Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Bearing Clearance

General engine tech -- Drag Racing to Circle Track

Moderator: Team

saleen385
Member
Member
Posts: 124
Joined: Thu Apr 08, 2010 7:56 pm
Location:

Bearing Clearance

Post by saleen385 »

Ok guys a 12cyl. diesel engine with a 10.236in main journal turning 950rpm max 18-1 compression making 4500hp.
What would you run for clearance & what kind of oil pressure?
Thanks
Kevin Johnson
HotPass
HotPass
Posts: 9022
Joined: Tue Nov 22, 2005 5:41 am
Location:

Re: Bearing Clearance

Post by Kevin Johnson »

Last edited by Kevin Johnson on Sat Jan 11, 2020 4:49 pm, edited 1 time in total.
engineguyBill
HotPass
HotPass
Posts: 1215
Joined: Fri Feb 26, 2010 11:15 am
Location: Gold Canyon, AZ

Re: Bearing Clearance

Post by engineguyBill »

Best to consult the engine manufacturer for their recommendations on bearing clearance and oil pressure specs. I don't think any of us on a high performance site will have the background and experience to offer you any viable recommendations concerning this issue . . . . . . . . . .
Bill

Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
User avatar
Caprimaniac
Expert
Expert
Posts: 922
Joined: Fri Nov 18, 2011 1:17 pm
Location: NORWAY

Re: Bearing Clearance

Post by Caprimaniac »

Ship engine?
Maybe stationary powerplant?

Sorry, very little knowledge to share.
How to turn GURU in an instant.....
bentvalves
Pro
Pro
Posts: 261
Joined: Mon Dec 12, 2016 3:37 pm
Location:

Re: Bearing Clearance

Post by bentvalves »

let us know what you come up with!

.010" oil clearance ?
100psi ?
BillK
Expert
Expert
Posts: 562
Joined: Wed Aug 26, 2009 8:30 pm
Location: Beautiful Southern Maryland
Contact:

Re: Bearing Clearance

Post by BillK »

Exactly which engine is it ? Make and model ?
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

www.enginerepairshop.com
saleen385
Member
Member
Posts: 124
Joined: Thu Apr 08, 2010 7:56 pm
Location:

Re: Bearing Clearance

Post by saleen385 »

Ok, I am not allowed to say what it is. They are running .003 clearance and 90psi. I really feel that is to little clearance and not enough pressure. Engineers say that is enough but we keep having failures.
Was just looking for other opinions.
Thanks
Kevin Johnson
HotPass
HotPass
Posts: 9022
Joined: Tue Nov 22, 2005 5:41 am
Location:

Re: Bearing Clearance

Post by Kevin Johnson »

saleen385 wrote: Sun Jan 12, 2020 8:42 pm Ok, I am not allowed to say what it is. They are running .003 clearance and 90psi. I really feel that is to little clearance and not enough pressure. Engineers say that is enough but we keep having failures.
Was just looking for other opinions.
Thanks
Check it against the Tribology handbook.
engineguyBill
HotPass
HotPass
Posts: 1215
Joined: Fri Feb 26, 2010 11:15 am
Location: Gold Canyon, AZ

Re: Bearing Clearance

Post by engineguyBill »

saleen385 wrote: Sun Jan 12, 2020 8:42 pm Ok, I am not allowed to say what it is.
Why are you not allowed to share the make of engine with us? Secret Service project or FBI? Maybe powerplant for Bill & Hillary's yacht?? I smell BS.
Maybe a Cooper-Bessemer pump station type powerplant?? You are not going to get viable answers to your quiry on a high performance engine site, just too many variables. Contact the engine manufacturer or a factory authorized remanufacturer for accurate answers to your questions.

For instance, my recommendation for natural gas fueled pump station 12 cylinder engine with 38.25" bore, 44.50" stroke and 54.125" center to center connecting rods would be .0065" crankshaft oil clearance and 185# of oil pressure. Considering the use of 22.50 gallons of 70# oil in the crankcase.
Bill

Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
User avatar
modok
Guru
Guru
Posts: 2630
Joined: Sun Jun 06, 2010 1:50 am
Location:

Re: Bearing Clearance

Post by modok »

No less than .0005 per 1 IMO
so, .0055" minimum

.003", no,
.03"mm maybe?! double check your units :shock:
User avatar
ptuomov
HotPass
HotPass
Posts: 2982
Joined: Fri Aug 07, 2009 3:52 am
Location:

Re: Bearing Clearance

Post by ptuomov »

So 0.05-0.1% of the journal diameter?

For the pressure, one would want to know what the rpm is and how the oil passages run.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
bentvalves
Pro
Pro
Posts: 261
Joined: Mon Dec 12, 2016 3:37 pm
Location:

Re: Bearing Clearance

Post by bentvalves »

guy, the oil pressure has been stated.

apologies....misread above post. rainy dreary monday.

GUY, the RPM has been stated!
novafornow
HotPass
HotPass
Posts: 97
Joined: Mon Feb 04, 2019 2:23 pm
Location: california

Re: Bearing Clearance

Post by novafornow »

I have studied this a little and will go out on a limb and say .008 .
User avatar
ptuomov
HotPass
HotPass
Posts: 2982
Joined: Fri Aug 07, 2009 3:52 am
Location:

Re: Bearing Clearance

Post by ptuomov »

bentvalves wrote: Mon Jan 13, 2020 5:27 pm guy, the oil pressure has been stated.

apologies....misread above post. rainy dreary monday.

GUY, the RPM has been stated!
This to me? For oil pressure, very little should oil the mains. However the big question is how do the rod journals get oiled, given the large main journal diameter. At 950 rpm it shouldn’t require a lot of oil pressure even with that big main, compared to say (2.75”*7000rpm)^2.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Kevin Johnson
HotPass
HotPass
Posts: 9022
Joined: Tue Nov 22, 2005 5:41 am
Location:

Re: Bearing Clearance

Post by Kevin Johnson »

If the engineers are saying the clearance and pressure are correct (presumably these are the OEM recommendations ) and engine failures are occurring regularly then it is logical to examine other possibilities.

If the engine uses a fluid damper then it could be the case that despite appearing okay visually it needs rebuilding or replacement. The article below points out that this is a common cause of heavy duty diesel engine failure.

Good luck.

http://www.engineprofessional.com/artic ... _64-72.pdf
Post Reply