Hamilton Cams
ignorant
- Joined
- Jun 28, 2007
- Messages
- 2,639
A few of you have pmed me recently with questions about how to see if you have installed height issues or issues with your pop pressures on your injectors. There is a lot of misinformation and opinions that have absolutely no truth to them.
For installed height, you need to install an intake and exhaust valve, the retainer and the locks. You will measure from the bottom of the spring pocket to the bottom of the retainer on the O.D. This needs to be done with a valve spring height gauge. If you use calipers, they will be on an angle and will give an incorrect reading. Another option is to get two screws with a turbuckle in the middle. Keep adjusting until both ends fit snug. Then remove the screws and measure the outside dimension with a dial caliper. This is your installed height.The pressure of the spring at this height is your seat pressure.
If you get a valve job, have valve seats installed or go with different valves, this WILL affect your installed height. Do not listen to people that don't know their butt from a hole in the ground.
To calculate spring position and pressure on the nose of the cam you will need to do a little bit of math.
You will need to know installed height, rocker ratio, lash, and spring pressure at different lifts.
To find rocker ratio, measure lobe lift on the cam. This can be done by measuring, base circle to lobe tip or "toe-Heel", and then base circle to base circle. Subtract base circle from the “Toe-heel” measurement. This is lobe lift.
Next you install the cam (without pistons), attach head with valves assembled on the cylinder to be checked. Set lash at .000” put a dial indicator on the valve retainer and measure maximum lift.
Next divide the maximum lift by the lobe lift. This is your rocker ratio. 12vs vary from 1.66-1.7, 24vs vary from 1.36-1.39 on the intake and 1.33-1.35 on the exhaust.
An example of this would be .5208” lift from a .310” lobe .5208”/ .310” = 1.68 to 1 rocker ratio. Use this method to verify higher ratio rockers are correct.
Now to find how far you are from coil bind, you will need to do some more math. You need to figure out how much lift you are seeing at the valve. To do this you will need to know rocker ratio, installed height, lash, coil bind and pressure of the spring at those points.
First you need to see how much lift the lash is eating up. Divide the lash by the rocker ratio. On a 12v with a 1.68 rocker ratio you would divide .020”/ 1.68=.011904” or .012” if you round up. For the intake divide .010”/1.68= .0059” or .006”
Next subtract the lost lift caused by the lash .020”/1.68=.012” , .320”-.012"=.308” Next multiply the .308” by the rocker ratio. This will be your maximum valve lift. .308”/1.68= .5174”.
Next you will need to subtract the maximum lift from the installed height. 1.880” installed height minus .5174”= 1.3626”. This is the maximum lift point and how tall the spring is at that point. Check the spring at that height and you will know the maximum spring pressure. I have seen pullers with crazy cams run as little as .025” to coil bind but I suggest a minimum of .075”. If you have a wide lobed cam and are running a competition engine, I suggest a maximum of 460 lbs of pressure on the nose of a cam. If you run over 450lbs of pressure on a 12v, I suggest a bushed block, as insurance.
If you are running a street truck with a 12 valve, I suggest a maximum of .330” lobe lift and maximum pressures of 420 lbs. If running over 375 lbs of pressure on a 12valve, I suggest zinc additives in every oil change.
The reason that 24valves can run more pressure without hurting the cam is that they have a much lower rocker ratio. The pressure of the springs is multiplied by the rocker ratio and applied to the cam lobe and onto the cam journals. Less rocker ratio is less pressure on the cam.
Although I have yet to see any issues with any of our locks and retainers, There has been a lot of fuss about this. This is a way in which you can verify if there is an issue. If there is, feel free to call us and we will do whatever is necessary to rectify the situation.
As far as pop pressure, people do not want you checking it. They will tell you that you can't check it, you do not have the knowledge and that your machine is not certified. This is all smoke and mirrors to keep you from busting their chops. People will tell you that you will have to have the tester calibrated for the test to be valid. Not so much. That is true if you are trying to sync your tests up with everybody else in the world. This is not needed for the most part. The issue that I have seen with injectors has to do with a variance in pop pressures. Regardless if the pop tester is calibrated you can still easily tell if your injectors are matched as far as pop pressure is concerned. If they are not matched well, send them to a shop that has a calibrated tester for madification. Some of the best keep them within 10 bar or less variance, but I have seen some that vary more than 30 -50 bar. This is sloppy workmanship plain and simple. Setting pop pressure can take time and can be a pain in the neck. For this reason, people that are in the biz to make a buck not crank out quality work, usually fudge this stage as most people never check the pop pressures anyway. So who will know, right? Do yourself a favor, check your pop pressure. Hold us manufacturers to a higher standard.
Another thing that you will see is that people with "issues" usually have many factors that they do not account for. Unless every measurement in the valvetrain is accounted for, the numbers mean little. Also, if you look at some of the calculations that people are using as examples use a higher 1.8 rocker ratio and are not correctly accounting for valve lash or measuring rocker pedestal deflection. More or less I am saying that their numbers are null and void, and do not make an argument for anything other than our education system is failing us. Use this formula to verify your clearances and pressures and to hold ignorant nit-wits at bay.
Zach
For installed height, you need to install an intake and exhaust valve, the retainer and the locks. You will measure from the bottom of the spring pocket to the bottom of the retainer on the O.D. This needs to be done with a valve spring height gauge. If you use calipers, they will be on an angle and will give an incorrect reading. Another option is to get two screws with a turbuckle in the middle. Keep adjusting until both ends fit snug. Then remove the screws and measure the outside dimension with a dial caliper. This is your installed height.The pressure of the spring at this height is your seat pressure.
If you get a valve job, have valve seats installed or go with different valves, this WILL affect your installed height. Do not listen to people that don't know their butt from a hole in the ground.
To calculate spring position and pressure on the nose of the cam you will need to do a little bit of math.
You will need to know installed height, rocker ratio, lash, and spring pressure at different lifts.
To find rocker ratio, measure lobe lift on the cam. This can be done by measuring, base circle to lobe tip or "toe-Heel", and then base circle to base circle. Subtract base circle from the “Toe-heel” measurement. This is lobe lift.
Next you install the cam (without pistons), attach head with valves assembled on the cylinder to be checked. Set lash at .000” put a dial indicator on the valve retainer and measure maximum lift.
Next divide the maximum lift by the lobe lift. This is your rocker ratio. 12vs vary from 1.66-1.7, 24vs vary from 1.36-1.39 on the intake and 1.33-1.35 on the exhaust.
An example of this would be .5208” lift from a .310” lobe .5208”/ .310” = 1.68 to 1 rocker ratio. Use this method to verify higher ratio rockers are correct.
Now to find how far you are from coil bind, you will need to do some more math. You need to figure out how much lift you are seeing at the valve. To do this you will need to know rocker ratio, installed height, lash, coil bind and pressure of the spring at those points.
First you need to see how much lift the lash is eating up. Divide the lash by the rocker ratio. On a 12v with a 1.68 rocker ratio you would divide .020”/ 1.68=.011904” or .012” if you round up. For the intake divide .010”/1.68= .0059” or .006”
Next subtract the lost lift caused by the lash .020”/1.68=.012” , .320”-.012"=.308” Next multiply the .308” by the rocker ratio. This will be your maximum valve lift. .308”/1.68= .5174”.
Next you will need to subtract the maximum lift from the installed height. 1.880” installed height minus .5174”= 1.3626”. This is the maximum lift point and how tall the spring is at that point. Check the spring at that height and you will know the maximum spring pressure. I have seen pullers with crazy cams run as little as .025” to coil bind but I suggest a minimum of .075”. If you have a wide lobed cam and are running a competition engine, I suggest a maximum of 460 lbs of pressure on the nose of a cam. If you run over 450lbs of pressure on a 12v, I suggest a bushed block, as insurance.
If you are running a street truck with a 12 valve, I suggest a maximum of .330” lobe lift and maximum pressures of 420 lbs. If running over 375 lbs of pressure on a 12valve, I suggest zinc additives in every oil change.
The reason that 24valves can run more pressure without hurting the cam is that they have a much lower rocker ratio. The pressure of the springs is multiplied by the rocker ratio and applied to the cam lobe and onto the cam journals. Less rocker ratio is less pressure on the cam.
Although I have yet to see any issues with any of our locks and retainers, There has been a lot of fuss about this. This is a way in which you can verify if there is an issue. If there is, feel free to call us and we will do whatever is necessary to rectify the situation.
As far as pop pressure, people do not want you checking it. They will tell you that you can't check it, you do not have the knowledge and that your machine is not certified. This is all smoke and mirrors to keep you from busting their chops. People will tell you that you will have to have the tester calibrated for the test to be valid. Not so much. That is true if you are trying to sync your tests up with everybody else in the world. This is not needed for the most part. The issue that I have seen with injectors has to do with a variance in pop pressures. Regardless if the pop tester is calibrated you can still easily tell if your injectors are matched as far as pop pressure is concerned. If they are not matched well, send them to a shop that has a calibrated tester for madification. Some of the best keep them within 10 bar or less variance, but I have seen some that vary more than 30 -50 bar. This is sloppy workmanship plain and simple. Setting pop pressure can take time and can be a pain in the neck. For this reason, people that are in the biz to make a buck not crank out quality work, usually fudge this stage as most people never check the pop pressures anyway. So who will know, right? Do yourself a favor, check your pop pressure. Hold us manufacturers to a higher standard.
Another thing that you will see is that people with "issues" usually have many factors that they do not account for. Unless every measurement in the valvetrain is accounted for, the numbers mean little. Also, if you look at some of the calculations that people are using as examples use a higher 1.8 rocker ratio and are not correctly accounting for valve lash or measuring rocker pedestal deflection. More or less I am saying that their numbers are null and void, and do not make an argument for anything other than our education system is failing us. Use this formula to verify your clearances and pressures and to hold ignorant nit-wits at bay.
Zach
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