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« on: March 30, 2008, 11:00:13 PM »
Many shops prefer to shot abrade the rods, as glass bead is extremely difficult to completely remove from parts. Also shot abrading strengthens the rods slightly, while glass beading weakens them. If you are installing new rod bolts and nuts(and you should), oil the threads and torque and loosen, then retorque the hardware a total of 3 times before the rods are resized,this burnishes the high spots and results in more consistant torque, whether you will finally torque them or if a rod bolt stretch gauge is used. Also tell your machinist whether you will just torque the bolts or if you have a stretch gauge so he can duplicate the method that you will use during final assy. There won't be a lot of difference in the big end distortion, but there will be some. It takes no more time to do this the best way. If ARP bolts are used, use the supplied moly grease on the threads.But DO NOT use anything but motor oil on stock or stock-replacement bolts, useing moly lube on stock bolts will result in an over torque situation and failure will result. Simply weighing the rods may not help since you don't know where the weight is, two rods can weigh exactly the same amount, but have the weight distributed differently between the large and small ends. We have seen two identical weight rods be off by more than 12 grams from end to end to each other. You must also maintain .012"+ between the rods as installed to allow oil to escape from the bearings, mock-up and check this before balancing is done, and don't forget to number the rods too so you know which journals the side clearances were checked for. Aftermarket crank balancing from some companies is a JOKE!!! Most factory balanced rotating/reciprocating assys. are not usually within 12-15 grams. They don't balance the rods end to end or balance the pistons either. They just weigh one rod and one piston in the set, and then use what typical rings and bearings weigh, not yours to figure the bobweights. Did they get the light or heavy piston or rod to use to make up the bob-weights? This is why race shops charge more to balance than the factories, it takes longer to do it correctly, and time is money. A street motor lives its life typically under 2500 RPMs, a drag motor usually runs at high RPM for 10-12 seconds, not full throttle across the lake, like we do. Thats why car engine builders aren't as picky(anal) as the better boat engine builders, they don't have to be. One full throttle lake blast lasts longer than a drag motor sees all season. Sorry about the length of this post, but I have a reputation for being picky. TIMINATOR