Hi, was asked by Imola to weigh some various pistons and rods to make an assesment of imbalance, i thought the info contained in the pm may be useful to others so decided to start this post, please note, the weights i am quoting here are just a guideline and should not be used in the calcs for balancing of crankshafts, the differing weights of the same components is staggering as i weighed a pair of 916 rods and found an 8 gram difference between the two, so remember only a guideline. 900 ss/mon 2v pistons 512g st2 pistons 482g 916 pistons 502g JE 94mm 2valve 11:1 475g shells 15g ea 900 ss/mon con rod 482g 916 con rod early 518g 996 con rod 512g these are all weighed without shells and pistons with rings pins and clips. there are differences in the pin weights on some, particularly with the 996, this could be useful for swapping about to get to a certain weight but i have not had the time to do this as yet, as i dig more from the parts bin i will add to this, remember, its not dead accurate, just a set of kitchen scales.
Now this is interesting... Using calibrated scales i use for my work. I found. ST2 Rods no shells 500g 1997 916 rods no shells 500g unknown 916 pistons c/w pin rings 460g (year unknown) ST4 pistons c/w pin rings 470g 2000 ST2 pistons c/w pin rings 495g 1997 Thanks for the info spike
Hmmm, just goes to show you. how does the 916 rod weigh the same as the st2, when it is 6mm shorter. have you weighed them as rotating and reciprocating ends, if so what did you find. i am now going to sort out a pair of st2 rods to weigh.
You got me going, i weighed two sets of st2 rods both a 97 and 98 , also on two sets of scales, best i got was 492g worst was 478g, obviously duc has messed with this probably by switching manufacturers and all that. just shows it pays to check everything, twice.
Piss poor quality control! With me doing my maths for my ST2/916 engine to match the original weight (if it was balanced any were near when it left the factory) of the pistons and rods... I'm 25 grams short... 888 piston pins weigh 20g more than a 916 so i'm well in the ball mark.
The dual spark rods are the same as the 900 mon rods at 490g and thats three phase, so i think thats out the window, as i said what about the rod end weights, when the crank is balanced its a descision made on the end weights with the piston weight added and as you said looking at the 916 it looks stronger, that will make the big end heavier screwing up your calculations massively, you will get away with piston weights being the same but then calculate the stroke difference..........
Hi Spike, I have discussed this in great length with The legend Mr R last night with calculation of weights etc. As he said i might get lucky :wink:
