I have made a decision to do some technical videos and explain some of the ways we do things. The start of this is today.

One question we get all the time is how do I measure for pushrods. We field about 4 of these a week from customers and others just needing some direction. I feel this is an area that the DIY guy is not comfortable with during engine building.

So I hired a videographer and last week we shot a video on how to establish proper rocker geometry so that one can find correct pushrod length. This is our way, Straub Technologies and my staff, to give friends, customers, and performance crowd something that they can use as an educational tool. The method Scott Foxwell uses in the video is the way that it is done here.

If the board wants to make the link to the video a sticky that is fine.

 

Excellent presentation, Chris. Thanks for making the time to address the needs of the community and your customers.

 

Thanks Chris. Very nice presentation and a topic that gets asked about 4 times a year. Boy Scott looks alot older than I had pictured. It would be nice to see a video on basic head porting to give guys an idea of how much work goes into port work.

oops!

 

Engine building will weather you!!!!!

 

I get this when I try to view the vid....

 

I have no idea what has happened.

 

Try searching for it on you tube.

oops!

 

yep...video gone

 

 

I see it and thanks. When I swap heads I'll follow this.

Do you also do a valve tip check or is it not needed when following this?

 

Great video! Wish that had been around when I did my motor.

 

Love this video Thank you so much Please keep going on!

Regards, Günther

 

Nice tutorial! That'll come in handing for many on here.

 

Chris,

Here's where I'm a party pooper or I demonstrate my ignorance or both. I'm assuming that the pushrod length adjustment procedure takes place with the cam located at mid-lift on the valve in question. If the video is for a novice, like me, I'm not sure that point was made and it might be good to show how you determine that mid-lift position on the lifter.

I was born a sh-thead, I can't help it.

 

Its on the base circle.

Excellent video by Scott Foxwell. It should be kept as a sticky.

 

Thank you for this. I'm just about to do this for the first time and I was wondering as I removed my stock pushrods how the heck I was supposed to measure the new ones.

 

If it's on the base circle and the video is to teach people that don't do this for a living, like me, how to set-up the geometry and pushrod length, then it seems that knowing where the cam lobe should be set when the pushrod length is adjusted should be stated in the video. I listened to the whole video twice before I wrote my post and I didn't hear it addressed. I'm not trying to pick apart the video. I was watching it as an interested party trying to learn and it just seemed like a part of the puzzle was missing. The whole idea of making the video is great, just not sure it's where it needs to be.

If the cam lobe is on the base circle and the pushrod length is set to bring the valve to half lift, what happens when the lifter is at max lift? The first thing that comes to mind is ...coil bind? Something isn't making sense to me. Not trying to be a wise guy.

 

Good topic and nice job. Really made a difference having a pro take the video doesn't it.

 

You are confusing finding pushrod length with setting lash/preload. Once you have established the correct pushrod length and have those pushrods, you can set your valve adjustment. What you will end up with regarding the number of turns of the adjustment nut to set lash/preload will be around half (3.5 turns or so) from what it took to find pushrod length. The reason for this is when he turned the adjuster down 7.1 turns, that represented half the gross valve lift based upon the 20tpi@.050" per rotation of the nut in order to put the rocker tip at the valve stem centerline.

 

I have commented on this issue before in various posts since I just went through this with my Howards Roller cam with the AFR heads. i spent hours researching how to measure the pushrods, spoke to howards, AFR, and my engine builder for the bottom end. The result was MUCH simpler than I expected or seem to gleem from posts. The basic premise and technique cam from comp cams:

http://www.compcams.com/Pages/417/va...-geometry.aspx

1. howards and my engine builder BOTH stated that you do NOT have to use checker valve springs in the head on an engine staying below 6,500 RPM.

2. Not mandatory to calculate but lifter pre load for Howards roller lifter was .3/.4 on a dry lifter which i had to push to get from them if I was to add to the length using the adjustable pushrod checker. I did not use this value when calculating the length but I did soak the lifter in oil and manual pumped it up before I installed it in the block for the check--tip from my builder.

3. By far, the most important point is understanding that the rocker needs to move in an arch over the tip of the valve stem when you manual rotate the engine-see comp cam link above. When the roller lifter is on the base circle of the cam the rocker ball needs to be on the inside tip of the valve stem toward the intake, as you rotate the engine and the pushrod starts to move the valve open at mid lift-approximately-the rocker ball should be in the center of the valve stem, and at max lift the rocker ball should be at the other end of the valve stem towards the exhaust manifold side-an arch.

I used this technique and it worked perfectly. Am I missing something?

The other mystery solved was that pushrod length was unknown using retro roller and AFR heads. My builder stated that "normal" pushrod length for a roller cam is about 7.2 inches. He guessed with my AFR heads, the pushrod length would be 7.1-7.2. I measured 7.15 and that is what ordered. It turned out to be spot on....

Just a novice's experience...