Calculating compression...
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Calculating compression... If you had a motor with 10.1 flattops in it, and the 10.1 is the compression with a 64cc head, how much will the compression be with a 70cc or 72cc head?
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From: rochester,ny
Re: Calculating compression... huh..............the answer is 7 <img border="0" alt="[worship]" title="" src="graemlins/gr_hail.gif" /> <img border="0" alt="[judgement]" title="" src="graemlins/gr_judge.gif" />
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Re: Calculating compression... Is this a 346? Kinda hard to get 10.1:1 cr without a big head gasket and pistons that are in the hole with a 64cc head on a 346.
BUT
If you put a 72-70cc head on a combo that was 10.1:1 cr with a 64cc head it would drop the cr down to ~9.3-9.5 respectively.
John
<small>[ February 11, 2003, 05:42 PM: Message edited by: XLR8NSS ]</small>
BUT
If you put a 72-70cc head on a combo that was 10.1:1 cr with a 64cc head it would drop the cr down to ~9.3-9.5 respectively.
John
<small>[ February 11, 2003, 05:42 PM: Message edited by: XLR8NSS ]</small>
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Re: Calculating compression... The latter what? <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" />
72cc head = 9.3:1 cr on that combo. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
72cc head = 9.3:1 cr on that combo. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Re: Calculating compression... ive been told a general rule of thumb is for every 10cc a chamber is changed the compression chenges about 1 point
ie.
10:1 with 64 cc means about 9.3-9.2:1 with 72cc
ie.
10:1 with 64 cc means about 9.3-9.2:1 with 72cc
Re: Calculating compression... You really need the following info John:
- Bore
- Stoke
- Deck Height
- Gasket Thickness
- Combustion Chambers (cc)
- Valve Reliefs (cc)
Using 3.9" bore, stock stroke (3.622), stock deck height (.006), gasket thickness of .056, chamber of 70cc, and no valve reliefs, the CR comes to 9.63:1
Use this web site:
www.prestage.com/carmath/calc_compression.asp
- Bore
- Stoke
- Deck Height
- Gasket Thickness
- Combustion Chambers (cc)
- Valve Reliefs (cc)
Using 3.9" bore, stock stroke (3.622), stock deck height (.006), gasket thickness of .056, chamber of 70cc, and no valve reliefs, the CR comes to 9.63:1
Use this web site:
www.prestage.com/carmath/calc_compression.asp
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Verdad Gallardo Re: Calculating compression... You are correct Ryan....I forgot to make the deck height negative <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> Damn me! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
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Re: Calculating compression... Reckless - The only thing about your calculation is that those specs don't come out to 10.1:1 with a 64cc head. John said in his first post that the cr was 10.1:1 with a 64cc head. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
With the specs you have the cr with a 64cc head would be around ~10.6:1.
Here is another calculator that uses a few more variables. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
http://www.smokemup.com/auto_math/compression_ratio.php
John
With the specs you have the cr with a 64cc head would be around ~10.6:1.
Here is another calculator that uses a few more variables. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
http://www.smokemup.com/auto_math/compression_ratio.php
John
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Re: Calculating compression... I've been offered a motor that supposedly has JE slugs in it, and JE rates the 882 pistons at 10:1 with a 64cc head that's why I am asking. I'm not super interested in it but am kicking it around due to the low price.
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Re: Calculating compression... Do those pistons have small valve reliefs? If so that would explain how they get 10.1cr on a stock bore/stroke/deck height motor with a 64cc head. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
John
John
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Re: Calculating compression... BTW, 77cc heads(TEA has them) would get you to around ~8.8:1 cr on that shortblock. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
John
John
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From: Orange, TX
Re: Calculating compression... I get the same thing as above with my spreadsheet.... 9.45 w/70cc.... 9.25 w/72cc and 8.8 w/77cc.
It's good to see my #'s jive with other calculations.
<small>[ February 12, 2003, 06:08 PM: Message edited by: ScottyG ]</small>
It's good to see my #'s jive with other calculations.
<small>[ February 12, 2003, 06:08 PM: Message edited by: ScottyG ]</small>
Re: Calculating compression... </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by BIGBOS:
<strong> I have a stock 346 c.i. motor, I'm putting 73cc chamber 5.7L TEA S2 heads on...
Will I drop to 9.5:1 or 9.3:1? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Should yield about 9.4:1 BOS <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
<strong> I have a stock 346 c.i. motor, I'm putting 73cc chamber 5.7L TEA S2 heads on...
Will I drop to 9.5:1 or 9.3:1? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Should yield about 9.4:1 BOS <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
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From: Austin, TX
Re: Calculating compression... if you use that calculator and enter .006 and .056 you will get 9.32. I was under the impression that the .006 is negative deck height. the piston is actually out and over the deck height, effectivly making the gasket thinner within the area of the bore. did that make sense?
if i enter -.006 and .056 I get 9.56 which i think is right. When i enter the stock values (68cc) for the LS1 i get 10.11.
I think entering .006 (not negative) makes the calulator think there is addtional deck height over the piston, when there is not.
can anyone verify this?
<small>[ February 12, 2003, 12:35 PM: Message edited by: Ryan ]</small>
if i enter -.006 and .056 I get 9.56 which i think is right. When i enter the stock values (68cc) for the LS1 i get 10.11.
I think entering .006 (not negative) makes the calulator think there is addtional deck height over the piston, when there is not.
can anyone verify this?
<small>[ February 12, 2003, 12:35 PM: Message edited by: Ryan ]</small>
