MikeD.

So im assembling an lq9 for my truck, and got everything put together to the point where I can start measuring for pushrods. Cam is 228/234 cam motion custom cam, and a set of NGP 799 CNC heads, which I then had milled .020, and fresh ls7 lifters. So in my mind I'm already assuming I'd be in the 7.375 PR length, but I figured I'd measure anyway.

The first method I used was bolting the rocker down, and adjusting the checker to get zero lash, then adding .080 for preload. So at zero lash, I got roughly 7.300+.080=7.380.

I then tried the getting the other method of checking how many turns you get to 22ftlbs. I threw a stock ls3 pushrod in there I had laying around (7.400) and at zero lash, i got 1 3/4 give or take.

So I'm a little conflicted.. do I order 7.375s or 7.400s, I don't want a noisy valvetrain but I don't want too much pre load either

HappySalesman

iTrader: (3)

With LS7 lifters I believe the preload range is .070 to .1

What you want to do is measure till you get zero lash, then add your preload. In this case you got 7.380. Then take your checker and increase the size to 7.380. Install the rocker and by hand, turn the bolt. You'll hit a point where the bolt will stop spinning freely with just your fingers (what I did was put an extension on the socket and spin it by hand) at this point you've hit where the rocker will now start moving down and putting pre-load on the lifter.

Since you're aiming for .080, you'll want just a hair past a full revolution (figure each revolution is about .075). As long as you're within about 30 degrees of a full turn you're fine.

vettenuts

iTrader: (4)

Not sure how you got that but don't think is correct. First turn will provide approximately 0.052", however using the adjustable pushrod with the valve springs will also change the numbers because there will be several thousandths compression of the pushrod due to the threaded section.

vettenuts

iTrader: (4)

1-3/4 turns is approximately 0.110" of preload. Your direct measurement was 0.080" with a 0.020" shorter pushrod. Not as far off as you might have thought. How are you measuring pushrod length? Make sure you are not mixing gauge length and overall length as there is a difference in measurement value for the same pushrod. Here is a good thread on counting turns and measuring:>>>>>>Link

farmington

iTrader: (14)

base circle of cam must be a little smaller than stock.

MikeD.

How easy is it too over shoot the base circle? I used the EO/IC method, so for example, checking the intake side, I would watch the intake valve fully open, close, then the exhaust valve would just start to open, and the rocker would move approximately 1/4" down (open) and that's when I would remove the intake rocker and start checking for that? And after that, I would let the exhaust open, close and just as the intake rocker begins to open, again approx 1/4" of travel, I then pull the exh rocker and check that length.

I just needed to type that out so I know I'm getting to the base circle correctly lol

patSS/00

iTrader: (6)

With the turns method I think going to 22 ft/lbs will overshoot. You should just turn until the rocker is hand tight. After that the rocker is not moving down any more. With those round head bolts you get with after market rockers, for example, they compress down some into the hole slightly after the rocker has stopped moving but the torque wrench is still turning.

jimmyp3353

iTrader: (3)

Don't use the turns method. I always set the adjustable pushrod to zero lash then take it out and measure it with a micrometer. Way more accurate.

mOtOrHeAd MiKe

iTrader: (8)

Been there done that.

https://ls1tech.com/forums/generatio...-pushrods.html

HappySalesman

iTrader: (3)

Per what Darth_V8r and Tony Mamo have told me:

I got .048" on the bolt threads. Being very clear, I'm talking about the rocker bolt. The valve tip end is fixed, and the length ratio is 1.7:1. So, the distance traveled by the pushrod end is 2.7/1.7 or 1.58x further. I rounded down to .075

Considering the Johnson lifters I installed want .038 preload, which equates to half a turn of the rocker bolt, a full turn would then equal .076 would it not?

vettenuts

iTrader: (4)

Except 1/3 of that turn to reach the 22 lb-ft is taken up in bolt stretch and not in bolt movement downward that preloads the lifter. This is the reason Shane was finding one turn in 0.049" of preload, when you use 2/3 turn instead of 1 turn of actual bolt preload movement the numbers will come out. I verified all this several years ago with a dial indicator. Unfortunately the link I provided above is missing the photos and diagrams because photobucket changed their policy and many were using it for photo hosting. A lot of the older threads are screwed up because of that.

Dian

where do (a lot of) people get the idea to torque the bolts beyond snug?

HappySalesman

iTrader: (3)

I'm not talking about full torque, I'm talking about turning until you're no longer adding preload and instead torquing the bolt. Since torquing just stretches the bolt and doesn't really add pre-load, there's no sense in making that part of the measurement

vettenuts

iTrader: (4)

OK, that would work. Counting turns method is still not very accurate in general.