CR calculators
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 960
Likes: 25
From: Middlesboro KY
CR calculators
I'm aware of two calculators which are listed below. I'm trying to select the appropriate head gasket to achieve 10.5:1 CR while keeping the quench value between .030 to .040. The first listed allows me to do this while the second one puts me at 11.5:1. Not sure I want to go that high on CR. Which calculator computes most accurately? Thanks,
http://www.rbracing-rsr.com/compstaticcalc.html
http://www.pontiacstreetperformance....p/CRcalc2.html
http://www.rbracing-rsr.com/compstaticcalc.html
http://www.pontiacstreetperformance....p/CRcalc2.html
Drifting
Joined: Dec 2002
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From: Long Beach CA
Burning Brakes
Joined: Oct 2004
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From: fighter pilots make movies, bomber pilots make history
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 960
Likes: 25
From: Middlesboro KY
Gosh Scott, you've got a good memory. FTs are 5.4cc. Left side of engine has a deck clearance of .023 (in the hole). Whereas the right side has a deck clearance of .018 (in the hole). I'm looking at head gasket thicknesses of .015 and .020, respectively. Should give me a CR or 10.7:1 with a quench value of .038. Other than quench value, 10.7:1 depends on which calculator I use. What's your thoughts?
Advanced
Joined: May 2010
Posts: 81
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From: Quartzsite Az
I'm going based off of assumption:
My calculator says 11.13:1 with the following information
Bore: 4.125"
Stroke: 3.760"
Chbr cc's: 67
Gsk Bore: 4.125" (not sure what gasket bore is available, could be more)
Gsk + Deck: .018 + .020= .038"
Dome cc's= -5.4
My calculator says 11.13:1 with the following information
Bore: 4.125"
Stroke: 3.760"
Chbr cc's: 67
Gsk Bore: 4.125" (not sure what gasket bore is available, could be more)
Gsk + Deck: .018 + .020= .038"
Dome cc's= -5.4
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 960
Likes: 25
From: Middlesboro KY
Gsk Bore is 4.1
Bore is 4.030
Stroke is 3.25"
Advanced
Joined: May 2010
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From: Quartzsite Az
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Le Mans Master
Joined: Apr 2005
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From: Seattle Area WA
How do you get a +5.4 dome with flat tops, if they have valve notches cut your value should be -5.4 in which case your CR is about 9.4:1, I'm curious about how where you got that value?
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 960
Likes: 25
From: Middlesboro KY
Brand Speed Pro
Manufacturer's Part Number ZL2165F
Part Type Pistons
Product Line Speed-Pro Power Forged Pistons
Summit Racing Part Number TRW-L2165F
Bore (in) 4.000 in.
Bore (mm) 101.600mm
Piston Style Flat top, with four valve reliefs
Piston Material Forged aluminum
Compression Distance (in) 1.671 in.
Piston Head Volume (cc) +5.40cc
Wrist Pin Style Press-fit
Pin Diameter (in) 0.927 in.
Piston Ring Thickness 5/64 in. x 5/64 in. x 3/16 in.
Quantity Sold individually.
Advanced
Joined: May 2010
Posts: 81
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From: Quartzsite Az
Brumbach, with what you posted I believe your at 9.35 like Scott mentioned.. I'm really not to sure why they say +5.4cc.. I guess it's adding 5.4cc to your overall chamber volume.. It's kind of confusing.. I think of it the other way typically.. I have a set of JE's and on the job sheet (custom piston) it states 17cc dome.. So go figure.. Anyways, hope this is clear as mud..
Thread Starter
Burning Brakes
Joined: Jan 2007
Posts: 960
Likes: 25
From: Middlesboro KY
I looked up his part number and they are indeed valve reliefs..
Brumbach, with what you posted I believe your at 9.35 like Scott mentioned.. I'm really not to sure why they say +5.4cc.. I guess it's adding 5.4cc to your overall chamber volume.. It's kind of confusing.. I think of it the other way typically.. I have a set of JE's and on the job sheet (custom piston) it states 17cc dome.. So go figure.. Anyways, hope this is clear as mud..
Brumbach, with what you posted I believe your at 9.35 like Scott mentioned.. I'm really not to sure why they say +5.4cc.. I guess it's adding 5.4cc to your overall chamber volume.. It's kind of confusing.. I think of it the other way typically.. I have a set of JE's and on the job sheet (custom piston) it states 17cc dome.. So go figure.. Anyways, hope this is clear as mud..
Advanced
Joined: May 2010
Posts: 81
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From: Quartzsite Az
Oh well.. Guess you have something to work on?? If the heads are off you could always do some angle milling but that will also affect your manifold which will need to be milled also.. Just a thought!!!
Safety Car
Joined: Sep 2004
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From: St. Clair Shores MI
C2 of Year Finalist (track prepared) 2019
2017 C2 of the Year Finalist
horribly..
the L79 can bleeds off static compression, the valves are open a long long time.
my 11.86:1 L79 runs fine on 93 pump gas.....
the L79 can bleeds off static compression, the valves are open a long long time.
my 11.86:1 L79 runs fine on 93 pump gas.....
