Like to hear thought on main bearing crush when its out a .0002 loose?

[NXBOY]

Would assume factory ,but eagle Hbeams always are a little tight or smaller then factory specs.

[jed]

Where I work only king bearings are bought simply because they get a good deal on them.
The rod bearings are ok but the main bearing are terrible. You can have .002 main bearing clearance
And put a set of X bearings in and check the clearance and come up with .0035 or .004.
Or u can have .0035/.0038 put in a set of .001 under and go to .0015/.002 they are cot consistent.
Check them with a ball micrometer and they are all over the place. The mains have very little eccentricity.
If I had any say and I don't I would use ACL or Clevite.
John

[NXBOY]

I got pretty lucky , they wasnt't off much on the mains torqued down and I gained oil clearance . Crank Turner was given a number that should of gave me .003 if everything was in spec and they hit it! Itwill see high RPM and nitrous some so I'd rather have it a little loose then tight on Mains, Rods where all around .0023 . Thanks for the oppinions , not Ideal I know, I'll drive it for a while to be safe first. Thanks again for the reply.

[Walter R. Malik]

You're worried about TWO - TEN THOUSANDTHS ... really ???

[NXBOY]

You're worried about TWO - TEN THOUSANDTHS ... really ???

No read the first post, was asking about what friend did I was going to run it. He been doing engines way before me and his dad's a master machinust , Really lol

[modok]

I think you missed my point but let me put it another way.
Say you are .0002 over the housing bore specification, you might suspect there is not enough crush. This is reasonable. i can think of three options.
1- you can get the housing bore in spec, and trust king bearing company
2- you could measure the crush and see if it's enough
3-you could use bearings that you know will have enough crush at that size

I don't mind which choice you take. All are correct.

[NXBOY]

Thanks sir , I do realize now that's something the bearing could be wrong with. But I do remember not much in block with the bearing ends sticking out above, thought the crush might be more in the cap now? So what's the correct way to measure crush?

[Warp Speed]

How do you measure an error of 0.0002 inch?

I know I can't.
Maybe with a high tech laser tool?

A change in temperature of a few degrees will make an error like that.
But still..........how do you measure it?

Yeah as a machinist that used to air gauge in millionths, I think its funny too. There are very few machined items that need such close tolerances.
In the Wright brothers time they couldn't even dream of .0002, and engines ran then too.
Fuel injection systems need close tolerances, hydraulic lifters need close tolerances, and that's all I can think of on an engine that needs super close tolerances. And unless you have a standard temperature controlled shop and inspection area you will not be accurately measuring anything.

We.uae air gauges also, but if you can't consistently measure .0002 of a hard surface with a quality bore gauge, you shouldn't be machining IMO. LOL
The areas in an engine that need close tolerances vary with the expected product quality.

[modok]

Usually have one side of the main cap tight together at maybe half torque, other side just snug, and use a feeler to measure the gap.

You can also compare the measured ID at partial torque, to the housing ID minus thickness, in other cases.

[NXBOY]

Usually have one side of the main cap tight together at maybe half torque, other side just snug, and use a feeler to measure the gap.

You can also compare the measured ID at partial torque, to the housing ID minus thickness, in other cases.

Thanks will do!, I did know bearing have added length for crush, but wasn't sure how much the bore dimension would effect it. It looks like not much. Good thing this is only a Hobby lol.

[blown265]

Just for clarity in this thread- are we discussing 0.002 or 0.0002 ? Ie 2 thousandths or 2 ten thousandths ?
Regards
Paul

[bigmike]

Just for clarity in this thread- are we discussing 0.002 or 0.0002 ? Ie 2 thousandths or 2 ten thousandths ?
Regards
Paul

0.0002 / 2 ten thousandths

[superpursuit]

In reality .0002" more on a 3.000" diameter main tunnel will only give you 0.0006284" less crush on the bearing. Yes, that's 6 tenths of a thou less. Good luck measuring that with a feeler gauge.

[modok]

I agree .0002 is rather trivial. But I also agree that it's either in spec or it isn't. And, it isn't.

[user-23911]

If you look up the rate of expansion with temp, you might find that measuring 3 inch diameter at 0 deg C then measuring again at 20 deg C will give a change of 0.00066 inch.Maybe a bit less depending on the material.

So that's 3 times your error over 20 deg.
Or to put it another way a change of 7 or so deg will give a similar error to what you've measured.


Is it worth worrying about?


If you like to play with fancy tools you need to play with them in a controlled environment.