I'm finding a huge difference in main bearing oil clearances b/w the different ways of measuring.

For example:
1.) Plastigaging with brown bearings shows: .0014"

2.) Mic'ing the crank @ 2.1646", zero'ing the mic and measuring with brown bearings: .0007" to .0009"

3.) Mic'ing everything separately and doing the math: .0006"
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The discrepancy b/w the two different ways of mic'ing (#2 and #3) isn't much so I'm not at all concerned.

It's the difference b/w the plastigage and mic'ing the clearances that bothers me. A relative difference of 100% really bothers me.

I'm wondering if anybody else has checked it both ways and come up with similar results.

Also, is .0035" to .0045" [CORRECTION: I forgot to subtract the readings...it should be .0026" to .0038"] of bearing eccentricity ok? I've never checked before and I was just curious what kind of eccentricity people were running.

 

Quick Question, what was the temperature in the room?

 

Room temp. Probably right around high 60's to low 70's.

I went and rechecked with a thermometer. It's 68.5 deg F.

 

To get accurate readings of rod bearing bore you need to measure it w/the bearings in the rod torqued up.The bearing is a press fit in the rod bore.This is also the only accurate way to measure the eccentricity.Oem and oem replacement bearings will generally have more eccentricity to help compensate for the rod bore elongating.Race spec bearings have less because they assume the rod is stronger and will elongate less.I believe my measured clearances over plastigage.
Glenn

 

I'm definitely more inclined to trust my mic and bore gauge over the plastigage as well. It just means that I need to be on the exact opposite side of the bearing color chart. It'll be YLW's and PNK's for me.

BTW, I haven't gotten to the rods yet. I'm still diddling with this mess on the mains.

 

Mains still need to be measured with the bearings in the bore and torqued.Not as much eccentricity in the mains as the rods.After many years I still don't see how the aluminum block works with cast iron caps.There is no way that bore is anywhere near round at running temp but it works.Still makes me scratch my head.
Glenn

 

That's exactly how I got the .0007" to .0009" measurement. That was with the bearings in and the caps/girdle torqued to spec.

Without the bearings, my main bores weren't very concentric. The out-of-roundness was:

(1) .0009" [all were wider on the horizontal]
(2) .0014"
(3) .0006"
(4) .0010"
(5) .0011"

I expected them to be within .0005", but I guess not. I'm not sure what to make of it. I've never measured a freshly torn down OEM motor before, so I don't know where my motor stands.

Oh well, as long as it runs well enough. I've pretty much had it with building motors. Girls are much prettier than a 50lb chunk of aluminum.

 

The bores should be round within .0002"-.0003".This may be your discrepancy in your measure/plastigage results.I've measured lots of original bores and I've never seen anywhere close to .001" out of round.Are you sure those are the original caps for that block.
Glenn

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IN VTEC &raquo;</TD></TR><TR><TD CLASS="quote">Girls are much prettier than a 50lb chunk of aluminum.</TD></TR></TABLE>

The amount of *** yu get goes up exponentially with every dollar yu don't spend on cars.

 

yeah cause you're buying em purses and shoes and crap

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">Are you sure those are the original caps for that block</TD></TR></TABLE>
Yeah. I've never had a reason to change main caps.

I went back down and re-plastigaged them again and this time they came back just under .001".

I'm not 100% sure how they got to be so off, but I think it's b/c of the plastigage. The first strip of plastigage I used liked to come off in chunks when I removed the caps, but it was always consistent when I measured it two or three times with that first strip. That was about a week ago.

I used a different package of plastigage this time and the consistency across the journal is much much better.

I don't know. I really don't.

 

anychange that the rod or crank moved while you were measuring with the plastiguage. even a slight movement would mess the measurement.

 

There is only one way for correctly measuring these clearances with plastigage.
The secret lies in the disassembly of the con-rod caps. Otherwise the reading will always be inaccurate.

After plastigaging try this.

Step 1: Loosen the rod-bolts or nuts almost all the way.

Step 2: Disassemble the ratchet from the socket.

Step 3: Place the socket on the rod-bolt or nut.

Step 4: Softly hammer the socket only.

This will seperate the two-halves without making any inconsistent impression on the plasti-gage. This is due to the rod be hit away from the crank.

I posted this because alot of people wiggle the rod bearing cap or hit it apart resulting in really inconsistent reading.

I have mic'd this against my plastigage methods and returned strikingly similar clearances.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by neogenesis2004 &raquo;</TD></TR><TR><TD CLASS="quote">anychange that the rod or crank moved while you were measuring with the plastiguage. even a slight movement would mess the measurement.</TD></TR></TABLE>
I'm fully aware of that precaution.

 

I mic'd another block. It's a '95 JDM GS-R block that was stripped down when we first got it last summer and was never finished and ran. So I tore it back down and remeasured a bunch of parameters.

Main bore out-of-roundness:
(1) .0005"
(2) .0007"
(3) .0004"
(4) .0004"
(5) .0009"

The piston-to-cylinder wall clearances were also tighter and less egg-shaped. The .010" overbore and honing were done by Schmidt in Indy.