New Trick Flow FE cylinder heads & Intake

[winr1]

How much power is to be made on the mid lift deal if I may ask ??


What if one were to use a factory hydraulic or adjustable rocker arm ??
Is the geometry off and is there power to be made ??


 A few questions our home builders might be interested in




Ricky.

[andyf]

If you are handy with calculus you can figure out the location that gives you the lowest combination of load and travel. The Mid Lift setup gives the minimum travel across the valve which is fine for low load springs. But if you have high load springs, the load at full lift is much greater than it is at low lift so you might want to reduce the amount of sideways travel near full load.

Mid Lift gives you max travel at full load which might not be good for things. It takes some advanced math to figure out but you can minimize the product of load and travel by moving the shaft down. You do end up with more travel across the valve, but that extra sideways travel occurs at the beginning of the lift cycle when the rocker arm is lightly loaded.

[mbrunson427]

If you are handy with calculus you can figure out the location that gives you the lowest combination of load and travel. The Mid Lift setup gives the minimum travel across the valve which is fine for low load springs. But if you have high load springs, the load at full lift is much greater than it is at low lift so you might want to reduce the amount of sideways travel near full load.

Mid Lift gives you max travel at full load which might not be good for things. It takes some advanced math to figure out but you can minimize the product of load and travel by moving the shaft down. You do end up with more travel across the valve, but that extra sideways travel occurs at the beginning of the lift cycle when the rocker arm is lightly loaded.

I'd like to understand this more. What Scott's last post and his video illustrate make a ton of sense, but then if you're building something a bit more high-end and high lift, this also makes sense.

I may have to do the math and build a spreadsheet....I know you guys love my spreadsheets.

[scott foxwell]

If you are handy with calculus you can figure out the location that gives you the lowest combination of load and travel. The Mid Lift setup gives the minimum travel across the valve which is fine for low load springs. But if you have high load springs, the load at full lift is much greater than it is at low lift so you might want to reduce the amount of sideways travel near full load.

Mid Lift gives you max travel at full load which might not be good for things. It takes some advanced math to figure out but you can minimize the product of load and travel by moving the shaft down. You do end up with more travel across the valve, but that extra sideways travel occurs at the beginning of the lift cycle when the rocker arm is lightly loaded.

This is Jesel's philosophy for their rocker geometry and why I won't use their rockers. The problem with this is that it changes the acceleration rate of the valve and if I want to do that, I'll do it with the cam. I don't see the load differences being worth the trade off and I want the rocker to be as neutral as possible. I've had this conversation with just about every engine builder I come in contact with since I'm so intrigued by this and I can say even at NHRA/IHRA Pro Stock level, there are those who prefer mid lift, and those who prefer what you describe. Bottom line here is either are very close to one and other and unless you have the exact rocker height for your combination, and the pushrod side has the same perfect geometry, you're going to end up with a variation. Using mid lift is easy and basic and will get you a whole lot closer than "centering the pattern on the valve tip". There are also load dynamics that play into all this that take a little deeper understanding of what's going on but for the most part I prefer to keep it simple. At full lift, there may be zero load on the rocker and under (lifter) acceleration, there may be way more than spring load on the rocker. An ex rocker is trying to open the valve against cylinder pressure. Just other things to consider.

[scott foxwell]

How much power is to be made on the mid lift deal if I may ask ??


What if one were to use a factory hydraulic or adjustable rocker arm ??
Is the geometry off and is there power to be made ??


 A few questions our home builders might be interested in




Ricky.

Mid lift geometry doesn't apply to factory shoe type rockers in the same manner as it does a roller tip. Completely different dynamic through the motion of the rocker.
Power to be made on the mid lift deal...all of it. Power to be lost by NOT using mid lift, or a derivative of, depends on too many variables. Not just about power, but also about reliability and longevity. Poor rocker geometry will wear guides out in a heartbeat.

[andyf]

If you are handy with calculus you can figure out the location that gives you the lowest combination of load and travel. The Mid Lift setup gives the minimum travel across the valve which is fine for low load springs. But if you have high load springs, the load at full lift is much greater than it is at low lift so you might want to reduce the amount of sideways travel near full load.

Mid Lift gives you max travel at full load which might not be good for things. It takes some advanced math to figure out but you can minimize the product of load and travel by moving the shaft down. You do end up with more travel across the valve, but that extra sideways travel occurs at the beginning of the lift cycle when the rocker arm is lightly loaded.

I'd like to understand this more. What Scott's last post and his video illustrate make a ton of sense, but then if you're building something a bit more high-end and high lift, this also makes sense.

I may have to do the math and build a spreadsheet....I know you guys love my spreadsheets.

Yeah you can find the answer with a spreadsheet. Just have to iterate it a few times. The answer will be around 2/3 lift for the point where the rocker arm is perpendicular to the valve. If you have an old Chevy Power book you'll find an explanation on the low mount theory. The Chevy engineers figured this out a long time ago and it is what they recommended back in the day. I think Jesel adopted the Chevy engineering theory but I don't know for sure. You would have to ask Wayne why he did what he did.

[andyf]

I used to make and sell a scrub measurement tool for setting up the rocker arm geometry. Sales were so slow on the tool that I just stopped making them. Most guys don't care enough about the subject to actually buy a tool. But if anyone wants to make one of their own here is what it looked like.

[jayb]

That is a cool tool, Andy, I think I might just make one of those myself!

[scott foxwell]

I used to make and sell a scrub measurement tool for setting up the rocker arm geometry. Sales were so slow on the tool that I just stopped making them. Most guys don't care enough about the subject to actually buy a tool. But if anyone wants to make one of their own here is what it looked like.

I've made several using different retainers. That's really the best way to set up shaft rockers. Doing the "math" and measuring off the shaft, trying to find the valve height, etc. can be a bit "challenging".

[andyf]

That is a cool tool, Andy, I think I might just make one of those myself!

Jay, I have some of the parts on hand to make more of those tools. If you're interested I could send you a few sets of parts and you could make your own tools.

[jayb]

Thanks Andy, I will PM you on that - Jay

[Tommy A]

How do you check your geometry?

I check for the usual items. The roller tip is well positioned on top of the valve, the pushrod cups don't interfere with the bottom of the rockers and pushrod holes in the intake have enough clearance. I try to avoid anything that involves the use of Math. Keep in mind I'm just a home builder much like the majority here so I leave the technical stuff to those who know what they are doing.

In the past 12 years of racing I've bent a total of 2 pushrods and broken zero rockers. Did lots of other damage but rocker geometry wasn't the issue. Over rev and valve float cause trouble.

So basically you guess -and I don't mean that insultingly. Geometry is all about math. Rocker geometry is so simple, yet so completely misunderstood and ignored throughout the industry and one the most important things there is when assembling a performance engine. I put it right there with bearing clearances and degreeing your cam. The internet is a great place and has really opened my eyes to how much terrible mis-information there is regarding pushrod length and rocker geometry, even by so called "experts" and "professionals". For decades, Comp Cams put in print, in their catalog, probably the absolute WORST technical information and diagram when it came to measuring for pushrod length but hey, it's Comp Cams, so it has to be right, right? A lie repeated enough times becomes the truth. People invest thousands of $$ in a performance engine, buy a custom cam, custom rockers, custom pushrods, and have NO idea whether or not their rocker geometry is even close. The engine's performance DEPENDS on that geometry being correct in order to get the most accurate information from the cam to the valve, yet it gets passed off as almost trivial. The first and BIGGEST misconception and most repeated lie about rocker geometry is this; proper geometry is when the roller tip sweep pattern is in the center of the valve. That is absolutely wrong and you're almost guaranteed to have improper geometry if you use that as your guideline. Another misconception is that you use pushrod length to establish proper geometry. Pushrod length is a result of proper geometry. Shaft rockers can be set up with the heads on the bench. You don;t even need a pushrod. All you need to know is your net lift @ the valve. Proper geometry is this; when the centerline of the rocker is at 90* to the valve at mid lift. The center line of the rocker being an imaginary line that passes through the center of the rocker pivot, and through the center of the roller tip. When this imaginary line is 90*to the valve stem at mid lift, you have proper "mid lift" geometry. There are those who prefer a slight variation to this but for the most part, this is the industry standard. What this accomplishes is to give the minimum amount of roller sweep over the valve tip. Contrary to popular opinion, it is not being off centered that causes guide side loading and excessive wear, but it is excessive roller sweep on the valve tip that causes premature guide wear. Of course, in a perfect world we would like to have minimum s weep and be perfectly centered on the valve tip but that rarely occurs. Being centered is secondary to proper geometry and having the minimum amount of sweep. I use the center third of the valve tip as my "safe" working range for the sweep pattern. If it's within that range, it's good to go. If outside that range, then we have to do something about it and start looking at options.
My 390, basically all stock as far as deck height, cyl head milling, head gasket thickness and valve length needed .220" spacers to get the geometry right with Sharp roller tip rockers. That's not even close!!!! And yes, when I got the rockers where they should be, I had to clearance them for the pushrod cups. Oh well. That's what you have to do sometimes. I talked to Randy Jr at PRI about this and he seemed receptive to the suggestion of raising the stands. Of course, he's probably got bigger fish to fry so I'm not sure where that landed, but he said he had heard the same thing from several "FE" people.
Here's a diagram to help visualize what I'm talking about afa "mid lift" geometry;



Here's a short video I did for stud mount rockers but the principles apply to shafts as well.

https://www.youtube.com/watch?v=o5is9BsH5OU&feature=youtu.be

Because I work in cylinder head and induction development, rocker geometry is a real pet peeve of mine. There is power to be had or lost with it. There is longevity and reliability to be had or lost with it, and it's about as simple as it gets to do it right. I've had many, many, professional engine builders call me to thank me after watching my video, telling me how much sense it made and how easy it was, and that they had been doing it "wrong" their whole life.
I will edit to add: this all above only applys to roller tip rockers. The factory shoe type rocker has an entirely different geometry and NONE of this works with that type of rocker.

Scott, thank you so much for that video, You are the only one that has shown the 'Correct way to establish Geometry'@ 90degrees....an old engine builder/racer showed me that method in 1981 and told comp the way they had it there catalog was going to get people in trouble, but they were right and he was wrong. Thanks again.............Tom

[Felonious79]

andyf, can you tell me what your total timing was on the motor you built with the trick flow heads?  My dyno guy just ran an FE with these heads (stock) and ended up at 28 degrees. Mine is going on the dyno on Monday and he expects the timing will also be under 30 with these heads.

[andyf]

We used 32 degrees. We had the first set of TF heads on a dyno so nobody knew any better. 32 seemed to work just fine, the engine ran hard and the plugs looked okay so we left it there. I wouldn't be surprised that slightly less or slightly more timing would work even better but we had lots of other things to try during the dyno session.

[Felonious79]

Cool, thanks for the info.  I’ll definately report back next week the results of my session for anybody that’s interested.  I’ll try to get more info later, but I do know that the trick flow headed FE I mentioned earlier made 620 hp at 6000 rpm.  It had the trick flow single plane intake and the 4.25 scat stroker kit on a 406 motor.  The intake matched perfectly with no port matching needed.