i checked it lol but mine can go either way.

 

Probably should have clarified but I too thought there was a certain way that the rocker stand had to go and on LS engines but my 05 Tahoe 5.3 LS upon disassembly I noticed the GM logo was upside down when removing them but in my case it did not matter if the logo is upright or upside down because the bolt holes for the rocker arms are still aligned and all of the pedestals are the same meaning no change in height from one side to the other or should I say a perffect concave surface for the trunnions to sit on. I have a set of 706 heads sitting over here behind me and I can certainly post a video proving this.

 

OP..As stated by others the only way to know what length of pushrod to use is to know what the desired preload is for the lifter being used and to measure the length of the pushrod at zero lash and add the desired preload. This is done by using an inexpensive pushrod length checking tool Comp Cams 7702 I believe. Milling the heads will shorten the length yes and so does switching from an .051 compressed thickness to say .035 compressed thickness. You can factor these in and come up with an approximate length of pushrod to use but the correct way is to measure. I'm sure you've heard the expression that an assumption is the mother of all F ups.

 

Gotcha. You’ve got .046” between the heads being cut, and the thinner headgasket. This .046 difference will ADD preload. It’s significant but not enough to keep your valves open. If this was the case, you’d have all 16 valves open, and poor compression numbers in every hole. A 7.34” pushrod is what will LIKELY work, but that’s a guess. With pushrods not exactly being free, I’m not sure if I would guess at it like your wanting us to do. Your going to have to use the correct tools and measure unfortunately.
Were the heads rebuilt by a shop, or did you just have them cut and sent out the door?
From your compression check numbers, it looks like you might have something hurt…valves or rings…in those cylinders.
Did you put new headgaskets on it, or were they used? Crazy question I know, but I’ve seen crazy stuff on the webz.
Try this test…take all 16 pushrods out. Leave the rockers off, and do another compression check in all 8 holes. Report back please.

 

ok you almost got me on that one. there is no compression if a valve wont open to allow air in to compress. so any way i look at it this way if i used every thing stock just like what came out of the motor shouldn't have to do any measuring . and it would work just fine. so the only difference i took .030 off the head so why not just take .030 off the push rod. now this is a shade tree mechanics way of doing it lol so that would put me at 7.370 but you cant get pushrods that length do im going with the next smallest is 7.350 as right about where you suggested that's all i can do unless i start over so what you should had suggested was a leak down test instead of compression test

 

If you're unwilling to take the advice of numerous people trying to help you, and insist on doing it the wrong way, why then are you continuing to ask if such and such pushrods will work? Just use what you think will work and not post up about it later when you have noise or the engine fails. Che70velle knows what he's talking about, and he wasn't trying to "get you", he's asking you to do a legit diagnostic test.

 

I cant measure the pushrods after running the engine, the preload on the lifters have changed . every one wonts me to measure but how do you measure if the preload on the lifter has changed unless i start over so what i was asking other people story on what they did . and after asking yea more confused, so im going back to the shade tree mech way . unless you have a way to measure the pushrods after running the motor. you ever done a compression on a cylinder that both valves are closed . there is no compression and he should have known that or was he testing my knowledge. lol i thought ok i would try it anyway and like i thought there was no compression

 

You can still check pushrod length after the fact. Lifters expand/extend (internal spring) with the rockers unbolted.

 

Your lifters are a mechanical part, they don't change after running. Do you have old ones somewhere? Pop the clip out of the top of one and disassemble it. Your screen name says "learning", well - learn how this component works. There's a small spring internally that holds the top of the plunger up. It's not there to do anything mechanically to the engine when it runs. It's there to hold the plunger at the top. This is why, when tightening a rocker down, the pushrod sinks into the lifter a bit, pushing the plunger downward. That is your preload. You don't want the plunger riding at the top against the clip all of the time, which is why you need preload. Now, beneath the plunger is an area that fills with oil while the engine is running. Once running, that little internal spring does absolutely nothing. There's a reservoir of non-compressible fluid (oil) in the lifter which fills the space below the plunger. The plunger likely doesn't ride perfectly at the top, especially at low RPM. Valve spring pressure can push a bit of the oil out. At higher RPM, oil pressure can keep the lifter fully pumped up, but this isn't always true either. The point of hydraulic lifters is the oil reservoir is always taking up the internal space to cut down on valvetrain noise and the need to constantly do valvetrain adjustments. When you measure for pushrods in a non-adjustable valvetrain ( the LS ), it's a critical measurement because when you change the deck height, gasket thickness, or mill the heads, you move the fulcrum point of the rocker arm towards the camshaft ( or away, depending on components ). If you remove a bunch of stack height and don't change your pushrods, you can have excessive preload which can, at high RPM, allow the oil to fill the lifters so much that the valves won't completely shut. If you just guess at a number, you may or may not be correct. You may have little to no preload which will probably cause valvetrain noise and damage, or too much, which may cause engine damage or problems running at minimum. It's not difficult to measure for pushrod length, but it needs to be done correctly. Valves fully shut on the base circle of the cam. Torque rockers down. Have your pushrod tool installed and open it up gently until there is no up and down slack between the lifter and rocker arm. Remove the rockers. Pull the tool out and measure it. Add recommended preload to the value you measure. i.e. , if the tool measures 7.375" and you need .050" preload, order 7.425" pushrods. Repeat process as needed.

 

thanks question thow when i pulled the rocker arms off after running the motor the lifter cylinder extended out fully so when i put the tool in there how do i know where to push the lifter back down too or bleed it back down. i relise that a lifter is a shock absorber of sorts. ok nother thought. if i measure the rod length as the lifter is fulling extended and add a pre load to that for the rod length.

 

I think you are thinking you need the lifters fully collapsed to check pushrod length, am I correct in this?

You want to measure pushrod length to the lifter cup fully decompressed (up as far as it will go), as soon as you remove a rocker arm, the cup will extend due to the internal spring. When we talk about "lifter pre-load" we are talking about how far the plunger in the lifter is compressed with the valve closed, not how fat the lifter cup is from bottoming out in the lifter.

 

no but dont they come prelaoded where the lifter cylinder is some where in the middle like a shok absorber. so are you saying measure when the cup in the lifter is all the way down NOT when it is fully extended pushing the rod up as far as it will go and then subtract a payload which is?

 

You can still find pushrod length at zero lash with a pushrod length checking tool with the lifters in the engine. The lifter cups will come back up once you've taken the pressure off of them. Just install the checker tool onto the lifter and bolt the rocker arm down hand tight and then take your fingers and start turning the adjuster on the pushrod length checking tool until you have removed all the slack.

That's your zero lash!

Remove the rocker arm and carefully remove the tool and with you caliper gauge measure the overall length.

Add this to your desired lifter preload and that's what length pushrod you need. I would do this several times until I was confident that I had the correct measurements for the intake and exhaust.

It's really that simple.

Now I personally have big hands/fat fingers and I cannot get my fingers on the tool to adjust it out so I have to keep removing the rocker arm and turning the adjuster out until I find zero lash.

BTW you can still build compression in a cylinder by rotating the crankshaft even though both valves are closed.

 

thanks and i tried two cylinders two different compression gages and still came up with no compression with both valves closed. but i need to do a leak down test instead but thanks again this helps on learning how to measure for push rod length

 

You have it backwards here. When you remove any pressure on the lifter, the spring under the cup will push it up to the clip holding the internals together. This is the position of the lifter cup you would want to check for PR length. As far a preload is concerned, I have seen and heard so many numbers its not funny. On your lifters, the consensus seems to be about 0.030"-0.060" of preload on the lifter (the amount the cup is pushed into the lifter body) 01CamaroSSTx gave a good run down on how to check.

 

ok guys went and got a digital caliper for the pushrods . after putting the push rod checker in i cam up with 7.186 from what i have read maybe wrong but is .070 a good preload that would put me at 7.256. ok the push rods i bought before understanding the measuring. they are 7.33 by the digital caliper will these push rods work? or should i go ahead and order 7.325 rods

 

The 7.33 pushrods are too long and you're probably opening the valves when you torque the rocker arms down which would explain the zero compression. If you're coming up with 7.185 @ 0 lash and you add .070 preload then a 7.255 is what you'll need. When it's done correctly on a hydraulic you will be able to lift the tip of the rocker arms up off the valve and feel the pushrod going up and down as it's riding in the lifter cup. I bet you're feeling nothing as they are maxed out and there's no give at all.

 

thanks i sorta thought so and thanks for the help threw this i ordered the new rods

 

you can lead a horse to water but you cant make it drink lol

 

IDK how long the Summit PR length checking tool has been around but after seeing @Che70velle recent thread on the Corvette engine build it's a gotta have for me.