Hi! I recently got my 455 short block parts back from the machine shop and started putting rings on the pistons. I noticed that when they balanced the rods, they ground material from the ends of the caps and the tops of the rods. The balance pads on the sides of the rods near the big end were not even touched. The steel ground off the caps varies from none to almost all of the raised portion gone (about 3/16"). It's hard to see how much material is missing from the tops of the rods due to the piston being there. This just looked wrong to me, so I took the rods back to the machine shop and questioned them about their methods. They said they have done hundreds of sets this way and had no problems and that they would not hesitate to run a set of rods done this way in their own motors. They felt balancing them by grinding metal off the balance pads would involve a lot of back and forth to get it right and would be too difficult. Is grinding material off this way an appropriate method for balancing buick rods or were they just taking short cuts? Have the rods been weakened in any way? Or have these rods been ruined? Thanks for your advice.
I have never heard of a shop that is actually knowledgable about Buick engines to do it this way. The big end of the rod (especially the 400-430-455) is the most critical part, strength-wise and is where most failures occur. I hate to say it, but if it were me I'd scrap the rods and find another shop. Welcome aboard, wish your first post had been under better circumstances! Devon
Not offhand, but they're easy to spot...some material will be ground or sanded from the top of the small (pin) end, and fresh grinding/sanding marks will be present only on the balance pads on each side of the beam above the big end. Other than general deburring/smoothing/shotpeening/what have you, the rod caps should be left untouched. Devon
Sorry Puddle,the shop is full of BS.Those weight tabs on the side of the rods are there for a purpose.Yes,they do chevy and other rods this way,but they have weight material on the bottom of the cap for balancing purposes.The way they did it weakens the cap on buicks big time.If this is strictly a steet motor may me ok,but I've sent rods back with new ones to be redone several times,even after I explained the correct way to do it.Some people never listen. They don't want to redo it because they'll have to R&R the pistons and rebalance,time consuming.We only use a machine shop that understands buicks anymore.If it was my motor I'd redo them,sorry. If you need rods I'll send you some for shipping and boxing.
Thanks for the advice guys! Just as I suspected, but nice to have confirmation. Glad I checked into now... Much better than throwing a rod through the side of the block! Gary, I think I will take you up on your offer. That would be outstanding, Thanks! What would be the best way to get my shipping address and $$$ to you?
The PROPER way to balance connecting rods is to get all the big-ends to weigh the same, and get all the small-ends to weigh the same (within whatever tolerance you choose.) This will require weight to be removed from each end of the rod, just as was done by your shop. The PROBLEM is that Buick DOES NOT PROPERLY BALANCE THE RODS, and as you've discovered, the rods are not designed to be balanced properly. Buick chose to cut corners, and uses only the overall weight (not big-end weight and small-end weight) of the rod as a balance factor. I'd love to see photos of your rods.
Don't be dissuaded; if you find a shop worth their salt, the big block rods can be properly balanced without carving up the cap. Yes, it's labor intensive, yes having more than eight rods on hand can help. Devon
Here are some photos of those connecting rods. The one on the left is one of the worst (there are 3 this bad) with about 3/16" taken off. The one on the right is the one left unground. Two of them have about 1/16" ground off and two others have about 1/8" removed. I realize the the first little bit is the forging parting line, and that it is helpful to get ride of that. Hope the visual helps.
+1 !!! :eek2: If they took that much material off of some of the rods, and left even 1 of them alone, there is NO WAY those rods are balanced.
The ones that I balanced on my 350 were within 10 grams of each other to start.. I just made them all weigh what the lightest on weighed I am curious as to exactly where material should be removed. I accomplished my balance by removing casting flash from the sides of the rods.
You haven't compared the as-installed rod weights of factory-assembled engines; or seen the huge variation in the size of balance pads as machined by the OEM. Those photos look pretty ordinary to me in terms of "visual" weight differences. Gotta say that I'd have cut them differently, though. Taken more off the "balance pads" and less off the cap--and HOPE things work out. Can't be easy trying to get them matched big-end and little-end when Buick's balance pads are in the middle of the rod. HOW do you plan to use this engine? Those rods are probably fine for Grandma; I'm a bit concerned about using them for performance. Maybe in "real life" they don't look as bad as in the photos. I'm thinking one of the SAE papers claimed that Buick assembled the engine, motored it on a balancing fixture, and then GROUND THE ROD BALANCE PADS as an assembly. I'll have to look for that again...maybe I'm thinking Nailhead, maybe not.
Balancing the rods that way also will cause the big end to go out of round. If you find that your rods are to far out to get them all to weight the same just get them as close as you can. Tell your shop you need them to stay together more so than weighing within a gram.
Oh yes, I did neglect to mention my plans for this engine: moderate street performance in the 450 to 500 HP range, with probably a 5500 redline. Mainly street use, but I will be taking it to the track now again, and I will be getting on it... a lot. Definitely not going in Grandma's LeSabre. As I said, I did pick out one of the worst 3 to photograph. Actually, they do look that bad in real life. They look scary thin! I am sure they are balanced to a tee, though. But gee it would have been nice if they would have taken the time to use the factory balance pads. Thanks again for all the feed back. I plan on printing this thread and presenting it to the shop, if nothing else to get some money back. Don't want to make them the bad guys and rub their noses in it. Just want to have a motor that will stay together. And from what I am seeing here, I have no confidence that it would with these rods. Thanks again. You guys are great! Would be interesting to know just how the factory balanced the rods...
