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Is .002" rod bearing clearance to tight ?

Posted By: rlm2268

Is .002" rod bearing clearance to tight ? - 04/26/12 06:32 AM

Do You think .002" rod bearing clearance is to tight for a street strip type 500" motor turning 6500-6800 rpm. Or should I try and get another bearing set in .001 looser and use half the set or the whole set to try to get it .0025"-.003" p.s my bearings are clevite CB-527 HD .
Posted By: cudabin

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 06:40 AM

I would shoot for .0025" to .003",

3/4 groove King Alelecular bearings are great!

Cheers,

Arnie
Posted By: Twin Turbo Mower

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 08:24 AM

Quote:

Do You think .002" rod bearing clearance is to tight for a street strip type 500" motor turning 6500-6800 rpm. Or should I try and get another bearing set in .001 looser and use half the set or the whole set to try to get it .0025"-.003" p.s my bearings are clevite CB-527 HD .



Yes too tight buy the .001 loser and you will be fine. My friend did the same thing been running his 511 for 3 years now.
Posted By: MR_P_BODY

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 01:44 PM

How did you read the clearance... mics or plastigauge
Posted By: Moparnut426

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 01:49 PM

I agree what did ya use plasti guage or did ya use a micrometer?

and Honestly depending on how much ya pound on it, 2 would be fine as long as ya know to use correct oil with that clearance. My first 360 was 2 mains and 1.5 rods, and its still fine. Im not nice to that engine at all, and its living fine.

Kasey
Posted By: rlm2268

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 01:54 PM

Hi, I used a mic. on the crank and used a snap type guage on the rods and measured it with the mic. My full groove mains came out between .0025-003
Posted By: MR_P_BODY

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 02:00 PM

There is a rule of thumb for clearance... its something
like .001 per every inch of diameter (dont quote
me on that number... I forget what it is)
Posted By: rickseeman

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 02:09 PM

The book says 2 to 3 so you are in spec....you are just tight.
Posted By: DJVCuda

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 02:23 PM

Quote:

Hi, I used a mic. on the crank and used a snap type guage on the rods and measured it with the mic. My full groove mains came out between .0025-003



better to be a little loose then a little tight.

were you able to repeat the results with the snap gauge? I find it difficult to get that precise with them and prefer to use an inside mic to be exact.
Posted By: maximum entropy

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 04:04 PM

Quote:

There is a rule of thumb for clearance... its something
like .001 per every inch of diameter (dont quote
me on that number... I forget what it is)



what's your rod journal diameter?
Posted By: BradH

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 04:54 PM

If you go for the 'X' bearings w/ the additional .001" clearance, be prepared to spend about twice what the standard size bearings cost.
Posted By: 66er

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 05:05 PM

.002 will be fine. That what my engine is set up with and it has 500+ passes on it shifting at 6800 RPMs. I just rolled new bearing in it this winter, but I think that I could have just kept running the old ones. I like them to have .003 on the main and .002 on the rod to keep the oil pressure up at the rods. do you have Mopar or Chevy size?
Posted By: Cab_Burge

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 05:17 PM

Quote:

do you have Mopar or Chevy size?

The CB527 sereis bearings are for the standard BB Mopar rod journals, 2.375 diameter. The HD are narrower, and have a chamfer on the crank side ,than the standard rod bearings are OP, your crank rod journals must be ground on the large size of the specs, usually when I used the HD bearings I ended up with .003 to .0038 clearances thats using a inside mike to get the diameter and then using the outside mike to see what size it was on the inside of the bearing. I now have several dial bore gauges and they are easier to see the clearances once you get them set up, modern technology OP ,a lot looser (.0005) is better than a tiny bit to tight(.0001)
Posted By: 66er

Re: Is .002" rod bearing clearance to tight ? - 04/26/12 05:25 PM

Quote:

Quote:

do you have Mopar or Chevy size?

The CB527 sereis bearings are for the standard BB Mopar rod journals, 2.375 diameter. The HD are narrower, and have a chamfer on the crank side ,than the standard rod bearings are OP, your crank rod journals must be ground on the large size of the specs, usually when I used the HD bearings I ended up with .003 to .0038 clearances thats using a inside mike to get the diameter and then using the outside mike to see what size it was on the inside of the bearing. I now have several dial bore gauges and they are easier to see the clearances once you get them set up, modern technology



Yep, I see that now. I missed the number when I read the post
Posted By: rlm2268

Re: Is .002" rod bearing clearance to tight ? - 04/27/12 02:52 AM

Hi, thank's for the imput, with the mic. on the crank journals I come up with 2.3745 and using a snap guage on the inside of the rod I come up with 2.3765 with the clevite 527 hd bearings I see you weren't kidding on the cost of the X .001 bearings, like around $200.00 for rod bearings now what to do?
Posted By: Cab_Burge

Re: Is .002" rod bearing clearance to tight ? - 04/27/12 03:57 AM

You do have the rods torque down to the specs your going to use in the motor, hopefully If not do that now
Posted By: rlm2268

Re: Is .002" rod bearing clearance to tight ? - 04/27/12 04:13 AM

Yes rods were torqued when measured, short block is acually assembled and ran into a side clearance issue on 7 and 8 rod, figured that out the bearing must have been slightly touching the crank fillet, scraped the bearing a little on the chamfer side and now the side clearance is the same as the rest but now having second thoughts about the bearing clearance.
Posted By: BradH

Re: Is .002" rod bearing clearance to tight ? - 04/27/12 03:26 PM

Quote:

... I see you weren't kidding on the cost of the X .001 bearings, like around $200.00 for rod bearings now what to do?


Unfortunately, nobody ever said this hobby was cheap... or that all the "right" parts will always bolt together w/o any unforseen hassles. I do feel your pain...
Posted By: 66er

Re: Is .002" rod bearing clearance to tight ? - 04/27/12 03:48 PM

Check it with plastigauge. If it still measures at .002 then run it. In the Mopar Performance manual, it list the connecting rod clearance .001-.003 I would never set a engine up with .001 clearance, but it has been done and the engines survived. I would not sweat it, .002 is fine, you are rite in the middle of the spec. Plastigauge is not the most high tech method , but it can confirm your snap gauge reading.
Posted By: rlm2268

Re: Is .002" rod bearing clearance to tight ? - 04/27/12 05:02 PM

Thank's again for everyones imput FYI i did some seaching while I was deciding what to do and wanted to pass along to you guys needing the cb527HXND .001 X bearings, summit wants like $200.00 for a set and jegs is a little more But Competition Products in Oshkosh Wis. has them for $82.99 on there website
Posted By: 8urvette

Re: Is .002" rod bearing clearance to tight ? - 04/27/12 05:17 PM

i am rebuilding a motor too, and thanks to your post i rechecked my side clearances on my 3/4 rods cuz they were a little tight, and will be fixing that.
I used plastigage on all my bearings and every one came up tight. like one and half thous. i took the crank and the torqued rods with bearings in them to a machine shop and they verified i actually have 26thous. perfect! they also told me my crank had been turned to the low limit, which i was told, but they did verify it.
Posted By: gregsdart

Re: Is .002" rod bearing clearance to tight ? - 02/21/19 07:21 PM

I don't like plastigauge or snap gauges, taking the parts to a machine shop was the right move.
On clearances
: if the clearances are a little loose, only you will know. If they are too tight, everybody will know!
Posted By: CMcAllister

Re: Is .002" rod bearing clearance to tight ? - 02/21/19 07:33 PM

You can buy your own stuff and measure it yourself instead of paying somebody. Good, used measuring tools are all over ebay. If that type of precision is beyond you, maybe you should just let someone screw it together. Not bashing, just being practical. Blowing stuff up is expensive.
Posted By: lewtot184

Re: Is .002" rod bearing clearance to tight ? - 02/21/19 07:46 PM

see if you can get a dial bore gauge to check the i.d of the rod bearing. I've never had a warm fuzzy feeling using snap gauges for precision measuring and usually just throw plasti-gauge away.
Posted By: dvw

Re: Is .002" rod bearing clearance to tight ? - 02/21/19 09:19 PM

I find plasigauge is good to measure taper but tends to measure a touch tight. Maybe because the other side of the journal isn't pulled tight to the crank? I think you'll be fine.
Doug
Posted By: dthemi

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 01:52 AM

No kidding, I'd rather have 6 than 2. .0035 is my norm until it's going over 2,000, then .004 or more.

I've never once seen wide hurt anything, ever. I've seen tight destroy everything.

Even saw a motor that was raced all season on spray with a .010 under crank and standard bearings (.013 clearance) never missed a lick. Made about 1500hp on spray. Idle oil pressure was about 20 cold, and 5 hot. Would climb to about 50 psi on a 7500rpm run. No damage to anything.
Posted By: Cab_Burge

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 02:35 AM

Originally Posted By lewtot184
see if you can get a dial bore gauge to check the i.d of the rod bearing. I've never had a warm fuzzy feeling using snap gauges for precision measuring and usually just throw plasti-gauge away.
iagree on both subjects up
I've used gauges and plastiguage, once only on the plastigauge down
On using a inside mike compared to a snap gauge the individuals feel can be the difference between .0020 and .0023 shruggy
I've bought three different dial bore gauges( .0010, .00050 and one .00010 accuracy) and finally realized that setting them up is the key to a decent, accurate reading shruggy
If the gauge is marking a line in the bearing is it removing material or not work Does that mark really matter work grin
As far as this old post goes, it would be interesting to hear how much clearances the OP ended up with and how those clearance have worked work
I'm like a lot of the other posters on this subject, a lot looser( 0.0010) is way better than a tiny bit (.00010) to tight up twocents
Posted By: merpar

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 02:56 AM

I'm a retired tool-maker, any measuring too you use is only as good as the user. snap gauges (telescope gauge) is as accurate as an inside mike. Its just how you use them. Once you pull it through, don't do it again. Measure it and you're done. On any inside measureing tool its a good idea to put some light oil on the contact ends. Dial bores will always leave lines on bearings. A little oil will help a lot. The set up on dial bore gauges is very critical . If you don't have a ring gauge you can put your mike lightly in a vise lock the barrel on your mike to the size you want have the mike in vertical position. With the solid end of your dial gauge down on the center of the mike anvil. lightly swivel the plunger around on the top anvil and set it at your smallest reading. If you have Jo blocks its much easier and most accurate. Hope this is of some help. Good luck
Posted By: 451Mopar

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 06:53 AM

You could have the crank polished down a bit, but 0.002" should be fine.
Posted By: fastmark

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 03:11 PM

Originally Posted By 451Mopar
You could have the crank polished down a bit, but 0.002" should be fine.


I would not do this. Sorry to disagree but polishing it does not guarantee it will still be round when the guy is finished. As a matter of fact, I can almost guarantee it won’t be round. Several years ago, my machine shop sold out to a new guy and he had never run a crank grinder at this shop. He could do everything else very well. So I had to go elsewhere for one crank. That guy made so many mistakes on that crank he ruin it. Over polishing was one of them. It was .0005 out of round plus it had a taper on the end of each journal. Terrible job, it was. I caught it with plastiguage. I hardly ever use it. I found different brands of snap gauges will measure differently. I use Starrets before I got my dial bore guage. The snap gauges measure slightly bigger than a dial bore guage IMO. Maybe .0002. But as said before, it’s mostly in how you mic or feel the mic. After saying that, I think you’ll be fine with that. Now you could do what I do. I have the cranked turned FIRST. Then if I need some more clearance, I size the rods to the correct clearance. This works best for my shop.
Posted By: polyspheric

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 04:01 PM

There is a rule of thumb for clearance... its something
like .001 per every inch of diameter
Industry standard for 100 years.
If you decide to run .002", use a light value for the oil grade first number: 5W, not 20W.
Posted By: moparx

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 06:19 PM

Originally Posted By merpar
I'm a retired tool-maker, any measuring too you use is only as good as the user. snap gauges (telescope gauge) is as accurate as an inside mike. Its just how you use them. Once you pull it through, don't do it again. Measure it and you're done. On any inside measureing tool its a good idea to put some light oil on the contact ends. Dial bores will always leave lines on bearings. A little oil will help a lot. The set up on dial bore gauges is very critical . If you don't have a ring gauge you can put your mike lightly in a vise lock the barrel on your mike to the size you want have the mike in vertical position. With the solid end of your dial gauge down on the center of the mike anvil. lightly swivel the plunger around on the top anvil and set it at your smallest reading. If you have Jo blocks its much easier and most accurate. Hope this is of some help. Good luck


as a retired machinist, the above is spot on. up
beer
Posted By: cudatom

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 06:25 PM

Originally Posted By rlm2268
Thank's again for everyones imput <img src="/ubbthreads/images/graemlins/thumbs.gif" alt="" /> FYI i did some seaching while I was deciding what to do and wanted to pass along to you guys needing the cb527HXND .001 X bearings, summit wants like $200.00 for a set and jegs is a little more <img src="/ubbthreads/images/graemlins/eeek.gif" alt="" /> But Competition Products in Oshkosh Wis. has them for $82.99 on there website <img src="/ubbthreads/images/graemlins/thumbs.gif" alt="" />

I buy a lot from them, saved almost $400 on my rods vs what Summit and Jegs listed. They also ship fast.
Posted By: CMcAllister

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 07:45 PM

Big clearances with light oil. You can't be squeamish about oil pressure if you go down that path. Especially at hot idle. You may as well take that 30# transducer for the light and throw it in the trash. Put a 15# in it and put up with the light flickering at you coming back the return road.
Posted By: Cab_Burge

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 10:09 PM

Originally Posted By CMcAllister
Big clearances with light oil. You can't be squeamish about oil pressure if you go down that path. Especially at hot idle. You may as well take that 30# transducer for the light and throw it in the trash. Put a 15# in it and put up with the light flickering at you coming back the return road.

I use the old ten lbs. per thousand RPM rule with hot oil, 10 lbs. at 1000 RPM, 65 lbs. at 6500 RPM with 5W20 weight oil up
Posted By: BobR

Re: Is .002" rod bearing clearance to tight ? - 02/22/19 10:14 PM

Originally Posted By dthemi
No kidding, I'd rather have 6 than 2. .0035 is my norm until it's going over 2,000, then .004 or more.

I've never once seen wide hurt anything, ever. I've seen tight destroy everything.

Even saw a motor that was raced all season on spray with a .010 under crank and standard bearings (.013 clearance) never missed a lick. Made about 1500hp on spray. Idle oil pressure was about 20 cold, and 5 hot. Would climb to about 50 psi on a 7500rpm run. No damage to anything.

I agree. Use a good oil pump and run a lot of clearance.
Posted By: mopar dave

Re: Is .002" rod bearing clearance to tight ? - 02/23/19 05:03 AM

I built 2 408 with .002" rod and crank oil clearance and never had a failure with that at 7000rpm. Bearings had odd markings but never burned to copper on rebuilds. Street/strip deal. Local circle track engine builder builds all his sb chevys that way. I would never do that again thou. Always better to have .0025-.003" on rod and .003+ on mains. I have my 511 at .003 on rods and mains. I sleep better with it that way.
Posted By: polyspheric

Re: Is .002" rod bearing clearance to tight ? - 02/23/19 05:11 AM

W/r/t using sequential sizes, such as one +.001" and the other +.002" to get the intermediate +.0015" total where desired (Ford factory manuals for the “Indy” 255, “Le Mans” 427, and “Trans Am” Boss 302 recommend this): the larger oversize (looser clearance) is generally the upper rod bearing half, and the lower main bearing half.
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