head block combo
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head block combo

  1. #1
    Member bubbledeck55's Avatar
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    Default head block combo

    have a 78- 90 gm 15 454 block with 66-67 396 heads (hydraulic)trying to figure out why this combination ? all help is apreciated thanks was told they went .60 over also but have not broke out the micrometer to check... any ideas?

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    21 Daytona Outlaw's Avatar
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    Default

    get the casting #'s off the block and heads, then you can tell what you have
    #55

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    Member bubbledeck55's Avatar
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    Quote Originally Posted by Outlaw View Post
    get the casting #'s off the block and heads, then you can tell what you have
    casting numbers = 396 heads and 454 block ???

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    Default Your questio?

    Quote Originally Posted by bubbledeck55 View Post
    casting numbers = 396 heads and 454 block ???
    What are you asking? Apparently you have a MK IV 454 block, with 396 heads... The idea that they are 396 heads, based on the casting #s is only a small part of the "big picture"... All the MK IV series heads and blocks are pretty much interchangeable. Some of the good heads came from the early versions of the MK IV series.. The real questions should be, bore and stroke, type of pistons etc etc... The 454 and 427 shared the same stock bore size, 4.250, and the difference was the stroke, 3.760 vs 4.000... It should be noted that the 396 shared the same stroke as the 427, just a smaller bore at 4.096 if memory serves me correctly.. There is a vast amount of combinations that can be built out of the MK IV parts and pieces, and the actual casting numbers don't reflect what is inside as far as cubic inches or compression ratio. The head #s will tell you what the original chamber size was, but that can be changed. Some stockers had flat top pistons with small chambers, and some had domed pistons and larger chambers... So, what are your questions?...It should be noted, no one can tell you what is inside, by looking at the outside, or the casting numbers...

    Ray
    LOUD BOATS SAVE LIVES

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    Member bubbledeck55's Avatar
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    Quote Originally Posted by Moneypit View Post
    What are you asking? Apparently you have a MK IV 454 block, with 396 heads... The idea that they are 396 heads, based on the casting #s is only a small part of the "big picture"... All the MK IV series heads and blocks are pretty much interchangeable. Some of the good heads came from the early versions of the MK IV series.. The real questions should be, bore and stroke, type of pistons etc etc... The 454 and 427 shared the same stock bore size, 4.250, and the difference was the stroke, 3.760 vs 4.000... It should be noted that the 396 shared the same stroke as the 427, just a smaller bore at 4.096 if memory serves me correctly.. There is a vast amount of combinations that can be built out of the MK IV parts and pieces, and the actual casting numbers don't reflect what is inside as far as cubic inches or compression ratio. The head #s will tell you what the original chamber size was, but that can be changed. Some stockers had flat top pistons with small chambers, and some had domed pistons and larger chambers... So, what are your questions?...It should be noted, no one can tell you what is inside, by looking at the outside, or the casting numbers...

    Ray
    i understand i can 't tell whats in side without pulling it.. and thanks for the bore and stroke specs those will come in handy.. my question was why do so much work to 396 heads to make them work with a larger block maybe higher compression ? ? it just seemed odd to me and i am a newbie , but all appreciated.

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    Default 454 = smog after a certain year

    Quote Originally Posted by bubbledeck55 View Post
    i understand i can 't tell whats in side without pulling it.. and thanks for the bore and stroke specs those will come in handy.. my question was why do so much work to 396 heads to make them work with a larger block maybe higher compression ? ? it just seemed odd to me and i am a newbie , but all appreciated.
    Some 396 heads were also used on 427 lo po engines. It is not so much the "size" of the block, as much as it is the pistons used and the end resulting compression ratios. The later model 454 heads are referred to as "peanut port" and not really considered a "performance" head. Based on that, a 454 can be helped with some earlier heads and intake manifolds... In this day and age, there are a lot of "aftermarket" head choices that will really wake up the larger displacement engines, but the head/piston combination has to be the deciding factor...
    Ray
    LOUD BOATS SAVE LIVES

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