Swapping rod and main bearings w/o crank work done?

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sadisticsavage

Not-quite-so-new-guy
Jun 16, 2013
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Has anyone ever done this? Just kinda looked the crank journals over and throw in standard sized bearings. I hear the bottom end of BBO are among the strongest ever made in stock form. So I was wondering if this has been done by any other 455 olds owner. Ive had my Dad and a couple of uncles who are all pretty good mechanics say they have done this just to refreshin a block and raise the oil pressure and never have a problem. Ive drove a couple of the rigs theyve done it to without knowing and never noticed the difference.One was a Pontiac 455 and the other was a 454. I am just planning on this 1st stage of the motor to be a new edelbrock performer intake with a 750 carb and the stock cam. Just figured Id ask because money is rather tight and if I cant get the car going soon Ill have to sell it and give another olds guy a chance at building a Cutlass with a BBO. Thanks guys.
 

Fox80

G-Body Guru
Jun 27, 2013
563
4
16
Jamestown NY
You don't have to have the crank polished unless it has some damage on it. However I would never trust mass produced bearings enough to just install them without checking each and every journals clearances, I know many people have had luck just slapping them in, but I have also seen motors spin a bearing in the garage from poorly made bearings. You can use that plasti-gauge stuff for at least a generic ballpark measurement if you don't have mic's and bore gauges. Regardless just make sure you check each and every rod/main journal and you should be fine
 

Rocketeer

Not-quite-so-new-guy
Jan 15, 2013
5
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I've never tried it on a Olds motor while the engine is in the car. I have put rod and main bearings in a 300 straight six ford before in a van. I've pulled many olds big blocks a part and I've found the crank and bearings to be in fairly decent shape most of the time. If the bearings are showing a lot of wear on them, you'll want to get some platiguage and check your clearances if you plan on hot rodding. Those 455 olds motors are pretty tough and can take a lot of abuse before they start wearing down.
My 66 425 crank only had to be turned .010 and that's after I had slung a rod bearing at 6300 rpm...Oooops! :blam:
 

Bonnewagon

Rocket Powered Basset Hound
Supporting Member
Sep 18, 2009
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I agree with the above. You never want to change bearings without at least checking them with Plasti-gauge. I have changed bearings many times that way, with no machine work. But then I've also had a scratched journal that I polished with a strip of emery cloth and oil, like polishing the toe of a shoe. Got lucky I guess.
 

-83MONTESS-

Comic Book Super Hero
Nov 4, 2010
4,570
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Bellevue, Ohio
Also verify that the journals are in fact stock size. I helped a buddy rebuild a 350 that was supposedly all factory. Long story short the crank had been cut just over .010" IIRC and "stock" bearings didnt fit right. Just a heads up
 

sadisticsavage

Not-quite-so-new-guy
Jun 16, 2013
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Alrighty guys thanks. I was a little sketchy about the whole idea but I guess the more I read up about it the more I feel better about it. I have always bought a built and balanced block and did everything else. But my Dad and Uncle has always freshened blocks up that way but they also only built low end motors for lifted mountain trucks. This motor will only be a cruiser and occasional block stomper should the local ricer get ballzy.
 

spidereyes455

G-Body Guru
Mar 6, 2013
776
1,614
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Northeastern PA
I replaced mains and rods in a sbc and even without removing the crank didnt have a problem. One rod journal looked questionable so I gave it a quick polish with emery cloth and I made sure to plastiguage every one, and unbeliveably they all came out within perfect factory specs even though it had over 100K on it and was abused alot. And I've abused the snot out of it since especially since it was backed by a T-5 and 4.11's in my 81 GP.
 

GT_80

Greasemonkey
Apr 23, 2013
240
7
18
Massachusetts
I have done it before in Small Block Chevy's - Lately I have taken a more scientific approach with a caliper to measure the crank bore, and thickness of the bearings I took out to make sure they will have enough clearance. I still have gotten away with stock size bearings, but it's better to know and not assume they are stock. You will be grateful in the long run

From the factory GM often used .002-.005 undersize bearings- to account for tight clearances. Often factory built stuff was less than perfect. They made do :)
 

rustyroger

G-Body Guru
Mar 14, 2007
502
6
18
Margate, UK>
sadisticsavage said:
Alrighty guys thanks. I was a little sketchy about the whole idea but I guess the more I read up about it the more I feel better about it. I have always bought a built and balanced block and did everything else. But my Dad and Uncle has always freshened blocks up that way but they also only built low end motors for lifted mountain trucks. This motor will only be a cruiser and occasional block stomper should the local ricer get ballzy.

Dad & uncle probably knew the engines and therefore the bearing journal sizes, if you put standard mains on an engine with a -010" crankshaft grind you will get dismal oil pressure and a loud rumble from the engine. Do the same with big end bearings and you will be lucky to save the crank if you don't shut it down immediately on startup.

Of course the right thing to do is inspect and measure the crank and rods carefully, as well as the bores etc, and have anything out of tolerance machined. But then you get into "while I'm doing this I might as well check that" until you end up doing a full body off restoration (and you only wanted to change the oil :D ).
 
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