How many lbs of compression ???
#1
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Wondering how many lbs of compression my motors should have.
540 Ci, 9.0 to 1 comp roller cam .641 lift and approx 242 degrees int dur and 248 ex duration on 114 lobe separation.
I was thinking 160-170 psi but I am being told possibly less ???
540 Ci, 9.0 to 1 comp roller cam .641 lift and approx 242 degrees int dur and 248 ex duration on 114 lobe separation.
I was thinking 160-170 psi but I am being told possibly less ???
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#5
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I was just curious where it should be because I have someone interested in buying my motors. They are all at 140 cold compression, but the guy said he thought they should be at 160 or more. I guess I should run it and get it hot and then check again ?? Maybe it will be higher when hot ???
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I was just curious where it should be because I have someone interested in buying my motors. They are all at 140 cold compression, but the guy said he thought they should be at 160 or more. I guess I should run it and get it hot and then check again ?? Maybe it will be higher when hot ???
#7
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Sometimes compression will be tad lower with cold engine.
You'll have lower than normal readings if you do not have the throttle blades all the way open during testing.
Cranking rpm can have a good influence on readins too. Faster cranking = more cranking compression. A restricted compression rule engine will more than likely have a slower starter to help pass tech.
So, yup, a fresh battery will cause more psi than a weak battery.
Most gauges read different from each other too.
The cams you have along with your static compression will tend to be around where you see it. You could always put in truck cams, have the cranking compression skyrocket to 180psi, but will that make him happy ??? No way !!!! LOL.
All my opinion and experiences.
You'll have lower than normal readings if you do not have the throttle blades all the way open during testing.
Cranking rpm can have a good influence on readins too. Faster cranking = more cranking compression. A restricted compression rule engine will more than likely have a slower starter to help pass tech.
![Evil](/forums/images/smilies/evilB.gif)
Most gauges read different from each other too.
The cams you have along with your static compression will tend to be around where you see it. You could always put in truck cams, have the cranking compression skyrocket to 180psi, but will that make him happy ??? No way !!!! LOL.
All my opinion and experiences.
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Sometimes compression will be tad lower with cold engine.
You'll have lower than normal readings if you do not have the throttle blades all the way open during testing.
Cranking rpm can have a good influence on readins too. Faster cranking = more cranking compression. A restricted compression rule engine will more than likely have a slower starter to help pass tech.
So, yup, a fresh battery will cause more psi than a weak battery.
Most gauges read different from each other too.
The cams you have along with your static compression will tend to be around where you see it. You could always put in truck cams, have the cranking compression skyrocket to 180psi, but will that make him happy ??? No way !!!! LOL.
All my opinion and experiences.
You'll have lower than normal readings if you do not have the throttle blades all the way open during testing.
Cranking rpm can have a good influence on readins too. Faster cranking = more cranking compression. A restricted compression rule engine will more than likely have a slower starter to help pass tech.
![Evil](/forums/images/smilies/evilB.gif)
Most gauges read different from each other too.
The cams you have along with your static compression will tend to be around where you see it. You could always put in truck cams, have the cranking compression skyrocket to 180psi, but will that make him happy ??? No way !!!! LOL.
All my opinion and experiences.
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your compression will be lower on a cold motor with forged pistons cause you run a little more wall clearance than cast pistons. do another comp test on a fully warm motor, use a hot battery for good cranking speed and have the throttle wide open, bet it will be higher
#10
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Cams with overlap will bleed off some compression. My compression #'s went down on some cylinders after a valve job and install of a bigger cam in my 525SC. It had 7.5 static and was around 130# with a Crane 731 cam. Before the valve job/cam, I had a couple cylinders at 120 and the rest at 140.