I Have been trying to figure out the 90° reference for 4 hours, this video finally made me understand it and made it seem so easy! This was the only one I could find on the internet. Thank you so much 🤘🤘
I talked to Scott over the phone about this process to determine pushrod length. I checked all the corner cylinders of my build and I can say that this process worked flawlessly as it delivered the most lift and least amount of rocker sweep across my valve stems, each and every time I checked and double checked. Great video! Thanks Scott.
I’m literally just down to determining the pushrod length for my TT 383 build and someone on a different video told me about this one and man am I glad I watched it because it made the process so much easier
So I spoke with Scott on the phone and he took the time to explain to me in more depth the problem I was having with this method. Basically I was off a bit measuring my 90 degree angle. You have to understand the importance of being precise as possible on this step cause the slightest miscalculation is magnified because of the angles and ratios. Once I got it right the pattern on the valve was very narrow and just barely off center, which tells me my valve is being pushed straight down with very little sweep from side to side. This is the correct way to set up valve train.
THANK YOU FOR THIS VIDEO!!!😊 Very informative and helpful 👍. Can't make everyone happy. Just some miserable people out there. I got EXACTLY what i was searching for and understood the material exactly. This is not a 72 hour highly detailed engine build, instructional video. So obviously and naturally, some things are going to be assumed. It's a great video about a specific step. No one is perfect. I appreciate the time you took to make this great video. Helped me tremendously in my journey!! My project and i thank you sir. 😊🙏
For those of you that are being sidetract about the rocker ratio and thinking the ratio affects how many turns of the adjusting nut....this doesn't matter.The rocker ratio could be 1.2:1 or 1.9:1........ you still want to have the centreline of the trunions at 90 degrees to the valve at mid lift.....and then when that is established, measure for pushrod length.
Forrest Miller to be fair, the rocker ratio does affect how many turns you need to turn the adjuster, it’s just that it’s already been included. He is making his calculations based on 1/2 of total VALVE lift, which is your cam lift multiplied by rocker ratio.
Awesome vid! And Id like to take a moment to add you’re hands down the most helpful fella Ive run across. Ive never seen anyone say throw out call me if you need help/have questions as you. Hats off to you sir. 👍🏻👍🏻👊🏻
I was reading "Rocker Geometry" by Jim Miller from Engine Professional, Apr.-Jun. 2010 issue, and trying to wrap my head around it. It's not the easiest article to understand the first time around, and after a couple read overs I looked to see if anyone had done a video on it. This one here made it click right away, and makes it easy. For anyone who watches this, I suggest checking that article out for some more background on why this method works, why measuring "swipe pattern" is tedious, and no way to measure for proper pushrod length, and why a good narrow swipe pattern is simply a by product of using the mid-lift geometry method. Thank you Scott for the easy to understand demonstration.
Man I cannot thank you guys enough for this video. This is the absolute best I have ever seen this process explained and it made measuring my pushrods so much easier. I can't like a video harder. :D
I’m dyslexic AH. The whole geometry and pushrod length calculations voodoo have always been scary to me. This! I understand. This I can do and repeat over and over and check it and feel good about it. This gives us dyslexics a simple “visual” way to see it, understand it and accomplish it without the hoping and praying it correct and that we haven’t made a mistake. Thank you sir. Wish I’d seen this years ago!
I've watched a variety of videos read a lot about setting this up. Everything was all guess work. You're the first to introduce math and when dealing with precision measurements, you can't guess, you must measure. But... HOW? Well you clearly cleared that up. I've been stressing for days about doing this and if I'd get it right. Tons of second guessing and re-watching yours and other videos but your's is the only one that made the most sense. Sure enough, I did everything you said and with the first turns of the cam, I am 100% in spec with the rocker roller on the top of the cam. I'd like to offer you a virtual hug cuz you're amazing :)
Great video, I’ve been racking my brain trying to figure out pushrod length without swapping springs or using solid lifters like almost every other video says you have to do. Thank you.
Would just like to say big Thank you for your Talent. At 7:30 in the video your comment, You just established proper pushrod geometry. I then marked the top of my valve stem with a marker and held my rocker up and moved it back and forth over the valve stem. You now can actually see exactly where the rocker roller is located at half lift. Thanks again Scott for the video.
Here it is I was pondering how to figure it out, knew the info was somewhere, It’s HERE!! Now I can do my Pontiac heads like this with an entire different set up and get the correct PR pieces .. Thank you Very much for this valuable wisdom teaching!!
This is what a video should be, I clicked he told me what he was meant to....I didn't hear about his wife, weather, or saw wrist and tired....made my day, Thank you.
Great video! Thanks for the excellent explanation. I spent a full day of my life trying to figure out push rod length for my 498 stroker BBC. I used 3 different measurement techniques and got consistently different length estimates. Your technique resulted in the longest measurements by about 0.10 - 0.15 over the other methods I used. I decided to rely on your method rather than collapsing lifters, looking at marker patterns, etc. Hope it works properly for me!
His method works on Crane roller rockers, but my roller rockers have a bigger wheel roller on the valve end, so the straight line theory doesnt work for me.
Ummm? Just because the roller at the valve tip is larger, or smaller for that fact, doesn’t change where the center is. You go from center of the trunnion bearing to the center of the tip roller to determine your “center line”. Only hitch I can imagine would be if the intake and exhaust had different size rollers at the tip. And even in that particular case you would just have to measure/setup the intake and exhaust independently.
Best video I have seen yet on how to properly set up rocker geometry. I just watched a different video that was like you said, full of misinformation. Thank you for teaching proper techniques. Awesome video!
Thanks for sharing I was taking notes as you are teaching because I will be performing this method this weekend on my 468 BBC Hyd Roller Cam . I commend Howard Cams wouldn’t sell me push rods when I ordered the cam now I know the reason. More performance and longer life!!!!
I know this vid is like 7 yrs old and contains stellar info I was wondering why no-one has done a video when it comes to shaft mounted roller rockers as setting the pushrod length is quite a different process..I know you said its ok to call I still believe in being courteous and let you ultilize your time in the manner you need to utilize it in instead of me calling at an inopportune time.
So happy to have found this vid. This has been the most logical explanation of doing this. It all makes sense this way. Hands down. I can't wait to apply this. Thx.
Should edit the video to add a note about stock rocker studs sometimes needing to be swapped out for longer to get this method to work. I’m in the middle of trying to figure this out now. Thanks for the vid!
Dare I call this an introductory, no obligation, gift. Absolutely Free! Shirt, pants, wallet and watch... ✔️. I'm not waiting around for the catch here, this is simply well articulated, sound advise offered to showcase a preview of what potential, existing and past customers shall receive. Thank you sir.
Using this method I found out the pushrods I originally bought were dangerously short, .25” too short. Damn I’m glad I took the time to do this. I haven’t put too many miles on it yet so I hope the damage to the valve heads is minimal, it was good on the #1 exh valve I used to check this although my wear pattern was obvious, about 3/32” wide but centered over the top. So centering the roll pattern is obviously not the right way to determine PR length.
+David Sanders Why not use marker??. Marker technique seems much more fool proof than this!. The greater your rocker ratio... the more difficult (read: INACCURATE) this method gets.
If your mocking up the engine, it's best to use a used (previously compressed) head gasket. This will save wasting a new one to get the head in the location it will be on the finished engine.
I wish you could do a video on shafted rockers. This video was fantastic! I am trying to apply what you taught me to find proper shafted rocker arm alignment. Thank you
I'd like to say thank you very much for posting this. After trying to do the marker method and seeing how unreliable it is, I am convinced this is the only way get get an accurate measurement when setting up a hydraulic cam.
Scott, I read through all the comments and appreciate all the advice you willingly give. I had another question. I may be confused on where a hydraulic lifter sits when pumped up and in a running engine. I think I understand all the measurements and rationale however, here is the question. If I set up the geometry as you say, how is the lifter collapsing due to the 3/4 to 1 turn of the rocker arm nut and the resulting lifter collapsing and or where the push rod seat/lifter top cup (where the push rod sits) affect the measurement that we are calculating. In other words, it seems that the collapsing of the hydraulic lifter (versus solid lifter) would change our measurement (and the 90 degrees and so forth). Thanks in advance for your reply.
with hydraulic lifters you need to add the proper preload for the lifter used. Different manufacturers may require different preload for the same engine.
J Cunningham 1/2 turn on your rocker stud wont make a big difference. A 3/8 fine thread bolt has .042 per turn, a 7/16 bolt has .050 per turn. You buy custom pushrods at .050 intervals. Some builders like Ralph Johnson, Smokey Yunick etc. run their rockers on the outboard side of the valve, it turns a 1.5 rocker into a 1.65 rocker. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RjaosX63DkM.html
I loved the video! Was exactly what I needed! No fat, all meat, and not drawn out. Takes time and effort to do these videos and unfortunately, not everyone appreciates that.
Good Video; I have found that if your using Hydraulic Lifters, especially aftermarket anti-pump up types (i.e. isky,crane,etc.) not only do you want to completely submerge the new lifters in Fresh oil (same as your going to use) over night; but before installing them in your engine; leave them submerged and install a pushrod in your drill press and pump the plunger up and down of each lifter until no bubbles come from the purging hole/s in the lifter, Than you have no worries of collapse,preload,etc, after installation
Take an old lifter the same measurement as you are using, take it apart and fill it up with JB Weld, then put it back together to get a good measurement.
great explanation, except he forgot to explain the different measuring requirements for solid lifter and hydraulic lifter. when measuring pushrod length, add .020 for preload, if using hydraulic lifters.
Norm, thanks for the kind words. We add .050" because most hyd roller today have around .140" of plunger travel and the OEM have found more preload allows the lifter to recover quicker.
Loved the video. Well done my friend. Easily understandable and well versed and it tought me a thing or two that for sure.thanks. you just made a subscriber out of me.
Simple and easy to understand, but what do you do with hydraulic lifters? How do you adjust for getting the lash set to the middle of the hydraulic lifter's range? Do we add that to the length?
Finally got to try the half lift method and have to say I dont know what it is but it gave me a length that put the roller tip on the outboard side of the valve tip center line. Something is not right and I did this measurement multiple times and still keep coming up with a pushrod length of 6.50" length. If I use the OE pushrod length of 6.25" the roller tip is on the inboard side of the valve tip center line. Using 6.35" puts the roller tip slightly closer to the center line of the valve tip. Even adding the thickness of the head gasket would still put it at 6.40".
With the length you must have a SBF. Rocker geometry from different mfg vary. You will need backset rocker. If not used a wide centered sweep pattern will wear out valve guides.
@@straubtechnologies9011, yep ford 302 OE roller. I did the math on the 2/3 lift method which in all my reading the other day kept coming up in posts after 2015. With the 2/3 lift method it actually gives me a 6.35" pushrod which puts the starting point just on the intake side of the center of the valve. Still doing some reading on the 2/3 lift method how ever and seeing if it would be a viable alternative for a street driven engine that wont turn over 6,000 rpm.
I use the Manley pushrod checker, comp cams tech had me do it like in the video and the pushrod length were the same both ways …… slip it over stud till it touches top of valve then adj pushrod to touch the checker
The problem I ran into using this method is: when using valves with +0.200" length and lash caps +0.080" the resulting height causes the intersection of angles between the rocker stud and the valve to become such that the roller tip is far to much toward the exhaust side of the stem. So I'm having to find a happy medium between this method and center, or not so center of valve methods.
I've tried this method several times and it leaves my roller tip way off center of the valve. The wear pattern is way outboard like the pushrod is too long.
Hi, I kind of have a confusion about how rocker arm geometry is met when you have a larger cam, because if an aftermarket cam was installed with a larger amount of lift then the stock one, wouldn’t the larger lift cause the rocker arm to be out of spec with 90 degrees at mid lift. And if the push rods were changed to gain 90 degree geometry at mid lift with this new cam wouldn’t you lose the effect of the larger lift. My next question is how do you find correct rocker arm geometry with stock rocker arms, to my knowledge all you can do is just color in the valve tip and then rotate the motor over a few times and keep adjusting the push rod until the mark left on the valve is centered- is this the best way to this with stock rockers? Then how do you find the proper lifter preload, I am working on a 1979 302 Ford and I have been told to give each rocker arm nut a half a turn to set the preload after running the motor at idle loosening each rocker nut until the rocker arm clatters, then tightening the nut just until it quits clattering. When it comes to lifter preload wouldn’t this also change the rocker arm geometry.
Scott, excellent video! You explain the process so that it's very easy to understand and you're very well spoken. Thank you for taking the time to help us all out. I had a quick question though. Do you measure for both intake and exhaust lengths if you have a split pattern cam? Would you use a different push rod length for both if the gross valve lift is different for the intake and exhaust?
Mr. Foxwell, lots of mixed info out there about finding true TDC, how to degree the cam, check it’s specs and measure piston to valve clearance, too. Would love to see what you have to say on these matters. Thanks
I’m using a Howard’s cams lifter and they recommend 1/2 to 3/4 turn for preload so if I were to go 3/4 turn with a 3/8 stud would that mean preload is .0315?
Awesome video indeed! But just to see if I get this right, at the point of extending the adjustable pushrod (9:48) and taking up all the slack, the valve is still in it's fully closed position. So, at this point the lifter was sitting on the base circle of the cam, right?
This works, but you need to add another .050 to compensate for lifter compression, stud flex, and to achieve a better angle at the lift zenith, where spring pressure is highest. Also, this theoretically provides a little more lift...
@@lamont814 Yeah. As regards my original comment; I'm satisfied that I knew what I was talking about at the time, and made the statement to help others. I just don't remember the precise reason at this point, my focus has moved on to other non related subjects, and I honestly don't feel like watching the video again, just to refresh my failed memory. :)
Now THAT was impressive and best of all, you made it EASY to understand, So I gather if my MAX intake lift is .499 is the number to use divided by 2 or the .510 exhaust??Also, if you use a marker on the valve stem tip, is it going to look different than the typical method (center it, rotate, check the mark? ) Part of why I understand this so well is that LP records and tonearms work the same. The angle of the arm outside is very different tha n the inside . So when aligning a tonearm cartridge (using tools) what you are trying to achieve is a balance in the middle because alignment centering at either extreme will cause a flaw at the other end (sorry I digress) hope you can answer my questions and again...AMAZING video
Great video! This is definitely going to help me out. I see it's and old video so I'm not sure if Scott still works there. From the video I could tell if the head gasket was in there. Once you get the measurement shown do you have to add to the measurement for head gasket and valve lash?
Good question. I myself didn't notice if the head gasket was there or not, but curious if it needs to be accounted for. Seems like it would affect the final rod length.
I am building a 540 bbc with dart pro 1s. The question I have is to get proper rocker geometry do u need to torque the head down with the gasket? I also need to check my piston to valve clearance. I would hate crush a brand new gasket in order to set the geometry right. What I am really saying I want the proper pushrod for when I check my piston to valve clearance. Any advice would be greatly appreciated. Thanks
A way to verify that you are checking the pushrod length correctly, is to put black marker or dye on the valve stem tip and rotate the engine by hand after getting the pushrod length correct, and check that the rocker roller is centered and rolls in and out from that center point of the valve stem, through valve lift and back. This is done with Low Pressure checking springs! Thanks
With roller tipped rockers, this is not really a concern anymore. Smokey Yunick learned this after 7 years of hard passes on an engine that had the sweep pattern at around .020 from the outboard edge of the valve tip. The rest of his geometry was all that really mattered. All of his valve guides were perfect, even after 7 years of hard passes on that engine. Sure, in a perfect world, you'd have a perfect 90 degrees between the pushrod and rocker, the valve stem and rocker, AND have a perfect sweep pattern on the valve tip, but with ALL modern roller rockers, the geometry is off by a good margin. Miller rockers were the only real option that addressed this issue perfectly.
