Static vs. Corrected comp?
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Static vs. Corrected comp?
I'm thinking of adding a big bore, unless I already have, but I don't think so. I will try to do the compression test as suggested on this forum.
However, the ones I'm looking at are 95ci with Wiseco high comp pistons (10.5:1). When selecting a cam for this build, are those numbers stated as static or corrected compression? For example, Andrews TW37b is stated to work from 9.0 to 9.5 CR. If this is static, 10.5 would be way above, right? Also, planning on headwork, but not sure exactly what to do in that area, is poolising and porting affecting the compression or is that only affected by milling and gasket size? If I were in US, I would probably go to one of the forum sponsors for this but unfortunately I'm not.
Ohh, and my aim is a long flat 105+ ft-lbs torque curve :P HP at max rpm is not that important to me.
However, the ones I'm looking at are 95ci with Wiseco high comp pistons (10.5:1). When selecting a cam for this build, are those numbers stated as static or corrected compression? For example, Andrews TW37b is stated to work from 9.0 to 9.5 CR. If this is static, 10.5 would be way above, right? Also, planning on headwork, but not sure exactly what to do in that area, is poolising and porting affecting the compression or is that only affected by milling and gasket size? If I were in US, I would probably go to one of the forum sponsors for this but unfortunately I'm not.
Ohh, and my aim is a long flat 105+ ft-lbs torque curve :P HP at max rpm is not that important to me.
Last edited by HarleyViking; Feb 13, 2020 at 08:08 AM.
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Cruiser
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Found this site (by this forum):
http://bigboyzheadporting.com/TwinCamComp.htm
Is the corrected compression calculated here what I should go with?
So this says that a 95ci with the 10.5:1 pistons, stock head cc (85cc?), stock head gasket (0.045) and TW37 cams gives 9.63-9.79 corrected compression, am I right?
http://bigboyzheadporting.com/TwinCamComp.htm
Is the corrected compression calculated here what I should go with?
So this says that a 95ci with the 10.5:1 pistons, stock head cc (85cc?), stock head gasket (0.045) and TW37 cams gives 9.63-9.79 corrected compression, am I right?
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Found this site (by this forum):
http://bigboyzheadporting.com/TwinCamComp.htm
Is the corrected compression calculated here what I should go with?
So this says that a 95ci with the 10.5:1 pistons, stock head cc (85cc?), stock head gasket (0.045) and TW37 cams gives 9.63-9.79 corrected compression, am I right?
http://bigboyzheadporting.com/TwinCamComp.htm
Is the corrected compression calculated here what I should go with?
So this says that a 95ci with the 10.5:1 pistons, stock head cc (85cc?), stock head gasket (0.045) and TW37 cams gives 9.63-9.79 corrected compression, am I right?
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I'm thinking of adding a big bore, unless I already have, but I don't think so. I will try to do the compression test as suggested on this forum.
However, the ones I'm looking at are 95ci with Wiseco high comp pistons (10.5:1). When selecting a cam for this build, are those numbers stated as static or corrected compression? For example, Andrews TW37b is stated to work from 9.0 to 9.5 CR. If this is static, 10.5 would be way above, right? Also, planning on headwork, but not sure exactly what to do in that area, is poolising and porting affecting the compression or is that only affected by milling and gasket size? If I were in US, I would probably go to one of the forum sponsors for this but unfortunately I'm not.
Ohh, and my aim is a long flat 105+ ft-lbs torque curve :P HP at max rpm is not that important to me.
However, the ones I'm looking at are 95ci with Wiseco high comp pistons (10.5:1). When selecting a cam for this build, are those numbers stated as static or corrected compression? For example, Andrews TW37b is stated to work from 9.0 to 9.5 CR. If this is static, 10.5 would be way above, right? Also, planning on headwork, but not sure exactly what to do in that area, is poolising and porting affecting the compression or is that only affected by milling and gasket size? If I were in US, I would probably go to one of the forum sponsors for this but unfortunately I'm not.
Ohh, and my aim is a long flat 105+ ft-lbs torque curve :P HP at max rpm is not that important to me.
If a cam profile allows pressure to bleed off due to cam profile it would lower cylinder pressure.
Thats why radical cams recommend high mechanical CR because at low RPM cylinder pressure would be unacceptably low.
Last edited by stixvrad; Feb 13, 2020 at 01:47 PM.
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Cruiser
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Thanks!
At what corrected compression would I need compression releases? Also, if anyone knows it those numbers are OK for the TW37 cams, I read some posts that recommends 10:1 as best compression for those cams but maybe that was max 10:1?
At what corrected compression would I need compression releases? Also, if anyone knows it those numbers are OK for the TW37 cams, I read some posts that recommends 10:1 as best compression for those cams but maybe that was max 10:1?
Thread Starter
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Cruiser
Joined: Apr 2019
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Hey guys,
Still confused about this, according to many posts 10:1 is the sweet spot for Andrews TW37 cams, still not sure if that's static or corrected? With the Big Boyz calculation I get these values:
95ci
10.5:1 pistons
0.045" head gasket
85cc head volume
Andrews TW37 cams
Static compression: 10.39:1 - 10.56:1
Corrected compression: 9.63:1 - 9.79:1
Cold crank compression: 201.8 - 206.1 psi
With a head volume of 90cc (not sure if possible) I get:
Static compression: 9.85:1 - 10:1
Corrected compression: 9.13:1 - 9.27:1
Cold crank compression: 188.7 - 192.5 psi
Some posts also suggests a corrected compression of max 9.4:1 for street use , so I assume the sweet spot at 10.1 for TW37 is static?
Still confused about this, according to many posts 10:1 is the sweet spot for Andrews TW37 cams, still not sure if that's static or corrected? With the Big Boyz calculation I get these values:
95ci
10.5:1 pistons
0.045" head gasket
85cc head volume
Andrews TW37 cams
Static compression: 10.39:1 - 10.56:1
Corrected compression: 9.63:1 - 9.79:1
Cold crank compression: 201.8 - 206.1 psi
With a head volume of 90cc (not sure if possible) I get:
Static compression: 9.85:1 - 10:1
Corrected compression: 9.13:1 - 9.27:1
Cold crank compression: 188.7 - 192.5 psi
Some posts also suggests a corrected compression of max 9.4:1 for street use , so I assume the sweet spot at 10.1 for TW37 is static?
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