[grandville455]

I was checking my pushrod length today, and have 3 pics with different lengths , I was wondering what you guys thought? I brought it to TDC #1 , I wasn't using checker springs, but its a solid roller anyway. The Exh Is at 8.950, The Intake next to Exh pic is 9.100. The other 2 pics are The Intake one is 9.050, the other is 9.150 , narrower, but lower, Lift on Intake IS .745 , zero lash, and ,.720 Exh. The Pattern is about .090 wide, a tad smaller on EXh. Any longer and it pushes to far to exh side. I'm pretty happy with the .9.050 , but want your opinions, I know narrower is better, but this is a lot of lift?

[BB70]

Have you seen Scott Foxwell's vid over on the bullet about determining pushrod length- I think it's also on u tube also.

John

[grandville455]

No, u have a link?

[BB70]

No, I'm at work and both are blocked

[cnc]

https://m.youtube.com/watch?v=o5is9BsH5OU

Pretty slick ****

[4dblnkldude]

Very good video!!!!

[indymanjoe]

Helpful vid,Thanks.

[BruceWilkie]

Thanks for the video... I'll be trying that next time I'm doing pushrods

[grandville455]

Awesome video! Will try that this weekend, see how close I am the old school way.He said gross can lift, guessing that's with your rocker ratio added, n not just lobe lift?

[BB70]

Yep- thats the vid, thanks cnc. Yes on the gross lift, cam lobe x rocker ratio.

[Old Man Taylor]

There is another way to do it. When the rocker is at the 90 degrees described in the video, The roller tip is as close to the outside edge of the head as it will get. They make a fixture for a dial indicator that stops on the keeper and measures the throw of the roller tip. Maximum extension of the roller tip is the 90 degree point.

[chuckies76ta]

Wow, That video is assume.. Thanks for posting Chris. I just went and check my length using this method and came out .050 longer than what I have. I bought 9.5 and the measurement came out to 9.55. Close enough.. The witness mark looks really good to me..
Best I've ever had. .030

Charles

[grandville455]

Very Nice! How much lift? That the OF Cam? What IH?

[chuckies76ta]

Originally Posted by grandville455

Very Nice! How much lift? That the OF Cam? What IH?

Darby: That's SD Performance Old-faithful Cam. That cam comes with a gross lift of .570 and .574. I think Dave has the springs installed at 1.7 the lobe lift is .380x 1.5 that I,m using given .570

Charles

[grandville455]

Originally Posted by chuckies76ta

Darby: That's SD Performance Old-faithful Cam. That cam comes with a gross lift of .570 and .574. I think Dave has the springs installed at 1.7 the lobe lift is .380x 1.5 that I,m using given .570

Charles

Thanks Charles, I was just curious. I tried that method too, but my studs aren't tall enough to get it to 90 degrees. Their a 1.90 IH height stud, but My springs are at 2.0. My mark is a lot wider at .085 , but I have .745 lift too at zero lash! lol. Its centered Im leaving it as I epoxied up where the stud was thru the head so its all smooth.

[jonmachota78]

And finally add .050" to the needed pushrod length if you're running hydraulic lifters to compensate for the preload.

[Skip Fix]

Watched the video-one thing doesn;t make sense-they use the thread on the stud to go down to half lift-seems to me rocker ratio would change that since you really want lift at the valve.

[chuckies76ta]

I'll take a stab at this Skip, cause I was like you when someone mentioned rocker ratio.
Let's take Old faithful cam for ex: So the gross lift on my cam is .570/.574. My lobe lift is .380/.383. Will just use the intake gross lift of .570 for caculation.
.380x1.5 ratio rocker = .570/2=.285/.050=5.7 turns
If I were to use 1.65 rocker it would be: .380x1.65=.627/2=.313/.050=6.27 turns.

Hopefully I'm correct.
Charles

[Skip Fix]

But they are just dropping that lift distance at the stud the correct amount, I would think the distance from the trunnion to the valve tip might decrease a different amount even assuming a 90 degree angle is kept, and since often the valve drops at a different angle than the stud. Granted most different ratios the difference is on the pushrod size so that might not make as much difference if using ther same brand rocker.

I've found different brands use different roller tip diameters, different relation between the angle of the trunnion and pushrod cup and roller tip, diffeent lengths fromt trunnion to valve tip. Using the 90 degree deal tried to compensate for some of that but all my old geometery tell me the distance is going to be different at the valve tip than at the stud.

[jonmachota78]

They are establishing the 90° rocker/valve angle at zero lift. Then maintaining 90° as they bring the entire rocker down to mid lift. Since the 90° angle is being maintained, the rocker ratio is not in play, so it works for any ratio rocker.