Pray

iTrader: (7)

I just had my 799 heads milled .015" and I am running a .040" Cometic gasket from the stock .060" head gasket. My lifter preload was inbetween 1 1/2 and 1 3/4 turns. It started to open the valve when I locked them down. I don't do much stock stuff and usually only run 1/4 to 1/2 turn max on my normal builds. I was just going to get some .035" shims tomorrow if it is a problem. What is the stock setting? I need help ASAP. Thanks in advance.

mark21742

I like to stay right at 3/4 turn to torque if possible, but max around 1 1/4 turns

3rdCoastPowerSports

iTrader: (5)

not sure if i understand you correctly or not. did you measure for correct length pushrods

Pray

iTrader: (7)

The truck just had a cam till today. I am running the standard 7.400 push rods. I re-installed them tonight trying to get this thing finally fired up again and it took a about 1 3/4 turns to torque. I always use Comp 850-16 lifters in my builds and do check push rod length along with valve train geometry, but since this is just my daily driver truck and wanted to spend minimaly I didn't go change the lifters or the rockers. I usually set my preload to a minimum. I just need to know what the stock specs are.

mark21742

If your just looking to get by, you should be good with what you have. It's not optimal, but in specs

Pray

iTrader: (7)

I was just reading that optimal is .080" and each turn is worth .047". So 1 3/4 turn comes out to .083". Does that math seem right? It would be too easy to put some shims under the rocker pedestal. I was thinking between a turn and a turn and a half would be best.

mark21742

No, for stock you are golden....you would be suprised at how far out of tolerance stock stuff can be.

Pray

iTrader: (7)

Cool thanks. I am going to run it as is. I think I will pull out the dial indicator and see for sure how much one turn is really worth. Then I will know if I am good.

mark21742

Stock they FI run a little on the tight side to keep the valve train noise down

Spartan7

iTrader: (7)

FWIW, I just finished replacing my lifters with LS7's on my truck. I torqued them to 22 ft-lb, GM spec. They are dead silent.

Pray

iTrader: (7)

How many turns past 0 lash did it take to tq them down. I think I am going to shim mine tonight or tomorrow to see what happens. It is quiet but it is idling like it has an intake leak. Won't come down form the 900rpm area. Before the heads it idled at 750 like rock with the air on. I also have less idle vacuum now.

Spartan7

iTrader: (7)

I didn't look for zero lash or count the turns. I just used the EO/IC method and torqued them to 22 ft-lb. But I'm also using stock valvetrain.

Pray

iTrader: (7)

When replacing lifters or any part of the valve trane you might want to know what your preload is as. Especially since there are two different types of LS7 lifters now.

Spartan7

iTrader: (7)

GM says nothing about checking the preload. This isn't a race motor either. They're silent, and the truck has plenty of power. I'm not concerned with it.

ZeeOSix

That's because GM has already figured out the correct parts (pushrod length, etc) to give the lifter plunger the right pre-load. GM doesn't write the manual assuming people are going to be modifying and put different parts in the engine. GM assumes all the OEM parts are being used, and in that case there would be need to worry about lifter pre-load.

ZeeOSix

So if nothing else has changed in the system (including pushrod length), then milling the head 0.015 and using a head gasket that is 0.020 thinner will essentially give you 0.035" more lifter pre-load then you had before.

0.035" is about 3/4 turn on the rocker arm bolt. So target of 1 +/- 1/4 turn seems like a good target.

Getting the correct lenght pushrods seems like the best fix vs. shimming the rocker arms. I like the rocker arms seated down as they were originally designed to do, without shims.

Pray

iTrader: (7)

I do too as long as the geometry is correct. I don't think the geometry is correct anymore once you go with a higher lift cam.

Pray

iTrader: (7)

Didn't get to finish my thought earlier. I know on a non adjustable system the geometry is not dependant or related to the pushrod length but I remember reading that over .550 lift the stock geometry goes to crap. You end up putting side load on the valve and wearing out valve guids. I am not sure what the fix is for the stock rockers. I would assume shimming them would do it but I don't think you can get a good wipe pattern with the stock rockers.

The other thing is the actual thickness of the stock gasket. I always thought it was .052. When I smashed it with the dial calipers I could get it down to .052. But if I smashed it with pliers and measured it lightly with the calipers it came out to the .060ish it was supposed to. Either way we are only talking .008 between those two numbers. I used to run 7.350's with my 59cc .040 gasketed AFR's with no problems. Maybe I can find some used 7.350's. I already spent way more on the heads than I wanted to.

Here is my last deal. I read that whole thread about Shawn's method which I buy because I went with it. Then Vettenuts and another dude were basically adding almost double to Shawns number due to math involved with where the push rod is located on the rocker. So we either have .047-9 per rocker bolt revolution by Shawns method that I varified with a dial indicator or Vettenuts .020 per 1/4 revolution of the rocker bolt. Which freakin one is it? Do I have around .080 at 1 3/4 turn or do I have .160?

Darkman

iTrader: (2)

As I understand Vettenuts uses a constant 1/3 turn to offset the number of turns based on seating the rocker when reconciling to Shanes method.

https://ls1tech.com/forums/15087505-post42.html

Pray

iTrader: (7)

Correct but that would have you end up with less preload if you don't count that part of the revolution. But his numbers end up larger. I guess that is why I am confused on his math.