rod bearing clearance

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rod bearing clearance

Post  10SHOTS on September 12th 2012, 2:33 pm

is .0023 just to tight for a 2.200 rod journal? or will it work
14.1, about 7000 rpm, 20w50 kaase oil pump.


Last edited by 10SHOTS on September 12th 2012, 3:49 pm; edited 1 time in total
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Re: rod bearing clearance

Post  Lem Evans on September 12th 2012, 2:40 pm

Depends on the application. On a full on race engine I prefer more than that.

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Re: rod bearing clearance

Post  Lem Evans on September 12th 2012, 7:15 pm

10SHOTS wrote:is .0023 just to tight for a 2.200 rod journal? or will it work
14.1, about 7000 rpm, 20w50 kaase oil pump.

I see you have the edit relative to comp ratio & rpm. In that case with 20W-50...I don't see an issue at .0028"

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Re: rod bearing clearance

Post  Frank Merkl on September 12th 2012, 7:20 pm

buy a set of 1X's and put the upper half's in should put you at .0028"
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Re: rod bearing clearance

Post  Lem Evans on September 12th 2012, 7:50 pm

Frank Merkl wrote:buy a set of 1X's and put the upper half's in should put you at .0028"
Frank

That's a good option.

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Re: rod bearing clearance

Post  LivermoreDave on September 12th 2012, 10:12 pm

10SHOTS wrote:is .0023 just to tight for a 2.200 rod journal? or will it work
14.1, about 7000 rpm, 20w50 kaase oil pump.

Not that I disagree with previous posters, but it seems you are in the ball park with that clearance on that journal. IMO, that heavy of an oil is unnecessary.

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Re: rod bearing clearance

Post  richter69 on September 12th 2012, 10:34 pm

mine uses the half sets like Frank mentioned, .0028, was 20-50 now 5-20 "green" oil........... bearings looked so good last time it was apart I just stuck um back in............
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Re: rod bearing clearance

Post  Lem Evans on September 12th 2012, 10:37 pm

LivermoreDave wrote:
10SHOTS wrote:is .0023 just to tight for a 2.200 rod journal? or will it work
14.1, about 7000 rpm, 20w50 kaase oil pump.

Not that I disagree with previous posters, but it seems you are in the ball park with that clearance on that journal. IMO, that heavy of an oil is unnecessary.

Dave.

But, that's what he has for oil and the answer is in that context. When the rpm is high....one will be suprised how much clearance is needed.

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Re: rod bearing clearance

Post  LivermoreDave on September 12th 2012, 10:44 pm

What's a guy to do? Buy bearings or buy oil.

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Re: rod bearing clearance

Post  Lem Evans on September 12th 2012, 11:32 pm

In this aplication.........bearings.

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Re: rod bearing clearance

Post  the Coug on September 13th 2012, 5:56 am

it is still beyond me why people still want to run oil that is that thick when they could use 10-30 and gain power. guess they still have the old school mentality huh?if you are gonna run oil that thick why not just run rear end grease?
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Re: rod bearing clearance

Post  richter69 on September 13th 2012, 8:11 am

my old school oil and thinking works........ and its plenty fast....... Wink
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Re: rod bearing clearance

Post  kjett on September 13th 2012, 9:19 am

So this discussion has me wondering if I'm setting up for the correct clearances. Totally assuming this whole discussion has been for steel rods and the clearances needed. What would be the clearance needed for aluminum rods on a 488ci motor spinnng closer to 8000 and wanting to use 10w30 oil? BME suggests .002-.0025 for street motors, but nothing for race motors. How much to y'all leave for growth there?
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RE

Post  HorsinAround on September 13th 2012, 9:26 am

Ok, we ran .0028 on the 470 pulling motor that saw 8000+ rpm every run down the track, I always used Valvoline 20w50 racing oil. Everytime we freshened the motor the bearing looked great and we only replaced them every other freshening.

Now I am building a 514 drag motor that will turn in the 6-7000 rpm range, so should I stay in the .0028 range and should I stay with the tried and true 20w50, or is a ligher weight oil just as good?
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Re: rod bearing clearance

Post  dfree383 on September 13th 2012, 9:40 am

I havent seen any issues running lighter oil. it does make a little more power.
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x bearings

Post  10SHOTS on September 13th 2012, 10:47 am

Frank Merkl wrote:buy a set of 1X's and put the upper half's in should put you at .0028"
Frank
does it matter if i put the x bearings in the lower ?
i have been thinking about using the 10w30
i have mixed it half and half before
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Re: rod bearing clearance

Post  Frank Merkl on September 13th 2012, 11:15 am

it's just my preference to put the slightly large clearance brg in the upper as thats were all the load is
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Re: rod bearing clearance

Post  richter69 on September 13th 2012, 11:32 am

I used a set of 4 std and a set of 4 X and just alternated um, saves buying 2 complete sets of each...................unless you want spares then I guess its ok.
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Re: rod bearing clearance

Post  Frank Merkl on September 13th 2012, 7:16 pm

a half a thousandths probably wouldn't make a difference upper or lower
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Re: rod bearing clearance

Post  Lem Evans on September 13th 2012, 7:34 pm

Over the years I've been ask "how tight can you run it". I really do not want to know.

At .0003"-.0005" wider than the "magic" number works real good.

I would not do a aluminium rod less than .003".

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Re: rod bearing clearance

Post  IDT-572 on September 13th 2012, 10:14 pm

Running thinner oil is ok as long as your pump can maintain pressure to keep the oil wedge in place to prevent metal to metal contact. The thinner the oil the more oil it has to pump to maintain the same pressure through the bleeds.

Tightening the clearances will allow the pump to maintain pressure with out having to pump the extra oil volume.

But you need to make sure you have enough clearance to take care off any elongation or distortion of the big end of the rod.

Rpm and type and quality of the rod dictates this mostly, Where should you be is a choice of the engine builder and what has worked well for him.

I have run .0028 on the rods for years with oil ranging from 10/30 to 20/50. But always had enough pump to maintain 65 lbs hot.

But when I ran oil that thin (10/30) it would drop pressure at the end of the track pumping the pan almost dry.

How tight you can run a Eagle, Oliver or Scat rod clearance and turn it 7500 plus I don't know, but .0028 works and works every time. Kinda of like asking how many prunes is enough to get the job done. Just keep adjusting until you soil your pants.

But if you don't want to soil your pants............. .0028 works........... Wink

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Re: rod bearing clearance

Post  460Dave on November 26th 2015, 6:14 pm

I know this is an old post, but it is still relevant. I have a quick question. Is .0033 too much clearance for the rods? Everything I read says .0028 - .003. Is it better to err on the high side or low? How much is too much?
Here is my measurements w/ King HP X bearings.
1 - .0029
2 - .003
3 - .0032
4 - .0029
5 - .0032
6 - .0029
7 - .0033
8 - .0031
Would I be better off to close up some of these with a half shell of a standard bearing? I might be able to move bearings around and get them all closer to .003. What do you guys think?

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Re: rod bearing clearance

Post  Lem Evans on November 26th 2015, 6:18 pm

What rods:?

Spray or not?

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Re: rod bearing clearance

Post  460Dave on November 26th 2015, 6:30 pm

Callies Ultra, on a Callies billet crank, yes, spray (300 - 400)

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Re: rod bearing clearance

Post  Lem Evans on November 26th 2015, 6:38 pm

460Dave wrote:Callies Ultra, on a Callies billet crank,   yes, spray (300 - 400)

Run it Very Happy

Clearance is application driven also.

Or, put coated bearings in it......best answer.


Last edited by Lem Evans on November 26th 2015, 7:46 pm; edited 1 time in total

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