PyroProblem

A few questions about honing rods...
I'm a little tight on my rod bearing clearances and would like to know if this an option. I only need another .0007 or so to get me right at .0018.

About how much can a rods big end be honed to get a little more clearance?

How far can you go before you have to worry about losing bearing crush and increasing the chances of spinning a bearing?

Thanks in advance!

birdd

Sorry I didn't get to answer in the other thread. With honing it out so little I wouldn't worry about it too much, just check the make sure the big end is still concentric after the hone.

PyroProblem

No worries man. I figured since it was a different topic, it deserved its own thread.

So having the rods honed definitely can get me the extra .0007" I need, without any negative effects, correct?

At what point does "crush" become compromised?
Thanks for the response!

TomCat39

I think the better option is to micro polish the journals over honing the rod bores.

Then you aren't messing with your crush and you get the added clearance. A typical micro polish I've seen takes about .0005" of material. I'm sure they can keep polishing a bit more and get you that .0007" you need.

That seems like the better option to me.

PyroProblem

Well I already installed the crank and have the oil pump and rear cover on and it's a brand new crank so I hate to have to remove it and have it reworked again.
I also read that some people believe micropolishing the journals doesn't take off an exact amount on all sides of the journal so you may end up with an ever so slightly out of round journal.
I have a ball anvil micrometer on the way so I can check some to see what these calico coated bearings measure.
Might order up a set of HX bearings that are supposed to give another .001" , measure them, and have them coated if needed..

PyroProblem

I'm gonna call some machine shops Monday and see what they think. Thanks for the input guys. I'll report back and share their advice as well. If the crank has to come back out, so be it. It'll come back out..

KevinEF7

Is this on all 4 rod bearings or do you have one offsized rod?

I personally would buy thinner bearings before having the rod honed or crank micropolished when it doesnt need it

PyroProblem

All 4. There brand new Eagle rods and acl/calico coated bearings. Crank is new as well. All the rod journals measured perfectly @ 1.7708 ish. All the rod big ends were measured without the bearings. They also were pretty much perfectly round with no more that .0002" out of round, which could partially be blamed on human error.

I just installed a rod bearing and measured again. Still coming up with .0011 clearance. Just need a little bit more...I don't really wanna mess with the crank either...

blackeg

I have used the hx's a few times and found them to ne somewhere between oem pinks and reds. if the regular acls are based off green then the .0003 or so difference x2 should theoretically net u something like ..0006. it may be worth trying

1HGEJ2

iTrader: (1)

i would never hone a rod 4 better oil clearence

PyroProblem

Thanks Blackeg, I might end up having to go this route.
I should know something by next weekend after I talk to my machine shop and when my ball anvil micrometer arrives.

PyroProblem

I thought this was a generally accepted procedure in the machining world. As long as it's not too much to affect bearing crush. I'm pretty sure it's a part of re-sizing rods isn't it?

That's my main concern about honing the rods is HOW MUCH the bearing crush will be affected.
Only looking for another .0008 additional bearing clearance so only .0004 of "lost crush" to each bearing.

I'm gonna send Eagle and ACL an email later tonight.

PyroProblem

It's kinda funny that calico states their bearing coatings are .0002-.0004 inches thick and do not generally affect clearances.
Well, .0004" additional thickness to each bearing half is .0008 which is pretty substantial if you ask me. That's almost an entire lost thousandth of an inch of rod bearing clearance...yikes!

Pro-SeriesFab

That is pretty silly of them to play off .0004" on a bearing isn't a whole lot . . .

If you are trying to do the least work possible, I'd send the bearings back to whoever you got them from and order +.001 clearance ones.

PyroProblem

I think that's what im gonna end up doing. Bearings are cheap enough. Hopefully I can use these bearings down the road on a future build.

Pro-SeriesFab, do you have any thoughts on how much honing out the rod big end affects bearing crush? I'm sure there has to be a standard rule of thumb or something, right?

PyroProblem

Geometrical parameters of engine bearings [SubsTech]

This link states that bearing crush is measured in a jig and should be .002-.004 for performance engines...So according to that, anything less that .002 is assumed to compromise bearing crush...

Pro-SeriesFab

I like the article you posted although I don't do much engine machining, or at least enough to know what range you want for bearing crush.

The only personal experience I have with an extraneous amount of bearing crush was with a set of King bearings in a SBC. Thrust bearing visually sat a little too high in the journal when I placed it in the block and sure enough when I torqued it down and checked with my inside micrometers I had .0012" more clearance than the others. Luckily SBCs are a dime a dozen and the machine shop had an extra thrust bearing pair but it goes to show how important checking everything is.

efHondefender

When rods are resized, the caps are cut to make the hole smaller, then they hone back out to the spec dimension. This causes the hole centerline to move up a few thous. No big deal. Don't hone bigger for clearance. Not only will you lose crush, you will also lose a little of the radius that the bearing back is designed for. This is why companies like ERL use a custom main bearing with a thicker shell to compensate when they line hone mains without cutting the caps. They do this to keep from moving the crank centerline up. They have to use a bearing with more back to compensate. This is basically what you would be trying to do with your rods. Just get different bearings. Micropolishing the crank will not give you a dimensionally perfect surface when trying to remove that much material. I think the calico coatings need to be taken into consideration when clearancing stuff pre coating. Like you would size everything before hand with the thickness of the coating in mind, but that's only if the coating is considered a permanent coating. Teflon like coatings like you see on most aftermarket piston skirts are basically just a break in coating that mostly wears away. I would hate for you to clearance your bearings at 0.0017" and then have 0.0008" quickly wear away. Although, that would still probably work, but you get my point. I'm personally not a big fan of bearing coatings. The bearing should never touch the crank in the first place. If friction between the 2 is a problem, you have larger problems. LOL. The babbit is there for debris embedability. It's better to have dirt wear into the bearing than have it get smashed inbetween 2 hard surfaces, causing damage to the expensive one.

PyroProblem

Thanks for everyones input. I spoke to two local machine shops, one that specializes in race oriented engines, and the other a regular automotive machine shop who has always done good work in the past.
According to one, polishing the journals to get another thousandth of Clearence is not recommended due to the belt not contacting the journal evenly. He said a stone is a different story but the abrasive belts for micro polishing would leave a slight concave shape in between the radiuses when taking that much off.

Neither Shop recommended honing the big ends of the rods that much either, but the race machine shop did say you can hone it out, but honing out a whole thousandth would compromise crush. Both shops also suggested I seek out the correct sized bearings instead of looking for clearance through honing or machining. So it looks like HX bearings will be the way to go.
I also spoke with a rep from calico. He couldn't really answer my question for sure.

PyroProblem

Efhondefender, I know your right about the bearing not supposed to be making contact with the journal and I never used coated bearings before either. But there are some pretty good arguments as to why they are beneficial and how they could be helpful in reducing wear (startup for example). I've read both good and bad about coatings, that was another reason I was curious to try them out. And or 26bucks for calico to coat some rod bearings, I figured why not.
Maybe I'll get to use them on a future build..

Mach1n1st

Call me on Monday and I can get you all straightened out. 5403135150.

PyroProblem

Will do sir!
Thanks!

saefifty

Do not increase the big end measurement to alter bearing clearance..

flesh199

thx for all of these info guys