SPA Modeler

I seem to remember you just put that motor in the truck

That's true. Sucker doesn't have 5000 miles on it. Thrust bearing was the culprit as the crank was trying to screw itself out of the block according to my engine machinist (he also assembled the engine) and he said that sometimes he runs into that on small block 400's. This guy builds in the upwards of 30 engines a year for the local speedway and has a fantastic reputation. Every rod bearing insert is showing copper and every main bearing has been pretty much wiped out. Funny thing is that I never heard a peep out of it at all until the couple of days before I pulled it. I was thinking a piece of gasket material or something else had broken loose and was bouncing around on top of the piston. The noise would come and go and not be there at all when the engine was cold which was strange. The way the bearings looked it should have been sounding like someone was taking a hammer and beating on the engine with it. I noticed a soft knock on the way home from work on a Wednesday night at idle only. Engine oil looked good and by the time I made it home the noise was gone. The next morning I started it up and didn't hear a peep out of it so I drove it 17 miles to work--no noise. Drove it the 17 mile trip home that night--no noise. Friday I was off so I still hadn't heard any noise out of it but decided to drain the engine oil and check that out. Nothing out of the ordinary that I could see with the naked eye. With fresh oil and a new filter on it I drove it that afternoon and the noise came back...only louder now. It only takes me around 8 hours to do an engine swap and I have my 383 in the garage so I just swapped it out. That's a good thing too because after tearing it down I found that none of the bearings spun which means that all of my connecting rods and the engine block are okay but DANG....I'm looking at a new crankshaft and all new bearings now. He's being pretty cool about it all because he took it upon himself to order a new crankshaft and bearings. The block has to be stripped, hot tanked and all new bearings to include cam bearings have to be replaced as well. Frickin' crazy.

Now you car guys out there are going to be wondering the same thing that I did....why wasn't thing making more noise than it did and why wasn't the engine oil just flooded with metal flakes? There's NO bearing material left on the #2 main bearing pictured here:



I've been working on cars my whole life and have never seen anything like this to where an engine can be this worn and NOT give off any signals that something like this should have. I would have stopped driving it long before I did if it would have as I've got around 6K invested in this motor.

I'm very fortunate that I still have my 383 stroker engine as backup which has been in the truck since last weekend when I did the swap out. At least I've got wheels.

Not a car guy, but your explanation makes me shudder. Could that have been a catastrophic fajilure? Good the builder is helping out. Could it be that is why it didn't let go. . . because of how well put together it was?

It is true that ol' Bruce builds a good motor but regardless of that, this IMO should've been hammering.

Should have just wrapped some leather stips around those bearings!

LyleW wrote: ↑Sat Jan 14, 2023 9:34 am

mustang1989 wrote: ↑Sat Jan 14, 2023 9:21 am It is true that ol' Bruce builds a good motor but regardless of that, this IMO should've been hammering.

Should have just wrapped some leather stips around those bearings!

I'm not an expert on engine rebuilding and whatnot but I am curious on one thing. Weren't any of the bearing new or the crankshaft new? Or was it a freak thing happening?

I hear ya Tom. I opted to keep the stock crankshaft because it's a nodular iron crank which makes it pretty strong. All the bearing were brand new I purchased the Racing bearing inserts instead of the standard passenger car inserts which were of stronger material. All of this was pretty much a freak event.

I was an auto tech more many years and when I was working at a GM dealer we had quite a few late 80's early 90's small blocks that came from the factory with a poor line bore. We did a TON of warranty engine swaps. The fix on all those motors is a good ole fashioned line bore. If you can still do it, I would have him do it, even if he thinks it doesn't need it. It's good insurance.
Every one of those engines had the same symptoms you described.

That would kinda piss me off. Interesting BK. If that's the case it will happen again with the new crank and bearing.