LS7 lifter preload
LS7 lifter preload I have a stock bottom end LS1 with ported 243 heads, 228/232 .625/.625 cam, and LS7 lifters. The heads/cam were installed by a shop several years ago. I've always thought the lifters seemed a little noisy at idle but I think it's gotten a little louder recently. The noise is worse when the engine is fully warm and at idle and goes away once the engine is revved. Most of the noise is coming from the area of cylinders 2 and 4. I removed the valve cover and inspected the valve springs and rocker arms, everything looks good. I disassembled the rocker arms and found that the CHE trunions are holding up great.
Next I checked pushrod length, I've always wondered if it wasn't right since the lifters have always been little noisy. I used the same method as @RB04Av posted in another thread.
Here are the 0 lash lengths and ..070 preload calculations for cylinders 2 and 4
...............0 lash...... +070 preload
#2 intake 7.256...... ..7.326
#2 exhaust 7.275..... 7.345
#4 intake 7.2625...... 7.332
#4 exhaust 7.2625... 7.332
My existing pushrods are 7.40 inches which would result in the following preloads if my math is correct? Seems like way more preload than it should have.
#2 intake .144
#2 exhaust .125
#4 intake .138
#4 exhaust 138
When I was checking the #4 exhaust for 0 lash I noticed that lifter wasn't firm like the others, it could be easily pushed down. Is this normal? Or does it indicate a problem? It does spring back up but has very little resistance to being pushed down. I know lifters can bleed down but the others weren't like this.
Any suggestions are greatly appreciated! Thanks
Next I checked pushrod length, I've always wondered if it wasn't right since the lifters have always been little noisy. I used the same method as @RB04Av posted in another thread.
:
- Put the cam lobe for the valve you want to measure on its "heel". I.e., zero lift. The EOIC method is plenty good enough for this, for a hydraulic cam: you rotate the motor in its normal direction until the exhaust is just beginning to open ("EO") to measure the intake push rod, and rotate until the intake is just arriving at fully closed ("IC") to measure the exhaust one. Obviously this is easier if you put some random push rod in the valve that's your "indicator" and also install its rocker, so that you can see its motion. A quick shortcut is, once you get the right location for a given valve and finish with it, you can rotate the motor exactly 90° and you'll be at the right spot for the next one in the firing order, so you can just go through the engine like that. Such as, find the right spot for the #1 intake by watching the #1 exhaust just beginning to open, measure its PR, rotate the engine 90° and do #8 intake, another 90° and do #7 int, and so on through all 8 intakes; then repeat for the exhausts. Saves the time trouble of futzing around with watching all of them without sacrificing any accuracy whatsoever.
- Install the rocker for the valve you're measuring, with the adjustable push rod. Install it fully, including ... tightening the bolt.
- While jiggling the rocker & adj PR, unscrew the adj PR until all free play in the rocker & PR is taken up. Take up ONLY "free play"; DO NOT allow the PR to depress the lifter plunger. It doesn't make any difference whatsoever if the lifter has oil in it or not, as long as its internal spring is able to push the plunger all the way to the top.
- Remove the rocker. Remove the adj PR without turning it. Screw the PR back together, counting the turns carefully.
- Multiply the # of turns times .050". Add this number to the screwed-together length of the adj PR; 6.800" for example. So as an example, you might end up at 10½ turns; that, times .050", is .525"; add that to 6.800", which gives 7.325".
- Add your desired preload to that. Since they're LS7 lifters, the total travel of their plunger is about .150" or maybe a bit more. Half of that is about .075" or .080" or so, which is why you see people recommend a setting somewhere around there. But like the SBC/BBC example above, the exact # isn't particularly critical, as long is it's greater than 0 and less than .150", since the one condition leaves lash which will be very noisy and not open the valve quite all the way, and the other will never allow the valve to close all the way. It's MUCH more important that it be consistent with your usage of the engine, and consistent within a reasonable tolerance throughout the entire engine. The lifter is "self-adjusting" within the range of the plunger's motion. To give you an idea of the precision you're working with, i.e. how "accurate" you need to be before the tiny errors get lost in the overall "noise" of uncertainty, an aluminum block and heads will expand by somewhere around .010" - .012" (half of a marketplace push rod length increment) going from cold to fully hot, thereby losing that much preload; the preload will vary by that much just between a cold start and 15 minutes later. So there's no need, with THOSE lifters, to get all wound up with getting it down to the closest thousandth. So, if you come up with 7.325" as the length of your adj PR, and you want .075" - .080" preload, your "marketplace" PR choice might be 7.400", because that's the closest increment you can buy, and puts the lifter solidly within the range you want it to be, which that range, is already .150" (plunger travel) wide. If you get within half of the market PR increment (.0125) on every PR, you're golden.
- Repeat for AT LEAST both valves on all 4 corners of the engine, since variations in block and head machining that affect this, are most likely to be greatest on those cyls. But by that time, you will have measured 8 of the 16 valves; might as well do the other 8 anyway. You never know until you KNOW, whether maybe some 1 or 2 or however many valves is different from the rest; or whether all the intakes are one length and all the exhausts some other; or who knows what. Eliminate guesswork, "assumptions", "I put it together and now it makes noise and runs terrible", etc. etc. etc. You might have to buy a set at one length, and 1 or 2 at some other; or 8 & 8; or whatever. Get the lengths you need in the most cost-effective way you can. That's the WHOLE POINT of measuring.
- WRITE DOWN AS YOU GO which valve needs what length. Especially important if they turn out different.
- Buy. Install. Tighten the rocker bolts. Doesn't matter whether the valve opens as you tighten the rocker; that makes less than 2 ft-lbs of difference on the bolt. Meaning, if a valve doesn't open or opens just a little, don't worry about it, and tighten to 22; if it opens all the way, tighten it to 24 ft-lbs; if it's open halfway, tighten it to 23. It doesn't matter that much. The bolt is tight, is all that matters. "Measure with micrometer, mark with chalk, cut with axe."
...............0 lash...... +070 preload
#2 intake 7.256...... ..7.326
#2 exhaust 7.275..... 7.345
#4 intake 7.2625...... 7.332
#4 exhaust 7.2625... 7.332
My existing pushrods are 7.40 inches which would result in the following preloads if my math is correct? Seems like way more preload than it should have.
#2 intake .144
#2 exhaust .125
#4 intake .138
#4 exhaust 138
When I was checking the #4 exhaust for 0 lash I noticed that lifter wasn't firm like the others, it could be easily pushed down. Is this normal? Or does it indicate a problem? It does spring back up but has very little resistance to being pushed down. I know lifters can bleed down but the others weren't like this.
Any suggestions are greatly appreciated! Thanks
TECH Addict
Joined: Dec 2017
Posts: 2,180
Likes: 969
The preload #s you quote w 7.400" PRs are too much. By at least .050".
I'd get 7.325" or 7.350" with the measurements you post. Like the guy in the post you quoted, one length will put you at the low end of the desired preload range, the other toward the high end; either would be acceptable, it's up to you to decide how much you want, within the mechanical properties of the lifters.
Might want to see what length is in there now, and if they're noisy, maybe go to the next longer PR.
Sounds like all the oil has drained out of that one lifter butt not the others. Not a problem in and of itself. May have just had its oil hole more exposed in the lifter bore than the rest. If they were all new, and empty, all would probably push down about the same.
I'd get 7.325" or 7.350" with the measurements you post. Like the guy in the post you quoted, one length will put you at the low end of the desired preload range, the other toward the high end; either would be acceptable, it's up to you to decide how much you want, within the mechanical properties of the lifters.
Might want to see what length is in there now, and if they're noisy, maybe go to the next longer PR.
Sounds like all the oil has drained out of that one lifter butt not the others. Not a problem in and of itself. May have just had its oil hole more exposed in the lifter bore than the rest. If they were all new, and empty, all would probably push down about the same.
On The Tree
Joined: Jun 2023
Posts: 186
Likes: 12
I would go smaller. Mine ended up being the same all around problem was is I didn’t account the exhaust valve was the first valve on passenger side so I was using the intake as my opening valve to get on base circle. Exhaust will always be to the right. I should
of Paid more attention. But my preload comes out to about .065 which seems ok. Over .1 seems like a lot
of Paid more attention. But my preload comes out to about .065 which seems ok. Over .1 seems like a lot
I'm going to check the rest of cylinders later this week to make sure they are all the same or close. Looks like I will be ordering some push rods, I hope this makes it a little quieter.
Thanks for the info. I measured for push rod length on all the other cylinders and they were all very close. I just ordered some 7.350 push rods. That should put me a touch over .080 preload on each lifter.
I installed the 7.350 push rods and got the engine back together today. I started it up and the noise is better than before. I still here more noise that I would like to hear but it's better than before. I only hear the normal sewing machine lifter noise when the engine isn't fully warmed up. Once it gets fully warmed up (running for about 30minutes) and everything is up to full temp I still hear a little extra clatter on the passenger side #2 or #4 cylinder. I'm not sure if this falls under the normal LS engine noise category or not? I made a video, let me know what you think? I'm running 5W30 oil, maybe a thicker oil would help since the noise only happens once everything is fully warm and the oil is thin?
You can hear it the most towards the end of the video after I rev the engine higher the 2nd time.
You can hear it the most towards the end of the video after I rev the engine higher the 2nd time.
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Sounds like an LS engine. They all have that clatter clatter…sewing machine…sound, unless you go with a solid roller setup. The solid roller setups can be very quiet when done right. Yours sounds very normal to me.
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