I have this 97 Sonoma with a Vortec 350 and NV3500 5 speed. Fun little truck with better performance thana stocker. I was just cruising down the highway 3000 rpm and 80 mph. Light throttle and had been driving for about 30 minutes. It broke number 1 rod. The engine didn't make any big bang, just vibration. It actually stayed running when i pulled over, albeit with lot of vibration. No oil light. After big PITA getting engine out, ready to dis***emble and see what all broke. There is no room to work and way too much wiring and stuff to be removed. The engine has unknown miles. See pictures. Nice oil streak behind the truck, holes in oil pan, big and little rod ends. Rod broke in the middle. Really ****s because I was trying to sell it. Now have to spend money and time to repair, just to try and put back for sale.
So the question is did it run real good before it went blewy? I've heard people say their motors were running really good just before they went.
I have first testimony to an engine running good right before it dies, I used to drive a 97 Nissan hardbody it was bone stock, anyways I was headed to my buddy's house to pick him up to go to the Long Beach performance swap meet on a Sunday morning and I remember thinking to myself how peppy the truck felt that morning... That thought left my head about 5 miles later it felt like somebody was hitting the brakes while I was hitting the gas at 65 miles an hour... It did that for a few seconds then it ran like normal again I got off the freeway over by my buddy's house and when the truck dropped below about 45 miles an hour I could actually hear what was going on instead of the typical freeway road noise and that stupid nissan KA24 had a bad rod knock... The only engine I ever had that I thought was unreliable and it had hardly any miles on it to this day I hate that truck, the guy that bought it from me drove it with a rod knock to central Mexico supposedly with a clanging away.
My buddy bought a truck once that had a "big oil leak out of the blue one day", didn't see any holes anywhere so we towed it to my shop and tinkered on it a bit. Got it to fire up, idled smooth and sounded good, 50psi oil pressure. Went to crack the throttle and sounded like all hell broke loose. Idled down again and went back to sounding great. I pulled the motor and dropped the pan and one of the rods had completely left the building, smashed up the block, cam, crank, everything. Still find it funny how great it ran as long as it stayed at idle. Probably had the same thing happen as whatever caused yours...
I didn't notice any changes in how it was running. Just cruising along. Since the big end stayed on the crank, it didn't lose oil pressure. I took the oil pan off yesterday and I think the block is best not used again. Especially when thevtruck us fun to winf up and shift 6000, not sure this block is good for that. It could be put back together as a beater and likely run. But the bottom of cylinder has a big notch out, where thrust surface would ride. Plus cam took a hit and so that's new obe required. Plus at least one rod, if not the neighbor rod that might gave gotten hit. Two pistons minimum. So looking like replacement engine vs repair. Some additional pics of bottom end. This is cylinder 2 piston, it took some hits.
I think the main issue is you were going to sell it ..... hurt the truck feelings and it reacted. Shifting it at 6000 I cant imagine that having any affect to the current problem I agree they are fun, I have same 350/nv3500 in my 1991 truck and it puts a smile on your face driving it.
Did the bearing spin in what was left of the big end? Or wrist pin get tight? Crazy thing with my buddy's motor was the big end completely left the crank so the oil p***ages were wide open, but it still had 50psi+ oil pressure. You'd think that even if the gauge was reading close to the pump that the pressure would've been low with that big of a leak. Circle track guys run these things 7k for long stretches so I'm not convinved that 6k alone was the culprit. Nothing looks like it got hot from an oiling issue, from the pics anyways.
The big end spins free and not too loose or too tight. Just like it should be. I'm not blaming 6k shifts at all. The rod just broke, and the kind of strange part was breaking in the middle. Oh I also previously said number 1 broke. That's incorrect, the number 2 is what broke. I was mixed up taking pics inside through holes in oil pan. Once I removed the pan, it's number 2 that broke. Number 1 cylinder, piston and maybe rod has some small post failure damage from parts and debris flying around.
During a speed stage at a road race in Mexico in the mid 90's, I was determind not to let a compe***or p*** me, I down shifted and punched the 331 Hemi just past 5,500 RPM it sounded fantastic as I blew away from that chump, I remember thinking, wow, this thing is really running good, got the checkered flag for that stage, drove about 3 miles further and BAM! sprouted number seven, it went with enough force to push the starter motor over a couple of inches. I guess I showed that guy. I rebuilt the engine and had the car at Las Vegas and an old guy heard my car and came out of his shop and looked over my set up, I told him about the failure in Mexico and he said I can see why, he said your oil cooler and lines looks good, but you need to run at least 3 more quarts of oil, you also need a windage tray and baffels in your pan with an extra quart of oil. Imagine he said, you are in a corner hard at 5,000 rpm all your oil is up in that cooler and the rest is on the side of your motor away from the pickup tube
The stock vortec has a bit of windage tray. Oil level was full. It didn't spin a bearing like an oil supply problem. Big end and little end were normal feel and wear, I've already taken engine apart. Rod just broke in the middle. Can't find any obvious reason. **** happens, my turn in the bucket. Bought another engine since mine had more internal damage to the block. Old engine needs a sleeve, plus the hurt parts. Easier just getting replacement.
I bent a rod over the crank in a 241 baby hemi once. It looked like a Salvador Dali painting in there!!! There is a YB vid floating around out there with a Vortec motor, doing dyno pulls, with a charger, then twin turbos. I think they got 1400 HP out of a stock motor...and over 400 dyno pulls before it went belly up...Solid motor.
Seems as nothing as it was made in the good ole days . I would of never expected to see this damage years ago in a SBC .
When a rod breaks in 1/2 and is still free swinging on the crank as its spinning, that rod has a lot of ground it can cover. With it spinning at 6,000 rpm, lots of damage can happen really fast. That piston in that one cylinder on that one rod is changing the direction it is moving two times with each stroke, and the rpm is only counting the plug firing which is on every other stroke. That makes 4 directional changes with each rpm, or 24,000 directional changes each minute @ 6,000 rpm. If you don't think the rpm had anything to do with the rod breaking, you have no understanding of how a motor works. The rpm just found the weak point on that one rod before it found what ever the next weakest link was. At 5,000 rpm, the rod probably would have lived a lot longer.
Years ago at the Carrera Panamericana I was talking to Ivan Zaremba, his Hudsan had just sprouted one and this guy walked up and had something in his hand, we both thought the guy wanted an autograph and then he looked again at what the guy was holding and it was a big chunk of the Hudson block
Just following up to close this out. Bought the $500 used engine. Came out of a 2000 van, but the casting was a 97 date code. Pulled oil pan and checked bottom end: Melling oil pump and stamped caps. So the engine was rebuilt at some point in it's life. Bearings (just 2 sampled) looked good, so cleaned pan and reinstalled it. Removed valve covers and heads were fairly clean with minimal sludge. Did not pull intake or the heads. Engine is installed and the V7 Sonoma has been upgraded back to V8 Sonoma status. Seems to be running fine with no bad noises or issues. Need to drive more before full confidence, but it seems good so far. Just a big PITA removing the engine and trans (almost no bellhousing bolts access), and then reinstalling. With all of the exhaust, wiring and everything else.
Glad you were able to get the stuff to fix it and able to fight the good fight and get it back together to sell. It's not glamorous or fun, but it served you and hopefully someone else in the future and will fund other things you need or want.
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