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my is engine knocked and a friend of mine has sn rb26dett in which he recently replance his stock pistons with forged ones, he said i could have the stock ones if i wanted. Has anyone tried the swapping rb26dett pistons into the rb25, what time compression could i expect, are the pistons stronger, any info would be appreciated.

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ok i have put the pistons in the block using rb25det rods and an rb25det crank, the sides of the pistobns however dont reach the top of the engine block, any idea how this affects the compression ratio

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hey kilo_gulf,

those two engines do have the same bore size but have a slightly different stroke.

rb25 has a bore x stroke of 86 X 71.7

rb26 has a bore x stroke of 86 X 73.7

take notice to the 2 mm difference in stroke.

THE PISTONS THAT CAME IN THE MOTOR ARE OK , THERE AFTERMARKET, I HAVENT BEEN ABLE TO IDENTIFY THEM, BUT THEY DONT HAVE A DOME ON TOP LIKE THE RB25DET OR RB26DETT PISTONS, THEYRE FLAT TOPS. I DID A COMPRESSION TEST ON THEM ABOUT A MONT BACK AND THEY AVERAGED BETWEEN 115 TO 120 PSI PER CYLINDER. I DONT KNOW WHY THE PERSON WHO BUILT THE ENGINE WOULD USE THEM MY GUESS IS NITROUS, IN ANY EVENT THATS WHERE I STARTED. THUS WHEN THE RB26 PISTONS BECAME AVAILABLE I JUMPED AT THE CHANCE HOPING FOR BETTER COMPRESSION BUT IT SEEMS ILL BE RIGHT WHERE I STARTED.

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