I just tried to plastigauge my mains and am coming up with some confusing info. I know plastigauge isn't all that accurate but I wanted to try it to start.

I am coming up with .002 for the 3rd main (the only good one) and the rest are greater than the .003 the plastigauge will read. The last main seems fine but the other three touble me and are hardly crush the plastigauge. They are crushed but it doesn't read a 'full' .003. I have a set of mic's and have miked the crank journals (but am a total amateur) and came up with:

#1 2.4481
#2 2.4482
#3 2.448(2 or 3)
#4 2.4482
#5 2.4482

The machine shop checked and polished the crank (which I put VERY lilght scratches on miking it) and said everything was good to go.

I have snap gauges but don't have a tip for my Mic's to measure the bearing thickness...can I torque the mains (without the crank) with the bearings installed and use my snap gauges to get the ID? Since I've already crushed the bearings doing the plastigauge...

Please throw some input this way...if you know me you know this entire motor has been hell and I thought I finally had it good to go this time.

 

Yep, that's exactly what you want to do. That'll give you a 2.451-ish number if you're at .003" as your plastigauge says.

Also you can zero your mic on 2.4481 say, and then use your snap gauge, then measure the snap gauge with your mic and it'll show you your oil clearance right off (if you can zero your mic).

Either way, measure your snap gauge with your mic, that way all measurements come from the mic, rather than reading a gauge on your snap gauge (if it has one on it), which my be a bit off.

 

The snap gauges are not marked but I had planned on using the mic anyway. I guess I need to mic everything then move on from there...I see another bearing purchase in my future...


On another note...how can I torque the rod caps to measure those clearances? I do not have a rod vise...

 

just put something on either side of the rods, and clamp it in your normal vise (you have a bench vise though right?)
I just clamped it as is, left small marks on the rods though. A chunk of wood or AL on either side would have cushioned it enough to work.

 

Is it okay to crush fit the bearings, take them out, and then use them on final assembly.

 

You should be able to assemble, disassemble, and reassemble as many times as you like. They bearings shouldn't get damaged or distorted by assembling them. Once the bearings are seated into the caps and saddles, they shouldn't go anywhere.

The only potential problem in using a bore gauge to check the bearings in the saddles is the spring of the new bearing shells. Checking the bores without the shells then using a ball- or blade-tip mic to check the shell thicknesses would be best. You can also use measured bearing ***** between the mic anvils, then calculate the difference when checking shell thicknesses. That can get a little cumbersome, but not a lot worse than PlasiGage.

By your numbers, you've got right about a tenth or two under .002 oil clearance in all positions already. That's getting close. You might want to consider a bit more polish and -.001 shells on the front main bearing only, just to restore oil clearance, so long as you're sure the numbers are correct. The front main is supposed to be tighter than the rest, and it's already a little on the loose side, but within the service limits.

 

Thanks for the help. I'm going to mic the crank again then use my snap gauges to try to get 'better' measurements due to the fact I don't have a ball tip for my mics. After what I've read I don't trust plastigauge as far as I can throw it but wanted to use it anyway.
The #3 main was the only one to crush what I thought was correctly and was the first one I torqued. Most of the time the plastigauge ended up stuck on the bearing and not on the journal.

Would you recommend getting .001 undersized bearings for #1, #2, and #4 (polish needed?)? #3 seemed just fine and the rear also seemed within spec.

 

Damn these snap gauges are a PITA!!! I had to take a break from getting the ID of the journals...

After rechecking the crank journals OD I came in with 2.4479-80 for each journal but #4. That came in to 2.4481.

Both the block and crank were sitting outside all night so the measurements should be more accurate (before the crank was inside the house).

I just found that my fingernail hangs up where the two bearing halves meet when fully torqued. Not badly at all but is this a problem?

 

They may not be fully seated into the saddles/caps, but there is a seam there so there will always be some detectable step. It may all depend upon your manicure.

 

I give up...I can't get a good measurement for the ID to save my life. These snap gauges are impossible to use. As soon as I think I get a good reading it changes the next time I check it.

Any advise?

I think my snap gauges may actually retract slightly when I tighten the set screw.....this is frustrating beyond belief.

 

try what Mr. Vader already said, it's the best method.

"The only potential problem in using a bore gauge to check the bearings in the saddles is the spring of the new bearing shells. Checking the bores without the shells then using a ball- or blade-tip mic to check the shell thicknesses would be best. You can also use measured bearing ***** between the mic anvils, then calculate the difference when checking shell thicknesses. That can get a little cumbersome, but not a lot worse than PlasiGage."

there's a feel for checking the IDs and it may take you a while to figure it out. i like a bore gage for checking IDs.

 

I like that method too but I don't have a ball tip for my mic and havn't found one locally yet. Looking online now...any places anyone knows of that won't kill me on shipping?

 

I think Vader's suggesting using a bearing ball, as in a ball bearing. As long as it's spherical enough that measures consistently any which way you decide to measure it, it should be fine.

You can also get inexpensive Chinese-made bore gages on eBay for around $35 that work well.

 

I get it now. I'll try to track some ball bearings down. Still can't get a consistent measurement whatsoever.

 

No luck with consistent measurements. I'm going to give it one more shot tomorrow but if it doesn't work out would my next best option be buying some undersized bearings and installing one half with one half of a standard bearing then plastigauge again?

What bearings should I do this to, if the rest seem to be within tolerances I will only mess with the first main.