Need help finding just over standard size main beaings. Doing full rebuild on tired 350, had block bored to 4.1255, decked .005, cam and crank journals align bored, cam bearings installed. I hand polished crankshaft slightly with 1000 grit to get shine going because it mics right at specs for mains and rods and looked good. Installed crank with new standard size bearings and red plastigauge barely touched on most mains...blue smashed to around 0.007 to 0.009. Only main bearings I can find online are .010 oversized, pretty sure that will make tolerance to tight......... Is there anything available around 0.001 to 0.005 oversized bearings?

 

I think what you really need to do is get some precise measurements on the crank journals. If you did indeed take that much off then you will really need to have the crankshaft reground. Hopefully it will clean up at .010" There are no bearings available in the sizes you are looking for.

Red plastigauge looks like it starts at .002 so if it is barely touching that might be what you have ? Are you sure you are not looking at the metric side of the package ??

By the way I typically use green plastigauge. Not sure I have ever heard of Blue. I am really wondering if you are measuring properly. Try this experiment on your #1 main. Put a .003" feeler gauge in like show in the attached picture and see if you can turn the crankshaft or pull the feeler gauge out. You can only do this on the front main but it will somewhat confirm if you are measuring correctly.

 

I tried feeler gauges...was able to get a .006 in and out and spin crank. I did not try green plastigauge as it is thinner than red and was barely smashing red so used blur which is thicker than red...did get some smash using blue plastigauge around .007 to .009 thousands. Specification is .0035 or below so looks like I'm about 0.004 too sloppy

 

If you really have .007-.009 then you need to have the crank turned. I find it hard to believe that you took that much off while polishing it but I guess its possible, especially if it was worn to begin with.

What does the crankshaft actually measure ?

 

They align bored the cam tunnel too? That’ll be your bigger problem, finding a cam bearing to fit.

And there’s no way you can polish .007 off a crank journal and have it be anywhere close to round and straight, especially with 1000 grit paper.. Did this crank come out of this same engine? Was it running ok beforehand? There are some real inconsistencies here.
My advice to you would be to take it all to a reputable machine shop and have them mic the journals and main saddles, not use plastigage. That stuff is useless. Then go from there.
Hope this helps.

 

they did align bore cam journals and sleeved cam journals to accept standard size bearings which they installed. I did not have great oil pressure before tear down but crank main journals and bearings looked good. I think mistake I made was having main journals align bored...possibly added some slop to allready loose clearances before tear down. I spent maybe 1 minute polishing each journal so doubt that did much other than remove varnish.

 

If anything that will typically tighten up clearances. I really think you need to take your block and crankshaft to the machine shop and have them measure it for you. Either something is really wrong with the crankshaft or the main bearing bore or you are doing something wrong measuring.

Only other remote remote possibility is that the bearings are made wrong. What brand are they ?

Why did they align bore the mains ? "because of low oil pressure" is not a good reason.

 

You need someone with the calibrated, proper tools to measure things ! There are some glaring inconsistencies here. Refer back to Cutlassefi's post. It would take half a pallet load of 1000 grit paper and MONTHS to remove a thousanth or two from a crank.

 

Ok so let me get this straight. They sleeved all the cam bearing holes and installed std cam bearings? I’d like to see a pic of that if possible. Did it spin the cam bearings? If so, why wouldn’t you just get another block?
And when they align hone the main saddles, they cut the caps to shrink the size of the tunnels. Then they’re honed back out to spec, not above that.
I think it’s safe to say you may have some bad info here. As I previously mentioned, take everything to a reputable machine shop, and have them check all your bearing sizes, tunnel, size etc. Then go from there.
Best of luck, sounds like you’ll need it.

 

actually just had to sleeve number 5 cam bearing journal due to small Crack that wasn't found when magnafluxed. Allready have 2400 in machine work on this block so no turning back now. Waiting on call back from machime shop that did work. Was planning on doing asswmbly myself and have done several chevy motors but never had issues with any bearing clearance after machine work was done

 

 

It doesn't look like they align honed the mains. Only checked them. Those guys are really cheap compared to this area.

 

Here are crank main measurements taken with 2 different micrometers to ensure accuracy.
#1- 2.4989
#2- 2.4990
#3- 2.4987
#4- 2.4988
#5- 2.4991
From what I see specification is 2.4985 to 2.4995.
I measured shells of old bearings and new ones. Old ones were maybe 0.0001 thinner than new which makes sense for minor wear of old part... so I'm stumped.

 

Now measure the main saddles and do the math.
Main saddle size - 2 bearing halves - journal size. That’ll give you your bearing clearance, ie 2.688( main saddle size)-.0931(bearing half)-.0931(bearing half)-2.4990(journal size)=.0028. That’s your bearing clearance for that journal/main saddle.

 

ok I had machinist friend help me measure out everything and with standard bearings I was very sloppy, around 0.008 to 0.009 give or take on all 5 journals. I had a set of 0.010 undersize and would think those would make me to tight but he measured out at 0.0015 to 0.002 on all 5 using method you showed above. I used green plastigauge to confirm that I was around 0.0015 plus on all 5 journals. Question is will that be to tight of clearance for me, running flat top pistons and extreme energy comp cam, and also have you seen that big of difference in bearings before? I am still leary to bolt this together with 0.010 undersize bearings because my crank has nor been ground and measures out towards low end of specification but not enough to account for 0.010 bearings

 

if you got .010” bearings in there and the crank turns freely, which it should do with .0015” clearance according to you, your crank isn’t standard.

on the other hand, if your crank measurements are correct, no way would it have the .0015” you say it has with .010” bearings….it would be locked up

you haven’t said if the crank turns freely?

your machinist didn’t bore or hone the mains..it was a check only. unfortunately they didn’t write the specs down ,,that’s bs. if they actually went through the trouble of measuring each main bore diameter, they should have written each measurement down and given it to you. you paid $140.00 for that , but got no actual specs.

look at the backside of your old bearings and post a pic of the numbers.

 

I wonder how this turned out?

 

everything was loaded up and sent to another machine shop. They say the bearings I sent with motor don't match what boxes they came from so thinking I may have mixed up bearings or were boxed wrong.

 

well there ya go… the bearings were standard then if your crank measurements were correct..if you ended up with what you thought was .010” under with your standard crank , yet still had clearance and you could turn the crank

you always need to check the backside of the bearings for the correct numbers. that’s why I asked what was on the backside