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Original Message
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| It depends on whether you have an "A" or "C" block |
| By Dave Shoe - 11/21/2000 8:01:09 PM; IP 12.2.11.131 |
If a large "A" is rough-cast into the rear of your 428 block it's likely that .030 is the limit you want to take it. If you have a "C" rough-cast into the rear then you've got the reinforced 428 block and .060 is frequently attainable.
Invariably, a $60 sonic map will tell you how far you can take the bore and whether core-shift requires you to "offset-bore" to safely reach these numbers.
It's my semi-experienced opinion that some standard bore 428 "A" blocks will have worst-case cylinder sections as thin as .100", which means core shift is really bad and you don't want to push this block very hard. If .110" is your thinnest standard-bore reading then the block can probably be offset-bored to remove minimal material from the thin area. Core shift is common in FE blocks, so a sonic test will help you make smarter decisions. It's nice to have .130" as a thin spot in an "A" block and even better if .140" is the thinnest spot, though this latter number, if I recall correctly, is relatively uncommon unless you have a "C" block.
I wish I had some maps with me so I could more accurately dump out "nominal thickness" numbers, but this is what I inaccurately remember from the last time I studied them. As I recall, average thickness in an "A" block cylinder is maybe .180", therefore if a .120" spot is found, you will likely find a .240" thick section on the opposite side of the cylinder. Average thickness on a "C" block might be .220".
JMO,
Shoe. |
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