PTV - Clay Method
PTV - Clay Method Ive searched and searched, but I would really appreciate some clarification.
I am checking PTV via clay - this is how I have been doing it (using a ls7 modified "solid" lifter):
1) Install checking springs
2) clay piston
3) tighten head
4) Using adjustable pushrod, find zero lash on the base circle with the non-adjustable rocker tightened down
5) Rotate motor
6) cut clay with a razor and measure thinnest point with a micrometer
There seems to be a lot of conflicting info surrounding the utilization of an adjustable pushrod/checking springs. Am I right to assume the adjustable pushrod will collapse under the load of a dual spring? This concern is what has led me to utilize the checking springs. I was utilizing checking springs with hydraulic lifters when claying the motor, but everyone seems to say that method doesn't produce accurate results - if that's true, then what's the point of checking springs?
Thanks in advance.
I am checking PTV via clay - this is how I have been doing it (using a ls7 modified "solid" lifter):
1) Install checking springs
2) clay piston
3) tighten head
4) Using adjustable pushrod, find zero lash on the base circle with the non-adjustable rocker tightened down
5) Rotate motor
6) cut clay with a razor and measure thinnest point with a micrometer
There seems to be a lot of conflicting info surrounding the utilization of an adjustable pushrod/checking springs. Am I right to assume the adjustable pushrod will collapse under the load of a dual spring? This concern is what has led me to utilize the checking springs. I was utilizing checking springs with hydraulic lifters when claying the motor, but everyone seems to say that method doesn't produce accurate results - if that's true, then what's the point of checking springs?
Thanks in advance.
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Joined: Nov 2013
Posts: 3,913
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From: White Bear, Mn
Ive searched and searched, but I would really appreciate some clarification.
I am checking PTV via clay - this is how I have been doing it (using a ls7 modified "solid" lifter):
1) Install checking springs
2) clay piston
3) tighten head
4) Using adjustable pushrod, find zero lash on the base circle with the non-adjustable rocker tightened down
5) Rotate motor
6) cut clay with a razor and measure thinnest point with a micrometer
There seems to be a lot of conflicting info surrounding the utilization of an adjustable pushrod/checking springs. Am I right to assume the adjustable pushrod will collapse under the load of a dual spring? This concern is what has led me to utilize the checking springs. I was utilizing checking springs with hydraulic lifters when claying the motor, but everyone seems to say that method doesn't produce accurate results - if that's true, then what's the point of checking springs?
Thanks in advance.
I am checking PTV via clay - this is how I have been doing it (using a ls7 modified "solid" lifter):
1) Install checking springs
2) clay piston
3) tighten head
4) Using adjustable pushrod, find zero lash on the base circle with the non-adjustable rocker tightened down
5) Rotate motor
6) cut clay with a razor and measure thinnest point with a micrometer
There seems to be a lot of conflicting info surrounding the utilization of an adjustable pushrod/checking springs. Am I right to assume the adjustable pushrod will collapse under the load of a dual spring? This concern is what has led me to utilize the checking springs. I was utilizing checking springs with hydraulic lifters when claying the motor, but everyone seems to say that method doesn't produce accurate results - if that's true, then what's the point of checking springs?
Thanks in advance.
Are you using mock-up head gaskets or new head gaskets?
Adjustable pushrod will bend with dual springs. You are doing this correctly. Same method I and many other use. Check springs makes the process easier on cam bearings, and it’s easier to turn engine over also. Is your camshaft degreed, or set to wher you want it?
Are you using mock-up head gaskets or new head gaskets?
Are you using mock-up head gaskets or new head gaskets?
I have tried to study how to degree a cam, but every time I try to understand the process the video/thread online loses me, and none of my friends have the knowledge to show me hands on. So, Im running dot to dot. I know that isn't the preferred method, but its the best I can do at the moment.
Well that's good to know, thanks. I am using previously compressed MLS gaskets - I will be running new MLS gaskets.
I have tried to study how to degree a cam, but every time I try to understand the process the video/thread online loses me, and none of my friends have the knowledge to show me hands on. So, Im running dot to dot. I know that isn't the preferred method, but its the best I can do at the moment.
I have tried to study how to degree a cam, but every time I try to understand the process the video/thread online loses me, and none of my friends have the knowledge to show me hands on. So, Im running dot to dot. I know that isn't the preferred method, but its the best I can do at the moment.
Dot 2 dot is fine as long as the camshaft was ground properly. You don’t have to torque the headbolts with this procedure, using a compressed gasket. Just get the 4 around the cylinder your checking good and snug. Saves wear and tear on both the block threads and the head bolts. You re-using GM headbolts or using ARP head bolts?
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You don't need to "torque" the head(s) down for this process. The change in the dimensions of the head casting due to bolt torque is negligible for the purpose at hand. Tightening the bolts enough that the head is firmly held in place ("snug" is entirely adequate.
You can use any number of things to simulate the head gasket. Washers, shim stock, even an old CD, depending on the thickness of the intended gasket. Again, the .001" or 2 of variation between this and your final build, are negligible compared to the numbers you're looking for.
Check springs are fine. You don't need full spring tension on the push rod for this.
Dot-to-dot is the usual relationship to build a motor at. It's actually NOT #1 firing however; it's #6 firing, and the instance of #1 TDC at which the exh valve is just closing and the int is just opening. These 2 conditions occur at the same time. Both dots at 12:00 is #1 firing, and the instance of #6 TDC at which the exh valve is just closing and the int is just opening. Build the motor at dot-to-dot because it's easier to see; rotate the crank exactly 1 full revolution (exactly ½ of a cam revolution) to get from there to #1 firing. None of that matters for PTV checking though, except as far as assuring that the cam is timed to the crank correctly... put it together dot-to-dot and rotate the motor several turns to create the clay impression.
Not sure what's hard about degreeing a cam... what part of it is giving you trouble?
You can use any number of things to simulate the head gasket. Washers, shim stock, even an old CD, depending on the thickness of the intended gasket. Again, the .001" or 2 of variation between this and your final build, are negligible compared to the numbers you're looking for.
Check springs are fine. You don't need full spring tension on the push rod for this.
Dot-to-dot is the usual relationship to build a motor at. It's actually NOT #1 firing however; it's #6 firing, and the instance of #1 TDC at which the exh valve is just closing and the int is just opening. These 2 conditions occur at the same time. Both dots at 12:00 is #1 firing, and the instance of #6 TDC at which the exh valve is just closing and the int is just opening. Build the motor at dot-to-dot because it's easier to see; rotate the crank exactly 1 full revolution (exactly ½ of a cam revolution) to get from there to #1 firing. None of that matters for PTV checking though, except as far as assuring that the cam is timed to the crank correctly... put it together dot-to-dot and rotate the motor several turns to create the clay impression.
Not sure what's hard about degreeing a cam... what part of it is giving you trouble?
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I use .030” valve spring shims around the cylinder I’m measuring, and set 2 shims on end of deck to keep head level. Head bolt goes through center hole of valve shim. Easy peasy. Shim measures exactly .030” so I know I have a constant to do my math from, according to what dimension headgasket I’m using for each particular build.
You don't need to "torque" the head(s) down for this process. The change in the dimensions of the head casting due to bolt torque is negligible for the purpose at hand. Tightening the bolts enough that the head is firmly held in place ("snug" is entirely adequate.
You can use any number of things to simulate the head gasket. Washers, shim stock, even an old CD, depending on the thickness of the intended gasket. Again, the .001" or 2 of variation between this and your final build, are negligible compared to the numbers you're looking for.
Check springs are fine. You don't need full spring tension on the push rod for this.
Dot-to-dot is the usual relationship to build a motor at. It's actually NOT #1 firing however; it's #6 firing, and the instance of #1 TDC at which the exh valve is just closing and the int is just opening. These 2 conditions occur at the same time. Both dots at 12:00 is #1 firing, and the instance of #6 TDC at which the exh valve is just closing and the int is just opening. Build the motor at dot-to-dot because it's easier to see; rotate the crank exactly 1 full revolution (exactly ½ of a cam revolution) to get from there to #1 firing. None of that matters for PTV checking though, except as far as assuring that the cam is timed to the crank correctly... put it together dot-to-dot and rotate the motor several turns to create the clay impression.
Not sure what's hard about degreeing a cam... what part of it is giving you trouble?
You can use any number of things to simulate the head gasket. Washers, shim stock, even an old CD, depending on the thickness of the intended gasket. Again, the .001" or 2 of variation between this and your final build, are negligible compared to the numbers you're looking for.
Check springs are fine. You don't need full spring tension on the push rod for this.
Dot-to-dot is the usual relationship to build a motor at. It's actually NOT #1 firing however; it's #6 firing, and the instance of #1 TDC at which the exh valve is just closing and the int is just opening. These 2 conditions occur at the same time. Both dots at 12:00 is #1 firing, and the instance of #6 TDC at which the exh valve is just closing and the int is just opening. Build the motor at dot-to-dot because it's easier to see; rotate the crank exactly 1 full revolution (exactly ½ of a cam revolution) to get from there to #1 firing. None of that matters for PTV checking though, except as far as assuring that the cam is timed to the crank correctly... put it together dot-to-dot and rotate the motor several turns to create the clay impression.
Not sure what's hard about degreeing a cam... what part of it is giving you trouble?
For me personally using the ICL degreeing method is the easiest. I'm pretty sure Comp Cam's(along with many others probably)have a good video on it.
Once you find true TDC, it's not too difficult.
Find max lift, zero the dial indicator out, back up to .100 before max lift, then move forward to .050(this takes the slack out of the chain) write down the degrees, then go .050 past max lift(slack is already out of the chain), write down the degrees. Add together and divide in half. That's your ICL.
If you are degreeing the cam, that has/should be done before checking PTV. You can advance/retard the cam timing to give you more PTV, however at the moment I can't remember which way to go to get more.
Once you find true TDC, it's not too difficult.
Find max lift, zero the dial indicator out, back up to .100 before max lift, then move forward to .050(this takes the slack out of the chain) write down the degrees, then go .050 past max lift(slack is already out of the chain), write down the degrees. Add together and divide in half. That's your ICL.
If you are degreeing the cam, that has/should be done before checking PTV. You can advance/retard the cam timing to give you more PTV, however at the moment I can't remember which way to go to get more.