[Vrodviddy]

Little new to the forum, so hopping im posting in right area. Just had a quick question. Im in the middle of a cam install of tsp vvt-3 235/239 32% fuel lobe and putting everything back together now went to check my lash and push rod length. I ordered the kit from texas speed. Push rod length they sent was 7.850 (actual length is 7.865). I don't know why they include this in the kit. Think the better option would be send kit and voucher for push rods once you able to check correct length needed to order latter. Anywho. I know stock pushrod i measured at 7.850 with caliper which i think they would really be like a 7.825 oem. the 7.850 is longest offered through , and next size up through tsp. So figured i was probably good. But i know i needed to check anyways. So whats got me puzzled is you would think that naturally the pushrod is going to need to be longer to account for the now Skinner base circle. Well when i use the 7702-1 7.800 to 8.800. Well at 7.800 there is no wiggle in rocker at all and yes im at base circle. And cyl 1 is at top dead center with cam gear arrow pointing at crank dot before i started to check for lash. Put pushrod in cyl 1 exhaust lifter turn crank and just as it starts to come up, switch it to intake where i am checking for lash. i tighten down just snuggly. When i do this no up and down wiggle what so ever. I didn't have heads ported (just for the cost didn't seem worth the money for hp gain you get) but springs are double spring and do seem slightly longer then oem springs, but wouldnt think this would matter cause valves are still stock. I ordered another comp cam pushrod tool, 6.8-7.8 and see where i am at with this when it comes in Wednesday. Just seeing if this kinda puzzles anyone else.

[KingLT1]

There is no lash on a hydraulic valve train. You should have preload and about .080 worth if you are using LS7 lifters.

[Vrodviddy]

I do have ls7 style lifters that come with TSP kit. The method i am doing was taught to me by my buddy who is a mechanic and done several engine builds before. he's been helping me out as i go, but won't be back for couple days, and figured i could at least get correct pushrods on the way. So he Said using an adjustable push rod ensuring that the lifter is on base circle. Start lose and slowly loosen the screw up till there no more up and down slack between rocker and push rod and its snug. That would give you correct pre-load and push rod length. Is there something I'm missing? Cause if not, then that indicates me i have to go shorter then stock, which is what puzzling me.

[KingLT1]

In order to find correct preload for hydraulic lifters with stock LS/LT rockers you use the adjustable pushrod to take the slack out of the rocker. No up and down movement is zero lash. Then you take the adjustable push rod, measure the length with a caliper, then add the amount of desired preload to the initial push rod measurement(.080). That will give you correct lifter preload. You can then Verify by counting the amount of turns it takes to get the the rocker bolt torqued to 22ft lbs. Should be around 1.5 turns to 22ft lbs from zero lash.

[Vrodviddy]

Ok, thats what i thought. So am doing it right. Just need to add .080 to adjustable push rod length once 0 lash is reached. which will give me the pre load and correct pushrod length i need correct? The 1.5 turn from 0 lash... Your saying to verify once i have my new correct length push rod in. Then 1.5 turns till 22 ft lb click?

[KingLT1]

yep that is correct.

[Vrodviddy]

Awesome. ty for your time

[shinysun]

https://youtu.be/OmzbHgVY3cI

Is it different from what you folks are saying? while they have never mentioned pre-load.

[KingLT1]

First off that video is addressing how to find correct push for length on a small block Chevy. While some of that applies the difference is most small block Chevy builds utilize fully adjustable rocker arms, so you adjust the adjuster nut for proper lash or preload. Solid roller lifters requires lash, hydraulic requires preload.

On LS/LT engines the rockers are not adjustable, so if you change cam, mill the heads, change head gaskets, then more then likely you will need to change push rod length to maintain proper lifter preload. On hydraulic stuff ideally you want to keep the push rod length around the half way point of the lifters plunger travel. LS7 lifters have around .200 travel so most shoot for .080-.100 pre load. So once you find correct push rod length @ zero lash, you add the desired amount of preload to the length of the push rod length @ zero lash then order the push rods.

On a SBC you would find correct push for length at zero lash like mentioned in the video then go across each valve and add 1/2 to 3/4 turn on the rocker arm adjuster nut then lock it.

Adjustable rockers allow for more precise valve adjustment but the rockers are normally heavier. Most prefer to stick with the stock style LS/LT rocker arm because it's light weight and easier to control the valvetrain and rev higher. So the trade off is worth it in most cases(mild-moderate street/strip builds). Shaft mount rocker arm systems are the Ultimate but not required for most builds where the cam lobes are under .630 lift or so.

Hope this helps.

[shinysun]

Originally Posted by KingLT1

First off that video is addressing how to find correct push for length on a small block Chevy. While some of that applies the difference is most small block Chevy builds utilize fully adjustable rocker arms, so you adjust the adjuster nut for proper lash or preload. Solid roller lifters requires lash, hydraulic requires preload.

On LS/LT engines the rockers are not adjustable, so if you change cam, mill the heads, change head gaskets, then more then likely you will need to change push rod length to maintain proper lifter preload. On hydraulic stuff ideally you want to keep the push rod length around the half way point of the lifters plunger travel. LS7 lifters have around .200 travel so most shoot for .080-.100 pre load. So once you find correct push rod length @ zero lash, you add the desired amount of preload to the length of the push rod length @ zero lash then order the push rods.

On a SBC you would find correct push for length at zero lash like mentioned in the video then go across each valve and add 1/2 to 3/4 turn on the rocker arm adjuster nut then lock it.

Adjustable rockers allow for more precise valve adjustment but the rockers are normally heavier. Most prefer to stick with the stock style LS/LT rocker arm because it's light weight and easier to control the valvetrain and rev higher. So the trade off is worth it in most cases(mild-moderate street/strip builds). Shaft mount rocker arm systems are the Ultimate but not required for most builds where the cam lobes are under .630 lift or so.

Hope this helps.

Thank you, King. I appreciate it.

[Vrodviddy]

Originally Posted by KingLT1

First off that video is addressing how to find correct push for length on a small block Chevy. While some of that applies the difference is most small block Chevy builds utilize fully adjustable rocker arms, so you adjust the adjuster nut for proper lash or preload. Solid roller lifters requires lash, hydraulic requires preload.

On LS/LT engines the rockers are not adjustable, so if you change cam, mill the heads, change head gaskets, then more then likely you will need to change push rod length to maintain proper lifter preload. On hydraulic stuff ideally you want to keep the push rod length around the half way point of the lifters plunger travel. LS7 lifters have around .200 travel so most shoot for .080-.100 pre load. So once you find correct push rod length @ zero lash, you add the desired amount of preload to the length of the push rod length @ zero lash then order the push rods.

On a SBC you would find correct push for length at zero lash like mentioned in the video then go across each valve and add 1/2 to 3/4 turn on the rocker arm adjuster nut then lock it.

Adjustable rockers allow for more precise valve adjustment but the rockers are normally heavier. Most prefer to stick with the stock style LS/LT rocker arm because it's light weight and easier to control the valvetrain and rev higher. So the trade off is worth it in most cases(mild-moderate street/strip builds). Shaft mount rocker arm systems are the Ultimate but not required for most builds where the cam lobes are under .630 lift or so.

Hope this helps.

Yup. The man knows his stuff! Just got down installing the rockers back in with 7.850 pushrod. And have me roughly .085 preload. Thanks king!

[KingLT1]

No problem.