Engine Parts & Problem:
I have a set of their HL2148 LS lifters in my 2005 Rainier 5.3 LH6 DoD removal/rebuild project. The valvetrain is the new lifters, a 39K mile L33 cam (same basic specs as my DoD cam w/o the DoD), and my OEM pushrods/valves & springs. I had a ticking in one lifter, so I took the valve covers off and measured pushrod lengths for all 16. Using an 8" digital caliper, my PRs were between 7.3860 and 7.3915" long, OE spec for the LH6 is 7.385, so with measuring variations (my errors) these are OEM length. I found I had between .102 and .115 of preload which is too much for a stock engine.

Data Needed:
I needed a reliable source (if one exists, best answer see solution below) for the preload specs on these. I looked online and found nothing, sent the company an email a few days ago and heard nothing, and then called their tech support today. Really nice fellow there, but they don't have the spec available. He thought it should be the same as the LS7 lifter, which is what these are according to Elgin. OK, so I looked in my online shop manual for the truck, and GM does not list a spec other than "net lash". Top secret stuff? Where is Col. Flagg when you need him?

Research:
GM apparently replaced the LS1 lifters with the LS7 style sometime, so possibly I had the older LS1 style in my LH6. The LS7 was produced from the 2006 model year through 2015.
From what I have researched, the LS1 lifter was the same height, but the LS7 had a different cup height, which requires shorter pushrods- supposedly 7.350.

Common knowledge from what I have read has preload for the LS7 style lifters as being anywhere from .050 to .100. My PR calc (attached as an Excel file) says depending on the preload (.050 to .075), I need 7.325 to 7.350 rods. I'm not in a position to pull one of the new lifters out since the engine is back in the truck.

Doing more reading, I found this post by a retired GM Engineer. It delves into the lifters, and in summary, he listed a total of 4 lifters used in the LS series of engines.

Here's the chart he posted:
5234670, 1984 design year: 6.03mm travel, 2.98mm preload
12564012, 1999 design year: 3.20mm travel, 1.58mm preload
12576400, 2001 design year: 3.20mm travel, 1.58mm preload
17122490, 2003 design year: 4.22mm travel, 2.09mm preload

In inches:
5234670, 1984 design year: .2374 travel, .1173 preload
12564012, 1999 design year: .1260 travel, .0622 preload
12576400, 2001 design year: .1260 travel, .0622 preload
17122490, 2003 design year: .1661 travel, .0823 preload

I also found a 2018 Enginelabs article by Jeff Smith dealing with hydraulic lifters in general and LS style specifically. The relevant portion says:
Solution:
The best estimate I have based upon the above for a street engine like mine with stock components is .040 to .080. Given my numbers (rod length at zero lash of 7.275 and 7.288 for all 16 valves), a 7.325 rod will give me .050 on the 7.275 valves, and .037 on the 7.288 valves. I'll note the late model LS GM pushrod #10238852 is shown as being 7.325" long. A 7.350 rod would give me .075 on the 7.275 valves and .062 on the 7.288 valves.

I'm going to try the 7.325 and see how this affects things.

Update May 2021-
After watching some videos, I think the startup noise on my engine is piston slap, which is fairly commonplace. At least I learned a lot about LS pushrods.

 

I'll bite. Can you get a set 7.325" long and another set 7.350" so you can use which ever length pushrod works best?

 

That's what I'm doing. As of today, I've got a set of Trick Flow 7.350 coming from Summit and a set of supposedly GM NOS 10238852 7.325 from eBay (the price sounded too good to be true, but if they are not as described the seller will eat the cost). Summit's will be here first, so I'll try them.

 

Here is a tip. If you are stuck between the two lengths - I.e. 7.340 would be ideal - put .010 machine shims under your rockers and use the longer rods.

 

I don't know why that chart lists a 1984 lifter since the LS1 wasn't around then unless it was a prototype.

 

Thanks, I'll keep that in mind depending on my results over the next couple of days.

Yeah, that hit me as odd also. Best guess is they used that one until the 1999 version was released, so maybe the 97-98 (and early 99) models used it? I know they used different computers, so it would not surprise me. It seems like my LH6 as a 2005 production would have used the later (latest) lifters from circa 2003, but on the other hand I have run into one discrepancy with it already in that the diff gasket is from a 2004 housing. I'm sure GM doesn't like to throw parts away, and they didn't make that many Rainiers, so my truck probably has a lot of carryover parts.

I did check the L33 cam- I pulled it from a JY motor circa 2009 when it was about 4Y old (back when you could buy a complete low-mile L33 for under $600), I think this is the one from my RX-7 swap where I used an LS6 cam & springs in the L33. I verified the PN etched on it was the right one, so if the lifters account for the slight difference here a parts changeover would explain it.

 

The Trick Flow pushrods arrived today, and I guess 7.350 is not really 7.350- I know different means are used here by different manufacturers, but in keeping apples to apples, I did end to end on my OEM ones. The TF ones are marked 7.350, but on my caliper end to end they are 7.3660, + .016 (the caliper read 7.3665 when I took the pic below). I measured different rods several times and got this same measurement. I re-measured one of my OEM ones and got 7.3875, so the new one is only .0210" shorter vs the calculated .0375".

Plugging in 7.3660 into my spreadsheet gives me .091" on the 7.275 rods,and .078" on the 7.288 ones. Since I can't return them to Summit if used, it looks like I'm going to have to wait for the 7.325 ones via eBay and hope they are within range.

Now I have to waste even more time on another return!

 

Gauge length vs overall length. They are made to gauge length. They always measure long via caliper

 

Excellent guess. When the all new GEN III 1997.5 LS1 debuted, the only thing carried over from the GENI/II was the bore spacing and the lifters.

 

Thanks for the info. I did some more reading, and Trend's site says to use a pair of .0140" ring terminals on the ends and then subtract the thickness of the terminals.

Comp Cams has a good section on it also. Copy & paste:
Using the .017" formula, a 7.325 "gauge length" becomes a 7.342" end to end, which should work better for my application. That will give me .062" on the 7.275 and .054 on the 7.288 measurements.

 

So, that only 0.008" difference between the 2, is that really going to make that much of a difference?

Thanks.

 

My method is simpler. I just know in my head on the caliper they are going to be a tad longer and do the math in my head.

Again, you can always put a machine shim under the rocker stand to get the preload perfect. With the stock rockers it is even easier since the pairs are not tied together.

 

You're using actual - gauge measurements, 7.350- 7.342= .008.
Let's show our math on this one:
Trickflow "7.350" gauge 7.3660 actual
GM "7.325" gauge, 7.342 actual (estimated)

Using the same measuring standards-
7.350- 7.325= .025
7.366- 7.342= .024

.008 would not make that much of a difference, but the above math shows we're dealing with at least 3x as much difference. I don't want to have to take this apart again after this repair.

 

Another typical eBay seller, these are 7.39x pushrods. I should have known better when they never replied to my inquiry to confirm the length. Now I have to wait for Summit to receive and resend the shorter Trickflow ones.:

 

Finally got the "7.325" pushrods today. They measured on average 7.3385" or +.014" (the pic shows 7.3390, it went there before I took the shot). This should put me within the desired range.

EDIT- Well something was off, likely my measurements. I installed these and there was about 1/8~1/4 turn from hand tight to 22 ft-lbs. Needless to say I had severe "sewing machine" upon running them. Recalculated and am going to try a set of true 7.400" and failing that 7.425".

 

My next attempt involved a set of Comp 7.400" pushrods. They measured out at a correct 7.414. I couldn't get the torque wrench in the clear to count all of the turns from hand tight to 22 ft-lbs, but a couple of them seemed like only about 1/4 turn or so.


Comp Cams 7.400 pushrod

I then fired it up and it still seems to be clattering more than it should. I did an audio recording and have attached it. It starts at the driver door (key in ignition ding), engine start, and then I walked from the driver side to the passenger side and back to the driver side with the hood up.

Any thoughts on the noises are welcome.

 

Doing more reading here & elsewhere, I see a conflict in measuring standards as far as turns for the 8mmx1.25 bolts. A common number used is .047" preload per turn, however, 1.25 / 25.4 (1 inch) = .049, not a huge difference, but not the same.Next, this site says the spec per turn is .078". They have a means of measuring preload that is fairly easy to do:
One valve open, loosen the other and then tighten til you can't spin the rod. I found I had been hand tightening these too much, which threw off my turn measurements.
The target is 3/4 to 1.25 turns or .060 to .100 preload.

Using this method and the 7.414" pushrods, I got a fairly uniform 1&5/8 turns for most, a couple were closer to 1&7/8, but that may have been measuring error since I was using a 1/4 drive ratchet to snug the bolts and didn't have a clear 1/4 arc for all bolts due to obstructions.

Using .049 with a 7.414" rod, 1&5/8 turns gives me .080, which is within spec. Using .078, 1&5/8 gives me .127", which is beyond spec.

This article on Super Chevy does not give an inches per turn figure, but does say the target number of turns is 1/2 to 1.0.

I tried one of my OEM 7.3875" rods, and got just under 1.5 turns. I then tried one of the 7.325 (gauge / 7.34 actual) rods and got right at 1 turn. Even though they are the right number of turns, I know those are too short due to the amount of clatter.

At this point I think I'll stick with the 7.414 unless more info is received.

I fired up my LM4 Durango motor yesterday that has the same lifters, a Summit 8712 mild cam, and OEM pushrods/rockers. Since it has headers and a bit of an exhaust leak I couldn't really hear any ticking, but it doesn't sound as valve-noisy as the LH6.

 

Ugh, the misinformation that's out there.... OK, here's the deal:

1. The thread on the rocker bolt is 1.25mm per turn or .049" per turn of the rocker bolt. However, that is not the same as the plunger travel when preloading the lifter.

2. The rocker ratio is 1.7. There is a fantastic coincidence of the mathematics that is going to jump out, but I'll get there. When you are running the motor, the rocker bolt is approximately the fulcrum (pivot point) of the lever. On the back side, if it moves 0.100, then on the front side, it moves 0.170. Easy right? Not so fast....

3. When you are preloading the valve, THE VALVE STEM IS THE FULCRUM, NOT THE ROCKER BOLT. So you now have to go to some quick trigonometry to get the real number. But it isn't too bad. The back side of the rocker is 1.0 and the front side is 1.7. The units don't matter, so we will call them GM's for argument's sake. The distance from the pushrod cup center to fulcrum center is 1.0 GM. The distance from the fulcrum center to the contact point for the valve tip is 1.7 GM's. The distance from the pushrod cup center to the valve tip contact point is 2.7 GM's.

4. Now, keep up here. The fulcrum is 1.7 GM's away from the valve tip and the pushrod cup is 2.7 GM's away from the valve tip. So, if you tighten the bolt one turn or .049", then the pushrod will compress the lifter 0.049 x 2.7 / 1.7, which is 0.078" preload.

5. For those of you wondering "What about comp's instructions that you should get 1.25-1.5 bolt turns when you torque the bolt?" Very simple. Comp's instructions INCLUDE THE TORQUIING OF THE BOLT, WHICH STRETCHES THE BOLT AND DOES NOT ADD PRELOAD..

6. So for your true preload number, find dead soft touch. Then, turn the bolt until you feel it bottom out, but do not torque it. That number of rotations times .078 is your preload. Then, put the torque wrench on and torque to 22 ft-lbs, and you'll see where the extra half roation in comp's instructions comes in. Comp likely worded their instructions for simplicity, as it is technically correct. If you preload and then torque the bolt for a total of about a turn and a half, you are about .070 preload. THAT'S NOT THE SAME THING AS LIFTER PRELOAD VS BOLT TURNS..

7. It is a fantastic coincidence of the math that .070 (desired preload) / 1.5 (bolt turns to 22 ft-lbs) is .047, resulting in the "1 turn is .047" assumption that it is so near to 1.25mm as to be negligible. But again - Bolt torque is not preload. The bolt won't torque until the pedestal is firmly against the head.

8. If you're counting rotations of the wrench and ratcheting it, mark the bolt at 12:00. Then look at the final position after it bottoms. If it goes past 12:00, you'll know if it was .25 turns or 1.25 turns just by the amount you turned it.

 

Darth, your 10,000th post is a good one! Nicely done!

 

So, what is the best or correct method to use? Would this procedure be best to double check the readings from the push rod checker?

Thanks.