rocker arm preload
TECH Enthusiast
Joined: Dec 2003
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From: Warner Robins, GA
Originally Posted by Gman2002Z06
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
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Originally Posted by DEEZ98Z
This is exactly the information that I was looking for. I have been told 1/4 -1/2 turn and 1/2 - 1 turn for proper preload. I just put in some 7.35's and they went 1/3 turn past 0 lash until 22lbs. I think this is correct. It is right inbetween 1/4 and 1/2.
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
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
You guys are talking about rocker bolt turns on a non adjustable stock rocker.
What does this have to do with preload???
Whether you shim or change p-rod size, with NON adjustables the bolt tightening is still the same 22lbs/ft.
Now which part didn't I understand ??
Has anyone ever measured the base circle of their higher lift aftermarket cam against the OEM cam? I am sure it will be smaller than OEM.
So you will most definitely have "less" lifter preload when using the aftermarket cam with stock length pushrods and OEM rocker arms torqued to specs.
I have seen people needing longer pushrods when going to a higher lift camshaft to get the correct preload.
So you will most definitely have "less" lifter preload when using the aftermarket cam with stock length pushrods and OEM rocker arms torqued to specs.
I have seen people needing longer pushrods when going to a higher lift camshaft to get the correct preload.
Originally Posted by gollum
Has anyone ever measured the base circle of their higher lift aftermarket cam against the OEM cam? I am sure it will be smaller than OEM.
So you will most definitely have "less" lifter preload when using the aftermarket cam with stock length pushrods and OEM rocker arms torqued to specs.
I have seen people needing longer pushrods when going to a higher lift camshaft to get the correct preload.
So you will most definitely have "less" lifter preload when using the aftermarket cam with stock length pushrods and OEM rocker arms torqued to specs.
I have seen people needing longer pushrods when going to a higher lift camshaft to get the correct preload.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Stock LS1 P-rods are 7.38 and most after market p-rods (advertised as stock) are 7.40. The reason for that is because of the slightly smaller base circle of aftermaket cams.
Now the LS6 cam is even smaller than that, that is why 7.45 p-rods are recommended for LS6 cam applications in a LS1 stock headed car.
Some poeple will tell you they ran stock p-rods with an LS6 cam and "no problem", but they are usually noisier as they rely on their lifters to compensate on pump up.
Now the LS6 cam is even smaller than that, that is why 7.45 p-rods are recommended for LS6 cam applications in a LS1 stock headed car.
Some poeple will tell you they ran stock p-rods with an LS6 cam and "no problem", but they are usually noisier as they rely on their lifters to compensate on pump up.
Okay please listen-this is where i get confused. The Ford 5.0 litre mustang had a non-adjustable valvetrain from 85-95. There are many aftermarket non-adjustable rocker arms available for these cars with Crane being probably the most popular. Now this is from Crane's website. I can't copy it because it is in a PDF but I willl point out the important points where I become confused. Rocker arm torque is 18-20ft/lbs-first reach zero lash then torque the rocker 18-20ft/lbs-this should be achieved within 1 turn which will equal approx-.02-.060 pre-load. If it takes more than 1 turn then u have to shim the pedastel. Now if u can torque the rocker within a 1/4 turn of zero lash then u need a longer pushrod. Now the valvetrain on the 5.0L is also non-adjustable and they sit onf fulcrum bases very similar to the Fords as well-this is why I'm getting confused. Basically what makes the LS1 different? BTW I checked the pushrods from my 02 Z06 and they were 7.38 as well and in 02 the LS6 head had longer valves and a smaller base circle. I'm not trying to cause a stink-I'm just trying to understand how it works.
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Joined: Mar 2004
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From: Fat Chance Hotel
First and foremost, rocker arm torque/preload can only be set when the cam lobe is "down." You do not torque (non-adjustable) or set lash (adjustable) when the cam lobe is opening the valve.
Vortech, the ford rockers are the same. Even when you have non-adjustable rockers there is still a preload on the lifters, but you have to adjust it with pushrods only just like the LS1 when using non-adjustable rockers. This doesn't mean pushrod length is negotiable when using adjustable rockers. You always need to use the correct length pushrods.
Vortech, the ford rockers are the same. Even when you have non-adjustable rockers there is still a preload on the lifters, but you have to adjust it with pushrods only just like the LS1 when using non-adjustable rockers. This doesn't mean pushrod length is negotiable when using adjustable rockers. You always need to use the correct length pushrods.
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Verdad Gallardo Yes I understand this but alot of LS1's change things like the pushrod length(7.4 from 7.38) and a smaller base circle cam. Where as on a 5.0 nobody changes pushrods unless your using TW heads and this is with sticking with the factory cam.
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From: Fat Chance Hotel
There still needs to be a check involved. Crane suggests that the desired spec should be obtainable within 1 full turn, otherwise the geometry is off. The geometry will *probably* be withing spec 99.8% of the time. But they give you a guideline in case there is a problem. With a stock 5.0, you'll drop those rockers on without a hitch. If you changed something like heads or a custom cam that has a smaller base circle or you picked up the wrong pushrods for some reason, then shimming, etc. is required.
On The Tree
Joined: Apr 2004
Posts: 119
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From: Quiet Place in the Country, FL
With any "torque to spec" rocker the torque spec just keeps the rockers from loosening. The preload is established by the relationship of valve stem height (varies if a valve job has been done) and pushrod length. Once the fulcrum is flat against the head, no amount of torque is going to increase the preload. Preload can be adjusted by shims under the fulcrum on some engines (Crane makes these for 5.0Ls and other non adjustable rocker systems, but not for LS1) or by pushrod length.
Most all aftermarket cams have the nose of the cam .005" below the height of the cam journal. This is so the cam can be installed throught the journals. It also is that way so the lobe can be as big as possible which is favorable to lobe dynamics. Since the nose is the same height and location on all cams, that means as the lift increases the basecircle decreases. If you measure your stock cam across the basecircle and then measure your performance cam across the base circle, you will find the performance cam indeed has a smaller measurement. Now if you take half the difference between the two basecircle measurements, you will have exactly how much longer your pushrod must be to have OE preload! It's called geometry!!!!
Now if you have screwed up the valve tip height by not measuring it before a valve job (so you would know how much to grind the tip back to OE height); or if you have milled your heads, the easiest way to accomplish proper preload is to buy a set of adjustable rockers. I happen to like my Cranes because they are extremely quiet; they have the accelerated lift geometry that really does provide a noticeable power increase, and they are adjustable!!
Most all aftermarket cams have the nose of the cam .005" below the height of the cam journal. This is so the cam can be installed throught the journals. It also is that way so the lobe can be as big as possible which is favorable to lobe dynamics. Since the nose is the same height and location on all cams, that means as the lift increases the basecircle decreases. If you measure your stock cam across the basecircle and then measure your performance cam across the base circle, you will find the performance cam indeed has a smaller measurement. Now if you take half the difference between the two basecircle measurements, you will have exactly how much longer your pushrod must be to have OE preload! It's called geometry!!!!
Now if you have screwed up the valve tip height by not measuring it before a valve job (so you would know how much to grind the tip back to OE height); or if you have milled your heads, the easiest way to accomplish proper preload is to buy a set of adjustable rockers. I happen to like my Cranes because they are extremely quiet; they have the accelerated lift geometry that really does provide a noticeable power increase, and they are adjustable!!
Teching In
Joined: Sep 2004
Posts: 25
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From: Colorado
Originally Posted by DEEZ98Z
What is the proper amount of preload after 0 lash? Is it up to 1 turn? 
Are the CRANE GOLD's quieter because of the prescribe preload adjustment (equaling 2 full turns of the adjustment nut, 0.090~0.100 compression) ? If so, wouldn't any rocker be just as quiet using the same amount of preload which is very close to the stock setting.
Last edited by gollum; Nov 23, 2004 at 10:23 AM.
Teching In
Joined: Sep 2004
Posts: 25
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From: Colorado
Originally Posted by technical
Yes, that is correct.
FWIW, in the old days you would adjust the rockers while the engine was running. Loosen then tighten until the tapping was gone.
FWIW, in the old days you would adjust the rockers while the engine was running. Loosen then tighten until the tapping was gone.
Originally Posted by 2001GMC
You forgot to share that even with a set of rocker arm oil deflector clips you got oil all over everything and the more radical the cam, the worse the hot oil bath...the good old days? *L*
Originally Posted by gollum
Are the CRANE GOLD's quieter because of the prescribe preload adjustment (equaling 2 full turns of the adjustment nut, 0.090~0.100 compression) ? If so, wouldn't any rocker be just as quiet using the same amount of preload which is very close to the stock setting.
The ideal preload for stock LS1 lifters is .060. They are forgiving and .040 to .090 will work. I like .060 and not much either way. If Cranes can stand a lot more, my guess is they have rapid bleed down.
