Crank & Bearing Help For 8BA V8

57ChevyWagonMan

57ChevyWagonMan

Member
I am working on an 8BA motor. I have it all torn down and ready to go out for hot tank and magnaflux. Nothing outwardly wrong with the motor so far. Good .040 over 4 ring pistons, pin ends tight on the rods, bores are smooth with no ridges. Will need a couple of heli-coils in one cylinder deck and 3 in the other. My only concern is the crankshaft. It looks like it may only need a light polishing. A couple of marks on the No. 1-2 Rod journal that I can not catch my finger nail on. A little light rust on the main journal in line with the oil grove. The problem is all the bearings are marked .030. I can not seem to locate bearings of a greater undersize. I fear this crank may be too badly worn to use again unless I can get smaller bearings. Are smaller bearings available? Where can I get them? Were they ever available? Does anyone know where some NOS ones might be sourced?

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I realy would like to brag that I got a complete engine on my first try and did not have to go through 2 or 3 to build a good one;)

Thanks so much for your help!

Mike:cool:
 
I think some measurin' may be in order after cleaning up the journals a bit with some scotchbrite and elbow grease. How do all bearings look? Hope you kept tract of where each bearing pair went on the crank if all checks out OK.

Jack E/NJ
 
Make sure the block is OK before you spend any money on the crank. That crank looks pretty rough from here. 8BA cranks are not that hard to find, and I'm sure you can find another.
 
Have someone with a micrometer go over your crank... As was pointed out, cranks are easy to find, and cheap...
If your crank mics out ok, get a sheet of crocus cloth, tear it into strips as wide as the crank journals and use a long strip of duct tape (I have what is known as gaff tape) making a real long strip... Put the flywheel on as a stand base, put it on a table, and walk around the vertical crank as you use your long strip to polish the crank...
Remove the plugs from the end of the rod journals to clean out... You can replace with threaded plugs, I just put in new plugs and peen them in place...
Karl
 
They always did make .040 bearings if the crank needs gringing. I wouldn/t be scared of .040 Have large end bore of the rods checked to make sure thay are round, and not worn, if so have them reconditioned. Walt
 
I tore down an 8BA this week and the crank needs to go 40 on the rods and mains but like you have had zero luck finding 40 main bearings . Found a few sets of rod bearings but no mains.
 
Well, I have good news and more good news. First of all my crank is in pretty good shape. I took a micrometer to it and found my mains to be 2.468" and my rod journals to be 2.109". The standard for 8BA mains is 2.4990 '48-'51 and 2.4985 '52-'53 that is only .0005 to .0010 from being a true .030 undersize and the rods were standard at 2.1390 '48-'51 and 2.1385 '52-'53. Makes the rod journals perfect. I am now planing to polish the crank and put new .030 under bearings in it.

Ken/Alabama,

I found my local independent parts seller sells Sealed-Power brand bearings and they list a .040 under main but only .030 under for rods. Likely someone did or does have them. I hope after another look you find your crank to be better.

Mike :cool:
 
57ChevyWagonMan said:
Well, I have good news and more good news. First of all my crank is in pretty good shape. I took a micrometer to it and found my mains to be 2.468" and my rod journals to be 2.109". The standard for 8BA mains is 2.4990 '48-'51 and 2.4985 '52-'53 that is only .0005 to .0010 from being a true .030 undersize and the rods were standard at 2.1390 '48-'51 and 2.1385 '52-'53. Makes the rod journals perfect. I am now planing to polish the crank and put new .030 under bearings in it.

Ken/Alabama,

I found my local independent parts seller sells Sealed-Power brand bearings and they list a .040 under main but only .030 under for rods. Likely someone did or does have them. I hope after another look you find your crank to be better.

Mike :cool:
Click to expand...

I have checked with the micrometer. Rods 2.110 mains checked 2.466 . I have two other 8BA cranks that will clean up at .010 on the rods and mains, I just hate to junk a crank but it is what it is. I have found that several suppiers will still list some bearings but in reality they are no longer supplied.
 
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Did you check with EGGE machine, they can come up with some odd stuff. They found a 1931 Knight connecting rod for me, I thought it was going to be tough to find.
 
I have found a supplier who can get me .040 under bearings. I have learned my crank is right at the lower limit and could be polished and use .030 under bearings. Should I just polish it out or should I have it reground for the .040 bearings to help tighten up my oil clearances?
 
Are your journals nice and round? That would make the difference to me. With today's oils, you could run it a little loose and it'll run fine for a long time. Are you going to be putting a lot of miles on it, or just an occasional driver? All things to consider in making your decision.
 
We're not building a satellite here. Polish it up, put new .030 shells in and get it built. Over the next few years you might see a set of .040 shells and buy them and put them on a shelf. If you drove it enough to get around to the next rebuild you could then take it to .040.

I'm a firm believer in making things last as long as you can.

I'm also cheap.

Mart.
 
Brass shim stock was available, years ago, for your situation... I also use it to check bearing clearances, as I don't feel that plastigauge is accurate...
Karl
 
I appreciate your input. I likely will not be racing the car but may make a pass or 2 at the local track just for kicks. I do want to be able to drive the car quite a bit. Hope to enjoy the hell out of it.

Mike :cool:
 
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