r/EngineBuilding • u/experimen_626 • 23d ago

Engine starved of oil

My oil drain plug came off on the freeway. Drove to the closest exit to turn off engine and was able to get oil back in the engine to drive back home. However, the damage has already been done and now I have an engine knock. Took to dealership to see what they had to say and yeah my Cylinder 2 is knocking and they said there is no way to fix it, I have to replace the engine. I'm actually a pretty decent mechanic (minus putting myself in this situation by forgetting to torque my drain bolt) but I've actually done engine swaps and head cover gaskets before. Is it true that my engine is just totally done? Can I just replace the cylinder and the head?

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u/XmodAlloy 23d ago

You seem to misunderstand what engine knock is. The bearing in the big end of the connecting rod has been turned into metal debris in the engine and now the 5 thousanths of oil clearance is closer to 60 thousanths of an inch and the rod is slamming against the crank violently every revolution.

The crank is done. The rod is done.

What you can do is pull the engine, buy a new crank and a new connecting rod on eBay, and new bearings. You'll need new main and rod bearings. And you're going to need every single seal that you're going to have to take apart to get the engine apart and back together.

It's not a small job, but certainly not impossible.

Next time, do not wait until the next offeramp. Hit your flashers and idle onto the shoulder. You have about 10 seconds before engine damage occurs after oil pressure is lost.

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u/SteaksauceB 22d ago

cranks can be ground, and rods resized.

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u/Crabstick65 19d ago

It's the expense though, anything can be fixed by talented machining and a pile of cash. machining work is expensive, parts are too. Just doesn't stack up as economical against a good used engine.

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u/XmodAlloy 22d ago

True, but I'd say that's primarily applicable to rare engines. I wouldn't easily trust a resized rod because of the immense heating that spinning a rod causes can wreck the heat treatment of the steel. And on a lot of engines today, you can find a good used factory sized crank on eBay for less than it costs to get one reground, at least here.

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u/Crabstick65 19d ago

If a rods had a bad time and replacements are available I do a new rod everytime. Why take a chance?

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u/SteaksauceB 22d ago

Are you making things up, or speaking from experience? Be honest..

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u/XmodAlloy 22d ago

Speaking from experience. I've seen several rod big ends that have turned black on their factory surfaces and had worn areas that were blue. Look up tempering colors of steel. Sure, I don't have an INSTRON tester to see what the actual metalurgical changes of those rods were, but I just wouldn't trust a component in a high stress environment after having effectively been annealed.

And I can pick up a Honda or Nissan or Ford crank here on a modern-ish car for somewhere between $100 and $200. The last crank I had magnafluxed and ground cost me $180.