Jump to content
itsLeon

Ow no another NA build!

Recommended Posts

On 12/01/2020 at 21:56, harryjackson said:

Any updates on this @itsLeon

Well yeah i got an update. 
After talking about clearances with alot of people and doing some heavy research on it we decided to change to main bearings again so that we have more clearance (from 0.0015 to 0.0025) because of the higher load and much higher RPM. 

@350Butcher is see that you have the same clearance as me, im changing that based on this article (and talking to king etc): http://www.substech.com/dokuwiki/doku.php?id=oil_clearance_and_engine_bearings
 

Other news. 
Yesterday i picked up some new buckets because still some aren't in spec. So hopefully i can finish the heads tonight. 

  • Like 2

Share this post


Link to post
Share on other sites
22 hours ago, itsLeon said:

@350Butcher is see that you have the same clearance as me, im changing that based on this article (and talking to king etc): http://www.substech.com/dokuwiki/doku.php?id=oil_clearance_and_engine_bearings

 

Cheers for passing this info on...........however I wont be opening up my clearances. My opinion is, that opening them up and especially for the reasons of increased load and revs. You'll just be losing oil pressure and wearing out the bearing faster as the load isn't spread as well across the bearing surface as with tighter clearances. 

 

The only advantage of increasing clearances would be additional cooling due to higher flow of oil but at a far higher cost to dropping the oil pressure. In a "modern engine" the components and obviously with the use of high quality oils the heat can be handled so isn't so much a consideration as if you were building say an old war time classic car engine for example. 

 

As always just my thought's on it........it's your build and I'm following it with interest. 

  • Like 2

Share this post


Link to post
Share on other sites
1 hour ago, 350Butcher said:

 

Cheers for passing this info on...........however I wont be opening up my clearances. My opinion is, that opening them up and especially for the reasons of increased load and revs. You'll just be losing oil pressure and wearing out the bearing faster as the load isn't spread as well across the bearing surface as with tighter clearances. 

 

The only advantage of increasing clearances would be additional cooling due to higher flow of oil but at a far higher cost to dropping the oil pressure. In a "modern engine" the components and obviously with the use of high quality oils the heat can be handled so isn't so much a consideration as if you were building say an old war time classic car engine for example. 

 

As always just my thought's on it........it's your build and I'm following it with interest. 

Just passing the info i can find. 
Well it was a though decision to make to change the bearings but the 'old' ones measured a clearance of 0.0015 while the minimum must be 0.0014. So the new ones will be around 0.0025. 
We have seen a couple of spun bearings here on build engines here with OEM spec clearances so people told me to go a little bigger.
In the article i linked they say: 

Quote

The optimal range of clearance is 0.0015-0.003” (for a bearing with 2” diameter). Looser clearances are more suitable for highly loaded engines working at high rotation speeds and with thicker oils. Tighter clearances provide a better combination of hydrodynamic parameters in less loaded engines working at lower rotation speeds and using thinner oils.

  This was for me the reason to go a little bigger. 

In my research i found that there is a rule of thumb (https://www.enginebuildermag.com/2017/03/high-performance-engine-bearings-2/). 

Quote

Most rod and main bearings run best with .0007˝ to .001˝ of clearance for every inch of crankshaft journal diameter, or .0015˝ to .002˝ inches of oil clearance for a 2-inch diameter shaft

My crank is 2.36 inches so that calculates to a min of 0.001652 of needed clearance again higher then what i have currently. 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

350z-uk.com

370z-uk.com

350z-uk.com

370z-uk.com

×
×
  • Create New...