Editing Big block Chevy heads

==Chambers== 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). 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 semi-closed chamber]] [[File:Bbc 820 sc.jpg|thumb|left|350px|c/n 820]] [[File:Bbc 702 cc.jpg|thumb|c/n 702]] <br style="clear:both"/> ==BBC L29 Vortec heads== [[File:ChevyBigBlockL-29vortec chamb.jpg]] [[File:454 vortec head.jpg]] ==Mark IV cylinder heads on later Mark V block== There are gaskets made specifically for this swap. Use other gaskets at you're own risk- these are what you want (from a V/R press release, '''presumably prior to the Gen 6 engine release'''): '''General Motors 7.4L Head Gasket Issue:'''<br> General Motors (GM) 7.4L (454 CID) engines use two types of engine blocks: the Mark IV and Mark V. The Mark IV is found on 7.4L engines in model years from 1965 to 1990, and the Mark V is found on 7.4L engines in model years from 1991 and newer. Often, installers will attempt to adapt a Mark IV cylinder head for a Mark V block. This conversion can be made if attention is paid to the coolant circulation. Mark IV and Mark V have different coolant flows and were originally designed for different head gaskets. If the conversion is not performed correctly, the engine will overheat, causing premature engine wear and damage. '''Resolution:'''<br> Victor Reinz has designed two Nitroseal® head gaskets to specifically allow for this conversion. The installation requires Victor Reinz part number 4918 be installed on the right cylinder bank to maintain proper coolant circulation, and part number 4923 to be installed on the left cylinder bank for the correct coolant flow. '''Application:'''<br> 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== [[File:Bbc head bolt tightening sequence.jpg]] ===Special considerations=== Aluminum heads require parallel ground hardened steel washers under the bolt head or nut to prevent galling the aluminum seat. Some or all bolts/studs are often a different length than the bolts used on the stock cast iron head. If aftermarket hardware is used, follow the manufacturer's instructions for lubrication and torque specs. Otherwise, tighten the hardware in at least three steps. New hardware should have the threads burnished before final torque is applied (see manufacturer's instructions). 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== <table table border="1" cellpadding="2" cellspacing="0" ><tr bgcolor="#FFF8DC" > <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> <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> <td>3993820</td> <td>&nbsp;</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> <td>3964290</td> <td>&nbsp;</td> <td>'69 427/390 &amp; 400 HP; '70 454/390 HP</td> <td>106</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3946074</td> <td>&nbsp;</td> <td>'69 427/430 HP L88 &amp; ZL1; '71 454 LS6</td> <td>118</td> <td>2.19</td> <td>1.88</td> </tr> <tr> <td>3931063</td> <td>&nbsp;</td> <td>'69 427/390 &amp; 400 HP</td> <td>100</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3919842</td> <td>&nbsp;</td> <td>'68 427/430 &amp; 435 HP L88 &amp; L89; '69 427 L89</td> <td>106</td> <td>2.19</td> <td>1.72</td> </tr> <tr> <td>3919840</td> <td>&nbsp;</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>&nbsp;</td> <td>'68 427/390 &amp; 400 HP </td> <td>100</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3909802</td> <td>&nbsp;</td> <td>Late '67 427/390 &amp; 400 HP</td> <td>100</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3904392</td> <td>&nbsp;</td> <td>'67 427/430 HP L88 &amp; L89</td> <td>106</td> <td>2.19</td> <td>1.72</td> </tr> <tr> <td>3904391</td> <td>&nbsp;</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>&nbsp;</td> <td>Early '67 427/390 &amp; 400 HP</td> <td>98</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3873858</td> <td>&nbsp;</td> <td>'66 427/425 HP</td> <td>108</td> <td>2.19</td> <td>1.72</td> </tr> <tr> <td>3872702</td> <td>&nbsp;</td> <td>'66 427/390 HP</td> <td>98</td> <td>2.06</td> <td>1.72</td> </tr> <tr> <td>3856208</td> <td>&nbsp;</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://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 *{{Note1}} The Mortec site is no longer available. BBC Mortec info is listed [[Identifying Chevy engines#Mortec_BBC_block_casting_numbers|'''here''']]. [[Category:GM]] [[Category:Engine]] [[Category:Cylinder head]] [[Category:Undeveloped articles]] [[Category:Undeveloped Engine articles]] [[Category:Undeveloped Cylinder head articles]]

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