Stock Rockers-does 22ft/lbs=1 3/8 turn?
10-09-2004, 05:00 PM
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Stock Rockers-does 22ft/lbs=1 3/8 turn? I'm just going over my AS 5.3 heads, the heads according to Jay were not milled any. Anyway I know the rockers get torqued down to 22ft/lbs. However I'm finding it takes 1 3/8 turns from 0 preload to get 22ft/lbs. This is with a Comp 7.4 pushrod and a comp cams XE grind 228/230 .571/.573 camshaft. Now I measured total lifter preload and it worked out to be .096 thou. Now I'm not sure about LS1's but on 5.0's with non-adjustable rockers after 1 full turn u would need to use a shim. Do I need a shorter pushrod like a 7.35?
10-09-2004, 05:35 PM
#2
Lots of people use shims on LS-1's. If you feel the lifters are to tight, just measure what thikness shim you want and use it. Adjusting rocker pre-load by using diffrent pushrods is the wrong way to go. If your rocker tip is located properlly on the valve tip, then I would not change the PR's. If your heads are indeed unmilled, then 7.400's should be perfect.
10-10-2004, 08:10 PM
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Kind of a contradictive statement, it's ok to use shims, but not ok to use a different length pushrod? Maybe I'm just seeing it wrong. Either would change geometry, just depends if it's correct or not, shimming would be easiest though. A shorter PR would be fine as would a shim. Personally, I went with a shorter PR...Even with adjustable rockers you need the proper legth PR to get the right geometry, there are a lot of factors involved though like cam base circle, milled heads, longer valves, etc..
What is OEM max preload anyway?
What is OEM max preload anyway?
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10-11-2004, 10:43 AM
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Okay guys now i'm getting confused? These heads are from Jay at AS, I don't know if the valves are longer than stock-I can't get a hold of him either to find out. I was told the heads are not milled-i asked him not too. One thing I do know is the springs did not have enough seat pressure(1.78 I, 1.8 E with crane duals )-but I fixed that. Now all I know is it took my 1 3/8 of a turn to hit 22lbs after 0 preload. I measured total preload and it was like .096 thou. Is that too much? I know from back in my Stang days 1 3/8 turn was too much too reach 22 ft/lbs-u would need to shim. U should reach 22ft/lbs within 1 turn or less. Now my cam is from comp and XE grind and my car is a 02 Z06. I run 7.4 pushrods-I just want to know what the best way is to correct this or is .096 preload fine? Thanks.
10-11-2004, 10:59 AM
#10
Let me make sure I'm reading this right:
you are saying:
1) you got everything to 0 lash/preload.....
2) you started turning the bolt until it clicked at 22ft/lbs
3) you measured the preload with a dial indicator and found you have thus put 0.096" preload on the lifter
if that is right, then your pushrods are too long (which to me says your heads were milled quite a bit as aftermarket cams usually have a 0.030" smaller base circle) and you should get a set of 7.350" pushrods......that will drop you down to 0.046" (which is still a lot more than I would run).....
once at 0.046" preload (with 7.350" pushrods), I would then see if I could find a set of shims that you can stack up (say a set that has 0.005", 0.010", 0.020", 0.030") and try to get that preload in the 0.005"-0.010" range.
The reason I say put the preload so "low" is because not only can you blow the lifter out with too much preload, but should you float a valve and the lifter pump up, you won’t be holding that valve open more than about 0.005"-0.010" (vs. the 0.040"+ that you would have with just shorter pushrods) and hopefully keep from bending a valve (might still bend a valve depending on how bad the valve float is but every little bit helps…).
you are saying:
1) you got everything to 0 lash/preload.....
2) you started turning the bolt until it clicked at 22ft/lbs
3) you measured the preload with a dial indicator and found you have thus put 0.096" preload on the lifter
if that is right, then your pushrods are too long (which to me says your heads were milled quite a bit as aftermarket cams usually have a 0.030" smaller base circle) and you should get a set of 7.350" pushrods......that will drop you down to 0.046" (which is still a lot more than I would run).....
once at 0.046" preload (with 7.350" pushrods), I would then see if I could find a set of shims that you can stack up (say a set that has 0.005", 0.010", 0.020", 0.030") and try to get that preload in the 0.005"-0.010" range.
The reason I say put the preload so "low" is because not only can you blow the lifter out with too much preload, but should you float a valve and the lifter pump up, you won’t be holding that valve open more than about 0.005"-0.010" (vs. the 0.040"+ that you would have with just shorter pushrods) and hopefully keep from bending a valve (might still bend a valve depending on how bad the valve float is but every little bit helps…).
10-11-2004, 11:07 AM
#12
Originally Posted by Vortech
One thing I do know is the springs did not have enough seat pressure(1.78 I, 1.8 E with crane duals )-but I fixed that.
Now my cam is from comp and XE grind and my car is a 02 Z06.
Now my cam is from comp and XE grind and my car is a 02 Z06.
two questions here:
1) how did you "fix" the spring pressure? did you shim up the springs or did you replace them? If you replaced them, did you figure in how that will affect your max lift vs. coil bind height (ie: will you max the spring out?)?
2) with your car being a Z06 (LS6 heads stock), did you stick with LS6 heads (and more importantly LS6 valves which are longer)? If you still have the LS6 valves, that might be where some of your preload "problem" is from (still solve the way I said to in the above post). My guess is still that your heads are milled some (could be something as little as a 0.005"-0.010" cleanup mill to make them flat).
10-11-2004, 11:22 AM
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Thanks for the responses guys. Now to answer a few questions. I don't have the LS6 heads anymore-I have the AS stage 2.5 5.3 heads. The valvelength I do not know. I replaced the old crane duals with the new ones with the stripes so I shimed the .075 which left the height at 1.705 I and 1.725 E, these new striped springs can take .700lift at 1.8 installed height. I wanted to get 145lbs on the seat so I shimmed accordingly. To double check the spring heights I figured it out like this (Got this from post from Paul at TR), 1.045(coil bind)+.060(clearance)+.571(lift)=1.676. So I'm at 1.705 so I'm okay. Now I also read a post from Roger Vinci where he suggested that alot of valve noise is from incorrect preload-he suggested that alot of people are recomending .04 while .060-.120 is recommended-I'll see if i can find the post. This is why I'm getting confused.
10-11-2004, 11:39 AM
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This is the post about preload:
Hello, this is Roger Vinci and I wanted to comment on spring failure.
I have been told some people are running as liitle as .004 lifter preload rather than .060 to .120 which is the preload VHP recommends. Apparently their cam manufacturer has given them this advice. As you know, the aluminum heads experience significant thermal expansion which would make the preload negative and, in fact, cause the rocker to have lash rather than preload. The result of this misconception is severe valve train noise, knock retard, power loss, and worst of all, severe trauma to the valve springs, which causes premature spring failure. Hydraulic roller camshafts have no clearance ramps and therefore must have lifter preload. We have done extensive dyno testing at our VHP facility and found significant power increases, as well as, much quieter valve train with lifter preload of .060, .090, and .120. Do your self a favor. Try running lifter preload in these ranges. This is easy to accomplish with VHP, or CRANE fully adjustable roller rocker kits.
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Hello, this is Roger Vinci and I wanted to comment on spring failure.
I have been told some people are running as liitle as .004 lifter preload rather than .060 to .120 which is the preload VHP recommends. Apparently their cam manufacturer has given them this advice. As you know, the aluminum heads experience significant thermal expansion which would make the preload negative and, in fact, cause the rocker to have lash rather than preload. The result of this misconception is severe valve train noise, knock retard, power loss, and worst of all, severe trauma to the valve springs, which causes premature spring failure. Hydraulic roller camshafts have no clearance ramps and therefore must have lifter preload. We have done extensive dyno testing at our VHP facility and found significant power increases, as well as, much quieter valve train with lifter preload of .060, .090, and .120. Do your self a favor. Try running lifter preload in these ranges. This is easy to accomplish with VHP, or CRANE fully adjustable roller rocker kits.
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10-11-2004, 12:09 PM
#15
What he is hitting at is that because the heads and block grow, you will "loose" preload. This is why solid cams are all given "Hot lash" settings (if you set the lash at 0.005" cold, you will end up at say 0.015" hot). He is right about the growth and the need for a little extra cold preload (I didn't even think to mention that) but this is why I always set preload and lash hot (fast idle till the oil heats up and then set everything). The reason he is saying have more preload is that the extra (say 0.045") will give you a more gental takeup from the base circle and as such not make so much noise (and stress) in the system. The down side is if you get any valve float, the lifter will pump up and hold the valve open. You can only run high preload settings on stock lifters. If you use something like the Comp-Rs then you HAVE TO run 0.002" preload when HOT (call Comp and they will TELL YOU!). Again, the trick is HOT preload.
If it were my car, I would still shoot for 0.005"-0.010" lash hot. This is going to mean you will need to start with something at about 0.020"-0.025" cold and work from there. The idea is to have as little preload as possible to prevent pump up while still having "some" (ie: 0.005"-0.010") when everything is hot.
Hydraulics are such a PITA.......thats why I went Solid and will never look back
If it were my car, I would still shoot for 0.005"-0.010" lash hot. This is going to mean you will need to start with something at about 0.020"-0.025" cold and work from there. The idea is to have as little preload as possible to prevent pump up while still having "some" (ie: 0.005"-0.010") when everything is hot.
Hydraulics are such a PITA.......thats why I went Solid and will never look back
Last edited by 2001CamaroGuy; 10-11-2004 at 12:21 PM.
10-11-2004, 01:13 PM
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One advantage of the shorter pushrods over shimming the rockers should be valve cover clearance. After I shimmed mine .050 I had to modify the covers....
