Thread: question on main bearings

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hi guys, got a question i need an answer for. I bought an engine the guy claims he's spun the mains. the question is how can i tell if this in fact did happen without opening up the engine?and is this repairable, meaning is the block still ok to use?

Imnuts

Hey Edmontonian,
We are going to kick your butt on Saturday night, hehhehe! Canucks Rule.

Anyways, if your main bearings are spun, there is a remedy. It is called, “line honing the mains” which will cost you about $185.00.

If you remove the oil pan and along with all the main bearing caps, you should notice that one of the bearings will not be in it’s place. Each bearing has an ear which is supposed to fit into a relief. Both the block and the bearing cap have a pocket for the ears of the bearings to fit into. If they are sheared flat, this tells you that the bearing has spun. Also if you take notice of the metal in the one journal area of the block, it should have scratches and shiny metal in comparison to the other areas of the four other bearing mating surfaces.

It is always a good practice to line hone all high performance blocks to ensure quality, so in essence, no money is wasted even if you bought a block with a spun bearing. Chances are you will get this block for free or maybe $50.00 , yes? Whereas a good block (one without a spun bearing) you might pay $350.00 for it.

Having said that, I was just offered three 350 ci blocks with spun bearings for a total of $150.00. All blocks were of the newer version with one piece rear main seals. One block was a roller block with four bolt main, the other was a 2 bolt roller block and the last was a none roller two bolt main.

Yeah, so put your money on the Canucks and when the game is over, you will be able to buy a crate motor with your earnings!

But there is a limit to how much material can be removed. So if the block and main caps are all black and burned around the bearing bores. Pass!, you are about to buy an expensive chunk of scrap iron! Buying a spun main engine is risky at best. Been buying cores for thirty years.

thanks for the responce guys, but is there a way to tell if the bearing has spun without taking the enigine apart?

go-Oilers-go Eh!!!!!!!!


imnuts

Originally posted by imnuts
but is there a way to tell if the bearing has spun without taking the enigine apart?

Hey I'm nuts;
You do not have to tear the engine apart for this, just the oil pan (14 -7/16 inch bolts and 4- 1/2 inch bolts), plus the main caps (10 - 5/8 inch bolts).

Other than that, if you can hear the engine run and if the oil pressure is low and if their seems to be a deep rumble to it, then the mains are spun. If you hear a knocking, then a rod bearing is spun.

Originally posted by imnuts
thanks for the responce guys, but is there a way to tell if the bearing has spun without taking the enigine apart?

go-Oilers-go Eh!!!!!!!!


imnuts

You could go by sound, what does the engine sound like?? You should look at the oil that comes out, look for brass or other metals, but this wont tell you exactly how bad it is, the only true way to do that is what Typoon said drop the oil pan and Main caps

Otto

Edited part: Well aint you fst with yer fingers there typoon you beat me by what 4 Seconds on the same reply!!
Thanks way to hog the glory

Great, i have never experienced a spun bearing so didn't know what to look for other then metal in the oil. Was concerned that if the bearing had spun the motor would be screwed and wouldn't even turn over. But it seems that if not excessivily run then it is repairable, thanks for the info guys. I'm only going by what the seller had told me and i have my suspicions that he may have
been wrong in his assessment. I haven't heard it run yet, but when i tried to start it, it would even fire and then i found the distributor to be loose and rotated so with a little luck i'm hoping that is all that is wrong. Guess i won't know till, i either get it running or pull the pan.
BTW, this is a great forum, will be spending alot of time here in the coming days as i complete the restoration of my firebird.

IMnuts