Max bore on 5.3 iron block?
Not sure but I've said this in countless other posts. You have to sonic check the block before you bore a block. There is core shift in the 4.8/5.3 blocks. While many are acceptable to bore to 3.905 or even 3.908; some aren't even doable to 3.898. Attached is the printout from my machine shop when they sonic checked a 5.3 block I was planning to bore to 5.7.
In short to go from a 5.3 bore to a 5.7 you have to take .118 total or .059 out of each side of the bore. In the case of the block I was considering would have left .107 ish on the thrust side of the bore on the number 8 cylinder. It is obvious there is quite a bit of core shift in this particular block. My machine shop recommended staying .150+ on the thrust side of the bores for a 450ish hp motor. If you go to0 thin cylinder walls will deform, crack, and so on.
In short to go from a 5.3 bore to a 5.7 you have to take .118 total or .059 out of each side of the bore. In the case of the block I was considering would have left .107 ish on the thrust side of the bore on the number 8 cylinder. It is obvious there is quite a bit of core shift in this particular block. My machine shop recommended staying .150+ on the thrust side of the bores for a 450ish hp motor. If you go to0 thin cylinder walls will deform, crack, and so on.
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Joined: Oct 2016
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From: PDX-OR-USA
My engine machinist won't cut without sonic checking the block and its included in the labor. If his boring machine breaks through he risks breaking a expensive bit of tooling..
I was there one evening he was cutting a brand new $25K Sprint block,, hit air long before he hit the spec'd max bore. HAd a casting fault.. Which the vendor covered..
Another thing to consider is the expected duty cycle of the engine, the walls may be strong enough , but go too thin and you'll shed massive heat in to the cooling system.
Which is OK if you planned on a 2x jump in radiator core...
I was there one evening he was cutting a brand new $25K Sprint block,, hit air long before he hit the spec'd max bore. HAd a casting fault.. Which the vendor covered..
Another thing to consider is the expected duty cycle of the engine, the walls may be strong enough , but go too thin and you'll shed massive heat in to the cooling system.
Which is OK if you planned on a 2x jump in radiator core...
My engine machinist won't cut without sonic checking the block and its included in the labor. If his boring machine breaks through he risks breaking a expensive bit of tooling..
I was there one evening he was cutting a brand new $25K Sprint block,, hit air long before he hit the spec'd max bore. HAd a casting fault.. Which the vendor covered..
Another thing to consider is the expected duty cycle of the engine, the walls may be strong enough , but go too thin and you'll shed massive heat in to the cooling system.
Which is OK if you planned on a 2x jump in radiator core...
I was there one evening he was cutting a brand new $25K Sprint block,, hit air long before he hit the spec'd max bore. HAd a casting fault.. Which the vendor covered..
Another thing to consider is the expected duty cycle of the engine, the walls may be strong enough , but go too thin and you'll shed massive heat in to the cooling system.
Which is OK if you planned on a 2x jump in radiator core...
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Not sure but I've said this in countless other posts. You have to sonic check the block before you bore a block. There is core shift in the 4.8/5.3 blocks. While many are acceptable to bore to 3.905 or even 3.908; some aren't even doable to 3.898. Attached is the printout from my machine shop when they sonic checked a 5.3 block I was planning to bore to 5.7.
In short to go from a 5.3 bore to a 5.7 you have to take .118 total or .059 out of each side of the bore. In the case of the block I was considering would have left .107 ish on the thrust side of the bore on the number 8 cylinder. It is obvious there is quite a bit of core shift in this particular block. My machine shop recommended staying .150+ on the thrust side of the bores for a 450ish hp motor. If you go to0 thin cylinder walls will deform, crack, and so on.
In short to go from a 5.3 bore to a 5.7 you have to take .118 total or .059 out of each side of the bore. In the case of the block I was considering would have left .107 ish on the thrust side of the bore on the number 8 cylinder. It is obvious there is quite a bit of core shift in this particular block. My machine shop recommended staying .150+ on the thrust side of the bores for a 450ish hp motor. If you go to0 thin cylinder walls will deform, crack, and so on.
TECH Senior Member
Joined: Jun 2016
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Likes: 3,615
From: Central Cal.
This was over 11 years old. I just said not to expect an answer as those involved are long gone. Besides, we've gotten past it a bunch of posts back.
Teching In
Joined: Aug 2020
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4.8 5.3 6.0 casting some blocks had the 4.8 5.3 an 6.0 casting on them an where cast for all three.Rare but do exsist so question is how far to bore this one? engines master chanenge seen a 6.0 bored to 4.1 an stroked 4.
Last edited by selinkcimleh; Oct 24, 2021 at 12:04 AM. Reason: adding content
TECH Senior Member
Joined: Jun 2016
Posts: 22,290
Likes: 3,615
From: Central Cal.
Go back and read thru the thread, all of it. It has been said here and elsewhere to SONIC CHECK THE CYLINDER BORES. Nobody will give you an answer that can only be found by doing this.
Ive heard this said, but in 20 years dealing with them daily I have never seen evidence of this!
