Changing crankshaft bearings with the engine in the car.

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Kern Dog

Kern Dog

Build your car to handle.
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Who has done this?
I've replaced rod bearings with engines still in cars but I don't think that I've replaced a full set of main bearings before. Rods are easy, pushing the rod UP a slight amount allows adequate clearance to slip the top shell out.
The mains though...it isn't as if you can pull the crank away from the block to give the upper shells room to move.
20+ Years ago I did replace a few bearings in a Honda 1.5 4 cylinder but that was a LONG time ago.
I've changed rear main seals in LA and Big blocks. That upper section just rotates around when you push it with something soft enough to not scratch the crank should it slip.
I'm thinking that a firm plastic stick could be used to clock the bearing shell a bit, then a pick could be pressed on the back side of the bearing that sticks out, slowly rotating it until it slips out.

This car.....

Dart blue 1.jpg


Looks like crap but is a fun dirt road drift car. It has a fairly stock mid 70s 360 with a stock bottom end, a 280/474 Mopar cam, #308 heads, a Weiand intake and Holley 600 carb. It runs strong but the oil pressure is low. The cheapo aftermarket gauge actually reads zero at idle. During a cold start, my 440 Power Wagon reads 70 psi. Another car reads 50. This was at 25 at fast idle. That is simply too low.
I'm hearing some rattling inside. I pulled a valve cover and let it run. The rocker arms are somewhat quiet. It seems like it is down low. I thought maybe the oil is just tired and maybe thin but it is clean. It does have a little smell of gasoline but I can't be sure. It has literally been YEARS since i changed the oil. The car sits until I decide to bash around dirt trails, then I park it for months. I might change the oil and see if that increases the pressure and eliminates the knock/rattle. If not, I can pull the pan and check the condition of the crank bearings.
 
I would change the oil and try a quality oil
pressure gauge before tearing into it.


Then if required:
I have made a dowel pin kind of a piece and put
into the oil hole and rotated the engine by hand
to aid in getting the main bearings in and out with
the crank in place. Just make sure it is not long enough
to damage the crank.
 
I have done it, but I am too old to want to lay on my back that long anymore. My buddy’s 71 Demon has a 360 with a deep oil pan, that he could barely get out of his driveway. He debated on changing the oil pan with the engine in the car, I had him drive it to my garage and pulled the engine, swapped the pickup and pan and had it back together. I felt that it was easier for me.
 
I've done it a few times when customers refused to pay to remove the engine. It's not difficult, but what is difficult is keeping it as clean as you need to. I always used a very small flat blade screwdriver to push the upper half of the bearing out. Once you get it pushed out about 1/2" you can just turn it the rest of the way out with your fingers.
 
the gargantuan pain in all nine assholes of laying on the ground with **** dripping and dropping on your face while cussing and fussing on this job aside... what happens when you're done and (insert sing-songy voice) the oil pressure's still low?

while it's likely just the bearings are beat down, the possibility does exist that the crank could be pooched as well.

or maybe the oil pump is waxed ***...

i say throw some 50 weight at 'er and let it rip, see what time it is.

but if i'm doing mains, i'm doing rods-- in for a penny, in for a pound. what's another few hrs to yoink a motor at that point for the ease of working standing up.
 
A buddy of my bought a 37 Dodge pickup. Very low oil pressure.I told him to buy Harley Davidson 60 weight oil.
He doesn't drive it often but said it runs fine with the 60 weight.
When it blows it blows. It may be never.
 
In my opinion, you will spend much more time and energy trying to change the bearings with the engine "in" the car. Pulling the engine isn't "that" hard and besides, once the engine is out and on a stand it's "much" easier to look it over to see if there are any other problems.
 
So.... low oil pressure just might mean the crank needs turned. Otherwise your new bearings wont last long nor bring the pressure up to snuff.
Id pull it and look everything over with a mic.
 
Lefty71 said:
So.... low oil pressure just might mean the crank needs turned. Otherwise your new bearings wont last long nor bring the pressure up to snuff.
Id pull it and look everything over with a mic.
Click to expand...
The right way to do it. You can used car it by sliding some bearings into it. It might make it better...................or not. Sometimes it's like lipstick on a pig.
 
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Kern Dog said:
Who has done this?
I've replaced rod bearings with engines still in cars but I don't think that I've replaced a full set of main bearings before. Rods are easy, pushing the rod UP a slight amount allows adequate clearance to slip the top shell out.
The mains though...it isn't as if you can pull the crank away from the block to give the upper shells room to move.
20+ Years ago I did replace a few bearings in a Honda 1.5 4 cylinder but that was a LONG time ago.
I've changed rear main seals in LA and Big blocks. That upper section just rotates around when you push it with something soft enough to not scratch the crank should it slip.
I'm thinking that a firm plastic stick could be used to clock the bearing shell a bit, then a pick could be pressed on the back side of the bearing that sticks out, slowly rotating it until it slips out.

This car.....

View attachment 1716305152

Looks like crap but is a fun dirt road drift car. It has a fairly stock mid 70s 360 with a stock bottom end, a 280/474 Mopar cam, #308 heads, a Weiand intake and Holley 600 carb. It runs strong but the oil pressure is low. The cheapo aftermarket gauge actually reads zero at idle. During a cold start, my 440 Power Wagon reads 70 psi. Another car reads 50. This was at 25 at fast idle. That is simply too low.
I'm hearing some rattling inside. I pulled a valve cover and let it run. The rocker arms are somewhat quiet. It seems like it is down low. I thought maybe the oil is just tired and maybe thin but it is clean. It does have a little smell of gasoline but I can't be sure. It has literally been YEARS since i changed the oil. The car sits until I decide to bash around dirt trails, then I park it for months. I might change the oil and see if that increases the pressure and eliminates the knock/rattle. If not, I can pull the pan and check the condition of the crank bearings.
Click to expand...
Think of it this way Greg, If you take some chicken **** and make soup out of it, what do you have?


Chicken **** soup. :poke: :rofl:
 
Also, consider what some have said. If the bearings and or crank need help, what about the cam bearings? What about the camshaft itself? The lifters? How sloppy is the timing chain? What about the rings? If this is a car you're gonna sell, then shyster it up and unload it. If you plan to keep it, you might want to rethink it.
 
Did that in a 307 SBC, 71 Nova on my back under the car, I assumed that I would have to drop the crank just enough to get the shells in and out.

In retrospect, I could have probably not had to drop the crank.

So, yes, if you can get the pan off, you can change the shells
 
RustyRatRod said:
Also, consider what some have said. If the bearings and or crank need help, what about the cam bearings? What about the camshaft itself? The lifters? How sloppy is the timing chain? What about the rings? If this is a car you're gonna sell, then shyster it up and unload it. If you plan to keep it, you might want to rethink it.
Click to expand...
I have heard/read that magnum cam bearings wear more than anticipated ??
 
I haven’t heard a lot about the cam bearings, but I do know that a considerable number of the cams produced weren’t adequately heat treated. I have seen an early 5.9 magnum before that had the cam bearings pretty well chewed up in it before. The cam was showing signs of delaminating on the lobes, so it may have had something to do with it.
 
Garrett Ellison said:
I haven’t heard a lot about the cam bearings, but I do know that a considerable number of the cams produced weren’t adequately heat treated. I have seen an early 5.9 magnum before that had the cam bearings pretty well chewed up in it before. The cam was showing signs of delaminating on the lobes, so it may have had something to do with it.
Click to expand...
Also, consider the higher spring pressure the roller camshaft use. It might not be "much" in comparison to aftermarket stuff, but that could be a factor.
 
I would bend up a cotter pin to slip into the oil hole, funny angle thing and just rotate the crank.
The cotter pin "flukes" laying across the bearing surface would just push the shell around till it'd pretty much fall out when nearly all the way around.
Just lay the new shell on the clean/lubed crank surface, finger pressure to get it started, the cotter pin/rotate shaft till you can engage the "tab".

Not my favorite job, hoist helps.
@Kern Dog

IMG_20240919_095752_505.jpg


IMG_20240919_095745_695.jpg
 
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