Help with Quench calculations!!!
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12 Second Club
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From: Cheyenne, Wy
Help with Quench calculations!!! Ok, so I was doing some research on my Static CR and Dynamic CR and all that jazz because I am getting excited about getting my car back, and wanted to just toy around, and I couldn't remember the numbers. While doing this, I came across something regarding my quench calculations that is kindof worrying me and I wanted to get some opinions...
So I know the calculation to determine quench is gasket thickness minus the piston out of hole...
I started trying to calculate this, and my final calculation is coming out to my quench being something like .010!!! Last I checked, you don't want to go below .035, right??!!
I am tired and suck at math so I could be wrong, so I wanted to throw some numbers out here for you all, and see if someone can either correct me, or verify....I am just going to throw out a fucktom of stats for you all so that you can check multiple things if needed, so, here is what I know:
Bore: 4.030
Block Deck: 9.010
Stroke: 3.750
Rod Length: 6.0
Gasket Thickness: .026
Head Chambers: 60cc
Piston Compression Height: 1.125
Pistons: Flat Top -5cc
Compression Ratio: 11.77:1
Static CR: Somewhere between 7.5:1, and 8.8:1???
Intake at BDC: 72*
Adv Duration at .006: 290/292
Lobe Lift: .370/.370
LSA: 111
ICL: 107
Rocker Ratio: 1.6
If I left anything out that needs to be known, ask and I will try and find it! Let me know what you all can come up with! I hope I just suck at math haha.
So I know the calculation to determine quench is gasket thickness minus the piston out of hole...
I started trying to calculate this, and my final calculation is coming out to my quench being something like .010!!! Last I checked, you don't want to go below .035, right??!!
I am tired and suck at math so I could be wrong, so I wanted to throw some numbers out here for you all, and see if someone can either correct me, or verify....I am just going to throw out a fucktom of stats for you all so that you can check multiple things if needed, so, here is what I know:
Bore: 4.030
Block Deck: 9.010
Stroke: 3.750
Rod Length: 6.0
Gasket Thickness: .026
Head Chambers: 60cc
Piston Compression Height: 1.125
Pistons: Flat Top -5cc
Compression Ratio: 11.77:1
Static CR: Somewhere between 7.5:1, and 8.8:1???
Intake at BDC: 72*
Adv Duration at .006: 290/292
Lobe Lift: .370/.370
LSA: 111
ICL: 107
Rocker Ratio: 1.6
If I left anything out that needs to be known, ask and I will try and find it! Let me know what you all can come up with! I hope I just suck at math haha.
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Joined: Dec 2010
Posts: 2,610
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From: Maricopa, AZ
Your quench is 0.036" calculated with the specs you gave us.
1.875" (3.75" stroke divided by 2)
+ 6" (rod length)
+ 1.125" (compression height)
=9.000"
9.010" (deck height)
-9.000"
=0.010" (Piston to deck clearance- in the hole)
0.026" (Head Gasket Thickness)
+0.010" (Piston to Deck Clearance)
=0.036" (Total Quench)
When you do your PTV check also check actual quench. Mine should've been .049" quench but I actually measured 0.043" quench when I did my PTV clearance check.
I do believe the target is .035-.040" quench. But it's not set in stone. Some run em tighter, some looser. It depends on expected RPM's the engine will see, forged or not rotating assembly, piston to wall clearance, and weight of reciprocating mass. That and how long they expect to go between rebuilds. The generally excepted clearance for forged street applications is .035-.040" and keeping it under 7Krpms, but again that's a general "rule of thumb" and can vary depending on your particular build. I do know that once a running quench of .060" is exceeded detonation and knock becomes a very real problem. Mind you, static quench (what is calculated here) is greater than running quench. Some race engine builders get the running quench tight enough to make the pistons kiss the heads at high rpms. But those engines don't last long at all.
Here's a good read on it.
Here's another for the technically interested. Very good read!
Also I got 11.7:1 SCR and 8.8:1 DCR from the info you provided.
Should be a good runner for sure.
1.875" (3.75" stroke divided by 2)
+ 6" (rod length)
+ 1.125" (compression height)
=9.000"
9.010" (deck height)
-9.000"
=0.010" (Piston to deck clearance- in the hole)
0.026" (Head Gasket Thickness)
+0.010" (Piston to Deck Clearance)
=0.036" (Total Quench)
When you do your PTV check also check actual quench. Mine should've been .049" quench but I actually measured 0.043" quench when I did my PTV clearance check.
I do believe the target is .035-.040" quench. But it's not set in stone. Some run em tighter, some looser. It depends on expected RPM's the engine will see, forged or not rotating assembly, piston to wall clearance, and weight of reciprocating mass. That and how long they expect to go between rebuilds. The generally excepted clearance for forged street applications is .035-.040" and keeping it under 7Krpms, but again that's a general "rule of thumb" and can vary depending on your particular build. I do know that once a running quench of .060" is exceeded detonation and knock becomes a very real problem. Mind you, static quench (what is calculated here) is greater than running quench. Some race engine builders get the running quench tight enough to make the pistons kiss the heads at high rpms. But those engines don't last long at all.
Here's a good read on it.
Here's another for the technically interested. Very good read!
Also I got 11.7:1 SCR and 8.8:1 DCR from the info you provided.
Should be a good runner for sure.
Last edited by hrcslam; May 7, 2014 at 05:13 AM.
Thread Starter
12 Second Club
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Joined: Mar 2007
Posts: 1,928
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From: Cheyenne, Wy
Awesome!!! Thank you very much for easing my mind. I was subtracting my Piston out of hole clearance from my gasket size and getting .16...Should have been adding the two I guess...haha.
