Valve Train Geometry ?

# Thread: Valve Train Geometry ?

1. ## Valve Train Geometry ?

As I'm pre-planning my next build, I'm really digging deep and trying to learn everything that I can in regards to proper valve train geometry.

I'll be running a Comp Cams XM278H cam with Comp Cams Pro-Magnum hydraulic lifters.

From everything that I've read, they say to use a solid lifter for setting up the geometry because a hydraulic lifter will deflect when it's not pumped full of oil. However, this raises a question.

If the pushrod cup on the solid lifter that is used isn't the exact same as the pushrod cup on the hydraulic lifter, will this give a different geometry than the pushrod cup on the hydraulic lifter?

Also, with a solid lifter you would obviously check the geometry at zero lash. However on hydraulic lifters you have a preload adjustment. Will a preloaded hydraulic lifter give a different geometry than a solid lifter set to zero lash?

2.

3. Originally Posted by Jetaholic
As I'm pre-planning my next build, I'm really digging deep and trying to learn everything that I can in regards to proper valve train geometry.

I'll be running a Comp Cams XM278H cam with Comp Cams Pro-Magnum hydraulic lifters.

From everything that I've read, they say to use a solid lifter for setting up the geometry because a hydraulic lifter will deflect when it's not pumped full of oil. However, this raises a question.

If the pushrod cup on the solid lifter that is used isn't the exact same as the pushrod cup on the hydraulic lifter, will this give a different geometry than the pushrod cup on the hydraulic lifter?

Also, with a solid lifter you would obviously check the geometry at zero lash. However on hydraulic lifters you have a preload adjustment. Will a preloaded hydraulic lifter give a different geometry than a solid lifter set to zero lash?
First things first, Take a hydraulic lifter apart and that will explain the hydraulic part! Then knowing that without the oil to "pump the lifter up" you will see that to set geometry will vary from a solid lifter. Lifters are designed at specific specs and demensions by the motor manufacturer and from what I have seen the specs dont vary until you get into roller apps, Even then the specs and so on remain the same. as for setting up your'e push rod length and so on, go buy two solid lifters and soft-set valve springs designed for what you are trying to achieve. If you roll a motor over and over with a new cam and full valve spring pressure you will create a wear patern on the cam that will bite you in the ass later on fire up. Just make sure that you set the spring height correct with the light springs and use a good thin lube( a thick lube with the light tension springs may throw the readings and angles off )as to not damage the cam. Reason being a cam starts its break-in on fire up and think about how much you will turn that motor to get the correct push-rod and rocker angles before you are done!IMLAO M

4. theres good info at mid-lift.com

5.

6. First off, Old is right. Don't do this with your recommended springs installed! Use checking springs.
It's easiest to do this with a solid lifter, and if you can find one the same length as your hydraulic, that makes life easier, but don't assume they're the same. The important measurement is from the face of the lifter (that rides on the cam lobe) to the seat that the pushrod sits in. The overall length of the lifter body is irrelevant. You need to compare these dimensions between the two lifters. A 5/16" ball bearing usually works, if it's tall enough to stick above the lifter body. Put it in the pushrod seat in one lifter, measure the length, and do the same to the other, and make note of the difference.
Now using the solid lifter, (use the moly lube on the cam that the cam company sent you) go ahead and get your pushrod lengths. I'm not going into detail here on how to do that...there are plenty of threads describing the correct method. Midlift.com is another good resource.
When you're done determining both your pushrod lengths, then either add or subtract whatever the difference between the lifters was, if there was one. Now, you need to know how much preload you're going to run on the hyd. lifter. Every turn on the rocker stud is .050", so if you're going to run 1/2 turn, add .025" to your pushrod length, 3/4 turn is .037", and so on.
That should get you close enough.

7. Originally Posted by Richard Till
theres good info at mid-lift.com
glad to see that site is back, it was gone for awhile.
http://www.mid-lift.com/MASTER-INDEX.htm

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8. Originally Posted by Jetaholic
As I'm pre-planning my next build, I'm really digging deep and trying to learn everything that I can in regards to proper valve train geometry.

I'll be running a Comp Cams XM278H cam with Comp Cams Pro-Magnum hydraulic lifters.

From everything that I've read, they say to use a solid lifter for setting up the geometry because a hydraulic lifter will deflect when it's not pumped full of oil. However, this raises a question.

If the pushrod cup on the solid lifter that is used isn't the exact same as the pushrod cup on the hydraulic lifter, will this give a different geometry than the pushrod cup on the hydraulic lifter?

Also, with a solid lifter you would obviously check the geometry at zero lash. However on hydraulic lifters you have a preload adjustment. Will a preloaded hydraulic lifter give a different geometry than a solid lifter set to zero lash?
Do this -- Mic the the hyd. lifter get your mesurment , NOte it down . Mic you solid and adjust the difference between the two ?

9. Originally Posted by Lucky
Do this -- Mic the the hyd. lifter get your mesurment , NOte it down . Mic you solid and adjust the difference between the two ?
That'll never work.

10. Originally Posted by Lucky
Do this -- Mic the the hyd. lifter get your mesurment , NOte it down . Mic you solid and adjust the difference between the two ?
Is this a question or a statement? Think this sorta like what Steelcomp stated earlier, only you left out the most important piece. THE BALL BEARING!

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11. Lots of interesting shit on that site. Let's see if I'm interpreting this correctly.

The geometry should be set so that with the valve closed, when referenced off of the same plane as the spring retainer, the distance between the trunion axis and the roller tip axis should equal exactly 1/2 your total net valve lift. This should put the trunion axis and the roller pin axis at the same height with the valve at half lift, and at that height an imaginary line drawn between both axis's should be at a 90* angle relative to the valve stem.

Is this correct?

12. Originally Posted by gn7
Is this a question or a statement? Think this sorta like what Steelcomp stated earlier, only you left out the most important piece. THE BALL BEARING!
I never said i was perfect lol

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