Thrust Clearance.. Confused!
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,892
Likes: 3
From: Springfield Illinois
Thrust Clearance.. Confused!
So, some of you know I'm building a 454.. I am just now putting it back together with a different block. This block was casted around '90-'91. What I noticed different about this block and my '66 block is that this has a dowel pin to locate the #5 cap. When the cap is in place not torqued down at all the #5 cap cannot move forward nor backward. How do I go about setting the thrust clearance?
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Ummm...thust clearance isn't ever set by moving the bearing cap. If it's too tight, the thrust bearing surface is sanded on a surface plate.
Perhaps I misunderstood what you were asking...
Perhaps I misunderstood what you were asking...
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,892
Likes: 3
From: Springfield Illinois
I'll just wait until my dad takes a look at it.. He knows what the hell he's doing. I was just wondering if they didn't have to be set on the newer blocks.. This is my first engine build and he basically did all the precision work the first time around.. I was just curious so I asked..
Here is another question tho.. What if the thrust clearance is too much? Say .008+
Here is another question tho.. What if the thrust clearance is too much? Say .008+
Burning Brakes
Joined: Jul 2009
Posts: 1,132
Likes: 14
From: A town SC
Think he was refering to seating the rear main. I give the crank a good wack back and forth with a dead blow to align the thrust surface of the rear main bearing. I do this to get an accurate thrust measurement.
Also the clearance of 4 thousanths will run, If your perticular you can pull the bearing and hold the halfs together and find a flat surface lay down some red scotch bright and evenly rub your clearance in. Claen the bearing really good before you reinstall it!!
Also the clearance of 4 thousanths will run, If your perticular you can pull the bearing and hold the halfs together and find a flat surface lay down some red scotch bright and evenly rub your clearance in. Claen the bearing really good before you reinstall it!!
Last edited by forvicjr; Feb 21, 2010 at 07:04 PM. Reason: Add
Burning Brakes
Joined: Jul 2009
Posts: 1,132
Likes: 14
From: A town SC
Yes .004 is out of spec,but by the time its started and broken in, IMO the spec would be met. As for as the cap movement, no arguement there. Locating pins wouldnt allow it. Movement would accur on engine without dowells. When seating thrust bearing rear main isnt up to torque, therefore it would move as much as the main bolts/studs would allow.
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Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
There's a difference between aligning the bearing and "moving" the cap - but I guess it's splitting hairs.
'nuff said from me
Last edited by billla; Feb 21, 2010 at 08:43 PM.
Burning Brakes
Joined: Jul 2009
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From: A town SC
Safety Car
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From: Oakland California
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
So, some of you know I'm building a 454.. I am just now putting it back together with a different block. This block was casted around '90-'91. What I noticed different about this block and my '66 block is that this has a dowel pin to locate the #5 cap. When the cap is in place not torqued down at all the #5 cap cannot move forward nor backward. How do I go about setting the thrust clearance?
*everything on internet's suspect; including the very words I just wrote.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Burning Brakes
Joined: Jan 2007
Posts: 1,057
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From: Concord Calif
I have never seen or heard of any under size bearing to take up wear. There are over sizes such as .001, .002 and .010 for the thrust but that is for gringing a crank that will make that size without welding not for wear.
Yes you do set the rear cap when there is no dowel pins but not with them. Also what one wants to call a spec makes a difference if you have a clutch or torque converter with a clutch needing more min clearance, .006 to .012 would not be out of line on a clutch car.
Safety Car
Joined: Aug 2000
Posts: 3,711
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From: San Antonio TX
You have to look at the bearing catalogs. They really are very common and used frequently when the thrust surface has to be machined.
As to setting the bearing, torque all the caps but leave the thrust cap loose. Get a large deadblow hammer or a 5lb sledge with a block of wood so you don't mess up the machined surfaces. Smack the front of the crank with a good blow, then do the same to the rear. Now torque the cap. Set up your dial indicator and measure the thrust clearance by first prying the crank backward with a screwdriver wedged between a cap and the crank, zero the indicator, then pry the crank forward and read the indicator. You can also measure with just a feeler gauge on the rear surface between the bearing and the crank, but the dial indicator is more accurate since there is no "feel" to it.
