Gen V BBC question, info needed
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Gen V BBC question, info needed

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    Senior Member jrider44's Avatar
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    Default Gen V BBC question, info needed

    I'm looking at buying a Gen V block to use in place of my mark IV. I can get a good deal on it and it has most of the machine work done on it but I am not familiar with all the differences between the two blocks(or the Gen VI). I do know about the one piece rear main and the adapter I need to run my crank. Will my 4.25 stroke crank clear without any work or do I have to clearance the block? Also the lack of the fuel pump boss on Gen V. Any helpful info would be greatly appreciated. I need a set of blower pistons and rods too, .060, 4.25 stroke, 6.385 rod.
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    Quote Originally Posted by jrider44 View Post
    I'm looking at buying a Gen V block to use in place of my mark IV. I can get a good deal on it and it has most of the machine work done on it but I am not familiar with all the differences between the two blocks(or the Gen VI). I do know about the one piece rear main and the adapter I need to run my crank. Will my 4.25 stroke crank clear without any work or do I have to clearance the block? Also the lack of the fuel pump boss on Gen V. Any helpful info would be greatly appreciated. I need a set of blower pistons and rods too, .060, 4.25 stroke, 6.385 rod.

    You will need a different oil pan and timing cover. Most of the time a 502 gen V block will take more stroke with none or minimal clearancing. Not sure about a 454.

    If you havent bought a cam buy a cam for the gen V VI
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    Quote Originally Posted by Infomaniac View Post
    You will need a different oil pan and timing cover. Most of the time a 502 gen V block will take more stroke with none or minimal clearancing. Not sure about a 454.

    If you havent bought a cam buy a cam for the gen V VI
    What's the difference in the cams Ron? Never knew there was any difference...

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    Senior Member SHAWN DAVIS's Avatar
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    Cam thrust retainer plate on the GenV

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    Quote Originally Posted by Retired Flatbottom Racer View Post
    What's the difference in the cams Ron? Never knew there was any difference...
    If you buy a cam for the late model it has a step machined into the front cam bearing journal. You can use the stock retainer plate for cam thrust.
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    Quote Originally Posted by Infomaniac View Post
    If you buy a cam for the late model it has a step machined into the front cam bearing journal. You can use the stock retainer plate for cam thrust.
    Oh ok. I have always used Mark IV cam and timing set and controlled the cam walk the old way.. Works fine for me....

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    And they don't put a fuel pump drive lobe on it. Saves weight. LOL
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    gn7
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    Quote Originally Posted by Infomaniac View Post
    You will need a different oil pan and timing cover. Most of the time a 502 gen V block will take more stroke with none or minimal clearancing. Not sure about a 454.

    If you havent bought a cam buy a cam for the gen V VI
    Quote Originally Posted by Infomaniac View Post
    If you buy a cam for the late model it has a step machined into the front cam bearing journal. You can use the stock retainer plate for cam thrust.
    Ron, I believe the cam for the Gen 5 is the same as the MK IV. the Gen 5 is not a roller block with the raised lifter bores, and does not use a cam retainer plate, although the block may be machined for one. MK IV cams work in Gen 5 blocks.

    The timing cover is also the same as a MKIV.
    you are correct in that the oil pan is different due to the one piece rear seal main cap, and the Gen 6 does not have a mechanical pump boss. ]]

    The Gen 6 has a cam retainer plate, and raised lifter bores and does use a different timing cover, although the front of the block can be tapped for the old style cover.



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    I had a gen v for many years and ran the retainer plate with late model cam..

    The bolt pattern on the timing cover is the same as a gen IV but the front seal to pan is not the same as gen IV.

    A gen IV timing cover would not fit the one piece pan.
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    Is the Gen 5 block stronger for forced induction?

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    gn7
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    Quote Originally Posted by Infomaniac View Post
    I had a gen v for many years and ran the retainer plate with late model cam..

    The bolt pattern on the timing cover is the same as a gen IV but the front seal to pan is not the same as gen IV.

    A gen IV timing cover would not fit the one piece pan.
    I an wrong. The T cover is different. Its a bastard cover that has a the "GEN" seal dimentions, and the MK bolt pattern. The GEN 6 has a totally different bolt pattern, but can be tapped to accept the MKIV/GEN 5 bolt pattern. The GEN covers also don't have the ears to accept the front oil pan bolts as well as a different seal diameter.
    Like I said, the GEN 5 comes tapped for the retainer plate, but OEM engines were flat tappet and did not use it. GEN 5s can be fitted with either GEN 5 or 6 cams, so long as you use the retainer plate with the 6 cam.
    Quote Originally Posted by Jspeeddemon View Post
    Is the Gen 5 block stronger for forced induction?
    Not really. And like Info said, its sort of a bastard child as some parts go.
    If you already have a pan and T cover for a MKIV, its hard to justify going to a GEN block unless its a siamese bore 502 block.



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    Last edited by gn7; 02-19-2013 at 09:29 PM.

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    Quote Originally Posted by Jspeeddemon View Post
    Is the Gen 5 block stronger for forced induction?
    It has an updated oiling system.
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    Quote Originally Posted by gn7 View Post
    Not really. And like Info said, its sort of a bastard child as some parts go.
    If you already have a pan and T cover for a MKIV, its hard to justify going to a GEN block unless its a siamese bore 502 block.

    Are there any advantages to the MKIV over the Siamese bore 502? maybe better distribution in cooling the cylinders with cold lake water???

  16. #14
    gn7
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    Quote Originally Posted by dnewps View Post
    Are there any advantages to the MKIV over the Siamese bore 502? maybe better distribution in cooling the cylinders with cold lake water???
    No. The GEN series are better in that they, like Info said, have better oiling.
    The siamese blocks can't cool as evenly as the small bore blocks due to the blocked pathway between cylinders. But this has nothing to do with the block being a GEN or MK. GEN blocks with 4.25" non siamese bores cool tha same as MK blocks.
    Their are no PRODUCTION MK blocks with siamese bores, so the question is kind of a moot comparison.
    Bowtie MK blocks with siamese bores don't cool any better than GEN blocks with siamese bores.



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