Complete noob needs help with pushrod length - LS1TECH - Camaro and Firebird Forum Discussion



Generation III External Engine LS1 | LS6 | Bolt-Ons | Intakes | Exhaust | Ignition | Accessories
Sponsored by:
Sponsored by:

Complete noob needs help with pushrod length

Reply
 
Thread Tools Search this Thread
Old 03-18-2017, 02:05 AM   #1
Teching In
Thread Starter
 
Join Date: Nov 2016
Posts: 17
Default Complete noob needs help with pushrod length

Hey everyone, I f***ed up and ordered the wrong pushrods.

I bought a length tool off of ebay and when I tried to check length myself it came out to 7.175 so I ordered BTR 7.2 since thats the smallest size available.

Some of my rockers after being torqued are extremely loose when not compressing the spring, pretty sure this isn't right... take it easy on me this is my first build so...

Is my pushrod length wrong? If so could someone tell me my pushrod length based off my cam and everything?

If so, Specs:
Torquer V4 Camshaft
LS7 Lifters
PRC stage 2.5 243 Heads milled .020
BTR .660 springs
Comp cams rockers with trunion

I believe there is a mathematical way to calculate length without the tool so if someone can do that for me that'd be great.... i dont know the base circle of the cam etc so.... IDK I'm just frustrated I didn't get it right. I'm not good when it comes to these things. The tool I used is ZZperformance I believe.
irocbob is offline   Reply With Quote
Old 03-18-2017, 04:53 AM   #2
Staging Lane
iTrader: (1)
 
Join Date: Nov 2015
Location: Nebraska
Posts: 97
Default

Are you sure your lifters were resting on the cam and not held in their lifter tray? Take your pushrod and give it a slight push to pop them out of the buckets if they are.

Drop the checker in. Torque your rocker down to 22 ft lb and adjust the length of the push rod so there is no more vertical play in the rocker tip. It may take a few tries to get the length right. Just put a piece of tape on the checker so it doesn't grow or shrink while doing this. Measure a few and check them with a caliper. Once you have this measurement don't forget to add your preload.
TrentB is offline   Reply With Quote
Old 03-18-2017, 08:25 AM   #3
TECH Fanatic
 
big hammer's Avatar
 
Join Date: May 2009
Location: over dere
Posts: 1,612
Default

It's possible the lifter wasn't all the way down when you measured
big hammer is online now   Reply With Quote
Old 03-20-2017, 01:00 AM   #4
Teching In
Thread Starter
 
Join Date: Nov 2016
Posts: 17
Default

Quote:
Originally Posted by TrentB View Post
Are you sure your lifters were resting on the cam and not held in their lifter tray? Take your pushrod and give it a slight push to pop them out of the buckets if they are.

Drop the checker in. Torque your rocker down to 22 ft lb and adjust the length of the push rod so there is no more vertical play in the rocker tip. It may take a few tries to get the length right. Just put a piece of tape on the checker so it doesn't grow or shrink while doing this. Measure a few and check them with a caliper. Once you have this measurement don't forget to add your preload.
Thanks for the info I really appreciate it. I'll do that for sure. Seems simple enough.. how hard of a push? don't want to force it enough to break it lol but just a good thud? Also, what should my preload be? not sure on that lol. And do I just add the preload number to the pushrod length? IE 7.4 + .070 which would make my length 7.470?
irocbob is offline   Reply With Quote
Old 03-20-2017, 06:51 AM   #5
Staging Lane
iTrader: (1)
 
Join Date: Nov 2015
Location: Nebraska
Posts: 97
Default

Quote:
Originally Posted by irocbob View Post
Thanks for the info I really appreciate it. I'll do that for sure. Seems simple enough.. how hard of a push? don't want to force it enough to break it lol but just a good thud? Also, what should my preload be? not sure on that lol. And do I just add the preload number to the pushrod length? IE 7.4 + .070 which would make my length 7.470?
Put your thumb on the pushrods and just keep applying pressure until they drop. Don't worry about anything breaking.
Preload is specific to the lifters you're using. Some use less some use more.
Yeah you add your measurement plus preload and that is your pushrods final length. You're really just tightening down the rocker and measuring the distance from the lifter to the rocker. Then add the distance you want the lifter to be preloaded.
TrentB is offline   Reply With Quote
Old 03-22-2017, 09:46 AM   #6
On The Tree
 
Join Date: Sep 2014
Posts: 127
Default

So what is the normal pre load people go buy when using ls7 lifters? I have to do this to mine as well. Plan on doing it today after work
5FOX3 is offline   Reply With Quote
Old 03-28-2017, 02:59 AM   #7
Teching In
Thread Starter
 
Join Date: Nov 2016
Posts: 17
Default

Quote:
Originally Posted by TrentB View Post
Put your thumb on the pushrods and just keep applying pressure until they drop. Don't worry about anything breaking.
Preload is specific to the lifters you're using. Some use less some use more.
Yeah you add your measurement plus preload and that is your pushrods final length. You're really just tightening down the rocker and measuring the distance from the lifter to the rocker. Then add the distance you want the lifter to be preloaded.
So I checked on a couple different valves I confirmed were closed shut...
Snug down rocker, it had barely any side to side movement and no up and down movement (which is what I should look for according to other threads?) . It took 12 turns to get to that point. After math (each turn on my specific tool is .035) I came up with a 7.22 length.

Now I add my preload which for ls7 lifters is apparently .050 which would make me at 7.272 .... Considering how snug the rocker was when I checked.. just snugged with a ratchet. I still feel like I'm wrong because my previous length I ordered was 7.2 and when the valve was closed the rocker was able to move a lot, although I did not add preload to that length as a mistake. Will that .75 really make a huge difference and stop all that play on final assembly? Do I order a 7.275 or should I go with 7.3 or 7.25? Don't want to get this wrong... thanks..
irocbob is offline   Reply With Quote
Old 03-28-2017, 08:41 PM   #8
Teching In
Thread Starter
 
Join Date: Nov 2016
Posts: 17
Default

bump....
irocbob is offline   Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Help! pushrod length. WS6GMguy Generation III Internal Engine 11 06-15-2017 05:10 AM
pushrod length dilemma Snow Dog LT1-LT4 Modifications 13 04-24-2017 06:01 AM
Help picking pushrod length nickb123 Generation III Internal Engine 12 05-03-2016 12:42 AM
PLZ HELP What pushrod length is needed for milled .020 243s? NewkidontheBlock93 Generation III External Engine 2 03-29-2016 07:26 AM
Pushrod length using base circle!! Jarren_b Generation III Internal Engine 21 03-24-2015 07:01 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 07:47 PM.


 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: