Hello all:

I need some help with an issue that is preventing me from putting the engine back together.

I purchased a brand new OEM Crankshaft to replace the old one that was damaged in the car after having a spun bearing on Rod #4.

I also bought standard sized Clevite Bearings, but the fitment is too tight. Well under 0.021 measurement suggested by the service manual. I understand it is not worth the effort of machining a brand new Crankshaft, but I'm having a bit of a hard time understanding the recommended bearing sizes using the Service Manual chart, in order to purchase the exact bearing of each of the 9 positions.

The numbers on the crankshaft are:
0 0 0 0 0
1 0 1 1
1 1 2 5 D

The numbers on my block next the Main Bearing positions are (front to back):
2
1
2
2
2

Conrods are still within specs according to the machine shop, so I'm reusing them and the same ARP studs I got for the previous rebuild (is 45lbs of torque too much?). Got brand new ARP studs for the Mains.

Thanks in advance.

The numbers punched into the crank and block are only valid if ALL of the below are true:
- brand new crank
- brand new block (or one that with 100% certainty has never been line bored and never spun a main bearing)
- you are using OEM bearings

The procedure is simple. The factory has 5 (!) different grades (sizes very close to each other) for new base size journals. Add the numbers on the crank to the ones on the block for each journal#, and you get the OEM bearing grade needed.
See Item 17 here: http://nissan4u.com/parts/200sx/el_s13/ ... tration_1/

Aftermarket stuff does not have 5 different grades for the base sizes, only ONE. You get what you get with those. I've never used Clevites, but I've read on here they're a wee bit on the tighter side. Given that much more people are using slightly worn, used crankshafts, than OEM brand new ones (which is $$$), maybe Clevite thought it would be better if they make their bearings a bit tighter, which suit slightly worn cranks well.

You could try your luck with a set ACL's, see if they loosen up the clearance a bit, or just get OEM bearings from a dealer by grade number, with the specific grade for each of your mains.

If you're using Plastigauge to measure clearance, I'd suggest measuring everything once more just to make sure.

The numbers on the crankshaft are:
0 0 0 0 0<------- these are your main bearing numbers for the crank
1 0 1 1<----------these are the rod bearing numbers for the crank
1 1 2 5 D<----I think this is just a part number, but isn't needed regardless

Then you simply add the correlating numbers together. Soooo
0 0 0 0 0
+2 1 2 2 2
------------
2 1 2 2 2

So you need (4) #2 main bearings and (1) #1 main bearing.

Did you measure with plastigauge? If so, don't trust it. On my most recent build I went ahead and bought a digital bore gauge because I was having issues getting a motor built locally that would build an engine to the clearances I wanted and that I trusted to do it properly. After seeing the HUGE differences I was getting in measurements between plastigauge and a bore gauge and micrometer, I'll never use plastigauge again. If I had trusted the plastigauge, I probably would have spun the #1 main bearing because it was so tight, but the plastigauge said it was in spec.

Hi guys, thank you very much for your replies.

I'll have a look at this information, and hopefully place the order today.

Fortunately, I've never suffered a spun main bearing failure.

I was having issues getting a motor built locally that would build an engine to the clearances I wanted and that I trusted to do it properly

surprisingly, a very common occurence it appears

Did you measure with plastigauge? If so, don't trust it.

Now that, is something you don't hear too often. Many a motors been fine with platigage
How did the crank 'spin' in the journals ?

Tedious measuring with mic & bore gauge. Room for operator error, but a good guideline here;
http://www.bracketracer.com/engine/mains/mains.htm

i'm wondering if a bent crank would affect plastigage readings on mains
I remember reading some veteran (oz/nz)ca18 builders discussing mentioning throwing away a few cranks before finding acceptable core to machine. The numbers were quite alarming. Their drag and drift cars 'delivered', so they must knew what they were doing

To the defense of plastigauge, I was building the motor with oil clearances that are considered tight by most engine builders, even though it was just the standard oil clearances listed in the FSM.

I didn't spin a main bearing, but I'm quite confident that had I not caught it, it would have spun. I looked at my notes from this build and here are the differences in measurements I got. Every measurement is the MODE (number that appears most often) of AT LEAST 3 measurements. So, if I got the exact same number the first three times, I didn't keep taking measurements. If I got a variance in the first three measurements, I kept taking measurements until I saw a repeatable clearance. I'll be the first to admit that I didn't have experience with a bore gauge and a micrometer prior to this, so it took a while for me to get the "feel" for a correct measurement.

Rod Bearing Clearances (in mm, OEM clearances are .018-.045mm)
Plastigauge----Bore & Mic (digital, accuracy to .0005mm)
#1 .030------------.040
#2 .025------------.034
#3 .025------------.036
#4 .030------------.038

Main Bearing Clearances (in mm, OEM clearances are .021-.048mm)
Plastigauge----Bore & Mic (digital, accuracy to .0005mm)
#1 .022------------.013 (I didn't keep this bearing in here, but this was with the #1 grade bearing that the crank/block combo said it should use)
#1 .035------------.028 (This is where I ended up when I used a #0 grade bearing from the #2 spot)
#2 .025------------.028
#3 .040------------.028
#4 .045------------.028
#5 .030------------.022

I ended up going back to the #1 grade bearing and removing .005mm from the crank so that I ended up at .022mm

And as a reminder here, I didn't get any of these clearances by taking 1 measurement. They're all the MODE of multiple measurements. As you can see, the #1 main bearing, as measured with Plastigauge, shows that I'm on the tight side of the OK range, but that I'm inside it. While the bore and mic show that I'm well OUTSIDE of the OK range. .013mm is REALLY tight. There was a noticeable difference in how easy it was to turn the crank by hand when I swapped the #1 and #2 two bearings. And it wasn't like the Plastigauge consistently read tight or loose. I'll also admit that trying to keep the crank from moving at all when tightening up the rod bearings was nearly impossible. So I may have improper readings for the plastigauge on the rod bearings. But if anything, that contributes to why I'm not a fan of plastigauge. Once I got the "feel" for the bore gauge and the micrometer, I could get VERY repeatable measurements, usually +/- .001mm, which is easily inside the variance of the tools I was using.

I'll also say this. I was purposefully wanting to build the motor to what is considered "tight" by most engine builders standards. Because of this, having accurate measurements was paramount. If you're building a loose motor, and aren't trying to run near the edge of the OK range, then Plastigauge is probably fine, as it was never THAT far off.

detailed response.

when i say 'spin', i meant did you turn the crank by hand after each main cap torqued in place
With the girdle, I haven't heard of instances with the ca18 mains saddle bore out of alignment.
I'm wondering if a slightly bent crank could possibly affect a plastigage reading, while the mic and bore main clearance measure perfect (but not affected by a bent crank)
Just pondering

Yes, I spun the crank by hand after installing the bearings and how tight it felt to turn is what tipped me off that something was wrong with my plastigauge readings. That was when I went ahead and bought the Bore and Mic gauges to double check the readings and then discovered that the #1 main bearing was off.

It would be really hard to have the main caps out of alignment. They're located in the block pretty solidly.

A bent crank would affect the reading on any measurement tool if it's being used properly.