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  #1  
Old 05-21-2009, 11:13 AM
bbfguy1 bbfguy1 is offline
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Default 460 Compression Ratio

Would anyone know the approximate compression of a 460 using a replacement 460 pistons (1973-1979) with a set of DOVE heads? The engine now has D3VE heads and is probably in the range of 7.5:1--8.0:1 compression. I figure losing almost 20cc in the combustion chamber should maybe bump compression into the 9.0:1+ range. Any thoughts?
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Old 05-21-2009, 11:22 AM
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Rebuilder pistons with the 22 cc "bathtub" dish, a zero deck [10.295-10.300"] and the D0VE-C heads 75-77 cc should yield about 9.7-9.8 to 1 C/R
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Old 05-21-2009, 01:32 PM
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Quote:
Originally Posted by RJP View Post
Rebuilder pistons with the 22 cc "bathtub" dish, a zero deck [10.295-10.300"] and the D0VE-C heads 75-77 cc should yield about 9.7-9.8 to 1 C/R

That is the key !!! 22 cc dish pistons at ZERO deck.

The typical builder piston has a 1.752" compression height. These pistons would require a deck height of 10.282". In an uncut early block that would net .018" below deck. Darned near .040" below deck in a late 10.322" deck height block.

My calc says:
9.91 to 1 at 0 deck with a 72 cc chamber
9.66 to 1 at 0 deck with 75 cc chamber
9.5 to 1 at 0 deck with a 77 cc chamber
9.15 to 1 at .018" below deck on early block
8.8 to 1 at .040 below deck in a later block.

We have had to deck the later blocks some .035" or a tick more to get 0 deck with the short compression height builder and sealed power pistons.

I have noted early 460's that were unopened and they are typically .010" below deck and a small dish. The later engines were .030" or better with a much larger piston dish OEM.

When I started checking piston compression heights, dish volumes and such I was shocked at the miserable oem c/r in the later engines.

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Old 07-13-2009, 11:03 PM
swamperspecial swamperspecial is offline
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so how do you know what the dish of the pistons are if it is given in inches. For example, summit sells a piston with .240 oblong recess deep. is this a 22cc dish?
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Old 07-14-2009, 11:22 AM
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Quote:
Originally Posted by swamperspecial View Post
so how do you know what the dish of the pistons are if it is given in inches. For example, summit sells a piston with .240 oblong recess deep. is this a 22cc dish?
Sounds like it. Can you link to a pic of what you are referring to???


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Old 07-14-2009, 11:25 AM
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My philosophy has been: if "they" won't give you the REAL numbers on the product they are trying to sell to you...I'm not interested in buying it, no matter how "good" the deal is.
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Old 07-14-2009, 03:18 PM
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Quote:
Originally Posted by The Mad Porter View Post
Sounds like it. Can you link to a pic of what you are referring to???


I am assuming they are:

http://www.summitracing.com/parts/STL-H418P/

Now this got me to wondering about my combo again.

With stock chamber size D3's and stock deck height (D1ve block)

http://www.summitracing.com/parts/UEM-KB137-STD/

Would those get me to 10 to 1 c/r or so? Not my final piston choice or source, just wonder.
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Old 07-14-2009, 05:34 PM
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Quote:
Originally Posted by OldRedFord View Post
I am assuming they are:

http://www.summitracing.com/parts/STL-H418P/

Now this got me to wondering about my combo again.

With stock chamber size D3's and stock deck height (D1ve block)

http://www.summitracing.com/parts/UEM-KB137-STD/

Would those get me to 10 to 1 c/r or so? Not my final piston choice or source, just wonder.
Your cam choice and intended use are the criteria used to determine appropriate c/r for the application. Which fuel you wish to use is of course a factor also. Do the above first before choosing a piston combo and an arbitrary static c/r figure.

The answer to your question. 22 cc dish at 0 deck with large chamber d3's wil be close to 10 to 1.


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Old 07-14-2009, 05:44 PM
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Quote:
Originally Posted by The Mad Porter View Post
Your cam choice and intended use are the criteria used to determine appropriate c/r for the application. Which fuel you wish to use is of course a factor also. Do the above first before choosing a piston combo and an arbitrary static c/r figure.

The answer to your question. 22 cc dish at 0 deck with large chamber d3's wil be close to 10 to 1.


Cam...Crane Cam duration 288/292 lift 522/530. This is the engine for my F100. Street/strip vehicle. Cam card lists 9.5-11.0 c/r. Pump gas would be nice.
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Old 07-14-2009, 06:12 PM
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Quote:
Originally Posted by OldRedFord View Post
Cam...Crane Cam duration 288/292 lift 522/530. This is the engine for my F100. Street/strip vehicle. Cam card lists 9.5-11.0 c/r. Pump gas would be nice.
Iron heads / pump premium...

10 to 1 is ok with tight quench at 466 inches.


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Old 07-14-2009, 06:35 PM
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So what would compression be on a D1 block with a set of SRP flat tops be at zero deck with a set of D3's that have been shaved .030? I was figuring around 9.5 or 10-1, but if a 22cc dish is there, would this get me closer to 11-1?
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Old 07-14-2009, 06:46 PM
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Quote:
Originally Posted by kjett View Post
So what would compression be on a D1 block with a set of SRP flat tops be at zero deck with a set of D3's that have been shaved .030? I was figuring around 9.5 or 10-1, but if a 22cc dish is there, would this get me closer to 11-1?
With 90cc chambers, you would have around 10.2 to 1.



Dave
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Old 07-14-2009, 06:53 PM
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so from a 22cc dish to a flat top on a zero deck block with D3's only gains .2 in compression? Seems almost a waste of my time to put them in, I figured it would be better than that.
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Old 07-14-2009, 08:53 PM
swamperspecial swamperspecial is offline
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so, what compression ratio would those pistons create with a set of dove heads?
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Old 07-14-2009, 09:01 PM
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They are supposedly 11:1 on 72cc heads, so figure from there.
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