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BBC 454 Bore

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BBC 454 Bore

Postby bbcvelle » Sat Dec 25, 2004 7:35 pm

Has anyone bored 454 out to 4.350 .100 over and used in street and long haul drives on expressway? Is it safe to bore out a STD 454 to 505 ?
Any input.
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Postby Wolfplace » Sat Dec 25, 2004 8:43 pm

bbcvelle wrote:Has anyone bored 454 out to 4.350 .100 over and used in street and long haul drives on expressway? Is it safe to bore out a STD 454 to 505 ?
Any input.


Yes & no, it depends on the block in question.

Bored quite a few of them to .125 over (481) years ago before I even knew what Sonic testing was.
I also installed a number of sleeves :(

I would have the block sonic tested as it is pretty inexpensive

It is going to be a little difficult to "bore it to 505" though :)
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Postby bill jones » Sat Dec 25, 2004 9:08 pm

-I made a pair of pliers into a measuring gauge where I can stick a probe (390 Ford pushrod) down thru the headbolt holes or water jackets, and a corresponding probe down into the bore and then measure the wall thicknesses.
-Once you do this and start getting real numbers you find that there's not too many bores on production engine that you'd really like to open up more than .040" and then you start looking at whether or not you can get the bore centerlines accurately moved 1/2 whatever you intend to bore the block so that you can save that precious metal on the thrust or the thin sides.
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-I had a pair of BBC's that were brand new in a Reggie Fountain drug runner boat that we wanted to bore out to the max and those blocks were suprisingly thin so .060" was what I considered acceptable at the time.
-At standard 4.250" bore those blocks ranged from .215" to to .309" on the passenger side of each of the 8 bores and .222" to .286"on the drivers side.
-Cylinder #8 on both engines were .215" or .217" on the passenger side.
-Needless to say I had the bores moved nearly 1/2 the overbore to save what I could of what little precious metal there was on the thin walls.
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-The worst part of the deal is the front or rear of the bores of 3 total 454's have all been was as thin as .105" and .136" on three different cylinders (which just happened to be either rear cylinder) so if I had just went and bored those holes with no interest in saving precious metal I'd have ended up with one wall at .055" and two .086" walls.
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-So if you think you can live that then have at it.
-I saved nearly every bit of that thin wall I had to start with by offsetting the bores.
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-It takes several hours at the most to fabricate a tool, maybe an hour or so to draw it out on paper, but I wouldn't consider large over bores without a way to accurately measure the wall thicknesses myself, and then get your faith in your machinest to get the hole centerlines dialed in and moved to where you want it.
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-I have had several different people offset bore my blocks and one guy moved it about 1/4 to 1/3rd of what I wanted (on every hole) and another guy can get it within .005" of what I measure.
-I have probably had 30 blocks offset bored this manner.
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-Back in the early 80's we ran a 74 Pinto BBC 454 drag car that was bored out .125" with no attention to wall thickness and it never gave us any problem but we weren't concerned about cooling on the street.
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Postby learner » Sat Dec 25, 2004 11:22 pm

That's one reason why i prefer to use a vertical boring machine such as a berco. It uses a dial indicator to center the bores. From there offsetting the bore is easy and accurate.
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