Hi,

I have been asking a few questions on this forum lately regarding a race engine im rebuilding after big end failure. I have sourced a new crank which i am waiting for but i also need to replace 2 rods that were sat on the worn scored journal. I have 2 rods from a previous rebuild which are good to use the problem i have is the conrod codes are no longer visible on either of the rods. The big end eye i can measure with a bore gauge and micrometer, i figured if im under 33.01 it will be rod code 1 and over 33.01 then code 2 so im happy on making the shell choice that way then fingers crossed when i plastigauge them. But the weight code is the real issue, i cant think of a way of paring them correctly,iv checked the haynes manual and it seems that you cant have two code A paired or two code C paired but other combinations are acceptable? Any ideas of how i can figure out if the two rods i want to use can be paired on the same journal because im stumped.

Thanks rigsby

Maybe if an A is the lightest and C is the heaviest, having two As or two Cs on the same crank pin results in heavy/light extremes that degrades the balance beyond the Honda limits. Whereas to average the differing weights,

A can be used with B or C,

B with A or B or C

C with A or B.

Weigh your unmarked rods and compare to marked rods, assuming you have some marked rods.

Hi,

Thanks for reply , i have now borrowed an accurate set of scales so weigh and compare so fingers crossed i can narrow it down, i do have other nc30 rods that are worn oval so i have 6 rods in total to weigh but none of them are marked so its still gonna be trick hopefully i can observe the different weights and come up with a solution.

Thanks again

I might be able to help you out a bit.

E-Mail sent

Hi,

I have weighed all sets and i have a pair that i think will match their is 2.9 g between the two rods, which is almost the same as the two rods i am replacing the two old rods that sat on the scored journal had 2.6 grams difference, the heavier of the two rods was the front cylinder, this seems to be the case with the other pairs i have weighed the heavier rod is the front cylinder rod. So i think i have sussed it eventually im happy to use the replacement rods as there is only 0.3g between the old rod combo and the proposed new rod combination cant see that been an issue, . Now have to figure out the big end shells as again the rod codes are missing but at least i can measure with a bore gauge. I t really is a pain if the codes have been rubbed off!

Thanks