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Discussion Starter · #1 ·
Considering the following information, is there a formula to calculate the approximate piston compression height to achieve a deck height of around .005" to .000"? I want to use flat tops, but there are so many pistons available with different compression heights and I don't know which ones will work for me:

454 (9.8" Deck)
4.25" crank
6.385" rods
Flat Top pistons (-3cc's) Compression Height ????
063 GM iron ovals (101cc's)
.039" Head Gasket
4.37" Head Gasket Bore
9.8+/- Final Comp. Ratio

Thanks for any help. Charles
 

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66 El Camino 57 Chevy pickup 2004 Tahoe
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unless you have the pistons custom made you're not going to be able to adjust the deck clearance very easy. Why don't you want to have the decks cut? on BBs it's often not a lot, they're closer than small blocks.
 

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Discussion Starter · #3 ·
Tom, I was assuming that there are some off-the-shelf pistons available with a compression height that would give me at a .005/.000" deck height when installed without having to do anything to the pistons or block. Maybe that's asking too much in an imperfect world.

I have nothing but a bare block and bare heads right now, nothing else. Which Pistons to get are a complete puzzle for me due to various compression heights.

Charles
 

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the height of production line blocks is too inconsistent for piston makers to accurately state what your deck clearance will be.

here's the deal, take 1/2 the stroke, add the rod length, subtract that number from the height of the block, that's your ideal compression height. .005 either way is not a big deal. measuring the height of the block takes tools the normal guys doesn't have though. it's the distance from the center of the main bearing bore to the deck. You might have a shop shop measure it for you. You might get pretty close with a 12" dial caliper, measure between the main bore and the deck, then add 1/2 the main bore diameter. Not real precise but close enough to get an idea.

If you're going to build a decent engine you'll at least want it to be parallel decked, you'll lose a few thou there anyway.
 

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Tom, I was assuming that there are some off-the-shelf pistons available with a compression height that would give me at a .005/.000" deck height when installed without having to do anything to the pistons or block. Maybe that's asking too much in an imperfect world.

I have nothing but a bare block and bare heads right now, nothing else. Which Pistons to get are a complete puzzle for me due to various compression heights.

Charles
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As Tom said, most stock blocks vary, some by a bunch.

There are some on here that advocate not decking a block which I disagree with for a performance engine.
I do not build a performance engine unless I square the deck

I did three blocks recently that are a great example
Two were 400 small blocks & one was a BB
The nominal deck height for a SB is 9.025 & for a BB 9.800 for the standard deck
The two 400's
Worst one was 9.011 on one corner, 9.031 on the opposite end of the other side.
Sweeping this block from intake to exhaust was over .010 from a 45° using the cam as a datum.
The other was better, 9.019-9.027
The 454 was 9.797 to 9.815

Now the question becomes,,,, which hole, side or corner do you want to use as your deck height :D

This is why I don't build performance engines without decking the block square from the mains to whatever piston height I require.
Usually zero to .005 down.
The only exception would be a numbers matching block for a restoration.

This is why almost all common combinations have a c/h of pistons that come out less then the nominal deck of the block.
It is a hell of a lot easier to adjust the block than to adjust the pistons,,
 

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Charles, your combo is almost identical to mine, except for the bore size....Im at 4.350...Im using SRP pistons, but I dont see a flat top listed for your 4.310 bore...Im almost postive they have one available though, it's a very common application. Here is a link for Probe pistons, they have one listed down near the bottom.
http://www.rpmmachine.com/probe-srs-chevy-454-ft.shtml

The head cc's in the chart listed is wrong, as you will see. But the c/r you specify in your original question is about right. Im at just about 10/1, 100cc head and .005 deck.
 

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Discussion Starter · #8 ·
I have been enlightened. I can now go forth and spread the wisdom!

GRN69CHV, will the .020 deck cut also require cutting the intake surface slightly or is it negligible?

Tom, thanks for the math formula, it verifies the 1.27 c/h that GRN69CHV quoted.

Wolfplace, great "block 101" basic rebuild info. My mother's maiden name was also "Lewis", any of your ancestry linked to mid/eastern North Carolina? That name, by the way, tracks back to Sir Francis Drake (remember your history?).

Johnny O, the Probe piston looks like it may work. I hadn't looked at that brand before.

Charles
 

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I have been enlightened. I can now go forth and spread the wisdom!

GRN69CHV, will the .020 deck cut also require cutting the intake surface slightly or is it negligible?

Tom, thanks for the math formula, it verifies the 1.27 c/h that GRN69CHV quoted.

Wolfplace, great "block 101" basic rebuild info. My mother's maiden name was also "Lewis", any of your ancestry linked to mid/eastern North Carolina? That name, by the way, tracks back to Sir Francis Drake (remember your history?).

Johnny O, the Probe piston looks like it may work. I hadn't looked at that brand before.

Charles
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Cutting the block to 9.780 has never posed an issue with intake fitment for me unless something was done to the heads.
I cut almost all Rats to this dimension as a matter of course.
SRP has flat tops in 30, 60, 70 & 100 & I like them better because of the pin oiling unless Probe has changed theirs.
SRP is 142980 for .060

Don't have a clue where most of my relatives are, I think they disowned me years ago,,, :D
History,,, crap man the only reason I got a diploma from High School is they needed to solve the delinquency problems,,,, :D
 

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I was carrying the torch up in Oregon.....

They found some reason I couldn't go to graduation, so I spent that evening pi$$ed off, roasting the tires off my car.
 

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I was carrying the torch up in Oregon.....

They found some reason I couldn't go to graduation, so I spent that evening pi$$ed off, roasting the tires off my car.
So Tom, share with us! Im sure you know what the reason was.

Did you almost run down your principal right in front of the high school while borrowing your friend's car, and drinking beer while skipping school? I spent two weeks on suspension for that one. But I did get to go to graduation!:thumbsup:


OK, back to the piston issue!
 
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