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CURSD

Main bearing clearances...problems...

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Currentely rebuilding my tractor..erm 180sx sr20det

 

Crank ground 10 thou , ACL race series bearings, closed & honed rods, new rings, etc.

 

Main bearing #1 is a touch over 1.5 thou clearance, all the rest are closer to 2. I was suggested to look for the clearance being between 2 and 2.5 thou.

 

Whats the best clearance to go with for these motors? its no dyno warrior motor...just a daily driven streeter.

 

p.s it was pulled down due to metal fatigue on no.3 big end bearing...the rest were wearing also...didnt spin in the rod but would of soon.

 

Any thoughts?

Edited by CURSD

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some builders wont worry to much on a variation of .5thou but i always run with factory figures

take the crank to get resized to the specs you want after doing your clearances or order different bearings

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some builders wont worry to much on a variation of .5thou but i always run with factory figures

take the crank to get resized to the specs you want after doing your clearances or order different bearings

 

Thanks mate,

The machinist said the .5 thou diff was okay, its just that its on the low side at 1.5 thou, he said between 2 and 2.5.

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Currentely rebuilding my tractor..erm 180sx sr20det

 

Crank ground 10 thou , ACL race series bearings, closed & honed rods, new rings, etc.

 

Main bearing #1 is a touch over 1.5 thou clearance, all the rest are closer to 2. I was suggested to look for the clearance being between 2 and 2.5 thou.

 

Whats the best clearance to go with for these motors? its no dyno warrior motor...just a daily driven streeter.

 

p.s it was pulled down due to metal fatigue on no.3 big end bearing...the rest were wearing also...didnt spin in the rod but would of soon.

 

Any thoughts?

 

 

You should generally work on rule of thumb of 1 thou per inch of crank journal size.

 

This means 2 - 2.25 thou is generally the best on your SR.

 

1.5 is too tight for any engine I have ever made. You would probably find the minimum spec for your engine would be 1.6-1.8 thou anyway.

Is there any reason why you had the crank ground....this is an extremely foolish thing to do if you did not spin a bearing and the journal size could have been polished to minimum spec. But now that it is done, you will have to run with it.

 

Also, how are you measuring the clearances?

 

Plastigauge, Micrometers etc?

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some builders wont worry to much on a variation of .5thou but i always run with factory figures

take the crank to get resized to the specs you want after doing your clearances or order different bearings

 

0.5 thou is a fairly decent variation in clearance. I never allow any more than 0.1 thou variance in clearance for any of my engines...but then again, these are putting out 5 times the hp of yours and probably see 2000-2500rpm more on a constant basis.

 

For a street car, 1.8-2thou minimum for a safe running engine. If your engineer has machined the crank properly, then all the journals will be the same size and you may have a bearing problem. If not, then you are measuring wrong. DON'T USE PLASTI-GAUGE!!!!

 

 

 

 

EVER!!!!!

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There was some minor wear on the big end journal, also across the crank the measurements were right down on the factory limit. On the advice of our engine builder the crank was ground, matched with the new bearings to bring the clearances back down. I didnt think I could keep the clearances at the 2-2.25 you suggested with standard bearings on the crank at its minimum spec. Then again i've been wrong before, usually am :P

But anyway,

 

At the moment using plastigauge but ill go and borrow the mics tomorrow to check and re-check.

 

I know its not the best stuff to use, but I just wanted to get an idea of how its looking tonight.

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For a street car, 1.8-2thou minimum for a safe running engine. If your engineer has machined the crank properly, then all the journals will be the same size and you may have a bearing problem. If not, then you are measuring wrong. DON'T USE PLASTI-GAUGE!!!!

 

 

 

 

EVER!!!!!

 

Not a fan huh. Thanks for the advice though!

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some builders wont worry to much on a variation of .5thou but i always run with factory figures

take the crank to get resized to the specs you want after doing your clearances or order different bearings

 

0.5 thou is a fairly decent variation in clearance. I never allow any more than 0.1 thou variance in clearance for any of my engines...but then again, these are putting out 5 times the hp of yours and probably see 2000-2500rpm more on a constant basis.

 

For a street car, 1.8-2thou minimum for a safe running engine. If your engineer has machined the crank properly, then all the journals will be the same size and you may have a bearing problem. If not, then you are measuring wrong. DON'T USE PLASTI-GAUGE!!!!

 

 

 

 

EVER!!!!!

 

the most hp one of our engines produced was around 420 (318kw) and had a limiter set at 8000 on the dyno but apparently later changed higher not huge i know but for a 4 banger its not to bad but 5 times that? what sort of engines are you making over 2000hp with over 8000rpm's

 

and yeah we run with .2thou variations at 2-2.2 i was simply saying some builders wont worry to much of the variation but depends who you take it to

and a good set of mics is a good thing to have but you dont want to go buying some just to doi one build so find out if one of your mates has a good set of mitatoyos or just take it back to the machinist and check, always make sure there calibrated before you measure as well.

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Crank ground 10 thou , ACL race series bearings, closed & honed rods, new rings, etc.

 

Main bearing #1 is a touch over 1.5 thou clearance, all the rest are closer to 2. I was suggested to look for the clearance being between 2 and 2.5 thou.

 

I was under the assumption that the ACL race series come with +1 thou extra oil clearance...

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Crank ground 10 thou , ACL race series bearings, closed & honed rods, new rings, etc.

 

Main bearing #1 is a touch over 1.5 thou clearance, all the rest are closer to 2. I was suggested to look for the clearance being between 2 and 2.5 thou.

 

I was under the assumption that the ACL race series come with +1 thou extra oil clearance...

 

No, that is the HX series. Race Series bearings part number ends with H.... an X on the end denotes +1thou extra clearance.

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some builders wont worry to much on a variation of .5thou but i always run with factory figures

take the crank to get resized to the specs you want after doing your clearances or order different bearings

 

0.5 thou is a fairly decent variation in clearance. I never allow any more than 0.1 thou variance in clearance for any of my engines...but then again, these are putting out 5 times the hp of yours and probably see 2000-2500rpm more on a constant basis.

 

For a street car, 1.8-2thou minimum for a safe running engine. If your engineer has machined the crank properly, then all the journals will be the same size and you may have a bearing problem. If not, then you are measuring wrong. DON'T USE PLASTI-GAUGE!!!!

 

 

 

 

EVER!!!!!

 

the most hp one of our engines produced was around 420 (318kw) and had a limiter set at 8000 on the dyno but apparently later changed higher not huge i know but for a 4 banger its not to bad but 5 times that? what sort of engines are you making over 2000hp with over 8000rpm's

 

and yeah we run with .2thou variations at 2-2.2 i was simply saying some builders wont worry to much of the variation but depends who you take it to

and a good set of mics is a good thing to have but you dont want to go buying some just to doi one build so find out if one of your mates has a good set of mitatoyos or just take it back to the machinist and check, always make sure there calibrated before you measure as well.

 

 

I was referring to CURSD's 'street only' driven car. He would be making, what - 200hp?

 

Not 2000hp but various engines from 308, 330, 355 and 383 Strokers to RB20, 25, 26 and 30 Hybrids. All ranging from 400hp at the wheels to 1000hp at the wheels topping 9 and 10k rpm.

 

You are right about your comment on some builders won't worry about it, but at the end of the day, if you are putting together an engine for yourself - even once - it pays to be pedantic. You don't need to spend very much money to get a decent set of mics either....Sure Mitatoyo are the top of the range but Mendham Engineering have Mitatoyo copy sets for sale for $180. They go from 0 - 6 inches. Combine these with a set of telescoping gauges or internal mics and your on your way to very accurate measurements. Plastigauge can be anywhere up to 1.5thou out so never trust your measurements unless done with calibrated mics.

 

I have known mechanics to put paper under bearing shells to fill up clearances that weren't right. This is obviously extreme dodgey but it does happen. What I am trying to get at really is:

 

If your engineer is a good one, there should not be a variance in bearing clearance like that. If the rods were re-sized and the crank ground, they should all be EXACTLY the same if you are using the ACL race series bearings. That is why it is odd to see one at 1.5 thou, and the other 3 at 2 thou.

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I have known mechanics to put paper under bearing shells to fill up clearances that weren't right. This is obviously extreme dodgey but it does happen. What I am trying to get at really is:

 

haha classic

where do you work man and just to get some comparison do you ever use king bearings?

i generally use king bearings in all my builds and dont use the acl's one of my first builds i used some acl's and spun it months later switched to kings and have never had a problem since.

to afraid to go back to acl but everyone recomends them to me all the time.

im one of those mechanics that get on a good thing and stay on it you know what i mean, if it aint broke dont fix it.

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200hp? lol I wish. My last car had a 330 stroker, that had balls.

 

I measured the main journals earlier, all at 2.1448 "

 

Sounds about right according to what the machinist said he took off.

 

Havent had time to bolt the main caps down and measure internal dia. but Ill get round to that tomorrow.

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I have known mechanics to put paper under bearing shells to fill up clearances that weren't right. This is obviously extreme dodgey but it does happen. What I am trying to get at really is:

 

haha classic

where do you work man and just to get some comparison do you ever use king bearings?

i generally use king bearings in all my builds and dont use the acl's one of my first builds i used some acl's and spun it months later switched to kings and have never had a problem since.

to afraid to go back to acl but everyone recomends them to me all the time.

im one of those mechanics that get on a good thing and stay on it you know what i mean, if it aint broke dont fix it.

 

 

Elite Racing Developments. I do use King bearings. I am putting together an engine in the next couple of weeks for a local race team. We will be using the King hard alloy bearings. Personal preference for the owner and I have used them before without problems. I have used king standards also without issue. King, NDC, ACL, Nismo, Clevite are all top of the line. I prefer to use Nismo or ACL race series but I often give my guys choice when amongst these brands. I try to keep king and clevite for my V8 customers though.

If all measurements have been taken correctly, then there should be no reason a bearing would spin - just because it is a particular brand.

 

I am exactly the same, stay on a good thing when you find it.

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200hp? lol I wish. My last car had a 330 stroker, that had balls.

 

I measured the main journals earlier, all at 2.1448 "

 

Sounds about right according to what the machinist said he took off.

 

Havent had time to bolt the main caps down and measure internal dia. but Ill get round to that tomorrow.

 

Standard minimum main journal size is 2.1636in. Standard maximum main journal size is 2.1646in

 

2.1448 ?

 

How many times did he grind it? That's 20thou under.

 

If you run a 0.50 bearing then you 'should' see around 1.5 thou clearance across the four seeing as though it's ground 19.8 thou under standard maximum.

That is too tight.

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Measured with the crank out, all main caps tourqued down etc,

bearing part no. is 5M2964h .25 ... so 10 thou under bearings witha 20 thou under crank :S

 

They all came up 2.1550 - 2.1560

 

With the crank at 2.1448 doesnt that leave the clearances at .0102 - 0.0114 "

 

Am I retarded or is it way out.

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Bearing has some clearances problem this was the main fact that they share this article it was good to present the services on it. I have to collect data on this so I can write bestessays or submit it back to my college this was the program that I assigned by teachers.

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