BBO wall thickness
#1
BBO wall thickness
I thought I'd post this for all to see. This was done on a standard bore 455 but it applies to all blocks.
It's been mentioned many times to "sonic check" the block before proceeding in any given build. However I'll bet many don't have it done.
Here's the sonic check sheet for a 455 build I'm doing for another member on here. Although the thinnest area is not on a thrust side, I think all would agree boring this block to .060, or even .030 over could cause a problem. At that point you're potentially left with a cylinder thickness of less than .080. Imo that's totally unacceptable in most if not all cases. A thin area in virtually any part of the cylinder wall will allow it to flex more than normal and adversely effect ring seal as well as overall longevity.
Needless to say, I'm not going to use this block. Hope this helps.
Note cyl#3 especially. Thanks.
It's been mentioned many times to "sonic check" the block before proceeding in any given build. However I'll bet many don't have it done.
Here's the sonic check sheet for a 455 build I'm doing for another member on here. Although the thinnest area is not on a thrust side, I think all would agree boring this block to .060, or even .030 over could cause a problem. At that point you're potentially left with a cylinder thickness of less than .080. Imo that's totally unacceptable in most if not all cases. A thin area in virtually any part of the cylinder wall will allow it to flex more than normal and adversely effect ring seal as well as overall longevity.
Needless to say, I'm not going to use this block. Hope this helps.
Note cyl#3 especially. Thanks.
Last edited by cutlassefi; April 10th, 2014 at 10:40 AM.
#9
Wall thickness by year yields no given pattern. I've seen thick and thin in all if the years of BBO. It all has to do with how well the pattern was put together and the mold built around it.
Another factor is just where the first cut off of the block was taken and what it was referenced to. Everything is machined off the first surface cut. If it wasn't referenced to a specific point on the casting then all machine work is going to be centerd or not in the casting. I think this to be the reason most blocks have one side or the other of the bores much thinner than the other.
Another factor is just where the first cut off of the block was taken and what it was referenced to. Everything is machined off the first surface cut. If it wasn't referenced to a specific point on the casting then all machine work is going to be centerd or not in the casting. I think this to be the reason most blocks have one side or the other of the bores much thinner than the other.
#10
Wall thickness by year yields no given pattern. I've seen thick and thin in all if the years of BBO. It all has to do with how well the pattern was put together and the mold built around it.
Another factor is just where the first cut off of the block was taken and what it was referenced to. Everything is machined off the first surface cut. If it wasn't referenced to a specific point on the casting then all machine work is going to be centerd or not in the casting. I think this to be the reason most blocks have one side or the other of the bores much thinner than the other.
Another factor is just where the first cut off of the block was taken and what it was referenced to. Everything is machined off the first surface cut. If it wasn't referenced to a specific point on the casting then all machine work is going to be centerd or not in the casting. I think this to be the reason most blocks have one side or the other of the bores much thinner than the other.
#12
I recently checked mine by hand with a long reach dial caliper through the water jacket cooling holes. I realize it's not the preferred method but I couldn't justify the cost of sonic testing it or purchasing the test equipment.
My block is currently .060 over and I never got a reading less than .240 anywhere I checked it. The range was .240 - .280. It should be noted this was in the diagonal positions so it's a little biased away from the ideal measuring points like yours is.
Looking at your chart you can see that the thinnest spots are always at 3 and 9 o'clock and the thickest are 12 and 6 o'clock. 12 and 6 o'clock would be the thrust side depending on whether it's the left or right side of the block. I've studied this and everything I've read said that as long as the thrust side isn't under .180 you'll be fine. Some even state a lower figure. I'm no expert here but I think your fine.
My block is currently .060 over and I never got a reading less than .240 anywhere I checked it. The range was .240 - .280. It should be noted this was in the diagonal positions so it's a little biased away from the ideal measuring points like yours is.
Looking at your chart you can see that the thinnest spots are always at 3 and 9 o'clock and the thickest are 12 and 6 o'clock. 12 and 6 o'clock would be the thrust side depending on whether it's the left or right side of the block. I've studied this and everything I've read said that as long as the thrust side isn't under .180 you'll be fine. Some even state a lower figure. I'm no expert here but I think your fine.
Last edited by TripDeuces; April 11th, 2014 at 10:59 AM.
#13
The 1968-69 had the thick wall. I have a motor that we bored .165 over and used Big Block Chevy pistons in. Back in 1986. Had to work with the carbs with bigger jets but it ran around 200 degrees all the time. It had over 5000 miles on before we pulled it and put a small block Olds in. About 7.5 to 1 compression.
In 1970 they made the blocks lighter. I will be weighing all 3 F blocks(F,F, Fa later on.
There are a couple guys that have done this here in the Midwest.
Mike
In 1970 they made the blocks lighter. I will be weighing all 3 F blocks(F,F, Fa later on.
There are a couple guys that have done this here in the Midwest.
Mike
#15
I recently checked mine by hand with a long reach dial caliper through the water jacket cooling holes. I realize it's not the preferred method but I couldn't justify the cost of sonic testing it or purchasing the test equipment.
Ok so let me get this straight, you have a roller cam, aluminum heads, a stroker assembly and a March pulley system and you didn't think $100.00 to sonic check the block was worth it, especially since you went .060 over? WOW!! I'm at a loss for words on that one.
My block is currently .060 over and I never got a reading less than .240 anywhere I checked it. The range was .240 - .280. It should be noted this was in the diagonal positions so it's a little biased away from the ideal measuring points like yours is. That's a lot biased, by at least .100 in most cases. That method tells you nothing. I'll eat my shirt if you have any non thrust wall that's more than .150 right now. In fact I'll bet they're closer to .100.
Looking at your chart you can see that the thinnest spots are always at 3 and 9 o'clock and the thickest are 12 and 6 o'clock. 12 and 6 o'clock would be the thrust side depending on whether it's the left or right side of the block. I've studied this and everything I've read said that as long as the thrust side isn't under .180 you'll be fine.
Ok so let's say the thrust sides are .200 thick, but at 3 and 9 o:clock they are only .060 thick. You don't think that the bore will move around? Really? Guess what's holding the thick walls in place? The thin walls, and on a BBO a less than stellar main web and not an overly thick deck. Does that give you a warm fuzzy feeling? It doesn't for me, that's why I didn't use that block. Some even state a lower figure. I'm no expert here but I think your fine.
Ok so let me get this straight, you have a roller cam, aluminum heads, a stroker assembly and a March pulley system and you didn't think $100.00 to sonic check the block was worth it, especially since you went .060 over? WOW!! I'm at a loss for words on that one.
My block is currently .060 over and I never got a reading less than .240 anywhere I checked it. The range was .240 - .280. It should be noted this was in the diagonal positions so it's a little biased away from the ideal measuring points like yours is. That's a lot biased, by at least .100 in most cases. That method tells you nothing. I'll eat my shirt if you have any non thrust wall that's more than .150 right now. In fact I'll bet they're closer to .100.
Looking at your chart you can see that the thinnest spots are always at 3 and 9 o'clock and the thickest are 12 and 6 o'clock. 12 and 6 o'clock would be the thrust side depending on whether it's the left or right side of the block. I've studied this and everything I've read said that as long as the thrust side isn't under .180 you'll be fine.
Ok so let's say the thrust sides are .200 thick, but at 3 and 9 o:clock they are only .060 thick. You don't think that the bore will move around? Really? Guess what's holding the thick walls in place? The thin walls, and on a BBO a less than stellar main web and not an overly thick deck. Does that give you a warm fuzzy feeling? It doesn't for me, that's why I didn't use that block. Some even state a lower figure. I'm no expert here but I think your fine.
I'll post some more sheets. Even the earlier blocks aren't that much thicker, maybe .020-.040 or so.
And you all are forgetting one thing. These can be bored incorrectly from the factory as well. You'll see when I post the other sheets. I had a D block and a '70 F block that had what looked like core shift when in fact they had poorly bored holes. It was evident at the top as well. It had a huge chamfer on one side with nearly a sharp edge on the opposite side.
And I believe the reference point for initial machining is taken from the dowel hole in the pan rail. But it can be screwed up from there. I've seen it more often that not.
Last edited by cutlassefi; April 11th, 2014 at 03:19 PM.
#16
Its also very possible that the locating dowel hole Mark mentioned are in the wrong location. Everything is located off the first surface cut on the raw casting. If it is not located perfectly in relation to the casting then everything will be off.I'm sure that since they never intended for us to be going 1/8 over bore that it wasn't something they worried about. In tolerance is all that counted to a guy running piece work.
#17
Here are two more. Both became more concentric once they were bored with the BHJ, especially the 455. It was bored .055 over. After boring we checked cyls 4 and 6 especially. Again they were much more even afterwards with thicknesses no less than .115-.120. Conversely look how much more concentric cyls 3 and 5 are on the 455. And that showed up on the BHJ plate as well. That side cleaned up more quickly than the other side.
Trip D- notice the top measurements on the 350. See all the .300+'s? Now look below them, see anymore? Same with the 455, most all of the thickness is at the top, especially on the 455 like you have. Imo I think you missed the boat on your priorities.
The 350 is a '69, the 455 is a '70. Both will have near stock or higher rod ratios with lighter internals as well. That lessens the load on the cylinder walls.
Hope this helps.
Trip D- notice the top measurements on the 350. See all the .300+'s? Now look below them, see anymore? Same with the 455, most all of the thickness is at the top, especially on the 455 like you have. Imo I think you missed the boat on your priorities.
The 350 is a '69, the 455 is a '70. Both will have near stock or higher rod ratios with lighter internals as well. That lessens the load on the cylinder walls.
Hope this helps.
Last edited by cutlassefi; April 12th, 2014 at 07:25 AM.
#19
#20
Cutlassefi, why stir the pot on this and use me as an example? I've never heard of anyone having a problem at .060 on a BBO but now I have a suspect block because you think so? Besides, what I do with my money and how I want to spend it is my business. Sonic checking was not going to happen on a .060 over block in my world no matter what the cost. If it breaks then I have two more blocks ready to go and I'll start over. There is also a lot more than the thinnest wall supporting that cylinder. You have the deck and main area not to mention water pressure from the cooling system ( I wouldn't put my money on this but I added it anyway). Did you also check the walls from top to bottom in half inch increments or just took the reading from the center of the bore? Maybe the tech just moved the transducer around until he found the thinnest spot? There are a lot of variables here.
I was only trying to help and offer my experience but since you've decided to make me a target you can pound sand. Anyone who's read these forums long enough knows you have an agenda and it mostly involves two topics: What to use as a reference point when machining a block and water temps. on dyno pulls. You can also add in cam selection. I already know you don't like my choice there either.
Stick to bickering with the other knowledgeable engine builders and so called Olds experts but lay off the little guys like me. I can bite back just as hard.
I was only trying to help and offer my experience but since you've decided to make me a target you can pound sand. Anyone who's read these forums long enough knows you have an agenda and it mostly involves two topics: What to use as a reference point when machining a block and water temps. on dyno pulls. You can also add in cam selection. I already know you don't like my choice there either.
Stick to bickering with the other knowledgeable engine builders and so called Olds experts but lay off the little guys like me. I can bite back just as hard.
Last edited by TripDeuces; April 12th, 2014 at 07:29 AM.
#21
Best of luck in your build.
Last edited by cutlassefi; April 12th, 2014 at 09:57 AM.
#25
The more I see, the more I think bore and sleeve and your worries are behind you. Does anyone have real world numbers for that? I mean, if you're going to have to buy 3 blocks and sonic each one to get you to where you're confident, ...?
#27
I thought I'd post this for all to see. This was done on a standard bore 455 but it applies to all blocks.
It's been mentioned many times to "sonic check" the block before proceeding in any given build. However I'll bet many don't have it done.
Here's the sonic check sheet for a 455 build I'm doing for another member on here. Although the thinnest area is not on a thrust side, I think all would agree boring this block to .060, or even .030 over could cause a problem. At that point you're potentially left with a cylinder thickness of less than .080. Imo that's totally unacceptable in most if not all cases. A thin area in virtually any part of the cylinder wall will allow it to flex more than normal and adversely effect ring seal as well as overall longevity.
Needless to say, I'm not going to use this block. Hope this helps.
Note cyl#3 especially. Thanks.
It's been mentioned many times to "sonic check" the block before proceeding in any given build. However I'll bet many don't have it done.
Here's the sonic check sheet for a 455 build I'm doing for another member on here. Although the thinnest area is not on a thrust side, I think all would agree boring this block to .060, or even .030 over could cause a problem. At that point you're potentially left with a cylinder thickness of less than .080. Imo that's totally unacceptable in most if not all cases. A thin area in virtually any part of the cylinder wall will allow it to flex more than normal and adversely effect ring seal as well as overall longevity.
Needless to say, I'm not going to use this block. Hope this helps.
Note cyl#3 especially. Thanks.
#28
Filling the block makes worlds of difference as to what is acceptable. I worry about what will be exposed. Not about what will be backed by the block filler. Within reason of course. There would still be a limit as to what I'd accept.
#29
I don't think it makes worlds of difference. You are only filling the block to the bottom of the water pump holes. Most usually the thin spots are up towards the top. The main reason for block filler is to keep the cylinders round.
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