Why did I spin a main bearing?

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I have seen tight cam bearings MELT and cause a hard crank, not being able to idle and low oil pressure.
 
Yeah if they're tight, they're metal to metal somewhere. Last I checked, that wasn't good. lol
 
yeah i realize that now, but i didn't know much at all 3 years ago (was only 15 years old) so i was just the eager kid doing what i was told and building a car with burger-flipping money haha. responding to moper
 
zinser72 said:
yeah i realize that now, but i didn't know much at all 3 years ago (was only 15 years old) so i was just the eager kid doing what i was told and building a car with burger-flipping money haha
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We've all done something...lol
 
had a 440 one time spun a #4 main bearing. would still spin around, found molten bearing in the oil pan.
 
Did you ever rev it while cold? I always thought that could spin a bearing. I have seen people in 3rd world countries do that routinely. They start, then rev it high in neutral for 30 sec, then race up and down the block. They seem to think that wakes up the engine's spirit or such. They also floor it as they shut off the motor, which hasn't been needed since the model T. Our problem is that after a new cam install, you are supposed to run >2000 rpm, which always bothered me on a cold engine.
 
I have had main bearing problems in a 360 and a 340 block. They would both kill the center 3 bearings like some kind of balance problem. I rebuilt the 360 four times!! I was about to scrap the block as it was the only part that wasn't changed the previous four times. Long story short----The main oil feeds that intersects the lifter galley hadn't been drilled the right diameter all the way through---So the bearings would receive just enough oil to live--Until this engine exceeded 5000 rpm. I drilled them out to 9/32" and found that the bottom 4 inches wasn't drilled from the factory--which is why it lived for so long--never having enough cam or valve spring to rpm over 5000rpm. I found the same thing on the 340 block--actually worse.

Both engines are now living happily--The 360 with J heads making 430hp and the 340/418 W2 heads making over 500hp.

I drill them no matter the application. J.Rob
 
RAMM said:
I have had main bearing problems in a 360 and a 340 block. They would both kill the center 3 bearings like some kind of balance problem. I rebuilt the 360 four times!! I was about to scrap the block as it was the only part that wasn't changed the previous four times. Long story short----The main oil feeds that intersects the lifter galley hadn't been drilled the right diameter all the way through---So the bearings would receive just enough oil to live--Until this engine exceeded 5000 rpm. I drilled them out to 9/32" and found that the bottom 4 inches wasn't drilled from the factory--which is why it lived for so long--never having enough cam or valve spring to rpm over 5000rpm. I found the same thing on the 340 block--actually worse.

Both engines are now living happily--The 360 with J heads making 430hp and the 340/418 W2 heads making over 500hp.

I drill them no matter the application. J.Rob
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I will definately look into that. Now that you say that i realize i forgot to say last year i babied the car with the 904 and 7 1/4 rear. this year with the 4 spd and 8 3/4 i have spun it up to 5000 quite a few times. only when its warm though
 
I had my filter relocated (not just an angle adapter.....a full double line relocation) and found that either the pump was not strong enough, or a line was partly blocked somehow........burnt one of my mains to a crisp..........it just starved........squealed really bad before it flew........

Rebuilt the motor and just did an adapter..........
 
All kinds of things can cause main bearing issues. Did you clean the oil passages in the crank perfectly? That's the #1 cause I see of a main bearing failure.

If it IS a main bearing, the rods that get fed by the main will be chewed up too, probably causing the "tight" issue.

High RPM main bearing issues are usually caused by oil starvation/restriction. Rod side clearance will also affect how much oil comes through the main bearing.

But yeah, 2 thou is pretty tight, I'm strange, but I like 3 thou.
 
RAMM said:
I have had main bearing problems in a 360 and a 340 block. They would both kill the center 3 bearings like some kind of balance problem. I rebuilt the 360 four times!! I was about to scrap the block as it was the only part that wasn't changed the previous four times. Long story short----The main oil feeds that intersects the lifter galley hadn't been drilled the right diameter all the way through---So the bearings would receive just enough oil to live--Until this engine exceeded 5000 rpm. I drilled them out to 9/32" and found that the bottom 4 inches wasn't drilled from the factory--which is why it lived for so long--never having enough cam or valve spring to rpm over 5000rpm. I found the same thing on the 340 block--actually worse.

Both engines are now living happily--The 360 with J heads making 430hp and the 340/418 W2 heads making over 500hp.

I drill them no matter the application. J.Rob
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could you elaborate more on this??
 
RAMMs talking about one of the oil system mods for sustained rpms. Different year engines may have different sized oil feeds from the lifter galley to the main saddle. It's standard practice to enlarge them to 9/32" with a long drill.
 
Well now im really confused. i inspected all main and rod bearings and everything looks fine. i took apart the oil pump and the chunk definately went through and caused a little damage (pic). all the cam bearings look questionable and the cam feels "sticky". i plan on getting them replaced by someone that knows what theyre doing. i could not budge the cam with the rockers on. also the cam drifts back and forth about 1/2 inch. this seems like a lot. is it possible the cam moved forward and it skipped a few teeth on the oil shaft? the teeth look a little wierd in one spot (pic). Im really confused on how it lost oil pressure and didnt run since and where did the chunk come from? Im getting a little frustrated still chasing this mystery issue. any help is greatly appreciated
 

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Just wanted to confirm, you said that "chunk" came out of the oil filter? I don't believe it could get thru the pick up.

I don't believe the cam would move that much with the cover and f/p eccentric in place, dont think that was a problem.

One cam brg. in perticular looks scarred but that could have come from removing the cam and catching it with a journal or two.

Still looking and thinking.
 
I think i see a little issue on your thrust bearing? is the lenght of that chunk the same as the width of that bearing? If that's the case i think you may have had a partial spin with the upper shell on that bearing, although i can't tell about any damage on the thrust area from that picture.
 
I'm guessing the cam bearing are not in square.... That front cam bearing looks funny.
The bearing for sure had a bunch of trash run threw them....
I would almost guess that the mains are tight.... Just a huntch...
 
moper said:
RAMMs talking about one of the oil system mods for sustained rpms. Different year engines may have different sized oil feeds from the lifter galley to the main saddle. It's standard practice to enlarge them to 9/32" with a long drill.
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That's the thing--The first 2/3rds of the hole was 9/32"--I just tried the drill bit in the hole and ASSumed it was drilled that size the whole length--It wasn't. It has nothing to do with sustained RPM's. It only has to go to an rpm where oil VOLUME is inadequate ONCE to sustain damage. Live and learn--It cost me alot to learn this lesson, but my customer is happy and I haven't had any bearing issues since, so I'm happy.

p.s. Your main bearings look terrible BTW--Either dirt or insufficient clearance. I don't understand the suddeness of your low pressure though---Unless your relief valve got jammed open. J.Rob
 
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