rocker arm preload
11-19-2004, 07:05 AM
#3
On The Tree
Join Date: Sep 2004
Location: St. Clair
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
Yes, it does depend alot on whos rockers you are using...They may have different thread pitches on the stud bolts...Crane recommends two full turns after zero lash to complete the preload...
From what I have read, anything between 0.060" to 0.120" is best for the LS1...If you go too little on the preload, as the aluminum engine heats up, the preload decreases and you will get a very noisey valvetrain...
After my cam install, my valvetrain is really loud after the engine gets hot...When it is cold, it doesn't make a single tapping noise, but after...Yikes...
Have a set of the Crane adjustables coming UPS today...Will be installing this weekend to hopefully take care of the tapping...
Peace...Gman
From what I have read, anything between 0.060" to 0.120" is best for the LS1...If you go too little on the preload, as the aluminum engine heats up, the preload decreases and you will get a very noisey valvetrain...
After my cam install, my valvetrain is really loud after the engine gets hot...When it is cold, it doesn't make a single tapping noise, but after...Yikes...
Have a set of the Crane adjustables coming UPS today...Will be installing this weekend to hopefully take care of the tapping...
Peace...Gman
11-19-2004, 07:36 AM
#6
TECH Senior Member
11-19-2004, 09:32 AM
#7
10 Second Club
Thread Starter
iTrader: (5)
Join Date: Dec 2002
Location: Maryland
Posts: 1,003
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by PREDATOR-Z
Trending Topics
11-19-2004, 09:47 AM
#8
TECH Regular
iTrader: (1)
Join Date: Nov 2003
Location: Washington Township, NJ
Posts: 490
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DEEZ98Z
What is the proper amount of preload after 0 lash? Is it up to 1 turn? 
11-19-2004, 09:51 PM
#9
On The Tree
Join Date: Sep 2004
Location: St. Clair
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
I have never measured what the stock preload was on either my Z06 or the FRC that I had...But, if your valvetrain is totally stock, then you don't have a choice as to what it is...You tighten the rocker bolt to 22ft-lbs and that is it...Preload is set by the rocker sitting on its seat...You have no adjustment from the factory...That is why there are adjustable units available, when you start modifying things, like changing a cam or something, you effectively change the geometry of all the parts alignments...
As per CraneCams set-up sheet...They recommend 0.06" to 0.12" of preload after zerol lash...
Peace...Gman
As per CraneCams set-up sheet...They recommend 0.06" to 0.12" of preload after zerol lash...
Peace...Gman
11-19-2004, 11:14 PM
#11
8 Second Club
iTrader: (18)
Join Date: Oct 2002
Location: Waterloo, Ontario
Posts: 2,609
Likes: 0
Received 0 Likes
on
0 Posts
I think this question needs to looked at further. What if your using stock rockers but using a stock head,ported heads, shaved heads, different valve sizes, different cam than stock. These factors can affect how much preload u have to get 22ft/lb of torque. There has to be a spec in a chev manual that says 22ft/lb's equal x amount of preload?
11-20-2004, 12:11 AM
#12
TECH Senior Member
Ideally once you start milling .020+ you should use adjustable rockers to get proper preload. Stock rockers are NON ADJUSTABLES. You can't adjust preload on them.
0 lash (meaning when the p-rods quits moving by tightening the rocker bolt) then 22 lbs/ft.
0 lash (meaning when the p-rods quits moving by tightening the rocker bolt) then 22 lbs/ft.
11-20-2004, 08:55 AM
#13
8 Second Club
iTrader: (18)
Join Date: Oct 2002
Location: Waterloo, Ontario
Posts: 2,609
Likes: 0
Received 0 Likes
on
0 Posts
But I don't see guys like LG or AFR switching to adjustable rockers when they mill the heads down to 59CC. They get the preload by using a shorter pushrod. Or u can shim the rocker base to with a shim to correct for how much u milled. I know in a 5.0 mustang with non-adjustable rockers the spec was 24ft/lb of torque after zero lash-this was supposed to be accomplished within 1 turn. Now i checked my car when installing heads-this is with AS stage 2.5 5.3 heads unmilled. After zero preload (7.4)it took 1 3/8 of a turn to hit 22ft/lb's-that was .96 thou of preload. I didn't thank that was right so I switched to a 7.35 pushrod and dropped preload to .46. Another thing with aftermarket rocker arms is I don't see too may people using them-they all seem to put too much of a load over the valve tip and lead to float.
11-20-2004, 09:01 AM
#14
TECH Senior Member
I switched to a 7.35 pushrod and dropped preload to .46
You measured all the rockers and got the same preload?
I'll cut my left nut if that is the case. (figure of speech)
11-20-2004, 09:28 AM
#15
Carcraft Magazine states:
In general, most LS1/LS6 engine builders say a stock valvetrain with the proper geometry will require the rocker holddown bolt be turned another 1 1/2
turns beyond the point where the pushrod will not spin between fingers. This is considered lifter preload with engine hot.
These same engine-builders have found power by running less valvetrain preload. The general concensus is that power exists in valvtrains with a preload of about 3/4 turn of the holddown bolts. On a stock head, this would mean you'd run about a 0.040 inch shorter pushrod to achieve this - but allways measure your valvetrain for this measurement. Most of the aftermarket valvetrain companies offer LS1/LS6 pushrods in multiple-length increments to allow geometry tuning. You could buy adjustable rockers, but they will just add valvetrain weight (not good for high- rpm applications) and cost that can be rectified with the proper pushrod length.
In general, most LS1/LS6 engine builders say a stock valvetrain with the proper geometry will require the rocker holddown bolt be turned another 1 1/2
turns beyond the point where the pushrod will not spin between fingers. This is considered lifter preload with engine hot.
These same engine-builders have found power by running less valvetrain preload. The general concensus is that power exists in valvtrains with a preload of about 3/4 turn of the holddown bolts. On a stock head, this would mean you'd run about a 0.040 inch shorter pushrod to achieve this - but allways measure your valvetrain for this measurement. Most of the aftermarket valvetrain companies offer LS1/LS6 pushrods in multiple-length increments to allow geometry tuning. You could buy adjustable rockers, but they will just add valvetrain weight (not good for high- rpm applications) and cost that can be rectified with the proper pushrod length.
Last edited by gollum; 11-20-2004 at 01:27 PM.
11-20-2004, 09:45 AM
#16
TECH Senior Member
Guys why are you stuck on this 1.5, 1.75, 1.2 1.2 turn BS......
0 lash THEN 22 LBS/FT trq with a really good torque wrench.
FGS how hard is this to understand.
0 lash THEN 22 LBS/FT trq with a really good torque wrench.
FGS how hard is this to understand.
11-20-2004, 09:57 AM
#18
Originally Posted by PREDATOR-Z
Guys why are you stuck on this 1.5, 1.75, 1.2 1.2 turn BS......
0 lash THEN 22 LBS/FT trq with a really good torque wrench.
FGS how hard is this to understand.
0 lash THEN 22 LBS/FT trq with a really good torque wrench.
FGS how hard is this to understand.
Last edited by gollum; 11-20-2004 at 10:32 AM.
11-20-2004, 06:36 PM
#19
On The Tree
Join Date: Sep 2004
Location: St. Clair
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
Prededtor Z asks..."Guys why are you stuck on this 1.5, 1.75, 1.2 1.2 turn BS......
0 lash THEN 22 LBS/FT trq with a really good torque wrench.
FGS how hard is this to understand."
Many of you are confusing "PRELOAD" with "THE ROCKER BOLT TORQUE SPEC"...So, me try to explain this simpler...
Stock LS1 rockers are not adjustable...The rocker pivot sits down flush in the rocker rail seat...You tighten the rocker bolt to 22ft.lbs. so that it does not come loose...
The rocker is totally down, as far as it will go...Even if you tighten the rocker bolt to 50ft.lbs., there will be no additional pressure added to the lifter...
This is the reason that if you need to physically change the amount of preload on a stock LS1 style valvetrain, you must change the length of the pushrod, or shim the rocker rail...
Now, with the adjustable rockers...There is no TORQUE DOWN spec for the rockers...And this is because the rockers DO NOT SIT DOWN ON ANYTHING...Preload from the lifters is all that keeps them in contact with the upper adjusting bolt...
I just finished installing the CraneCams Gold Race Adjustables on my Z06 at about 5 p.m. today...The install procedures were as follows...Hand tighten the rocker adjusting bolt until ZERO lash (no lifter compression and no spring tension)...Rotate the engine 1 full revolution and tighten any loose bolts...Repeat for a second revolution...
This determines the base starting point...Then is increments of 1/4 turn on each adjusting bolt, begin tightening all rockers down...Wait 15 minutes between each incremental adjustment...Do this a total of 8 times...
Now, what did that mean in actual inches of preload...
ZERO LASH...Measured 0.320"~0.330" from the top of the adjusting bolts down to the pivot bolts on all 16 rockers...
After final 8th 1/4 turn or 2 full turns...The same measurement now checked 0.230"~0.240"...
So, basically CraneCams is specifying 0.090"~0.100" of preload height...
Hope this helps...
BY THE WAY...THIS SWAP DID IN FACT ELIMINATE MY TAPPING...THE VALVETRAIN IS NOW VERY SWEET SOUNDING AND NO TAPPING...
As for you guys that are saying less preload has been making more power...I read a good thread on this last week, which sealed my decision to go with the adj. rockers...
Basically, what it said was this...With the all ALUMINUM LS1 engines...If you do not have enough lifter preload, i.e. 0.04" or less...As the engine and heads get hot and GROW...You loose that preload, effectively giving you less and less as the engine gets warmer and warmer...
In my case, when I first started my car in the morning...IT WAS PERFECTLY QUITE...Then as it warmed up, the tapping would get louder and louder...At first, I thought it was lifters going down/failing...Then I read this thread and it made alot more sense...So, I went with the rocker swap...
One other point I would like to clarify...Gollum...The ProGold rockers did not appear to be any heavier than the stock rockers...And the mounting bolt and adjusting bolt do not move with the rocker, so they add nothing to the "effective" valvetrain weight...
Peace...Gman
0 lash THEN 22 LBS/FT trq with a really good torque wrench.
FGS how hard is this to understand."
Many of you are confusing "PRELOAD" with "THE ROCKER BOLT TORQUE SPEC"...So, me try to explain this simpler...
Stock LS1 rockers are not adjustable...The rocker pivot sits down flush in the rocker rail seat...You tighten the rocker bolt to 22ft.lbs. so that it does not come loose...
The rocker is totally down, as far as it will go...Even if you tighten the rocker bolt to 50ft.lbs., there will be no additional pressure added to the lifter...
This is the reason that if you need to physically change the amount of preload on a stock LS1 style valvetrain, you must change the length of the pushrod, or shim the rocker rail...
Now, with the adjustable rockers...There is no TORQUE DOWN spec for the rockers...And this is because the rockers DO NOT SIT DOWN ON ANYTHING...Preload from the lifters is all that keeps them in contact with the upper adjusting bolt...
I just finished installing the CraneCams Gold Race Adjustables on my Z06 at about 5 p.m. today...The install procedures were as follows...Hand tighten the rocker adjusting bolt until ZERO lash (no lifter compression and no spring tension)...Rotate the engine 1 full revolution and tighten any loose bolts...Repeat for a second revolution...
This determines the base starting point...Then is increments of 1/4 turn on each adjusting bolt, begin tightening all rockers down...Wait 15 minutes between each incremental adjustment...Do this a total of 8 times...
Now, what did that mean in actual inches of preload...
ZERO LASH...Measured 0.320"~0.330" from the top of the adjusting bolts down to the pivot bolts on all 16 rockers...
After final 8th 1/4 turn or 2 full turns...The same measurement now checked 0.230"~0.240"...
So, basically CraneCams is specifying 0.090"~0.100" of preload height...
Hope this helps...
BY THE WAY...THIS SWAP DID IN FACT ELIMINATE MY TAPPING...THE VALVETRAIN IS NOW VERY SWEET SOUNDING AND NO TAPPING...
As for you guys that are saying less preload has been making more power...I read a good thread on this last week, which sealed my decision to go with the adj. rockers...
Basically, what it said was this...With the all ALUMINUM LS1 engines...If you do not have enough lifter preload, i.e. 0.04" or less...As the engine and heads get hot and GROW...You loose that preload, effectively giving you less and less as the engine gets warmer and warmer...
In my case, when I first started my car in the morning...IT WAS PERFECTLY QUITE...Then as it warmed up, the tapping would get louder and louder...At first, I thought it was lifters going down/failing...Then I read this thread and it made alot more sense...So, I went with the rocker swap...
One other point I would like to clarify...Gollum...The ProGold rockers did not appear to be any heavier than the stock rockers...And the mounting bolt and adjusting bolt do not move with the rocker, so they add nothing to the "effective" valvetrain weight...
Peace...Gman
Last edited by Gman2002Z06; 11-20-2004 at 07:17 PM.
11-20-2004, 07:51 PM
#20
10 Second Club
Thread Starter
iTrader: (5)
Join Date: Dec 2002
Location: Maryland
Posts: 1,003
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by gollum
Carcraft Magazine states:
In general, most LS1/LS6 engine builders say a stock valvetrain with the proper geometry will require the rocker holddown bolt be turned another 1 1/2
turns beyond the point where the pushrod will not spin between fingers. This is considered lifter preload with engine hot.
These same engine-builders have found power by running less valvetrain preload. The general concensus is that power exists in valvtrains with a preload of about 3/4 turn of the holddown bolts. On a stock head, this would mean you'd run about a 0.040 inch shorter pushrod to achieve this - but allways measure your valvetrain for this measurement. Most of the aftermarket valvetrain companies offer LS1/LS6 pushrods in multiple-length increments to allow geometry tuning. You could buy adjustable rockers, but they will just add valvetrain weight (not good for high- rpm applications) and cost that can be rectified with the proper pushrod length.
In general, most LS1/LS6 engine builders say a stock valvetrain with the proper geometry will require the rocker holddown bolt be turned another 1 1/2
turns beyond the point where the pushrod will not spin between fingers. This is considered lifter preload with engine hot.
These same engine-builders have found power by running less valvetrain preload. The general concensus is that power exists in valvtrains with a preload of about 3/4 turn of the holddown bolts. On a stock head, this would mean you'd run about a 0.040 inch shorter pushrod to achieve this - but allways measure your valvetrain for this measurement. Most of the aftermarket valvetrain companies offer LS1/LS6 pushrods in multiple-length increments to allow geometry tuning. You could buy adjustable rockers, but they will just add valvetrain weight (not good for high- rpm applications) and cost that can be rectified with the proper pushrod length.
PredetorZ. You are just not understanding things. I have a custom ground cam and apperently I needed a different length pushrod. Yes you torque the rockers to 22lbs and go IF you have the right valvetrain preload. If I were to keep the 7.4's I would be hanging valves open, so I had to go with a shorter pushrod.
Thanks for the replies guys... I think I am set now