Big block Chevy heads
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BBC heads have a few different chambers. But usually what you'll hear is "open" or "closed" chambers. In the image below, the closed chamber heads are on top, open chamber heads below. | BBC heads have a few different chambers. But usually what you'll hear is "open" or "closed" chambers. In the image below, the closed chamber heads are on top, open chamber heads below. | ||
| − | 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). | + | 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]] | + | [[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|C/n 820, note how the exhaust valve has less shrouding than the other chambers]] | ||
| + | [[File:Bbc 702 cc.jpg|thumb|Closed chamber,c/n 702 shown]] | ||
| + | <br style="clear:both"/> | ||
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| + | ==Exhaust valve guides== | ||
| + | |||
| + | {{Note1}}The following is an excerpt from an AERA technical bulletin: | ||
| + | |||
| + | '''Exhaust Valve Guide Caution On 1965-98 GM Big Block Engines''' | ||
| + | |||
| + | 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: | ||
| + | |||
| + | 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. | ||
| + | |||
| + | 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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'''Application:'''<br> | '''Application:'''<br> | ||
Victor Reinz part numbers '''4918''' (right bank) and '''4923''' (left bank) are available for GM 7.4L (454 CID) engines. | Victor Reinz part numbers '''4918''' (right bank) and '''4923''' (left bank) are available for GM 7.4L (454 CID) engines. | ||
| + | |||
| + | ==Spark plugs== | ||
| + | During the BBC production, the spark plugs changed from gasketed to tapered seat. Some heads are almost identical, the only significant s=difference being the type of spark plug used, so be sure to inspect the head closely to be sure the right plug is used. | ||
==Torque sequence for big block aluminum heads== | ==Torque sequence for big block aluminum heads== | ||
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Use anti seize compound on all threaded aluminum bolt or sender holes, especially the spark plug threads. Only remove fasteners or senders when the head is cold. | Use anti seize compound on all threaded aluminum bolt or sender holes, especially the spark plug threads. Only remove fasteners or senders when the head is cold. | ||
| − | == | + | ==Common BBC casting numbers== |
| − | ===BBC casting | + | <table table border="1" cellpadding="2" cellspacing="0" ><tr bgcolor="#EEEFFF"> <td>'''Casting No.'''</td> <td>'''Part No.'''</td> <td>'''Application'''<br>Year CID/HP RPO</td> <td>'''Chamber'''<br> (CC)</td> <td>'''Intake'''<br>(Inches)</td> <td>'''Exhaust'''<br>(Inches)</td> </tr> <tr> <td>336781</td> <td>336780</td> <td>'74 454/270 HP</td> <td>113</td> <td>2.06</td> <td>1.72</td> </tr> <tr bgcolor="#F1F1F1"> <td>353049</td> <td>353047</td> <td>'73 454/275 HP</td> <td>113</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3999241</td> <td>3999240</td> <td>'72 454/270 HP </td> <td>105</td> <td>2.06</td> <td>1.72</td> </tr> <tr bgcolor="#F1F1F1"> <td>3993820</td> <td> </td> <td>'71 454/365 HP</td> <td>113</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3964291</td> <td>3964287</td> <td>'69 427/435 HP</td> <td>118</td> <td>2.19</td> <td>1.88</td> </tr> <tr bgcolor="#F1F1F1"> <td>3964290</td> <td> </td> <td>'69 427/390 & 400 HP; '70 454/390 HP</td> <td>106</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3946074</td> <td> </td> <td>'69 427/430 HP L88 & ZL1; '71 454 LS6</td> <td>118</td> <td>2.19</td> <td>1.88</td> </tr> <tr bgcolor="#F1F1F1"> <td>3931063</td> <td> </td> <td>'69 427/390 & 400 HP</td> <td>100</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3919842</td> <td> </td> <td>'68 427/430 & 435 HP L88 & L89; '69 427 L89</td> <td>106</td> <td>2.19</td> <td>1.72</td> </tr> <tr bgcolor="#F1F1F1"> <td>3919840</td> <td> </td> <td>Late '67-'69 427/435 HP L71</td> <td>106</td> <td>2.19</td> <td>1.72</td> </tr> <tr> <td>3917215</td> <td> </td> <td>'68 427/390 & 400 HP </td> <td>100</td> <td>2.06</td> <td>1.72</td> </tr> <tr bgcolor="#F1F1F1"> <td>3909802</td> <td> </td> <td>Late '67 427/390 & 400 HP</td> <td>100</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3904392</td> <td> </td> <td>'67 427/430 HP L88 & L89</td> <td>106</td> <td>2.19</td> <td>1.72</td> </tr> <tr bgcolor="#F1F1F1"> <td>3904391</td> <td> </td> <td>'67 427/435 HP L71</td> <td>106</td> <td>2.19</td> <td>1.72</td> </tr> <tr> <td>3094390</td> <td> </td> <td>Early '67 427/390 & 400 HP</td> <td>98</td> <td>2.06</td> <td>1.72</td> </tr> <tr bgcolor="#F1F1F1"> <td>3873858</td> <td> </td> <td>'66 427/425 HP</td> <td>108</td> <td>2.19</td> <td>1.72</td> </tr> <tr> <td>3872702</td> <td> </td> <td>'66 427/390 HP</td> <td>98</td> <td>2.06</td> <td>1.72</td> </tr> <tr bgcolor="#F1F1F1"> <td>3856208</td> <td> </td> <td>'65 396/425 HP</td> <td>108</td> <td>2.19</td> <td>1.72</td> </tr> </table><br> |
| + | |||
| + | ===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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