Main bearing wear

[Boiler Ben]

So I am proceeding with the cleaning of my block after disassembling the short block assembly that I purchased.  The link to that post is below.  I am dealing with a lifter bore issue (also a separate post) but I would like to get some advice on the condition of the main bearings.  Supposedly these bearings were new when the short block was first assembled.  Everything seemed to be assembled properly and has assembly lube on it.  I expected the bearings to look perfect but there is some wear.  I just don't know if this is normal or not.  See the photo below.  I also notice some wear on the bottom of the front cam bearing and I am pretty sure that looked perfect when I installed the cam.  I turned the engine over a few times as I was degreeing the cam.  Only the front cam bearing has any wear.

What am I looking at here?  Is this thing messed up or is this normal?

https://fepower.net/simplemachinesforum/index.php?topic=12451.0

[My427stang]

That's not bad, a little taper, and likely tighter than most of us would go.  Best bet is to properly check clearances on the mains, adjust fire as needed

The front cam busing, also not horrible but no idea why they drove it in so far, I'd drive it back to make the oil holes line up.  That being said hard to tell what the top of the picture is showing. 

My gut tells me if the cam goes in easy and you push some oil through the main feeds and it turns easy, good to go (but I would drive that front one forward and look at ever feed on the other 4 to make sure they didn't miss the oil feeds  The back one can be tricky if you don't flip the engine on the stand or use a little hook

[blykins]

I wouldn't be excited about it. 

For one, it looks like the bearing clearances were bore gauged, which is good, but it also looks like they were not in the right spot on the bearing.  As you get closer to the parting line the clearance gets bigger, which could give you a false sense of security on clearance. 

If I were to throw something against the wall to see if it would stick, I'd say the clearances are tight and the mains aren't straight.

[Boiler Ben]

Looks like AutoZone has a loaner cam installation tool.  I’ll get that and position the front cam bearing better.

My plan had been to just clean and reassemble as is.  This is a street engine and I have a standard pressure HV pump for it.  Someday I’ll have to decide whether or not to restrict my Edelbrock heads but I’m not there yet.  So I could Plastigauge now or just trust what I have.  Any suggestions?

[My427stang]

I am not a Plastigauge fan, used to be until I started using bore gauges and realized it is so inconsistent that you can't even say "it generally reads tight or loose"

In the end, the range of factory stock (as tight as .0015) and common performance clearance (as loose as .003) makes it hard to say if you are good when the wax string is so variable.

If tight, things have to be super straight, which old parts often aren't. 

If you brought the block to a machine shop, with the crank on V-blocks, it'd take about an hour to get real numbers.  May even want to have a set of FM bearings on hand and return if not needed.

The cam bearing doesn't scare me at all if you can push it back, use the two oil holes for proper depth and be sure it can't hit the cam retainer plate

[pbf777]

       On the subject of the camshaft bearing:  I can not positively discern from the photograph, but is there an angle chamfer machined from the face of the block leading back to the current camshaft bearing position?  If so (and I have seen this before), then pushing the bearing forward might not be the best choice; rather determine if the bearing is better supported where it's at (front and back) and if the camshaft journal is wide enough to utilize the bearing surface where it's currently at?   

       The area presented of  the oil passage hole currently is more than sufficient so I wouldn't allow this to govern my decision.   

       As far as for guessing as to the issues that might be the cause for the nonuniform and perhaps somewhat excessive witness marking as presented on the bearings, remember that often there is going to be more than one participant in a melee (block bores out of size and/or alignment, crank not straight and/or journals out of size, heck........how taught was the timing chain?  ), but I would not be one to recommend to just ignore that which is in front of me, I'd have to say one should investigate this some before just bolting it all back together, particularly considering if what is being witnessed is a result of just turning the engine over on the stand with absolutely no actual "run-time".   

     Scott.

[bsprowl]

Looks to me like the front cam bearing may not be square in the bore. 

[Boiler Ben]

There is a chamfer on the block at the front cam bearing.  Looking at it from all angles, I think the bearing is supported optimally where it is.  Got the block clean this weekend.  Cylinders wiped clean with ATF.