Big block Chevy heads
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There are also "semi-closed" chamber heads like the c/n 215 heads. They are shaped more like an open chamber head, but with less volume. These heads are a decent choice for a production head especially on a smaller displacement engine (up to 454 cid). Casting number 820 heads are similar to the 215 semi-closed head, but with less quench pad area. | There are also "semi-closed" chamber heads like the c/n 215 heads. They are shaped more like an open chamber head, but with less volume. These heads are a decent choice for a production head especially on a smaller displacement engine (up to 454 cid). Casting number 820 heads are similar to the 215 semi-closed head, but with less quench pad area. | ||
| − | [[File:Closed vs open chamber bbc.jpg|thumb|left|300px|Closed chamber top, open chamber bottom]][[File:Semi-closed.jpg|thumb|350px|c/n 215 | + | [[File:Closed vs open chamber bbc.jpg|thumb|left|300px|Closed chamber top, open chamber bottom]][[File:Semi-closed.jpg|thumb|350px|Semi-closed chamber, c/n 215 shown]] |
| − | [[File:Bbc 820 sc.jpg|thumb|left|350px| | + | [[File:Bbc 820 sc.jpg|thumb|left|350px|C/n 820, note how the exhaust valve has less shrouding than the other chambers]] |
| − | [[File:Bbc 702 cc.jpg|thumb|c/n 702]] | + | [[File:Bbc 702 cc.jpg|thumb|Closed chamber,c/n 702 shown]] |
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| + | ==Exhaust valve guides== | ||
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| + | {{Note1}}The following is an excerpt from an AERA technical bulletin: | ||
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| + | '''Exhaust Valve Guide Caution On 1965-98 GM Big Block Engines''' | ||
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| + | These engines' valve guides were not intended as a replacement item from GM. | ||
| + | The guides were located into the head castings after the head was cast and | ||
| + | the exhaust guide is "water cooled". | ||
| + | The water-cooled guide also has two different size press fit diameters. Adding additional confusion to the matter, they also switched the location of the larger diameter sometime in 1985. | ||
| + | |||
| + | To determine which outside diameter guide you have and which direction to | ||
| + | remove an exhaust valve guide, the following procedure is suggested: | ||
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| + | Drive the guide no more than 0.250" (6.35 mm) toward the valve spring side of | ||
| + | the head and stop. Then, measure the newly exposed area of the guide | ||
| + | OD next to the spring pad. | ||
| + | |||
| + | If the measurement is 0.620" it is the first style guide. To remove this | ||
| + | style guide, continue driving it toward the valve spring side of the head. | ||
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| + | If the measurement is 0.616" , it is the second style guide. To remove | ||
| + | this style guide, you must drive it the opposite direction toward the combustion | ||
| + | chamber side of the head. | ||
==BBC L29 Vortec heads== | ==BBC L29 Vortec heads== | ||
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===BBC casting number resources=== | ===BBC casting number resources=== | ||
| + | *[http://www.mortec.com/bbc.htm Big Block Chevy V-8 Casting Numbers] by Mortec | ||
*[http://outintheshop.com/faq/casting/castings2.html Chevy BB casting number "go-to" site] from outintheshop.com | *[http://outintheshop.com/faq/casting/castings2.html Chevy BB casting number "go-to" site] from outintheshop.com | ||
*[http://www.nastyz28.com/bbcmenu.php Big Block Chevy Engine Parts Identification] from nastyz28.com | *[http://www.nastyz28.com/bbcmenu.php Big Block Chevy Engine Parts Identification] from nastyz28.com | ||
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[[Category:GM]] | [[Category:GM]] | ||
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