JanTore

When measuring gross lift for valvetrain geometry, do you use the intake and exhaust nr?
When they are different like mine, 610 .632 lift 236 244 dur. @ .050 114 lobe sep.

kornegle

Not sure what exactly you are trying to do, but if you want to measure the cam you would measure at least one intake and one exhaust lobe and they should measure at the specified intake and exhaust lobe lift. If you are checking geometry for pushrods, I usually get or make an adjustable pushrod, install it and change the lengths for each intakea and exhaust lobe until the rocker wipes the narrowest and best centered pattern possible on the valve stem. Then I call the company of my choice and give them the measurements to order the pushrods. Most companies sell them in 0.050" increments.

JanTore

I,m doing the top end and i'm trying to understand how it's done correctly. But the more videos i watch the more confused i get
Have somebody done it the Jim Miller way?

"A. Know your NET valve lift; divide in two; that is your MID-LIFT "motion" (MLM).
B. Measure the height of your valve tip above the retainer.
C. Measure the diameter of the roller; divide in half (this precisely gets you from the bottom of the roller to the AXIS).
D. ADD "B" and "C" together, to get the STACK HEIGHT.
An illustration can be found at: Jim Miller, Installed Geometry G1E.
Now, use a straight edge like the little machinist square shown in this video, and lay it across the valve spring retainer and alongside the trunnion.
F. SUBTRACT or ADD (as needed) the STACK HEIGHT to or from your MID-LIFT MOTION, by raising or lowering the rocker arm on the stud.>EXAMPLE:* NET VALVE LIFT IS .700", so MID-LIFT MOTION is .350".
That's cut in stone, now forget it for the moment (you've written it down).
* Valve tip is .050" above the top of the retainer; and the .500" rocker arm roller diameter tells you its radius is .250", so the STACK HEIGHT is .300".SOLUTION:If the STACK HEIGHT is .300" and the MLM is .350", then you need to place the trunnion .050" BELOW the valve spring retainer.
If your math has the inversion of this, then your trunnion centerline would be above the straight edge coming off the retainer.
SUMMARY:DO EVERYTHING IN THE CLOSED VALVE POSITION, AFTER YOU KNOW NET LIFT.
It's much easier to get an accurate DIAL CALIPER measurement on hard points, to find their true center-lines, than trying to use visuals that only give you approximate values. You can use the outer edges of the trunnion's diameter and divide in two for its center, which is far more accurate than eye-balling." Jim Miller-

hogie roll

BBC lifts are quoted x 1.7 rocker ratio, so your lobe lift is 0.359” and 0.372”.

The terminology used is “net lift” and lobe lift

TomZ

I may get some flak for this....

Mid-lift method - pain in the arse to get right. Much more trouble than it's worth.

Jeff Smith has a write-up that works and is recommended by Trend:

https://blog.trendperform.com/how-to...train-geometry

JanTore

Thank you very much!

Smitty275

Mid lift is to much work for no gain. Straub Technologies has a great video and it's easy as pie.

JanTore

Yes this was the video a was planning to use as my reference, but if you scroll down the comment section in this video, you will find a comment by Jim Miller saying the 90* measurement is wrong. That's why it's so confusing, everybody has their own opinion...
Maybe i'm just overthinking this whole procedure, but i will now use this video and the link from TomZ, and ignore all the rest

underpsi68

what about lifter preload?

TomZ

You really have to do this with a solid lifter that is the exact height of the lifters you’ll use. If the lifter is hydraulic and not pumped up, you have to be very precise with the feel while taking the slack out via the adjustable pushrod - you do not want the lifter plunger to move.

I use a 12-inch digital caliper to measure the overall length. Once you have your measurement, add your preload (I added .025 to the length - 1/2 a turn).