BadLtBlu99TA

iTrader: (9)

hey i have a 402cid shortblock , im putting stage 3 patriot heads with 64cc chambers on it with 2.080 intake valve and 1.6 exhaust valve in the heads with duel valve springs with 650 max lift springs , with LS7 lifters and stock gm mls head gaskets and a 240/244 , 610/612 lift on a 112 lsa + 2 or 3* ground into the hydralic roller camshaft for A4 automatic 4L60E tranmission. Now my 2 questions are what size pushrods would i need 7.400 ? or different then this ?

My second question is this , I understand the less preload you use when tightening the rocker arm bolts down the more intake and exhaust valve lift you will have , but what i dont understand here it confuses me , keep in mind here for the mean while im using my stock Ls2 crate engine rocker arms and rocker arm bolts too on this 402cid engine , is this a big worry , would these rocker arms break ?.

So what im having trouble understanding here is how can you use a preload of lets say .040 on the lifters when the rocker arm stock bolts have to be torqued to spec ? 22ftlb's ? how can this happen ? cause you wouldnt think that would all come out to the right preload or would it ? what am i leaving out here when im trying to understand this ?

What is a good preload to set for my 402cid alum block ?

If you could help me out here i would greatly appriciate it , thanks again ..

racecar

With anything other than stock heads, you are going to need to verify the correct pushrod length. When you make any change to the valve train, (mill the head or grind the valves, etc.) the total height can change.
If you have changed the valvetrain combination, you may need adjustable rockers, or the precise pushrod length to get the preload right.

fenix999

iTrader: (17)

from my understanding with these motors, you just torque the rockers all down to the specified amount, and they will "seat" themselves. They will also load up by themselves as the engine runs for the first few moments with oil pressure...but dont take my word for it maybe someone else has better info for you since your motor is not close to stock...good luck

chuckyt1

iTrader: (33)

This is a post from Vettenuts about measuring pr length,

Each turn of the pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker.

1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place but my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.

To figure out your pushrod length you do the following. Let’s assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".

Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:

6.800 +10.5 X 0.050 = 7.325"

This is the length you measured to zero lash without any lifter preload. Now let’s say you want to have 0.075" lifter preload, you add that to the measured number and you end up with 7.400" pushrods.

Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker.

This is from me...

Get a PR length checker and measure to make sure you have the right PR length, when you have the correct length PR and torque the rockers to 22 ft/lbs, you will get the correct preload. Your preload should remain relatively constant throughout rotation and will not change valve lift. Stock rockers should be fine although you can have them rebuilt by Harland...

vettenuts

iTrader: (4)

See below

BadLtBlu99TA

iTrader: (9)

Ok now Tsp is Telling me that .040 - .050 is the preload it should be
Speed inc is saying it should be .050 - .060 preload , and people on this board are saying .080- .100 ?????

Im using my Stock rocker arms with 7.400 pr length and from the time i Snug my rockers to zero lash , no preload . to 22ftlbs of torque , its about 1 3/8' of a Turn , which would come out to around .060 to .066 preload , that is saying that ever 1/4 turn of preload is .012 .. so what does everyone think here ? if i went to a 7.350 pushrod i wouldnt have but maybe .010 to .016 prelaod , and if i went to 7.450 i would have around .084 to around .090 preload , Thats why im thinking that these 7.400 pushrods will be ok .. with .060 to .066 preload ..

vettenuts

iTrader: (4)

You can't compute preload that way. If I remember correctly, the threads are 8mm X 1.25, so every turn is 1.25mm or 0.049". Using the rocker ratio (parallel triangles), you get every turn is 2.54/1.54 * 0.049" = 0.080". 1-3/8 turns should therefore be 0.110" or there abouts as an approximation. You really need to measure, and I don't agree with the low preload numbers these guys are throwing at you.

BadLtBlu99TA

iTrader: (9)

i dont see how your getting you get every turn is 2.54/1.54 * 0.049" = 0.080". 1-3/8 turns should therefore be 0.110" or there abouts as an approximation

I measured it , Zero lash is when you cant move the rocker tip at the vavle spring , then start your 22ft;b from there , and .060 is what i GET!!!

BadLtBlu99TA

iTrader: (9)

Do LS7 Lifters need more Preload then LS2 lifter or somthing ?

BadLtBlu99TA

iTrader: (9)

I checked the pushrod lenght 4 times with the Adjustable pushrod lenght checker ..

This I started basied on Zero lash , Bolts just snug when the stock rocker arm tip is just sitting on the vavle spring and there is no lash, then i tightened it down .. and here is what i got , This is Basied on 1 turn = .050 of an inch ..

For 7.350 Lenght pushrod = about 3/8" turn which would be about .01875 Preload. Which i know for sure it wouldnt be a 7.350 pushrod lenght That i needed .

For 7.400 Stock = 1 3/8 turn , which would be about .06875 preload. which seems more right

For 7.425 Pushrod lenght it would = 1 1/4 turn , which didnt seem right either = .0625 preload

For 7.450 pushrod lenght = 1 5/8" turn which would be .08125 preload

So what size pushrod does everything think will be fine for me ? im thinking the stock pushrods will be fine , but i would like some opinions ?

vettenuts

iTrader: (4)

If you have an adjustable pushrod, see post #4 above on how to use. You don't measure turns of the rocker bolts, it is turns of the pushrod. Let me know if you have questions.

jtl12419

iTrader: (13)

I was where you are. To much mysticism going on here. You are really being given alot of confusing info mixed in with engine jargon that makes no sense given your situation. No offense to those guys who have answered you questions already, and who know more than I do.

Preload refers to the amount of baseline displacement of the hydraulic lifter piston, or the amount of "tension" put onto the solid mechanical lifter.

If you are using stock OE style rockers, and stock GM lifters, you DO NOT ADJUST preload at the lifter- there is no way to do it. If you want to do that, buy an adjustable set of rockers You just torque them down to 22-25 ftlbs. while on the base circle. Period. Done.

You indirectly affect the lifter (preload) with this stock setup using the pushrod length. You must have the correct pushrod length.

You guess at the near correct pushrod length, and using the pushrod length checker, cycle the rocker on the valve/spring tip (by cranking the engine by hand) until the correct rocker roller footprint is achieved. (With the stock set up start with 7.400 and you will be pretty damn close if not dead on.) Tolerances within engines are allow for .05" pushrod variability.

Robin L

[QUOTE=jtl12419;9478764]
You indirectly affect the lifter (preload) with this stock setup using the pushrod length. You must have the correct pushrod length.

[QUOTE]

BINGO!!!


Lifter Pre Load is not an exact science. It is the one part in an engine designed to work in a wide lattitude. In building engines the last part to be ordered is usualy the pushrods. For that reason they are also neglected or dismissed in an effort to get the engine done or the car running. With hydralic lifters you have a range of length that will work. With a solid there are to many factors that effect pushrod length that it's almost impossible to use a "standard" size.
When you install a set of heads or a cam you are changing the figures. Some cam manufacturers hold the base circle as close to the stock cam as possible. Others do not. As you go to the more radical grinds they need to use up more of the core to get the numbers from a common core. Not too many people want to use a custom core in their cars. They are very expensive.
Most engines with hydralic lifters can run from negative .001 to fully bottomed out. We have seen racers run lash with a solid roller cam using hydralic roller lifters. We have run our lifters .002 from the bottom. All of these shops are giving you good advice. You should shoot for more than .040 to a max of .100 and everything will be just fine. Now if you are looking for the ultimate you should not be using hydralic lifters anyway! LOL Seriously hydralic roller lifters have a place. They dampen the shock to the valvetrain and are quieter because of their constant pre loading of the lifter.
There are many ways to "adjust your preload even when the design doesn't allow for any adjustment. Most quality pushrod companies such as Lunati or Trend have + or - pushrods available. They typically come in .050 increments. It's not hard to figure out that you need more preload and thus a longer pushrod. With the lifter down on the base circle install the rocker arm and slowly tighten the bolt while spinning the pushrod between your thumb and finger. Once it lacks any slop see how much more you have to turn the bolt before it is tight. If the pushrod is still sloppy or "just" tightens up as you bottom the bolt chances are you need a bit more preload. A .050" longer pushrod should solve this problem. Now how do you know if you have too much pre load? Well the valves hang open thats how! Now you have to be careful because you can bend valves if you bottom a lifter and hang the valves open. If while using the bolt tightening metheod the valve starts to open you need shorter pushrods. Oops, most lifters will bleed after adjustment. I should say if the valve is still open after it's bled down.
Other ways to efect geomtry or pre load is to shim the rocker stands. This may be needed if you have longer valves stems because you need more valve spring for that big lift cam you gotta have. Also we have shaved the lifter stands on some engines to get more pre load. I would not recomend either ot these on a LS engine because of the stand design.
In the end all these shops are correct, no mystery at all.

Robin

jtl12419

iTrader: (13)

The only wildcard of this discussion is the variable of Lifter "bleed down".

I have not heard a good explanation of how to determine the "preload" in the presence of bleed down (once again this is only in the realm of adjustable rockers-- does not apply to non-adjustable hardware like the stock). This is the most confounding, non-scientific area, that has not been explained well by any engine builder.

When you have "bleed-down", the base position of the hydraulic lifter piston is not at zero for that lifter. Thus on a bled down lifter, you cannot accurately establish where zero lash is on that rocker- that pushrod will continue to wiggle until you bottom out the lifter. Hmm...How do I know this?

Also there is fantastic disagreement amongst many I've spoken to about correct preload value on the GM stock lifter. Crane claims .08"-.1" startling. GM techs seem to think .06" Just like in Medicine, when there is so much uncertainty, that means there is no correct answer.

Robin L

First "bleed down" as I am using the term refers to when the engine is at rest or not running. It's when the pressure from the spring overcomes the oil in the lifter and slowly drains the lifter to the point the pressure is removed.

The dynamics of the engine, oil pressure and speed prevent this from happening while the engine is running.

As far as finding true preload, lets say on a lifter that has bled down I agree it's not as easy. It's an aquired talent! LOL, you have to push down on the rocker to be sure that you are not compressing the spring in the lifter. Once you play with a set of lifters without oil verse some with oil you will get the hang of it.
We have tested hydralic roller lifters with up to 500 pounds of spring pressure at the seat. That isn't a typo. After dyno testing our combination we settled on 380 pounds on the seat. After the 380 we found no gains in valvetrain control. Now remember that is with a steel valve/retainer/keepers.
Back to the point, the lifters bleed down pretty fast once you shut the engine off. Of corse that is only the valves with the lobe in the open position. Once you started the engine you would hear just a little rattle before the lifters filled up.
It's interesting to note that as the spring pressure was increased we would develop a dip in the horsepower curve on the dyno. The lifters would lose the ability to stay firm and begin to collapse loosing effective lift. I know this because when we bottomed the lifter the dip disapeared and the horsepower increased.

GM Tech's have no reason to investigate lifter pre load. The reason that they use the .060 number is because the total range of most hydraulic lifters is .000 to .120. hmm, .060 is right in the middle! LOL

I am saying that it's not an exact science. It will work in a wide range of adjstment.

OK here is the kicker....... I have seen some engines run BETTER at certain preloads. That is lets say .020 verses .100. But then I have seen others run the same no matter where we set them. Remember I have tested a lot on both engine and chassis dyno's as well as at the track.
Of course you will never know unless you have adjustable valvetrain or a lot of custom pushrods. I have coffee cans with pushrods from various projects over the years. We had pushrod in a .500 range every .050. That is 10 different sets to juggle. We would optimize the geometry once we had the preload set on the lifter.

Hope all this rambling helps. My collection of parts is almost complete again. I will be playing on the spintron and sharing some more info.

Robin

vettenuts

iTrader: (4)

If you are saying that the wipe is affected by pushrod length, which is what this sounds like, that is not correct unless they are stud mounted rockers. The only adjustment you can make to the wipe is the rocker height, once tightened in place the pivot point doesn't move and has no affect on wipe.

jtl12419

iTrader: (13)

Whaaa? If you are referring to the contact pattern on the tip if the valve as it cycles = wipe, then YES pushrod length WILL affect the wipe, especially with a fixed fulcrum.

How do you explain determining the right pushrod length?

jtl12419

iTrader: (13)

Are you saying that "spongy" feeling lifters are normal when the engine is off within the last hour? Is it normal to be able to push on the pushrod with a finger and depress the lifter, while others are solid?

That's where I have problems feeling for zero lash.

Robin L

Sometimes it can be spongy. But the reason can vary. Sometimes the check ball can leak down or depending on the orientation to the oil galley it can bleed the lifter through there.

I have had more problems with GM lifters being soft on the dyno than the brand X versions. They all come from the same place so I don't know why that is happening. Once the engineis fired it makes good power so I am assuming that the lifter s working.

We had lifters that were soft after a run at the track and the dyno. Unless it is down on power I don't worry about it.

To fing zero lash I move the pushrod up and down against the rocker arm until it doesn't have any slop. Then is repeat until I am sure it is at zero. IT takes a little time.


Robin

vettenuts

iTrader: (4)

That is not correct. Once the rocker seats against the support it can't move, so unless the pushrod is extremely short (loose) or too long (valve held open), it will not change the wipe pattern. In order to affect wipe, the pivot point must move up or down, with all other parts remaining constant (same valve stem height, etc.). Sine the rocker is bolted down, the pivot point cannot change up or down nor can it affect wipe.


Pushrod length only determines preload on a fixed fulcrum rocker. On a stud mounted, pushrod length determines both wipe and preload. With a fixed fulcrum rocker, you must first establish the wipe pattern by adjustment of the rocker pivot point up or down (down being harder). Once wipe is set up, then an adjustable pushrod is used to determine zero lash length from which desired lifter preload is added. Within the available pushrod lengths you can typically get one that will work, especially since there are several that vary only 0.025" near the LS1 7.400" length.