Main bearing crush

Daran Summerton · 03-25-2011, 09:36 AM

Thanks Alan I will not reduce the crush. I would like to know which bearings have the most clearance at the parting line. Guess the only way is to mic different brands. Good info on pumps, this is not my current issue because every other bearing looks like right out of the box. Just #4

Alan Roehrich · 03-25-2011, 09:47 AM

Darren, you'll have to measure the bearings, as they are installed in the block, and you'll need a really good dial bore gauge, such as a Sunnen, Starrett, or Mitutoyo, in order to do so. You can't just use a micrometer to measure the bearings to see how thick they are. The only thing that matters is their shape and size in the as installed position and condition.

The Federal Mogul is a fairly hard alloy bearing, and it is a 1/2 groove bearing set, as opposed to the full grooves in the Clevite bearings. I think the lack of the groove in the lower bearing shell may help to build a better film of oil, and hydrodynamic wedge, which may help keep the crank off of the bearings.

Dan Lattimore · 03-25-2011, 09:47 AM

Daran----What Alan said.-----After proper prep and clearances your old motor is running 10.90s in a Cutlass GT stocker with over 200 passes.------Danny

Daran Summerton · 03-25-2011, 10:15 AM

Thanks Guys!

Bill Edgeworth · 03-25-2011, 10:20 AM

Have any of you Olds guys tried one of the J&S main girdles to see if it will solve the problem? Seems girdle use is gaining popularity on some types of engines.

Daran Summerton · 03-25-2011, 04:37 PM

I intend to. The weight of that rotating assembly along with a 4.250 stroke is the challenge for me as well as thousands of others. Buicks seem to respond to the support as well.

bottombulb · 03-25-2011, 06:16 PM

Just a heads up, the 108m bearings are now a 3/4 groove.

Dan Lattimore · 03-25-2011, 06:55 PM

Daran ---Save your money bud. Alans advice is dead on.Our stockers don't make enough HP for that stuff, just pay attention to details. After hundreds of these things with no MB failure the only thing that needed a girdle was a windowed 403 and an ex girl friend with a fat ***.---Danny

Daran Summerton · 03-25-2011, 07:20 PM

03-25-2011, 09:36 AM	#1
Daran Summerton Senior Member Join Date: Jun 2003 Location: Las Vegas nv Posts: 600 Likes: 18 Liked 66 Times in 37 Posts	Re: Main bearing crush Thanks Alan I will not reduce the crush. I would like to know which bearings have the most clearance at the parting line. Guess the only way is to mic different brands. Good info on pumps, this is not my current issue because every other bearing looks like right out of the box. Just #4 __________________ 72 cutlass

03-25-2011, 09:47 AM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,132 Likes: 1,600 Liked 1,912 Times in 429 Posts	Re: Main bearing crush Darren, you'll have to measure the bearings, as they are installed in the block, and you'll need a really good dial bore gauge, such as a Sunnen, Starrett, or Mitutoyo, in order to do so. You can't just use a micrometer to measure the bearings to see how thick they are. The only thing that matters is their shape and size in the as installed position and condition. The Federal Mogul is a fairly hard alloy bearing, and it is a 1/2 groove bearing set, as opposed to the full grooves in the Clevite bearings. I think the lack of the groove in the lower bearing shell may help to build a better film of oil, and hydrodynamic wedge, which may help keep the crank off of the bearings. __________________ Alan Roehrich 212A G/S

03-25-2011, 09:47 AM	#3
Dan Lattimore Member Join Date: Jan 2003 Location: Beaverdam, Va./ Port St. Lucie,Fla. Posts: 362 Likes: 177 Liked 154 Times in 37 Posts	Re: Main bearing crush Daran----What Alan said.-----After proper prep and clearances your old motor is running 10.90s in a Cutlass GT stocker with over 200 passes.------Danny __________________ 66W30POST

03-25-2011, 10:20 AM	#5
Bill Edgeworth Member Join Date: Oct 2006 Location: Tacoma, WA Posts: 258 Likes: 0 Liked 0 Times in 0 Posts	Re: Main bearing crush Have any of you Olds guys tried one of the J&S main girdles to see if it will solve the problem? Seems girdle use is gaining popularity on some types of engines. __________________ Bill Edgeworth 6471 STK

03-25-2011, 04:37 PM	#6
Daran Summerton Senior Member Join Date: Jun 2003 Location: Las Vegas nv Posts: 600 Likes: 18 Liked 66 Times in 37 Posts	Re: Main bearing crush I intend to. The weight of that rotating assembly along with a 4.250 stroke is the challenge for me as well as thousands of others. Buicks seem to respond to the support as well. __________________ 72 cutlass

03-25-2011, 10:15 AM	#4
Daran Summerton Senior Member Join Date: Jun 2003 Location: Las Vegas nv Posts: 600 Likes: 18 Liked 66 Times in 37 Posts	Re: Main bearing crush Thanks Guys! __________________ 72 cutlass

03-25-2011, 06:16 PM	#7
bottombulb Junior Member Join Date: Feb 2005 Location: Hammonton NJ Posts: 28 Likes: 0 Liked 0 Times in 0 Posts	Re: Main bearing crush Just a heads up, the 108m bearings are now a 3/4 groove.

03-25-2011, 06:55 PM	#8
Dan Lattimore Member Join Date: Jan 2003 Location: Beaverdam, Va./ Port St. Lucie,Fla. Posts: 362 Likes: 177 Liked 154 Times in 37 Posts	Re: Main bearing crush Daran ---Save your money bud. Alans advice is dead on.Our stockers don't make enough HP for that stuff, just pay attention to details. After hundreds of these things with no MB failure the only thing that needed a girdle was a windowed 403 and an ex girl friend with a fat ***.---Danny __________________ 66W30POST

03-25-2011, 07:20 PM	#9
Daran Summerton Senior Member Join Date: Jun 2003 Location: Las Vegas nv Posts: 600 Likes: 18 Liked 66 Times in 37 Posts	Re: Main bearing crush __________________ 72 cutlass

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