So I'm bringing my crank to get micropolished tomorrow and I would like to measure the clearance on my rod and main bearings when I get it back. I have no intention of using plastiguage but am not sure what measurements to take to get my actual clearance. I would assume just put the bearings into the rods and on the mains then torque the mains down without the crank and the rod bolts down on a bench then measure the bearing surface with a bore gauge and then measure the journal with a mic. But ive never done this before so any input would be great.

 

am i just a jackass and everyone uses plastigauge?

 

theres plastigauge or get a good gauge caliper and put your bearing inside your rod and then tq the rod down and measure the inside of the rod. then measure the journal of the crank and subtract the 2

 

is there a difference between a gauge caliper and a dial caliper? thats not a precise measure device at all. you have no accuracy to figure out the actual clearance.

 

measure the crank journals with an outside mic (micrometer)

measure the rod big end with bearings, or the main/caps with bearings using an inside mic

and the difference is ur clearance,

combustion contraption did a very nice write up on this...

hope i understood his write up correct lol

 

1) Measure your crank journal diameter with micrometer
2) With an inside micrometer measure your main/rod diameters
3) Read the bearing thickness by color thread by earl laskey and use his formula BC = IDBT – ODC – (2 x BT)
https://honda-tech.com/zerothread?id=715505
4) Figure out what clearences you want to run ie: looser/tighter and order bearings.
5) Double check clearences with plastigauge

 

thanks for the replies guys. and i already have acl bearings so the laskey thread doesnt really help me with what ive already got. but if i decide to use oem bearings that will be nice.

 

Well I believe the ACL's are equivalent to honda greens. Do you have the standards or race?

 

plastiguage is fine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mar778c &raquo;</TD></TR><TR><TD CLASS="quote">plastiguage is fine.</TD></TR></TABLE>
I dissagree. I think plastigauge has it's place for clearances on commuters (stock rebuilds) and double checking clearances after measured. Plastigauge is by no means exact and for any race motor I build I want it to be as close to exact as possible.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by racebucket_eg &raquo;</TD></TR><TR><TD CLASS="quote">
I dissagree. I think plastigauge has it's place for clearances on commuters (stock rebuilds) and double checking clearances after measured. Plastigauge is by no means exact and for any race motor I build I want it to be as close to exact as possible.</TD></TR></TABLE>

exactly

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by racebucket_eg &raquo;</TD></TR><TR><TD CLASS="quote">
I disagree. I think plastigauge has it's place for clearances on commuters (stock rebuilds) and double checking clearances after measured. Plastigauge is by no means exact and for any race motor I build I want it to be as close to exact as possible.</TD></TR></TABLE>

The OP is a amateur builder lest he would not have asked this question. That is how the question was asked and answered.

How many people, who don't do this for a living, can afford to buy the mics and calipers with .00005 accuracy? If you are building a race motor then you already know what to measure and the question of plastiguage is mute.

 

i havent put together a motor, but im in a machine shop at least 15 hours a week. machining things to within .001" myself. i have access to all the tools i could ever need and i want to get it right. ive never had to measure that type of clearance and the one thing i dont have is a bearing mic.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bluedlude &raquo;</TD></TR><TR><TD CLASS="quote">i havent put together a motor, but im in a machine shop at least 15 hours a week. machining things to within .001" myself. i have access to all the tools i could ever need and i want to get it right. ive never had to measure that type of clearance and the one thing i dont have is a bearing mic. </TD></TR></TABLE>

OP, I did not mean to say you were incapable or lacked ability. In fact, I appreciate the fact you are building your own motor and I tried to give you the advice given to me on my 1st build.

 

i ment micrometer all i could think to call it was gauge caliper cause mine has an analog gauge on it.

 

is torquing an open main cap or rod cap going to affect the diameter rather than if something is in there...?

i mean

during clearance checking should the caps be torqued to a different spec because they aren't working against anything.
or is this not going to make a big enough difference to matter...?

 

Think about that for a second. If they are working against anything then your clearances are to tight, well you have no clearance.

 

correct me if i'm wrong
but when you assemble the motor
the tabs on the bearings expand
everything comes together
certainly there are more forces involved than with nothing in there

i'm not ignoring the fact that the goal is some kind of total clearance
just seems to me that the force isn't applied the same in both circumstances.
so therefore somehow the applied torque needs to be compensated.
i'm probably nitpicking...
but then again...isn't that what really experienced engine builders do...?
not that i am one...just looking for understanding.

you measure rod bolt stretch with crank & bearings right...???
well...how about without...?

beer...?
ok

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by digitalcongo &raquo;</TD></TR><TR><TD CLASS="quote">
you measure rod bolt stretch with crank & bearings right...???
well...how about without...?

</TD></TR></TABLE>

should be the same... the bearing and the crank should not touch each other under normal operations and on a perfect world... no force should be exerted from the cap being torqued down, there should be a magical gap that is the main thing people are talking here.. clearance.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris Tune &raquo;</TD></TR><TR><TD CLASS="quote">

should be the same... the bearing and the crank should not touch each other under normal operations and on a perfect world... no force should be exerted from the cap being torqued down, there should be a magical gap that is the main thing people are talking here.. clearance. </TD></TR></TABLE>

Yup, it dosnt make any difference at all if the crank is in the mains or the rods. That is, if the bolts are torqued down the same.

 

if youre in a machine shop for that kind of duration do the right thing and take advantage of the precision instruments...

plastigage is only used to double check after all final clearances are declared i cant stop thinking about how many backyard joe bobs out there think plastigage is accurate enough to do fresh builds without knowing exactly where they stand...plasti is good for rebuilding a stock motor with bearing clearances already specified and thats it...you wouldnt bone a prostitute without a condom on right??

bust out the .0001" bore gage, the mics, and stretch gage and start measuring

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by digitalcongo &raquo;</TD></TR><TR><TD CLASS="quote">correct me if i'm wrong
but when you assemble the motor
the tabs on the bearings expand
everything comes together
certainly there are more forces involved than with nothing in there

i'm not ignoring the fact that the goal is some kind of total clearance
just seems to me that the force isn't applied the same in both circumstances.
so therefore somehow the applied torque needs to be compensated.
i'm probably nitpicking...
but then again...isn't that what really experienced engine builders do...?
not that i am one...just looking for understanding.

you measure rod bolt stretch with crank & bearings right...???
well...how about without...?

beer...?
ok
</TD></TR></TABLE>

Well when you tq the cap with bearings in you will get a certain amout of crush, which is the amount of clearance between the bearing half's when their touching at the parting line. If you build the motor correct you check the crush on the bearing to make sure its not too much. If the crush is too much the bearing's will distort and push down at 12 and 6 oclock and will most likely will end up touching the crank..
I like to use the bearing in when checking .
I mic the crank with a micrometer
I zero my dial bore gauge to the inside of the mic.
I put the bearings in the block or rods and tq them-crank, stretch-rod
i check the bearing crush in between the bearings at the parting line by cracking one of the main bolts or rod bolts free and using a feeler gauge between the half's.
I then re tq if the crush is ok .
I then use the dial bore gauge which is already 0'd out to that paticular hole with the mic, whatever the bore gauge read's into the -'s from 0 is the clearance.
Then you can use plastigauge to final check when all is done.. I also dont beleive my first measurements so i check each multiple times.
Now some people dont like to do this as they say it scratches the bearing, well since I do coatings for a living I just coat them anyway so the minor surface marks come right off durning pre treatment for the coating process.
I run my motors very loose btw.


Modified by Tbone at 2:04 PM 1/19/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tbone &raquo;</TD></TR><TR><TD CLASS="quote">

Well when you tq the cap with bearings in you will get a certain amout of crush, which is the amount of clearance between the bearing half's when their touching at the parting line. If you build the motor correct you check the crush on the bearing to make sure its not too much. If the crush is too much the bearing's will distort and push down at 12 and 6 oclock and will most likely will end up touching the crank..
I like to use the bearing in when checking .
I mic the crank with a micrometer
I zero my dial bore gauge to the inside of the mic.
I put the bearings in the block or rods and tq them-crank, stretch-rod
i check the bearing crush in between the bearings at the parting line by cracking one of the main bolts or rod bolts free and using a feeler gauge between the half's.
I then re tq if the crush is ok .
I then use the dial bore gauge which is already 0'd out to that paticular hole with the mic, whatever the bore gauge read's into the -'s from 0 is the clearance.
Then you can use plastigauge to final check when all is done.. I also dont beleive my first measurements so i check each multiple times.
Now some people dont like to do this as they say it scratches the bearing, well since I do coatings for a living I just coat them anyway so the minor surface marks come right off durning pre treatment for the coating process.
I run my motors very loose btw.


Modified by Tbone at 2:04 PM 1/19/2008</TD></TR></TABLE>

awesome tips . so let me get this straight. if im trying to check the crush on the main bearings i torque down the main with the bearing in place. pop one of the bolts free and see what it reads with a feeler gauge. how do i interpret that clearance? how does it relate to the overall bearing clearance? and this is a going to be a street motor so i can sacrifice 4hp to run a little tighter clearance . i guess that wont make things any easier but thats what id like to do. middle of the stock spec.

any thoughts on mismatching bearing colors? how do you tell which side needs which bearing? an indicator on the snout and work your way from the center journal out?

i thought i started a fishy thread but im really learning something here

what do you coat the bearings with? a dry film?

 

alright, i was thinking about the whole crush thing all night and i think i finally get it. BUT, let say you loosen up one of the rod bolts after torqing them down and there is no clearance. how do you solve that problem? machine off a tiny bit off the bearing? but then you risk too much clearance and the bearing wont clear the gap you created. or do you hone the rod end or the main to get as close to zero crush as possible .

 

I also use T-bones technique.

Mic the crank. 0 the bore gauge to the mic. Measure the main with bearings installed and torqued.

I think plastigauge is "ok" for the amateur builder. A good dial bore gauge could run you almost $1000 which is just not a realistic option for some people. A cheap set of mics and a cheap dial bore gauge can be no more accurate then plastigauge.


Modified by kpowerdhatch at 9:04 AM 1/20/2008


Modified by kpowerdhatch at 9:10 AM 1/20/2008