push rod length questions
05-07-2018, 10:41 PM
#1
push rod length questions so finally into my dart 427 build and today found out my pushrods are to shorts. so based off my specs pat G gave me a great cam recommendation but i think it was based off stock lifters and i have gone to Comp short travel which i think are shorter than stock correct? is there a way to measure base circle off the cam card instead of off the cam? i ordered a pushrod checker and it will be here soon but this is driving me crazy. also the engine is at my shop and not at home so i can not go in the garage and measure items. i have limited info on hand. so any math guru's out there? also if im going to use the push rod checker, how do i account for the lifter to pump up when the engine is on the stand and i am assembling it?
05-07-2018, 10:55 PM
#2
Basically I spun the adjustable push rod until you feel it change from being free spinning to having a very slight amount of drag while spinning it, that’s your zero. Add whatever length of preload to it you desire. I think I went .050. If you have the intake and valley cover off it’s even easier and better. That method is just unscrew the pushrod and watch the plunger on the lifter. When the plunger just starts to move this is your zero.
05-07-2018, 10:58 PM
#3
Basically I spun the adjustable push rod until you feel it change from being free spinning to having a very slight amount of drag while spinning it, that’s your zero. Add whatever length of preload to it you desire. I think I went .050. If you have the intake and valley cover off it’s even easier and better. That method is just unscrew the pushrod and watch the plunger on the lifter. When the plunger just starts to move this is your zero.
05-10-2018, 09:54 PM
#5
11 Second Club
iTrader: (3)
If the intake and valley cover is off that is by far the best way to find zero lash. If your engine is already in the car and you do not want to remove the intake and valley cover you can still determine zero lash. What you do is.
1.) Remove all the spark plugs so the motor turns over easier and then start on a cylinder usually No. 1 and turn the engine over by hand by turning the harmonic balancer bolt clockwise with a ratchet until you see the exhaust valve on No. 1 begin to open. Once this happens the intake valve on the No. 1 is completely closed and on the base circle of the cam.
2.) Remove the intake rocker arm and the pushrod from the No. 1 cylinder and then put the rocker arm back on and start the rocker arm bolt until it just starts to grab the threads. Once this happens mark the top of the bolt at the 12:00 position with a white dot.
3.) Count how many turns of the dot it takes to fully seat the rocker arm in the pedestal. Do this by hand so you can get a feel for when the bolt is hand tight.
4) Remove rocker arm and bolt and take your PR length checking tool that you've turned out 7-10 turns and install it onto the lifter.
5.) Reinstall your rocker arm and start your bolt again with the dot at the 12:00 position and start counting the turns.
Example: Lets say you got 13-1/4 turns to seat the rocker arm on the pedestal without a pushrod being inserted onto the lifter, and after inserting the PR length checking tool and setting everything back up you started counting the turns and you only got 12 turns until you started feeling resistance. That is an indication that the pushrod length on the checker is too long. Now lets say you counted your turns and got to 13-1/4 turns and you know the rocker arm is now seated on the pedestal. At this point take your finger and see if you can lift the tip of the rocker arm up off the valve, also take your finger and tap repeatedly on the tip of the rocker and listen for a ticking sound. If so then that is an indication that the pushrod is too short. Continue doing this until you have the rocker fully seated and there is no play on the rocker arm. Now carefully remove the PR tool and measure it with a caliper gauge and write down the measurement.
To measure pushrod length on the No. 1 exhaust you would turn the motor over until the intake valve has fully opened and keep turning the engine over until the intake valve starts to close. This tells you that the exhaust valve is completely closed and the lifter is on the base circle of the cam.
6.) Remove the exhaust rocker arm and the pushrod from the No. 1 cylinder and then put the rocker arm back on and start the rocker arm bolt until it just starts to grab the threads. Once this happens mark the top of the bolt at the 12:00 position with a white dot.
7.) Count how many turns of the dot it takes to fully seat the rocker arm in the pedestal. Again by hand only, do not use any ratchets or power tools for this.
I would do this to as many cylinders until I felt I was getting a consistent measurement and this could vary by 0.005. Once your comfortable that you have determined the correct pushrod length at zero lash take that measurement and add the desired lifter preload and order your pushrods. Be sure to tell the company that is making the pushrods that you measured the overall length.
Hope this helps!
1.) Remove all the spark plugs so the motor turns over easier and then start on a cylinder usually No. 1 and turn the engine over by hand by turning the harmonic balancer bolt clockwise with a ratchet until you see the exhaust valve on No. 1 begin to open. Once this happens the intake valve on the No. 1 is completely closed and on the base circle of the cam.
2.) Remove the intake rocker arm and the pushrod from the No. 1 cylinder and then put the rocker arm back on and start the rocker arm bolt until it just starts to grab the threads. Once this happens mark the top of the bolt at the 12:00 position with a white dot.
3.) Count how many turns of the dot it takes to fully seat the rocker arm in the pedestal. Do this by hand so you can get a feel for when the bolt is hand tight.
4) Remove rocker arm and bolt and take your PR length checking tool that you've turned out 7-10 turns and install it onto the lifter.
5.) Reinstall your rocker arm and start your bolt again with the dot at the 12:00 position and start counting the turns.
Example: Lets say you got 13-1/4 turns to seat the rocker arm on the pedestal without a pushrod being inserted onto the lifter, and after inserting the PR length checking tool and setting everything back up you started counting the turns and you only got 12 turns until you started feeling resistance. That is an indication that the pushrod length on the checker is too long. Now lets say you counted your turns and got to 13-1/4 turns and you know the rocker arm is now seated on the pedestal. At this point take your finger and see if you can lift the tip of the rocker arm up off the valve, also take your finger and tap repeatedly on the tip of the rocker and listen for a ticking sound. If so then that is an indication that the pushrod is too short. Continue doing this until you have the rocker fully seated and there is no play on the rocker arm. Now carefully remove the PR tool and measure it with a caliper gauge and write down the measurement.
To measure pushrod length on the No. 1 exhaust you would turn the motor over until the intake valve has fully opened and keep turning the engine over until the intake valve starts to close. This tells you that the exhaust valve is completely closed and the lifter is on the base circle of the cam.
6.) Remove the exhaust rocker arm and the pushrod from the No. 1 cylinder and then put the rocker arm back on and start the rocker arm bolt until it just starts to grab the threads. Once this happens mark the top of the bolt at the 12:00 position with a white dot.
7.) Count how many turns of the dot it takes to fully seat the rocker arm in the pedestal. Again by hand only, do not use any ratchets or power tools for this.
I would do this to as many cylinders until I felt I was getting a consistent measurement and this could vary by 0.005. Once your comfortable that you have determined the correct pushrod length at zero lash take that measurement and add the desired lifter preload and order your pushrods. Be sure to tell the company that is making the pushrods that you measured the overall length.
Hope this helps!
05-10-2018, 10:47 PM
#6
Seems pretty hard to me... I hate work.
All I do is, slide the adjustable push rod in, put the rocker on, and tighten the bolt fully.(let's say, 20 ft-lbs... enough that the lifter, guide, and all that, are solidly held together) Then unscrew the push rod until all the play in the rocker is gone. Then take the rocker back off and pull the push rod and count the turns to come up with the push rod length that gave me "zero lash". At that point I know where "zero lash" is. I do just like this for acoupla intakes and acoupla exhausts on each side; maybe all of em if I'm feeling like it.
Then I buy push rods that are [desired preload] longer than that. Given that push rods we can easily buy come in .025" increments, I tend to shoot for .075" or so of preload with LS7 lifters or the like, and err toward the "more preload" side from there, up to .100". Follow your lifters' mfr's recommendation for how much preload THEIR lifters want and order push rods accordingly.
All I do is, slide the adjustable push rod in, put the rocker on, and tighten the bolt fully.(let's say, 20 ft-lbs... enough that the lifter, guide, and all that, are solidly held together) Then unscrew the push rod until all the play in the rocker is gone. Then take the rocker back off and pull the push rod and count the turns to come up with the push rod length that gave me "zero lash". At that point I know where "zero lash" is. I do just like this for acoupla intakes and acoupla exhausts on each side; maybe all of em if I'm feeling like it.
Then I buy push rods that are [desired preload] longer than that. Given that push rods we can easily buy come in .025" increments, I tend to shoot for .075" or so of preload with LS7 lifters or the like, and err toward the "more preload" side from there, up to .100". Follow your lifters' mfr's recommendation for how much preload THEIR lifters want and order push rods accordingly.
05-11-2018, 04:30 AM
#7
10 Second Club
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05-11-2018, 04:40 AM
#8
with the afr heads i came out with 7.75 just using a tape to measure since my batteries died right when i need my caliper. i talked with some real engine builder buddies and they say that real measurement they get with that combo is 7.77. the short travel lifters only like .020 preload from the instructions and people off here say. so i ordered 7.8 push rods ands the yella terra rocks come with shims for the pedestals. so i should be good.
05-11-2018, 09:39 AM
#9
11 Second Club
iTrader: (3)
Seems pretty hard to me... I hate work.
All I do is, slide the adjustable push rod in, put the rocker on, and tighten the bolt fully.(let's say, 20 ft-lbs... enough that the lifter, guide, and all that, are solidly held together) Then unscrew the push rod until all the play in the rocker is gone. Then take the rocker back off and pull the push rod and count the turns to come up with the push rod length that gave me "zero lash". At that point I know where "zero lash" is. I do just like this for acoupla intakes and acoupla exhausts on each side; maybe all of em if I'm feeling like it.
Then I buy push rods that are [desired preload] longer than that. Given that push rods we can easily buy come in .025" increments, I tend to shoot for .075" or so of preload with LS7 lifters or the like, and err toward the "more preload" side from there, up to .100". Follow your lifters' mfr's recommendation for how much preload THEIR lifters want and order push rods accordingly.
All I do is, slide the adjustable push rod in, put the rocker on, and tighten the bolt fully.(let's say, 20 ft-lbs... enough that the lifter, guide, and all that, are solidly held together) Then unscrew the push rod until all the play in the rocker is gone. Then take the rocker back off and pull the push rod and count the turns to come up with the push rod length that gave me "zero lash". At that point I know where "zero lash" is. I do just like this for acoupla intakes and acoupla exhausts on each side; maybe all of em if I'm feeling like it.
Then I buy push rods that are [desired preload] longer than that. Given that push rods we can easily buy come in .025" increments, I tend to shoot for .075" or so of preload with LS7 lifters or the like, and err toward the "more preload" side from there, up to .100". Follow your lifters' mfr's recommendation for how much preload THEIR lifters want and order push rods accordingly.
05-11-2018, 09:43 AM
#10
11 Second Club
iTrader: (3)
Try getting your fingers on the pushrod with that full roller rocker arm!
05-11-2018, 11:14 AM
#11
05-11-2018, 01:57 PM
#12
11 Second Club
iTrader: (3)
I'm on here to gain knowledge and try to help others from my own experiences nothing more. My profession is in land development not engine building. That does not mean that I'm not capable of building an engine because I've built mine and it's still running. I've often thought to myself how nice I'd be to become a professional engine builder but from my own experience with becoming a professional in my field I know that it takes years of doing something to become a professional at it. Duty calls so I wish you well and good luck with your build.
05-12-2018, 09:25 AM
#13
I'm not seeing anything unusual in the photo? Looks kinda mostly normal to me? Am I missing something?
You don't really "have to" physically adjust the push rod while it's IN the motor... you can adjust it to some initial guess, let's say 7.250", bolt on the rocker, check for play, if it has any take the rocker back off and adjust it out .025", put it back on again and check for play, etc., until you find the length that gives "zero lash". Doesn't take but a second or 2 to R&R a rocker.
You don't really "have to" physically adjust the push rod while it's IN the motor... you can adjust it to some initial guess, let's say 7.250", bolt on the rocker, check for play, if it has any take the rocker back off and adjust it out .025", put it back on again and check for play, etc., until you find the length that gives "zero lash". Doesn't take but a second or 2 to R&R a rocker.
05-12-2018, 12:18 PM
#14
11 Second Club
iTrader: (3)
Take a look at the stock rocker on the No. 1 intake valve and the T&D rocker on the No. 5 intake valve. Notice the area where the pushrod meets the rocker arm.