darknessxyz

iTrader: (22)

I'm doin a head & cam swap on a LS1. I was wondering how to pre-load the lifters what I put the head and valvetrain back? Thx

BriancWS6

iTrader: (18)

If your using stock rockers, you just tighten them down to 22 ft lbs.

What are the specs on your heads, gasket, etc? Comp XE-R lobes have a .050 smaller base circle, which will decrease pre-load vs the stock camshaft. If you mill the heads or use a thinner head gasket, this will increase the pre-load. The length of your push rods is what will be used to set the pre-load after all these factors have been taken into consideration, unless of course your using adjustable rockers.

Also, keep in mind that the actual length of the stock advertised "7.400" push rods, vary from the aftermarket "7.400". I measured them yrs back just to see.

Post up the details and I'll see what I can do to help you out.

darknessxyz

iTrader: (22)

Cam is a XE-R lobe Comp Cam 228/232 .588/.591 112LSA, Head is 241 ported and milled to 62cc, Stock non-MLS head gasket, TSP 7.4 pushrod, Stock LS7 lifter, Stock rocker.

So the pre-load actually is how many ft lb to torque the rocker arm? The above setup is for my friend. I've a different setup using GM MLS head gasket, 7.425 pushrod, Comp OE-R lifter and hardland sharp roller rocker. I assume the pre-load will be different from the two setup right?

99huggerorangeZ

iTrader: (2)

im interested gonna sit in on this

PREDATOR-Z

First question is what are the lifters?
second are your rockers adjustable or not?

darknessxyz

iTrader: (22)

On my friend's setup: Stock LS7 lifter and stock rocker and TSP 7.4 pushrod.

On my own setup: Comp OE-R lifter and Harland Sharp non-adjustable (IIRC) roller rocker w/stock ratio and TSP 7.425 pushrod.

darknessxyz

iTrader: (22)

My stock rocker arm had over 100k miles on them. I don't feel like re-use them. I got those Harland Sharp from a buddy, which cost me less than brand new GM stock rocker. Maybe cheaper than a rebuild lol.

PREDATOR-Z

On your friend setup, LS7 lifter cup is ~.060 higher than original LS1 lifters and his heads are milled, off the bat I would guesstimate 7.350 p-rods. But he will have to measure to be sure. I like .060 to .080 preload on those lfters.

On yours OE-R lifters is that 850-16 or magnum "R"?
The 850-16 can take anywhere from .030>.080, Comp Cam recommends .030>.050 but I've always ran mine a bit higher untill the valvetrain is quiet.

darknessxyz

iTrader: (22)

Sounds stupid but I don't know how to check and set the preload. He already bought the 7.4 pushrod, so do I already have 7.425.

I've the Comp 875-16 lifter. Is that make any difference?

vettenuts

iTrader: (4)

You really need to measure both. The tool is less than $20 and I think you are going to find both setups have the wrong pushrods. HS rockers are a major change and if the pushrod cup is lower (which many aftermarket are) then this will further change the pushrod requirement.

PREDATOR-Z

Comp 875-16 are also known as Comp "R" lifters. They are very preload sensitive and would require adjustable rockers to set them properly Preload range on them is .002>.004 so achieving that with nonadjustables is almost impossible.
More preload on these can lead to lifter failure, we all know where that can lead.

So as vettenuts said, get a checker and measure. Based on your findings get appropriate pushrods. And with the Comp "R" you'll also need adjustable rockers.

darknessxyz

iTrader: (22)

so on my friends setup, he should be ok to get by just torque the rocker arm to 22 ft lb, right?

On my set up, I've a smaller cam 224/230 .581/.588 114 LSA. Will that make a different or I should better yet change lifter? I think Pred-Z you recommended 7.425 on my setup b4 to avoid sewing. I'll double check my rocker and see if they're adjustable.

1 FMF

iTrader: (1)

lifters are the thing that ride the cam, but that's not important right now.

vettenuts

iTrader: (4)

No, recommend measuring both. If too long and you hold the valves open you will have problems. On the Comp R's, there is a very specific and narrow preload range. Better check the Comp literature, but I remember it as 0.002" - 0.004".

1 FMF

iTrader: (1)

you can google "lifter preload" and come up with some very good writeup's,
another keyword is "valvetrain geometry"

lifter preload is defined in distance, as to how far the pushrod depresses the lifter's plunger downward. The function of this is to allow the lifter to compensate for thermal expansion, meaning as parts heat up and cool down, distances change. The importance here is the slack that is or is not taken up between the cam to lifter to pushrod to rocker arm to valve stem tip. Ideally you want no slack, meaning everything is a tight fit, as soon as the cam lobe begins to contact the lifter, the rocker pushes down on the valve and the valve opens. If there is too much slack you lose duration (your valves open later and close sooner). And the opposite would be if there is thermal expansion and that mechanical system can't handle it, it will cause the valve to open like vettenuts said- meaning the valve will never fully close and you'll also have higher valve lift which can potentially be catastrophic.

i know traditional sbc lifters want 0.020-0.060" preload, the norm being 0.030" or less. The LSx lifters have much more preload, 0.070" comes to mind but I also remember reading that can vary quite a bit among brands of lifters. Once you know the amount of preload for the lifter you have, then you must have the correct pushrod length to give you the correct geometry of the rocker arm on the valvestem tip. With adjustable rockers (which you probably don't have) you have some leeway with pushrod length and what will work. The LS motors have non-adjustable rockers, so they simply get tightened down by a single bolt, that bolt is torqued to ~20 lb-ft and has nothing to do with preload. This bolt torque is simply a function of the bolt material and thread size and you tighten it down tight enough so it doesn't work itself loose. In this case, the lifter preload is completely determined by pushrod length... change distances anywhere else such as head gasket thickness, mill the head, deck the block, or valve stem height and your lifter preload will change.
To check lifter preload, one way you can do it is with a dial indicator mounted on a magnetic base (good luck) and see how far down the pushrod depresses the plunger when the rocker is tightened down. The other way, easier and probably cheaper, is with a pushrod length checker. Use that to find zero preload, as in no slack in the system with rocker tightened down and lifter riding on base circle of the cam, then measure what the length the checker is. If you need X amount of preload for a given lifter, then simply buy pushrods having what the checker length was plus X.
The other important factor in valvetrain geometry is rocker tip on the valve stem, but with non-adjustable rockers all that geometry on that side of the system, from rocker to valve stem, is fixed and never changes, so you don't have to worry about it.

BriancWS6

iTrader: (18)

No, the 22 ft lb has nothing to do with setting the pre-load. Think of it this way, before you insert a push rod, and then install a non-adjustable rocker arm, the plunger inside the lifter is all the way to one end. When you tighten everything up with a given length push rod, it applies the pre-load by depressing the plunger "x" amount. Different length push rods when combined with heads milled .030, for example, and or a .015 thinner head gasket, and a smaller base circle camshaft, will all play a role in the end result. The 22 ft lb is simply the torque value for that fastener.

To use the push rod length checker, you will install everything and torque to spec, while leaving the tool loose, or turned short. After everything is tightened properly, begin to spin it to make it longer. Once you get contact with the lifter on one end, and the rocker arm cup on the other, that's zero lash. Now turn it making it longer til you've reached your desired pre-load, .050, .060, for example, and then read the length on the tool, and this will be the needed push rod length.

PREDATOR-Z

OK you are getting lost here, let us recap:

On your friend's setup:
He needs to measure p-rod length to get the right length needed. His heads are milled and LS7 lifters have the cup higher than LS1 lifters by ~.060.
So he needs to measure with a p-rod checker at 0 lash, THEN add desired preload and that will be his p-rod length. His 7.400 will be too long.

On YOUR setup, you have Comp "R" lifters which require very light preload (.002 to .004) only. To achieve that you need non adjustable rockers.
Once you have non adjustable rockers, then you measure p-rod length at 0 lash. That will be your p-rod length. After that you set preload by adjusting the rocker.
Second option if your rockers are non adjustable:
Ditch the Comp "R" lifters, get a set of LS7, measure with a p-rod checker at 0 lash, add preload desired, get the pushrods, install and torq to 22ft/lbs.

Preload range on LS7 is .060>.100 so anywhere in .060>.080 is where I set them.

I hope this clears it a bit.

darknessxyz

iTrader: (22)

When measure the pushrod length, did the intake and exhaust side the same thing?

PREDATOR-Z

On the XE-R cam that you have, yes you only need to measure on intake. That will be sufficient. You need to measure with the cam on base lobe at TDC.

darknessxyz

iTrader: (22)

Pred-Z, by using the (A) menthod, I'll be installing the the checker lifter and checker pushrod with my new head gasket. Then I'll take the head and everything back off after the measurement. When I torque the head bolt (old ones of course I guess) to 22 ft lb for the first run, should I turn the 90* second run and third run to ensure the pushrod length?