bdc
That is what i'm afraid of. I should try with m20b27 rods to see if it clears. But forsure, M50nv rods will not work with the b30 crank.

Last edited by mini612; 01-24-2019 at 05:18 PM.
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Old 01-24-2019, 05:35 PM   #6
digger
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M20b27 is also 130 so it will be the same problem

The answer is to get pistons that work with 135 rods
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Old 01-24-2019, 06:23 PM   #7
mini612
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Quote:
Originally Posted by digger View Post
M20b27 is also 130 so it will be the same problem

The answer is to get pistons that work with 135 rods
Initially I was going to use the NV rods w/ b28 crank w/ b30 pistons but the compression will too low. So I might just have to go with custom pistons.

BTW, I tried with the 130mm rod i have and NOPE!!! Will NOT clear pistons skirts.
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Old 01-25-2019, 03:06 AM   #8
digger
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according tpo this stack height is

135+38.2+37.5 = 210.7



210.7-135-44.8 = 30.9mm

so use M52B28 pistons and skim the piston tops 0.9mm and the piston should come to the same height as the current NV ones
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89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

new build thread http://www.r3vlimited.com/board/showthread.php?t=317505


Last edited by digger; 01-25-2019 at 03:11 AM.
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Old 01-27-2019, 12:14 PM   #9
mini612
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I am really trying to not skim the pistons.
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Old 01-27-2019, 02:39 PM   #10
digger
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thicker head gasket, CR is still going to be up there most likely. the m54 pistons sit way down the hole to get the CR down
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89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

new build thread http://www.r3vlimited.com/board/showthread.php?t=317505


Last edited by digger; 01-27-2019 at 02:48 PM.
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