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 Blocks / Cranks/ Rods and Pistons
 decking a block
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dannygote
Tribal Scout

USA
1 Posts

Posted - 09 Mar 2020 :  2:19:56 PM  Show Profile  Reply with Quote
NOT SURE IF THE FIRST TIME I TRYED TO POST WENT THROUGH SO HERE IT GO'S AGAIN ==== hi ..I haven't been on in a while but I have ?? for some one who knows how much to deck the block to get 0 deck height on a 40 over 428 ..the pistons I am buying have a 1.5938 pin height .. I have done the math { the way I understand it } .0312 on the deck height is what I came up with but I need to know how much to deck the block is it .0312 ? are these figures correct ?? I really am trying to keep from possibly making a costly mistake

Danny Williamson

Steve C.
Chief PONTIAC

2127 Posts

Posted - 09 Mar 2020 :  3:03:36 PM  Show Profile  Reply with Quote
It is often necessary to remove some material from the block just to "square up" the cylinder heads. The deck of the block must be perpendicular to the crankshaft centerline. In a V-8, the decks on both sides of the block are at 90-degree angles to each other. A block should also be decked to ensure a good, flat surface so that you can achieve a good gasket seal. It is not always a set amount.
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Corncob2061
Crazy Horse

USA
645 Posts

Posted - 09 Mar 2020 :  6:36:13 PM  Show Profile  Reply with Quote
This varies for each block... The measured height number is also too specific of a number. No one can machine something to the ten thousandths of an inch (.0001). One thousandths of an inch is as close as most machine shop equipment come (.001 +\-.0005). Assuming 10.24 deck height and 1.594 compression height, 6.625 rods and 2 inch stroke it takes .020 cut to zero deck. Most Pontiac deck heights run between 10.23-10.25.

Edited by - Corncob2061 on 09 Mar 2020 6:37:13 PM
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Steve C.
Chief PONTIAC

2127 Posts

Posted - 09 Mar 2020 :  6:45:23 PM  Show Profile  Reply with Quote
Dick Duclow from the old Indian Adventures stated his factory blueprints on hand suggested 10.2437". However I've seen it stated from 10.225" to 10.235", but more often than not 10.230" is used.

That said, it was also stated the blueprint in question would specify the minimum height allowed by the casting house with the ability by Pontiac to machine to the 10.230" dimension prior to assembly. If it was less than that the QC inspector would reject the block castings.

I had one build where it ended up at about 10.215" to get it square.

Edited by - Steve C. on 09 Mar 2020 6:48:39 PM
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