Main Bearing Tolerance

cgstarry · August 13th, 2009, 09:28 AM

Hi All.

I am rebuilding a '66 200 Sprint engine with my Son. We are in the process of checking the main bearing to crankshaft journal clearances with plastigage. Two questions:

1) The Ford shop manual procedure says to apply a thin coat of oil to the journal and bearings prior to applying the plastigage and torquing. I did not do this. My tolerances are a little on the loose side, but servicable per specifications. (.0015 to .002 measured versus .0005 to .0015 desirable, .002 to .003 acceptable) Do you think that I should oil and re-torque / re-measure? It seems like the oil might make my tolerances a little tighter, more toward the perfect part of the scale.

2) My front three journal bearings plastigaged at .002 while the back four measured at .0015 to .0018. Is it a big deal for them to be off by five thousandths? My torque specs call for 60-70 lbs and we went 65 on all. Maybe we should go a little tighter on the loose ones? Would that make a difference?

Thanks!
John

460brevill · August 13th, 2009, 09:57 AM

five is a lot.did you cut the crank?

cgstarry · August 13th, 2009, 10:16 AM

Yes, the crankshart was cut. Maybe I need to put in slightly thicker bearings in the front three seats?

cgstarry · August 13th, 2009, 12:31 PM

The guy at Clevite (the bearing manufacturer) said that five ten thousandths of an inch difference is not a big deal. He said to lube them , torque them down and keep going.

The thing is I would feel better if they were closer and if they were all tighter.

Thoughts?

cgstarry · August 13th, 2009, 12:56 PM

Response from the Clevite guy: "No thicker bearing exist for what you desire to do! Your clearance is very acceptable, actually for engines driven in all sorts of weather conditions it is more desirable than to be on the low end!"

This is great news. So for review, here are my main bearing clearances:

cylinder 1 2 3 4 5 6
bearing 1 2 3 4 T 6 7
front | O | O | O | O | O | O |
clearance 0.0020 0.0020 0.0018 0.0018 0.0018 0.0015 0.0015
ideal 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010
delta 0.0010 0.0010 0.0008 0.0008 0.0008 0.0005 0.0005

460brevill · August 13th, 2009, 01:53 PM

when performance counts turn a crank for me all the clearance are the same.i run this engine at extreme rpm and tourqe so i want it right.if the clevite man said it is ok i would go with that.

cgstarry · August 14th, 2009, 09:31 AM

Thanks that helps my peace of mind!

John

August 13th, 2009, 09:28 AM	#1
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 125 iTrader: 0 reviews	Main Bearing Tolerance Hi All. I am rebuilding a '66 200 Sprint engine with my Son. We are in the process of checking the main bearing to crankshaft journal clearances with plastigage. Two questions: 1) The Ford shop manual procedure says to apply a thin coat of oil to the journal and bearings prior to applying the plastigage and torquing. I did not do this. My tolerances are a little on the loose side, but servicable per specifications. (.0015 to .002 measured versus .0005 to .0015 desirable, .002 to .003 acceptable) Do you think that I should oil and re-torque / re-measure? It seems like the oil might make my tolerances a little tighter, more toward the perfect part of the scale. 2) My front three journal bearings plastigaged at .002 while the back four measured at .0015 to .0018. Is it a big deal for them to be off by five thousandths? My torque specs call for 60-70 lbs and we went 65 on all. Maybe we should go a little tighter on the loose ones? Would that make a difference? Thanks! John __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

August 13th, 2009, 09:57 AM	#2
460brevill Hardcore Enthusiast Join Date: Apr 2007 Location: Farmville VA Posts: 1,327 iTrader: 0 reviews	five is a lot.did you cut the crank? __________________ i sixing 200 six with 300 hp.

August 13th, 2009, 10:16 AM	#3
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 125 iTrader: 0 reviews	Yep Yes, the crankshart was cut. Maybe I need to put in slightly thicker bearings in the front three seats? __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

August 13th, 2009, 12:31 PM	#4
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 125 iTrader: 0 reviews	The guy at Clevite (the bearing manufacturer) said that five ten thousandths of an inch difference is not a big deal. He said to lube them , torque them down and keep going. The thing is I would feel better if they were closer and if they were all tighter. Thoughts? __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

August 13th, 2009, 12:56 PM	#5
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 125 iTrader: 0 reviews	Looks like I am in good shape. Response from the Clevite guy: "No thicker bearing exist for what you desire to do! Your clearance is very acceptable, actually for engines driven in all sorts of weather conditions it is more desirable than to be on the low end!" This is great news. So for review, here are my main bearing clearances: cylinder 1 2 3 4 5 6 bearing 1 2 3 4 T 6 7 front \| O \| O \| O \| O \| O \| O \| clearance 0.0020 0.0020 0.0018 0.0018 0.0018 0.0015 0.0015 ideal 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 0.0010 delta 0.0010 0.0010 0.0008 0.0008 0.0008 0.0005 0.0005 __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

August 13th, 2009, 01:53 PM	#6
460brevill Hardcore Enthusiast Join Date: Apr 2007 Location: Farmville VA Posts: 1,327 iTrader: 0 reviews	clearance when performance counts turn a crank for me all the clearance are the same.i run this engine at extreme rpm and tourqe so i want it right.if the clevite man said it is ok i would go with that. __________________ i sixing 200 six with 300 hp. Last edited by 460brevill; January 18th, 2010 at 12:03 PM.

August 14th, 2009, 09:31 AM	#7
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 125 iTrader: 0 reviews	Thanks that helps my peace of mind! John __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

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Main Bearing Tolerance

Main Bearing Tolerance

Yep

Looks like I am in good shape.

clearance