Looking for advice on short block assembly

[Richard 302]

I'm stumped.  In an effort to explain my problem, this will be a long winded post. The machinist I have used for years and several engines has always been spot on.  In fact, I don't even purchase bearings anymore, he has the correct bearings packed when I pick up the parts. I always check bearing clearance, early on, just with plastigage, but years ago I purchased a set of micrometers and a dial bore gauge, learned how to use them, and now rely on those measurements.

So now I'm measuring the main journals.  I take 8 readings on each crankshaft main journal at different points, average the results for each journal, and zero the bore gauge to that value for each journal.  One journal at a time, I clean everything, install the provided standard bearings and torque the caps to 70 lb-ft.  On journals 1 - 4 I get readings right at .003. Main 5 comes in around .0035 with the oil pump torqued to 50 lb-ft.

So now I'm thinking if I put a set of .001 unders in the caps, I should be right where I want to be at .0025 on mains 1 -4 and at .003 on main 5.  So I do that.  Recheck everything and according to the bore gauge I'm right where I want to be.  As one last cross check, I decide to plastigage each journal also.  I install the crank dry, torque each cap 25 -50- 70, add the oil pump at 50.  When I remove the caps the plastigage is really wide on each journal. Easily showing less than .002 clearance on each journal 1 -4 and right at .002 on number 5.  I repeat the process.  Same result.

I've never had this happen before and I don't understand why the readings are so different. The one thing I wonder about is how I install the caps. As it should be, the caps are an interference fit in the register. Right or wrong, I've always used a rubber mallet to seat the caps in the register.  Could that hit on one side of the cap be smashing the plastigage?

[Kaanderson]

I would guess the .oo1 oversize bearing was made a little fat. I would and always pull the cap down with the bolts evenly, but hitting with the mallet to seat the cap is not going to get the bearing crush on it. I wouldn't think twice about running .0035 on the wide rear main bearing. Go with what the plastigauge says it won't lie to you.
Good luck

[Richard 302]

Alright.  Thanks for the response.  I've assembled other engines just using plastigage and they're still running.  What - me worry? said Alfred E. Neuman.

[adjudimo]

Alright.  Thanks for the response.  I've assembled other engines just using plastigage and they're still running.  What - me worry? said Alfred E. Neuman.

Now, That's just MAD :-)

[ko-lek-tor]

Are you using .001 shim stock? If that would have brought you in spec, I still wouldn't use anything under a bearing. That creates a heat barrier, I would think?