ive been doing some research on bearing crush as the car i recently bought at up some bearings in under 3000 miles. the bearings themselves show signs of trash (not clean), timing belt too tight, and other things i cant associate with wrong bearing clearances although i would like to.

I talked to a buddy of mine who mentioned bearing crush and that sparked a light bulb in my head. started doing some research and found this article which mentions measuring the bearing height in relation to the housing.
http://www.precisionenginetech.com/t...g-tech-part-1/

so basically.....bolts overtorqued? under torqued? improperly sized?

now obviously a bearing that makes a perfect circle in the housing is the best and allows for the most optimal crush, as well as the best heat transfer capabilities but what would be the best way to measure this?

I am making a thread about this as it appears this topic is not discussed often and possibly a topic, a very important one, that is left out in the process of building a motor and maybe some people just figure that it'll be ok.

if pictures are needed to spark this discussion, i can add them.

 

so is this one of those unspoken tech theories of honda-tech that engine builders dont want to talk about or what?

scared?

 

i didnt read the the link, but when i build an engine for a customer (or for anybody for the matter) i mic everything. i bolt the mains or bedplate on and mic the bearing holes, bolt the rods together and measure those holes, mic the main and rod journals and mic the bearing thikcness and then do the math to get ur oil clearances. if it isnt where it needs to be then u can change bearings or u may need some machine work done to the crank to get the clearances where u need them to be.


mike

 

do you measure the bearings in more than one place? how about the bearing housing?

im honestly really surprised that i couldnt find a tool to measure bearing height.....

 

So basically you put the rods/rod caps on with the rod bearings together and measure the clearance after you plastiguage the rods on the crank with the bearings?

 

I get what you are looking for Blake, When I built my H23, I took parts from 2 healthy engines, so I just plasti-gauged, and got what I was looking for. Since I busted a piston within 2500 miles, all the bearings are still in close to perfect shape.

Would it help you out if I micd the bearings at a few spots, and maybe gave some measurements of the rods, crank etc, and maybe plastigauged as it sits, before I send it all of to the machine shop again?

 

No im saying to mic the bearings in a few places, measure the housing bore in the same places, then measure the housing bore with the bearings in place and see if the correlation fits. No platigauge involve. Way too inaccurate for this procedure.


As I said, plastigauge is too inaccruate and too easy to get a false reading. What im after is a way to measure bearing crush with standard engine building tooling.and not some expensive equipment

 

post some pictures up of your current bearings. You will be able to tell by the wear pattern if there insufficient crush. Also you need to make sure the cap surfaces are totally spotless as anything on them will effect crush.

Btw, i don't think there is a tool by i'm in for the info.

 

I refuse to use plasi gage. U measure the bearings 90 degrees from the split (or the top and bottom centers). And yes put ur rods and pistons together and tq them to spec before micing them and also measure them to and bottom center.


Mike

 

whats wrong with plastigauge ? its great for double or tripple checking clearances ?? even Honda recommend the stuff.

 

The only way I know of to measure bearing crush is to torque both bolts of the journal/rod to spec with the bearing in place, then loosen one bolt fully. The bearing crush should push up the cap on that side and reveal the overall clearance.

I tried this before on oem rods with arp bolts with mixed results. I think the overtight fit of the bolts scued the readings.

 

I've never had an accurate reading any time I've tried using it. That's when I went and bought the mics. I tried once to install all the bearings in the holes and mic the inside but that just left marks in the bearings and the readings I got compared to the crank journals was not accurate. But when doing what I initially wrote above ive never had any problems with. And when final assembly comes the crank turns as it should.


Mike

 

Blake, bearing crush is just one of the many things engine builders hardly ever speak of, especially on forums like this. not that its any kind of secret, its just over most peoples heads. and when you try to tell someone a bearing isnt actually round they would rather disagree w/ you than learn why.


just as much over their heads as using a fish scale to set ring tension...

 

Most on here do not even know why you should hone the rods and block after installing higher strength studs/bolts. Now you want to bring in bearing crush (easy to measure) and the eccentricity of the bearing shell,( not as easy) you will screw up alot of theorys. On a used bearing, approx. 1/8 of each shell, at the parting line, should show no wear. that means the clearance was correct. Oh, Mains and rods go a little oval under heat and high stress (RPM's) which is the reason for the eccentricity in the shell.

 

Since you brought that up, people can read about it here: http://blog.raceology.com/2005/05/oil-ring-tension.html

 

seems to me to be something incredibly important to pay attention to.

how would this work for measuring crush:

measure the ID of the bearings, unloaded, at the parting line then make the same measurement, twice...180* apart, of the bearing with it loaded in the housing and the cap/main torqued down. would this not atleast give you some measurement of how the bearing is forming to the journal?

you already know the bearing thickness (even better if measured in a few places) and the measurements of the housing. if the loaded bearing measurements dont correlate to the housing measurements then you know something is off.

 

is this simply the thrust that is created from combustion reshaping the hot bearing?

 

thats an awesome article, thanks!

 

crush is set from the bearing mfr, if you look at ACL's specs they give an acceptable range for the size of the rod/main bore.

if the bore is too big then you will see marring on the back side of the bearing where it has moved around in the rod/block. I'm not too sure how to tell if the bore is too small other than the edges of the bearings pushing in off the side of the bore when you torque the caps down.

the rod/main bores should be perfectly round before the bearing goes in, once its in it wont be perfectly round anymore. Like someone said before, the rod and block will distort under high load/rpm so it doesnt really matter anyway.

 

yes its important since it holds the bearing in the journal and keeps it from spinning. but i wouldnt get to involved overthinking it...

you can measure but its not gonna form round to the journal

 

So that you do not overthink this. If after you have "scotch brited" the back side of the bearing shell ( what? why?) and installed it in the rod half or Main half the ends are even or below the rod cap or main cap/block, stop, you have NO crush. If they are above measure it with your depth mic. and figure out the "crush".

 

All right. That's it. I've had enough. Where do I find the books that talk about all this stuff? Which ones should I be reading? I wanna do my next build the right way.

 

The Clevite catalog. There is a section that explains more about bearings than you would probably ever need to know.

 

Actually, the eccentricity of the bearing is already designed into it to promote the hydrodynamic wedge that keeps the bearings and journal from rubbing. Sure, there is some distortion under dynamic conditions, but I don't think that's what we're talking about here.