Checking bore for roundness
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
Checking bore for roundness
When checking the bores on a block is it necessary to check them with a torque plate on it? How much can bolting the heads down change the bore? Can a shop spot a bad bore visualy?
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
So what would you guys say to this work. No miles on the motor just honed. I have the builder of the motor claiming the measurements are not accurate because no torque plate was used and I have 2 local shops tell me the motor is junk.
Here you can see the area(darker dome shape area) that measures larger on the top of ever bore. All are about the same size(1/4 size of bore).
These are the measurements at the bottom/middle of the bore.
These are the measurements at the top of the 2 worst bores.
So the top area of the stock bore is off over .002 on the worst one and over .001 on the other. It was my understanding that when you hone a bore that it should be within .000x of each other. That would make the .002 WAAAAAAY off. I can't see how bolting a torque plate down would round that out. Is it possible?
I had 2 well known shops in the area look at the motor and both said there is no way they would use a motor like that. They said it would definitly burn oil/smoke since the bore is 3.898 at the bottom and 3.90 at the top and that pit in the bore passes the 2nd piston ring.
Opinions on this hone job. Junk?
Here you can see the area(darker dome shape area) that measures larger on the top of ever bore. All are about the same size(1/4 size of bore).
These are the measurements at the bottom/middle of the bore.
These are the measurements at the top of the 2 worst bores.
So the top area of the stock bore is off over .002 on the worst one and over .001 on the other. It was my understanding that when you hone a bore that it should be within .000x of each other. That would make the .002 WAAAAAAY off. I can't see how bolting a torque plate down would round that out. Is it possible?
I had 2 well known shops in the area look at the motor and both said there is no way they would use a motor like that. They said it would definitly burn oil/smoke since the bore is 3.898 at the bottom and 3.90 at the top and that pit in the bore passes the 2nd piston ring.
Opinions on this hone job. Junk?
Drifting
Joined: Jan 2008
Posts: 1,722
Likes: 138
From: Florida
St. Jude Donor '09
From the service manual, cylinder bore diameter: 3.897 - 3.898" with a maximum bore taper of .0007" (thrust side).
The readings you are reporting indicate that your bore taper is beyond the maximum allowable tolerance. The service manual does not call for the use of a torque plate to measure the bore diameter.
The readings you are reporting indicate that your bore taper is beyond the maximum allowable tolerance. The service manual does not call for the use of a torque plate to measure the bore diameter.
Melting Slicks
Joined: Sep 2003
Posts: 2,062
Likes: 117
Hi nickolbag,
I made the exact same measurements 3 weeks ago on my freshly "honed" LS3 stroked with less than 500 miles of brake-in...
The missing torque plate was immediately brought up to my attention to justify the issue...
I did bolt the torque plate on the short-block and couldn't measure any major changes...
New pistons 0.010 bigger are going in today!!!
Christian
I made the exact same measurements 3 weeks ago on my freshly "honed" LS3 stroked with less than 500 miles of brake-in...
The missing torque plate was immediately brought up to my attention to justify the issue...
I did bolt the torque plate on the short-block and couldn't measure any major changes...
New pistons 0.010 bigger are going in today!!!
Christian
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
From the service manual, cylinder bore diameter: 3.897 - 3.898" with a maximum bore taper of .0007" (thrust side).
The readings you are reporting indicate that your bore taper is beyond the maximum allowable tolerance. The service manual does not call for the use of a torque plate to measure the bore diameter.
The readings you are reporting indicate that your bore taper is beyond the maximum allowable tolerance. The service manual does not call for the use of a torque plate to measure the bore diameter.
Hi nickolbag,
I made the exact same measurements 3 weeks ago on my freshly "honed" LS3 stroked with less than 500 miles of brake-in...
The missing torque plate was immediately brought up to my attention to justify the issue...
I did bolt the torque plate on the short-block and couldn't measure any major changes...
New pistons 0.010 bigger are going in today!!!
Christian
I made the exact same measurements 3 weeks ago on my freshly "honed" LS3 stroked with less than 500 miles of brake-in...
The missing torque plate was immediately brought up to my attention to justify the issue...
I did bolt the torque plate on the short-block and couldn't measure any major changes...
New pistons 0.010 bigger are going in today!!!
Christian
Tech Contributor
Joined: May 2008
Posts: 2,843
Likes: 16
From: Howell Michigan
St. Jude Donor '09-'10-'11
Torque plates are more common on open deck blocks like the North Star engines, not so much on closed deck like the LS engines.
When rebuilding an used engine the upper area of the bore normally wears more then the lower areas due to less lubricant getting there past the other rings and the higher heat load. The upper land area has higher concentration of abrasive combustion byproducts.
If it were me, I do as Christian did and have it bored oversize to clean things up and put it into proper spec.
When rebuilding an used engine the upper area of the bore normally wears more then the lower areas due to less lubricant getting there past the other rings and the higher heat load. The upper land area has higher concentration of abrasive combustion byproducts.
If it were me, I do as Christian did and have it bored oversize to clean things up and put it into proper spec.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
Torque plates are more common on open deck blocks like the North Star engines, not so much on closed deck like the LS engines.
When rebuilding an used engine the upper area of the bore normally wears more then the lower areas due to less lubricant getting there past the other rings and the higher heat load. The upper land area has higher concentration of abrasive combustion byproducts.
If it were me, I do as Christian did and have it bored oversize to clean things up and put it into proper spec.
When rebuilding an used engine the upper area of the bore normally wears more then the lower areas due to less lubricant getting there past the other rings and the higher heat load. The upper land area has higher concentration of abrasive combustion byproducts.
If it were me, I do as Christian did and have it bored oversize to clean things up and put it into proper spec.
What sucks is I bought this motor as a zero mile rebuild on this forum and it turns out to be junk.
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Melting Slicks
Joined: Sep 2003
Posts: 2,062
Likes: 117
Do you know if this engine was overheated???
May be only for some seconds...
This is another explanation I received and that was supposedly the cause of the same out of round measurements on my ex new freshly honed block!!!!
Christian
Race Director
Joined: May 2005
Posts: 15,960
Likes: 21
From: West Norriton PA
St. Jude Donor '08
This is one of the reasons to always go with a top notch engine builder and buy a complete short-block unit instead of buying pieces from various sources.
Hope you get it all worked out.
Hope you get it all worked out.
Melting Slicks
Joined: Sep 2003
Posts: 2,062
Likes: 117
I did buy my short-block with cylinder heads and valve train ASSEMBLED from a top notch engine builder...that was obviously not enough...
Christian
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
... and that's why the hone didn't take any material off those areas that are still dark. Cylinders usually have more wear at the top of the bore, and that's what you're seeing here. How far down from the top of the bore does the taper spec go out of tolerance?
Last edited by ZeeOSix; Jul 4, 2009 at 01:51 PM.
Drifting
Joined: Feb 2007
Posts: 1,993
Likes: 7
From: LaPine Oregon
GEN # 5300 block ............
The history of the GEN 3 5300 block is notorious for sloppy bore tolerances and taper. This attributed to design as well, being that the siamesed bores have such a small area of coolant passage between them. This cause hot spots , which inturn created distorted bore diameters at the top of the bore. This was the major cause of the infamous oil consumption issues, particulary before the Napier scraper faced , 13 pound rings were used. The OEM 9 pound rings could not handle the tapered , distorted bores , particulary at the higher operating engines speeds of the manual transmission equiped cars.
Check out the GEN 4 LS2 design changes that addressed the cylinder bores machine tolerance , coolant passages ( and the two oil control baffles /oil seperators). The LS2 piston rings are even thinner ( still using the aggressive Napier face), with less overall tension than the 2001 LS6 used. All directly related to the cylinder bores.
I'm a retired journeyman machinist and I wish you well on your rebuild.
Check out the GEN 4 LS2 design changes that addressed the cylinder bores machine tolerance , coolant passages ( and the two oil control baffles /oil seperators). The LS2 piston rings are even thinner ( still using the aggressive Napier face), with less overall tension than the 2001 LS6 used. All directly related to the cylinder bores.
I'm a retired journeyman machinist and I wish you well on your rebuild.
Race Director
Joined: May 2005
Posts: 15,960
Likes: 21
From: West Norriton PA
St. Jude Donor '08
Hope you get it resolved.
Burning Brakes
Joined: Dec 2005
Posts: 831
Likes: 2
From: Silver Spring, MD
My guess is that some machine work will be needed to even up the bores to the worst of the cylinders and then you'll probably need some custome size pistons. 
" Hopefully that will work and not the later
It's either that or toss the block and start over.
" Hopefully that will work and not the laterIt's either that or toss the block and start over.
7th Gear
Joined: Jun 2009
Posts: 7
Likes: 0
From: Rochester New York
The history of the GEN 3 5300 block is notorious for sloppy bore tolerances and taper. This attributed to design as well, being that the siamesed bores have such a small area of coolant passage between them. This cause hot spots , which inturn created distorted bore diameters at the top of the bore. This was the major cause of the infamous oil consumption issues, particulary before the Napier scraper faced , 13 pound rings were used. The OEM 9 pound rings could not handle the tapered , distorted bores , particulary at the higher operating engines speeds of the manual transmission equiped cars.
Check out the GEN 4 LS2 design changes that addressed the cylinder bores machine tolerance , coolant passages ( and the two oil control baffles /oil seperators). The LS2 piston rings are even thinner ( still using the aggressive Napier face), with less overall tension than the 2001 LS6 used. All directly related to the cylinder bores.
I'm a retired journeyman machinist and I wish you well on your rebuild.
Check out the GEN 4 LS2 design changes that addressed the cylinder bores machine tolerance , coolant passages ( and the two oil control baffles /oil seperators). The LS2 piston rings are even thinner ( still using the aggressive Napier face), with less overall tension than the 2001 LS6 used. All directly related to the cylinder bores.
I'm a retired journeyman machinist and I wish you well on your rebuild.
Drifting
Joined: Feb 2007
Posts: 1,993
Likes: 7
From: LaPine Oregon
