I have had my heads milled and thinner gasket to bump compression, But recently shattered 1 of my valvespring and I noticed with the 7.5 pushrods the i had the sewing machine sound. I replaced my springs and am measuring for pushrods and this is what I came up with. I went to what I believe is zero Lash and I used the eo ic method and with the original 7.5 pr I got 1 3/4 turns to 22 ftlb these may have been too long so I was thinking shorter. I measured with a comp cam pr checker and got 1 1/2 turns to 22flb with 14 turns to the pushrod checker which is shorter than the 7.5 i currently have.First question does the second length seem like the better option than the first 7.5 length? Im trying to avoid the sewing machine noise. Also some help figuring out the second length with the 14 spins on the comp cams pr checker would be helpful. Last, does this include the amount for the ls7 lifters or do I have to add more? Thanks

 

I would seriously look into a 8" digital caliper. Counting turns has bitten so many people recently.

Find zero lash, measure with caliper, add desired preload, confirm measurements, order - and tell the vendor this is as measured with a caliper.

The sewing machine sound is not always the result of pushrods length. It can also result from aggressive ramp rates.

Sorry for the shorter response. It's been a hot topic lately with a lot of the same info being posted repeating from other threads. But if you scroll through you'll see that the caliper method has successfully cleared up unclear situations like this.

 

Oh ok, I thought that every turn was supposed to be a precise amount and you could calculate it by the amount of turns.

 

It is supppsed to be that way, but check some of the threads where the OP did it that way, ended up way off, and then had to go back using a caliper and came out 050-075 different.

 

To many variances in turning and counting, to find zero lash takes a delicate feel, look at
this video at 4:30 into the video and see where he determines zero lash, that is not
zero lash, he does not know how far the plunger on the lifter is pushed in, if the lifter
is completely bled down it does not take much to push the plunger down, so who knows how much it got depressed, just a few guesses like this will throw you off. Just my .02

 

First, 14 turns is 7.500" and the difference in bolt turns may be because the adjustable pushrod is not designed for valve spring loads and may be compressing. Second, why are you tightening down to confirm fit. You should be measuring to zero lash. Third, 1-1/2 turns is a lot of preload. I am getting numbers well over 0.100" of preload.

 

Ok, it seems as though some people's zero lash description varies from person to person. I have watched several videos where I have seen zero lash when you get no vertical play in the rocker and I've also seen it's when u can just barely spin the pushrod under the rocker arm seat. What is the best description you guys can give me as to when I am at zero lash and I can be assured that I am not compressing the lifter? I watched a vid on the eo ic method performed on a ls1 with ls7 lifters and that's when I got the 1.5 turns on the rocker bolt to 22ft lb with 14 turns on the pushrod.

 

Ok, it seems as though some people's zero lash description varies from person to person. I have watched several videos and I have seen zero lash is when you get no vertical play in the rocker and I've also seen it's when u can just barely spin the pushrod under the rocker seat. What is the best description you guys can give me as to when I am at zero lash and I can be assured that I am not compressing the lifter? I watched a vid on the eo ic method performed on a ls1 with ls7 lifters and that's when I got the 1.5 turns on the rocker bolt to 22ft lb with 14 turns on the pushrod and that's before I add for preload and I'm being told that's too much preload.

 

I've always found zero lash by spinning the pushrod with my fingers and tightening the rocker until I feel a drag on the pushrod. Then count the turns when you torque it. I like to be in the .5 turns range for preload

 

Here's the problem with that method...

Once you start torquing the bolt, you are NOT adding preload. You are stretching the rocker bolt. Torque readings are affected by quite alot. Do two bolts side by side - grease one and not the other. Then see how much farther the greased bolt rotates to achieve the same torque.

Zero lash means exactly that. No preload, and no slop. it is a delicate thing, because you can easily preload by hand. I typically will torque the rocker and then wiggle it. If it moves, I lengthen PR, if not, I shorten PR. Once I get to a certain point, I start adjusting in 0.005" increments until I'm bouncing back and forth between no lash and lash. Then I use the number in the middle.

Example: 7.310 is snug. 7.315 wiggles. I record 7.313.

Then, I add the desired preload to the adjustable PR. Example 0.070. SO, I use the calipers to make the adjustable PR 7.383.

Then, I reinstall the PR and I find dead soft touch with the rocker bolt.

Then I mark the bolt and record how much wrench rotation is needed to tighten the rocker bolt BEFORE I start applying torque. Trust me, you can easily feel the difference. Using this method, one bolt rotation is 0.078"

If I get pretty close to one rotation, then i'm pretty clsoe tot eh 0.070" preload I wanted, so I go with the measurement.

If I get nowhere near the same number, say I only get a half rotation, then I go back and remeasure the PR until I get the two methods to agree with each other.

 

OK, I get it. The only thing is what is the recomended amount of preload for the ls7 lifters? I have read .020 to .050. That's seems like a large window.

 

0.070" will do great on LS7 lifters

 

OK, using eo ic i did the "spin pushrod " method u talked about and I came up with a pushrod length of 7.4 then I added the .070 for preload and came up with 7.470. I then checked it with the "spins to get to the 22 ft lb " method and came up with 1 1/4 turns and checked it with another cylinder on the opposite side head and they match.is this my pushrod length? Or is there something else I should do just to make sure?

 

Bump....

 

Sounds like it's perfect then. 7.470 seems longer than normal but your numbers are lining up correctly so it must be about right.

 

Yea. I have aftermarket trickflow heads that have been milled and also thinner gasket . The trickflow sent 7.5 pr and that was before I made changes to he head. So 1 1/4 turns is good for the rocker bolt to 22ft lb?

 

That makes sense. Then yeah 7.470 is going to be almost perfect

 

Ok, appreciate the help. Thanks