Small block main bearings

[mrbill426]

  I am a little confused about interchangeability of small block main bearings.  As far as I know the crank journals of the 318 and 340 are the same size, so I would think the main bearings would be the same too.  I have had a set of clevite 77s for a while that I thought were for a 340 but when I looked up the part number in the index my newly acquired master bearing catalog it says they are for later ('74 and up) 318s only.

Best I can tell the only difference from these (#MS-1344P) and the "340" mains (#MS-963P) is that these are full groove on all bearings, while the 340 ones are half groove except for the rear main which is full.  The rod bearing numbers are the same for both engines.  Am I missing something?     Is there any reason why I should NOT run full grooved mains in a 340?  I ran them in a 383 without any problems, but that was a big block, perhaps the small block has oiling issues?  I will be using a deep sump and HV pump. 

 

[Chryco Psycho]

I always use full groove brgs in any rebuild I do

[mrbill426]

So, I am correct to assume that even though the clevite book singles the full grooved set out as being for later 318s, they will work fine in a 340?  Wonder why they opt for half grooves in a "performance" 340, and fulls in a smogger 318 

[Chryco Psycho]

the only other thing to watch is the size of the thrust surface , it may have been made larger in the later block , I cannot think of qany other reason not to use them

[mrbill426]

Okay, I'll check that.  Do you mean the width of the bearing, flange to flange, or the depth (or height) of the flanges?

[Chryco Psycho]

height

[mrbill426]

I got ya, easy to check 

Will let you know...