connecting rod question...

I was wondering if LT-1 and regular 350 connecting rods are the same if they are stock size. I think I broke a rod or rod bolt and have to pull the motor. My buddy's got a 350 short block with aftermarket rods, stock size in it that hasn't been run. And I want to know if they're gonna work in my LT-1. I've never pulled an LT-1 motor before, but I know it's gotta come out the bottom w/ the cradle. How much time an I looking at w/ the use of a lift and air ? I don't know wether I'm going to fix this one or use the bottom end of the motor my old boss has out of a cop car. Is there any difference in the cop car motors ? This one is complete but was in a fire so I think the electronics were burnt and I don't know how many miles are on it. Thanx in Advance for any help I can get. Chris

whoa buddy. 1 question at a time.

first, you will need to have the motor rebalanced if you use aftermarket rods.

second, if you broken a connecting rod (or more likely a rod bolt) you will probobly need to replace the whole motor. its not like "ohh my alternator went so i'll repalce my alternator." it probobly scored the piston walls, messed up the crank and your piston is definately toast.

I dont know much about the police (B4?) package but i *think* its the same motor.

I'm pretty sure it didn't break while driving it. It drove fine to work. But when I went to leave, it wouldn't start. I tried to spin the flywheel and it wouldn't spin 360* in either direction. I pulled the plugs and went in w/ a bore scope. The #7 cylinder was up and looked like it was touching the head. That was the only cylinder up. From what I could tell, none of the valves are bent. I'm pulling the head on wed. That's what I'm saying though. If I can't fix it quickly, I'll throw the bottom end of the other motor in my car w/ the LT-4 heads as long as they're not hurt. I know I can't only throw 1 rod in it and go but I don't think it hurt the block. It didn't make any noise or anything. All the rockers appear to be moving when I turn it by hand and the crank spins when I turn the flywheel, so I didn't break the cam or crank. Getting the motor rebalanced won't be a problem cause I know guys at a machine shop. I just need to get it fixed ASAP cause my GF is getting tired of getting up early to take me to work.

paragraphs are your friend!

dude, if its your rod not letting the motor turn... best of luck.

I pulled the oil pan & head today. I broke the #6 piston and twisted/bent the rod. Thank God it didn't even scratch the cylinder or the head. What are the chances of putting only 1 piston & rod in and it lasting for a while? I know the other ones "could" break but is this more likely a freak thing or are my days numbered ? I don't have the money to replace all the rods & pistons right now, and I don't have anything else to drive.

What do you mean when you say "replace only one piston & rod"? I'd think you could replace only one piston and rod, as long as you also replace the crank and rod bearings, and weight match the piston & rod to your existing pistons and rods. While you have the other pistons and rods out, you'll of course want to hone and put in a new set of piston rings while you're at it. Make sure the other rods are straight with no nicks or cracks. Personally, being the anal retentive guy I am, I'd have the other rods magnafluxed, and pop in some new ARP bolts onto the whole set, then resize.

Personally, being the anal retentive guy I am, I'd have the other rods magnafluxed, and pop in some new ARP bolts onto the whole set, then resize.


I thought the same thing. Then I learned that you can't resize the rods while they're connected to the pistons, so you have to press them off. Problem is, pressing them off often breaks the pistons, so you end up replacing more than just the damaged pistons. You can't even replace rod bolts without resizing the rods, so you get into the same problem. This means you are spending more on pistons, and you might as well replace them all. One thing leads to another and you feel like you can't do it well without a full rebuild, full balance and blueprint, etc. In my case, the full rebuild wasn't realistic. I made the decision to only replace the bad pistons, leave the rods alone and reuse the stock rod bolts (along with new rings and bearings). No, I didn't want to reuse the rod bolts, but really there was no choice given the cost. It's certainly not ideal, but spending $2,000-3,000 plus on a great shortblock wasn't realistic either. It's possible to do this on a budget, but you have to accept compromises.

I thought the same thing. Then I learned that you can't resize the rods while they're connected to the pistons, so you have to press them off. Problem is, pressing them off often breaks the pistons, so you end up replacing more than just the damaged pistons. You can't even replace rod bolts without resizing the rods, so you get into the same problem. This means you are spending more on pistons, and you might as well replace them all. .

Pressing the pins out of the pistons often breaks them? I've never considered nor heard that before. The shop I use in Williamston, Michigan has a tool that, when used with an arbor press, pushes the pin out easy as you please, giving you a nice rod and nice piston. Could the piston breakage you've experienced be due to using an incorrect tool? Besides, how else, but by separating the pistons from the rods, is one to weigh the old pistons versus the replacement piston? Same story for the rod. For a stock engine they wouldn't have to be perfectly matched, but it would be much better if the piston and rod were weight matched to the median mass of the remainder of the set. That way crankshaft balancing might not be necessary.

Your points are well made. I talked with two engine builders who told me that even with the tool, the stock hyper pistons break pretty easily. Not being an engine builder myself, I had to take their word. At the point where we talked about balancing, it became clear that going to the next step was going to cost more than I was willing to spend, so I had to just replace the bad stock parts with replacement stock parts. So, you're correct on the mass and balance, but it starts getting expensive there.

That's what I was planning on doing if I only replaced one, use stock GM parts. You can't tell me that they match each and every piston and rod in every motor. If I can hold out till after X-mas, I'll probably go w/ the GMPP replacementa rods I can get from the dealer for $230 and probably a cheap to moderate replacement piston. Then I will weigh match everything. I'm not looking to make major power from this motor, just the LT-4 cam and intake to go w/ my heads.

That's what I was planning on doing if I only replaced one, use stock GM parts. You can't tell me that they match each and every piston and rod in every motor. If I can hold out till after X-mas, I'll probably go w/ the GMPP replacementa rods I can get from the dealer for $230 and probably a cheap to moderate replacement piston. Then I will weigh match everything. I'm not looking to make major power from this motor, just the LT-4 cam and intake to go w/ my heads.


II have 8 rods and 7 pistons (forged trw stock compression all you need to to is buy one piston) ... (ring land broken on the 8th piston) also the rods already have arp bolts. I will sell them to you really cheap.. Send me a pm if you want them.

THX JIm

If you want to try it, I might if I was broke. You need a LT1 rod not a regular SBC rod. If you replace all 8 and get it ballanced it's a diferent story but the LT1 uses PM rods and they are a bit lighter then the std SBC rod.