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Piston Grades Explanation

JamSkyRB20

By JamSkyRB20,
in Engines & Forced Induction

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JamSkyRB20 Apprentice

JamSkyRB20

Posted
Posted (edited)

I have 6 used pistons that i want to use replace my damaged set but the grading doesnt matchup on one piston....My cylinder #3 had a grade 1 piston and the used set i got no grade 1's. HELP

can i just simply drop in the grade 2 piston where the grade 1 was..or do i have to find a used grade 1 piston?

Edited by JamSkyRB20
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Duncan Grand Master

Duncan

Posted
Posted

Don't worry about the grades, they were for brand new pistons in a brand new bore.

If you are putting used pistons into a used block, the only way to do it is to hone the block, clean the pistons sure thoroughly, and then measure each in multiple places (especially the bore because it can become oval instead of round over time). Then drop the pistons in as the best match you can regardless of original grade.

Even then, the clearances may still be too large, that is why people commonly bore out 0.5mm when rebuilding.

GTScotT Grand Master

GTScotT

Posted
Posted

As above.

IMHO it would be cheaper and easier to buy another working RB20. If not, atleast buy some oversized slugs (non forged wont cost much) so you get the thing right (as mentioned above).

GL

Bl4cK32 Grand Master

Bl4cK32

Posted
Posted

IMHO it would be cheaper and easier to buy another working RB20.

As much as I agree about not spending money on 20s, I wish people would stop recommending "drop in a working 20". The cars are almost 20 years old now, and for the past 8 years every single r32 has only had 100,000Kms on it.

A freshen up with new bearings, rings and a hone at a minimum will save a wrecker motor getting tired fast.

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