ws6transam

The engine block is in the shop for inspection and line bore. We're installing the ARP stud w/windage kit, then line boring the thing. I expect we'll be going to a .040 overbore with torque plates as well.

I have had reservations on using the new LT4 pink rods, as Ligenfelter claims the beams are smaller than the old-style pink rods, and he's "heard of failures in the field" on these rods.

However, they weigh the same as the old rods, and are made of a completely different material, namely powdered metal. This is not even addressed in his book. Since I don't hear too many stories of blown-up LT1's on anything short of nitrous, I'm going to assume that GM is right about the survivability of the new rod, and that Ligenfelter is only looking strictly at rod profile in making his assessment.

That said, I'm going to install the ARP Waveloc Pro rod bolts, and go with 'em. I've weighed each rod, and they vary from 600.2 grams to 607.0 grams. I've been trying to find some written references that describe how to balance the rods: I've heard that you must balance not only static mass but also reciprocating mass. Static mass is easy, especially seven grams. However, how does one balance for reciprocating mass, and maintain static mass balancing at the same time?

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Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines,
5-point racing harness, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Speed-sensitive steering conversion, underdrive pulleys, Crane Hi-6 & more. 1.05g skidpad verified.
New best E/T! 14.400 at 98.6 MPH in 88 degree air at Stanton, Michigan.

FJK

Thus is easily done by whomever will dynamically balance your engine. Relative to the connecting rod, the correct terms are reciprocating weight which represents the small (pin) end of the rod and the rotating weight which represents the big (crankshaft journal) end of the rod. The rods are weighed using a fixture which allows each end of the rod to be weighed separately. For example for the small end of the rod, the fixture positions the the big end of the rod off the scale & only the small end of the rod is weighed on the scale. The total of the big & small end weights equal the total weight of the rod ( which you call static weight). This is the same principle involved when a car is "scaled", whereby all 4 corner weights equal the total weight. The exact procedure for balancing a set of 8 rods is to weigh big & small ends of all rods first, & then equalize all rods to the lightest weight rod.
Regards, FJK

ws6transam

Thanks for the advice. I have an electronic scale that measures mass to the nearest 0.1 grams. Can I simply tie a thread on each end of the rod, suspend the rod on the thread until it's sitting horizontal, and then rest one end on the scale? Would this not yield the same measurement as a fancy $200 fixture with roller bearings?

FJK

Maybe...but for whatever method you would like to try, you can run a capability experiment & answer the question for yourself. I would setup one rod, for example, to weigh the small end. I would repeat this at least 6 times (the set up & weight) & determine the repeatability of my weight readings. Then I would do it 6 times for the big end. I would say you would have to be able to reproduce your readings to the same accuracy as the scale, meaning 0.1 gm. Then add your small end weight & big end weight. Does it equal the total weight? If your setup passes both of those tests, then I would say you have an accurate setup.
Regards, FJK

ws6transam

Whoops, I've changed my mind yet again. I just ordered a set of 4340 forged Hbeam rods at 645 grams apiece. These are within 3 grams of one another so there's still some balancing to do. However, these rods should give me some breathing room in case I decide to utilize those nitrous spray bars already mounted in the miniram.