Preload/ pushrod length
Preload/ pushrod length Preload/ pushrod length question? I understand the zero lash but confused about when adding preload? Johnson link lifters states 35 preload but once u add the 35 preload and then torque to 22 wouldn't u be adding more preload by the time you've added the torque? Be nice I'm confused! Lol
I think the method is to check/adjust the intake valve when the exhaust begins to open and check/adjust the exhaust when the intake begins begins to close.
Pretty sure that's how I did it on my old BBC solid roller engine and it worked very well.
Pretty sure that's how I did it on my old BBC solid roller engine and it worked very well.
Once you reach zero lash, anything from that point to the bolt torque spec is preload, if the lifter is on the base of the cam. If you have too much preload, you need a shorter PR, same the other way. Never used link lifters on an LS, so dont know how they bolt down, but same deal, past zero lash is preload. Solid lifters is a diff thing, lol. When tightening or loosening the bolt, the cam should be on the base circle, spring pressure could cause the bolt to strip.
Trending Topics
TECH Enthusiast
Joined: Feb 2020
Posts: 734
Likes: 209
the turn method can and will provide accurate results if you do the math in regards to thread pitch and rocker ratio , also can be backed up by using a dial guage on the pushrod end of the rocker. If you like I will do the math for you ? Always adjust lash / preload with lifter on the base circle of the cam ( however you like to determine that ) weather it's TDC of the compression stroke or the tried and true adjust intake as the exhaust starts to open and exhaust as the intake is almost closed. Using the turning pushrod with fingers method turn the rocker bolt in until there's resistance ( now you're at zero lash) zero or note dial guage reading continue tightening bolt until the ro kernel stand is bottomed to head , difference is the preload . If lifters are full of oil wait for lifter bleed down to get a reading
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Heres what I came up with, 7.650 gives me zero lash and add the preload 0.035) I'm at 7.685 but there isn't a off the shelf 7.685 pushrod u either get a 7.675 or a 7.7 which one is to short and the other is to long? I'm wondering if I could get away using the 7.7 pushrod?
I'm having a heck of a time getting this right!! Kicking my ***!LOL. I went out and rechecked it again and I come up with 7.625 for zero lash and once I added the preload it takes 1.5 turns to get 22 foot pounds of torque which seems like alot? HELP!!
Heres what I came up with, 7.650 gives me zero lash and add the preload 0.035) I'm at 7.685 but there isn't a off the shelf 7.685 pushrod u either get a 7.675 or a 7.7 which one is to short and the other is to long? I'm wondering if I could get away using the 7.7 pushrod?
It's a hydraulic lifter and your looking for the sweet spot which is in the middle of the lifters preload. With a lifter that has a wide range of preload that .01 is not going to wipe out the lifter but it may not be enough to keep it in contact with the cam and quiet it down but what happens once things start to heat up? With too much preload you run closer to a solid and it will make more power but harder on the lifters There are some PR companies that will make any length of pushrod you need. Everyone I see on here pushes for the Manton pushrods and they're probably top notch but I've been running Smith Brothers in my builds without issues.
TECH Enthusiast
Joined: Feb 2020
Posts: 734
Likes: 209
I checked the recommended preload of those lifters .035" + or - .010" so .025 - .045 . Is it iron or aluminum block ? The higher expansion of the aluminum requires a little more preload , I recall one of the manufacturers had different lash specs for solid cams depending on aluminum vs iron block and of course hot or cold - makes sense to me . Have run hyd cams in race applications at only a few thou preload - no issues . Don't over think it , as long as the lifters plunger isn't bottomed out or you don't have actual lash it will work but I would try for the target spec. You mention turns to torque it but how many turns to just get it snug ? Like 50 lbs/in. Bolts are 8 × 1.25 , 1 turn = .049" the rocker ratio increases this ( more so with a low ratio , less with higher ratio ) to roughly. 080" with a 1.7 rocker . Some mathematician can probably get that more accurate but it's close. So you really want about 1/2 turn from zero lash to rocker stand just bottomed to head , any additional turning to reach torque is not part of the measurement. Must ensure you're on the base circle and you're getting zero lash , a bit of feel involved in that so minor variation there.
Thanks a million that makes me feel better knowing the bolt torque specs I didn't read your post until I got it all torqued down but after reading your post I think I did okay! I'm just a hair past a 1/2 of a turn to get 22 lbs of torque I had 7.625 at zero lash I put in a 7.650 I figured that would get me in the ballpark? Thanks for taking the time to write all that. I do have a iron block.