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#1
02-16-2005, 04:47 PM
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i have noticed i have 6x heads fitted to my 1973 formy YT block will this affect my performance as i believe these have a larger combustion chamber am i right in believing they came in different sizes if so how can i tell and would it be better to source some 4x heads ? thanks guys
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#2
02-16-2005, 04:47 PM
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i have noticed i have 6x heads fitted to my 1973 formy YT block will this affect my performance as i believe these have a larger combustion chamber am i right in believing they came in different sizes if so how can i tell and would it be better to source some 4x heads ? thanks guys
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#3
02-16-2005, 07:44 PM
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Are they -4 or -8?
Compression difference
__________________
71 Firebird Custom - Fuel Injected & Over-drived! |
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#4
02-17-2005, 01:35 AM
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 i dont know
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#5
02-17-2005, 04:30 PM
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am i right in thinking studs if so it has 8
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#6
02-17-2005, 06:28 PM
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I'm going from memory, but the -4 or -8 should be stamped on one of the lower bosses by the exhaust ports. 6x-4's are very good heads.
Mark
__________________
71 Firebird Custom - Fuel Injected & Over-drived! |
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#7
02-17-2005, 09:45 PM
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I think the 4's are 96CC and the 8's are 101cc. Either one should be better than the stock 4x heads if you have a 455. The 96cc heads should raise your compressions ratio to about 9.0 to 1 or better on a 455 which give you much better performance.
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#8
02-18-2005, 03:20 AM
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my engine is stock 400 formula 1973
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#9
03-29-2005, 06:46 PM
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THe 6x 4 heads that came on many 350's are your best bet. The also came on the 220 horse 400's in the late 70's I think 6x4 are about 92 cc and 6x8 are 98cc I may be off on the cc a little but the 6x4 are plentful and a great head for a 455 and decent for a 400
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