Checking push rod lenth with plastic proform push rod lenth checker

[garvir]

the motor is a sbc with comp cam XR282HR hydraulic roller, crane roller rocker arms. using the PROFORM tool the push rod lenth came out 7.150" long. doing the black marker on the tip of valve, install 7.150 pushrod, install rocker with 1/2 turn lash, turn motor over 3 times, check the mark on top of valve, it is toward the intake side by a little bit, so it is on the short side of lenth. i played around and made sure the push rod was in the middle of the hole, still the same. using my COMP CAM checker, it showed the height needed to be 7.200. doing the same thing with the 7.200" push rod, black marker test, the wear mark on top of valve was right in the middle. .050" off in the lenth of what the proform CHECKER indicated.

actually .050" is really not to bad (not good enough for me though) a lot of guys don't do the black marker check or have a comp push rod checker, JUST EYEBALL IT OR GUESS, THAT LOOKS CLOSE ENOUGH FOR ME. so the proform checker would get them close.

remember the rocker starts out at zero on the base circle, then half way is mid lift, then goes to max lift as it travels over the valve tip.

staub has another push rod lenth checking method that seems like it works well, but i haven't check it out.

[kimosabi]

Use an adjustable pushrod measuring tool and set it up to mid lift geometry. Don't focus too much on the roller has to hit middle on the valve tip, the valve doesn't care as long as you get the push straight.

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

[garvir]

Use an adjustable pushrod measuring tool and set it up to mid lift geometry. Don't focus too much on the roller has to hit middle on the valve tip, the valve doesn't care as long as you get the push straight.

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

proper geometry is when you are at the middle of the valve stem and 90 degrees to the valve with the rocker tip at half lift of the cam, that is what the staub guy said. base lift is 0, mid lift is half your cam total lift, max lift is full cam lift. to me that is the same thing as the black marker on the valve tip showing how the rocker is traveling across the valve tip, it goes from base lift to full lift, and mid lift is in the middle. there is something that i am missing here. i will watch the video a few more times

[gator68428]

The rocker arm needs to be at a 90deg angle wrt the valve axis when the valve is at half lift. Do not worry about the roller contacting exactly in the middle of the valve stem. The main thing is that the rocker arm is moving centered on 90deg at half lift. There isn't much you can do if the roller is off center a little.

[garvir]

The rocker arm needs to be at a 90deg angle wrt the valve axis when the valve is at half lift. Do not worry about the roller contacting exactly in the middle of the valve stem. The main thing is that the rocker arm is moving centered on 90deg at half lift. There isn't much you can do if the roller is off center a little.

one thing the staub guy didn't mention was the lenth of the push rod he uses?? he determined the push rod needed was 8.72", being that push rods go in .050" increments, he is right in the middle, i go to the long side.

a thought about the rocker arm ratios being around a 1.7 being a big block, it seems like that would have an effect on his measuring.

i like the idea, i am finally getting the concept, very simple once i caught on. my intake is on now so i cannot check it now.

[ford396]

Another thing to consider here is that the plunger in the hydraulic lifter is probably traveling in the body of the lifter while rolling engine over and checking contact pattern. This will mess with your measurement.

[garvir]

Another thing to consider here is that the plunger in the hydraulic lifter is probably traveling in the body of the lifter while rolling engine over and checking contact pattern. This will mess with your measurement.

when i check the lift i use a hydraulic roller lifter set down at solid at .031" (that is near 5/8 of a turn on the lash nut) that gives me a good reading without worrying about the plunger moving, basically a solid lifter

[kimosabi]

Pushrod length is different from engine to engine. It depends on what lifters you use, valve length, deck height, rockers, heads etc. I had to get a shortened rocker set to get the mid lift geometry correct.

[garvir]

Pushrod length is different from engine to engine. It depends on what lifters you use, valve length, deck height, rockers, heads etc. I had to get a shortened rocker set to get the mid lift geometry correct.

on my last reply i stated i use .310" for my solid lifter, i missed a 0, it is .031" which equates to 5/8 of a turn tightening the lash, that was pretty close to average lash.

on this last cam change i had 12 crane stainless rockers and had to buy 4 of the comp aluminum gold rockers, being retired and fixed imcome, i have to cheat on things. it worked out pretty good, they all needed the same pushrod lenth. it is kind of pretty seeing the gold rockers on all the corners. this last cam change was an adventure, nothing worked out, everything was difficult, just little stuff, LEARNING CURVE.

[kimosabi]

on my last reply i stated i use .310" for my solid lifter, i missed a 0, it is .031" which equates to 5/8 of a turn tightening the lash, that was pretty close to average lash.

on this last cam change i had 12 crane stainless rockers and had to buy 4 of the comp aluminum gold rockers, being retired and fixed imcome, i have to cheat on things. it worked out pretty good, they all needed the same pushrod lenth. it is kind of pretty seeing the gold rockers on all the corners. this last cam change was an adventure, nothing worked out, everything was difficult, just little stuff, LEARNING CURVE.

As long as you get good geometry I'd say it doesn't matter too much if you mix rockers as long as they have about the same mass. Did you weigh and compare the rockers? I have a .025 length difference between EX and INT pushrods. Got good help from Foxwell and Straub realizing that the rockers were too long and Randy at Harland S came through and made a custom set. Internet said my heads would take normal rockers. Not so.

[garvir]

As long as you get good geometry I'd say it doesn't matter too much if you mix rockers as long as they have about the same mass. Did you weigh and compare the rockers? I have a .025 length difference between EX and INT pushrods. Got good help from Foxwell and Straub realizing that the rockers were too long and Randy at Harland S came through and made a custom set. Internet said my heads would take normal rockers. Not so.

i talked to comp cams a couple times about the weight differance (alum is 150 grams stainless 210 grams) the first thing they asked was what rpm am i running, my car runs between 3000 and 6000, very seldom to i go to 6200, they said i should have no problem as long as i am not turning above 7500. the motor started as a zz430 sbc, several cam changes, somewhere around 430hp (gave up some hp to get great torque) but great torque off the corners. this a road race car, come off corners at 3000 go to 6000, hit the brakes and start all over again. being out there for 20 or 30 minutes is a workout.