main bearing differences

[swing69]

I'm looking at buying new main bearings for a 73 318, standard. I've seen some bearing mfrs list bearings for 65-84, and others list 65-73 then 73-85.

What changed in bearings around 73? why are some compliant for all years and others not??

_ _ _ just found an old thread that the middle thrust bearing size changed.

QUESTION: If I wanted to use a 1984 crankshaft in a 1973 block.....

What the cure for the middle thrust bearing issue?

 

[Plymouth 65]

If I'm not mistaken, I believe it's the center thrust bearing surface diameter that's different. 65'

 

[my68barracuda]

Mid 70’s is when the bi metal engine bearings started. The bi metal engine bearings took the lead / copper out of the formula and substituted aluminum / silicon.
So the bearing pre 73 may be tri metal and post 73 bi metal.
The only way to know with certainty is to contact the bearing manufacturer Tech Line.

 

[MOPAROFFICIAL]

Use the main thrust bearing for that year block.
You cannot use a later year thrust bearing in an earlier block because the saddle is not machined to receive that bearing, it will not seat.
In other words the early thrust bearing Works in all year blocks, so if you have a early crank you want to use the early thrust bearing, no matter what yr block.. if you have a later yr crank and want to put it in an early yr block, you need to use the thrust bearing for that year block. They enlarged the thrust face surface after 73.

 

[Wyrmrider]

what mopar official said
If you are doing a line bore on an early block you can enlarge the bearing register for the later bearings

is your block apart or are you fishing the new bearings in with the crank in the block?

 

[swing69]

I want to use the later post 73 crank/rods/pistons in the early - pre-73 block. the reason is the later engine was rebuilt without the crack being spotted, and it had a coolant leak into the valley AND into the oil feed to the right side rocker shaft.

Pulled the heads and intake....and found the crack. The crack is NOT repairable....so a replacement block was found...its a pre-73. Certainly the early block with keep its matched caps.

So now I know to get the earlier bearings to match the block. I just wanted to make sure the later crank can be used before cleaning/magnafluxing / boring +.020 the replacement block.
Sound to me like use early bearings and it all will fine.....

 

[krazykuda]

Use the main thrust bearing for that year block.
You cannot use a later year thrust bearing in an earlier block because the saddle is not machined to receive that bearing, it will not seat.
In other words the early thrust bearing Works in all year blocks, so if you have a early crank you want to use the early thrust bearing, no matter what yr block.. if you have a later yr crank and want to put it in an early yr block, you need to use the thrust bearing for that year block. They enlarged the thrust face surface after 73.

I know the 360 thrust bearing flange was increased on the 360 then, did they do the same for the 318's also???

 

[nm9stheham]

So now I know to get the earlier bearings to match the block. I just wanted to make sure the later crank can be used before cleaning/magnafluxing / boring +.020 the replacement block.
Sound to me like use early bearings and it all will fine.....

You have the reasoning right. Just do that to be safe.

FWIW, I have a 273 block where the fitment area for the thrust flange is quite large enough to accommodate the later, wider flange. So, either may work... I just don't have enough early blocks to check to see if they will all take the later bearing or if some early production blocks would not.