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Running a two piece rear main seal crank in a 1 piece rear main seal block

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Old 01-28-2014, 10:04 PM
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Car: 1991 z28
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Running a two piece rear main seal crank in a 1 piece rear main seal block

The tile pretty much says it, what all is required to convert to a two piece rear main seal crank from 1 piece?

My understanding is that I will have to:

Get a seal converter/assembly (bolt on, no machining required?)

Get a neutral balanced flywheel/flex-plate to replace the one piece one I currently have.

And thats it? That seems too easy...
Old 01-29-2014, 08:36 AM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

Why would you want to downgrade to the two piece main seal?
Old 01-29-2014, 10:06 AM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

most high end cranks are designed for a 2 piece, so to run the crank I want I need to

It also lets you run a neutral balance flywheel
Old 01-29-2014, 03:51 PM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

Originally Posted by sailtexas186548
My understanding is that I will have to:

Get a seal converter/assembly (bolt on, no machining required?).
Check with the maker ;
some adapters will take the 1 pce pan , some require a 2 pce pan
Old 01-29-2014, 04:46 PM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

ok good to know
Old 01-29-2014, 06:17 PM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

The adapter is in the center:

Old 01-29-2014, 09:24 PM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

Originally Posted by sailtexas186548
The tile pretty much says it, what all is required to convert to a two piece rear main seal crank from 1 piece?

My understanding is that I will have to:

Get a seal converter/assembly (bolt on, no machining required?)

Get a neutral balanced flywheel/flex-plate to replace the one piece one I currently have.

And thats it? That seems too easy...
I have used a lot of the later one piece rear seal blocks and used a 2 piece rear seal crank.

As mentioned you can get the rear seal adaptor for either for either the early pan or the late pan, I prefer the late pan as you can use the one piece oil pan gasket from GM = no leaks.

Also you will need an alignment mandrel to locate the seal adaptor.

Old 04-08-2022, 12:17 PM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

Originally Posted by HINKSON AUTO
I have used a lot of the later one piece rear seal blocks and used a 2 piece rear seal crank.

As mentioned you can get the rear seal adaptor for either for either the early pan or the late pan, I prefer the late pan as you can use the one piece oil pan gasket from GM = no leaks.

Also you will need an alignment mandrel to locate the seal adaptor.

so im contemplating putting my L.J. 68 steel 327 crank in a 1 piece block to get the added benefits of roller cams and what not. In your opinion, would i be better off doing a bit of work to say a late 70s 4 bolt to accept the spider and lifter holders ? Also, where did you get that shmansy looking adapter contraptor in the picture.
a slightly confused mind wants to know. 😁
Old 04-08-2022, 08:54 PM
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Re: Running a two piece rear main seal crank in a 1 piece rear main seal block

You want the later 1-piece rear seal block because the machining is much more accurate than any 70's block.
Not that a 70's block can't be corrected by a very competent machine shop, but you will pay dearly for that.
The better choice then is a DART block.
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