greenvortec97

iTrader: (1)

I am basically almost done assembling the lq4 370.. running the street heat stage 2 cam for cathedral port heads, i still have not bought pushrods.

here's what i need help figuring out..

1. I'm running brand new ls7 lifters with the gen IV lifter trays (all they had in stock)
2. the springs are PRC duals with titanium retainers
3. the cam is a 600+ lift cam so i'm assuming the base circle is alot smaller than stock.
4. i put in two stock pushrods on cylinder one, from ZERO LASH i get 3/4 turns until the torque wrench beeps at 22ftlbs on both intake and exhaust..

can anyone help me decide what pushrods i need?

mcdonald77

iTrader: (21)

with the money you've spent, you need the comp measuring tool. Any suggestion would be a guess even if close. I would say at lease another .025 longer but that mighht not cut it. The tool is easy to use.

greenvortec97

iTrader: (1)

went out and got one from my performance parts distributor, it's basically just the adjustable pushrod in a bag.. no instructions, i keep finding write ups and videos for solid lifters and threads with a lot of arguement back and forth over who's right and who isn't..


anyone have a surefire way to do this on an ls style stock rocker setup?!

therabidweasel

iTrader: (5)

Use vettenuts method

https://ls1tech.com/forums/showpost....93&postcount=3

greenvortec97

iTrader: (1)

awesome, thanks for the help, i tried this earlier with my phones calculator and the phone was giving me absurd numbers. tried it again just now using the notes i took when i tried this earlier, looks like i came up with 7.300.

now i need to know how much preload i need to run and add it to the 7.300 correct?
whats the safety margin on ls7 lifters? where are my boundaries at? too much wear, too much noise, etc. i want this setup optimal as can be..

Sales@Tick

iTrader: (3)

.060"-.080" is preferred with those lifters. Sounds like a 7.375 would be right where you'd want it. .075-.080 should give you the quieter operation you're after.

I think you will really like that cam Did we end up going with the 231/238 113+3 or the 234/240 113+4?

blow thru

So with the ls7 lifters running a little more preload,will this quieten the valvetrain noise?

greenvortec97

iTrader: (1)

you decided on the 231/238 i can't wait to hear it idle and see how it performs

dr_whigham

iTrader: (49)

Martin's right. A 7.375 is what you need.

Sales@Tick

iTrader: (3)

Yes it would.
I think you're going to really like the power band that cam gives you with your 370.
Am I ever wrong?

Don't answer that question LOL!

soundengineer

iTrader: (16)

Actually, I don't know of any lifters that like more preload... Typically its quieter when you run less preload so that the plunged in the lifter has more room to absorb the shock
All the engines I set up to be on the lower side have nice and quiet valvetrains.

The ls7 lifters are only good to about .130 so you definitely want less preload than .075...never want to be more than halfway thru the lifter travel to start with.
I would put your preload around .025~.050 depending on what pushrods were available off the shelf.

dr_whigham

iTrader: (49)

Agreed.

Mine is one full turn... about .047 and I'm pretty quiet given the cam lobes I have. The valves on the other hand are pretty loud.....

soundengineer

iTrader: (16)

Rocker bolt gets you measurement from thread pitch so 1.25 thread pitch = .0492

then we take into account for rocker ratio 1.7 rocker ratio on stock rockers.. we need to know the inverse because our pivot is now essentially the valve stem so, to get our new value, we need to add the difference back into our value effectively... .0492 + (.0492/1.7) = .078

In an ideal world, you want to be at 1/4 to 3/4 turns... Or .020~.060 preload

dr_whigham

iTrader: (49)

From zero lash to one full turn is between .047 and .049..... What am I missing here? I've never calculated rocker ratio for preload.

soundengineer

iTrader: (16)

Once you hit zero lash....the rocker starts to pivot....
The fulcrum being the bolt....
Only time you can use threads to count is if you are using an adjustable rocker with a lash cup adjuster.
Then you would be moving the pushrods only....
Otherwise, your bolt is moving a fulcrum with a multiplier ratio.

soundengineer

iTrader: (16)

To make it easier to think about....
Picture a lever, let's say a yardstick....
Put one end on a table, and hold the stick level...
Pick any spot in the middle and move that middle point 6 inches up or down....the far end will move quite a bit further...
This same movement happens with your rocker when you tighten the bolt... This is what rocker ratio does.

therabidweasel

iTrader: (5)

Being a little pedantic here, but by definition fulcrums do not move. The rocker tip is the fulcrum. The multiplication is by leverage though and the factor is 1.59, which is 2.7/1.7. But as vettenuts has previously posted, something like 1/3 of the turn is just stretching the bolt

soundengineer

iTrader: (16)

correct, technically the Fulcrum does not move...but I'm speaking in terms of what the fulcrum is when seated and you are moving that fulcrum point into position.

if you put a dial on it and actually measure, .078 is pretty dam close to what it actually moves(our rockers are not an exact 1.7 ratio....) until you get to the "Bolt Stretch" portion
do it till the bolt snugs up, and that is your preload basically... or close enough for the vast majority of people.



the math of the ratio is long side divided by short side of the fulcrum...(for easy math...1.7/1)
we have to make the inverse to find out how much that pushrod cup is going to move when the valvestem doesnt move at all

it becomes 1/1.7 or .588
.0492*.588 = .0289, which we have to add to the .0492 to get total movement of the cup..... 0.078 per one rotation of the Rocker Bolt.

therabidweasel

iTrader: (5)

Sorry it is ratated and in my very poor handwriting, but the geometry is shown above. Y is the amount of preload applied to the pushrod. I am perfectly willing to accept if I am proven wrong, but I do believe I am correct, and I have measured with a dial indicator myself. We're only talking a 10% difference here, which is why I indicated my response was somewhat pedantic. I'm wrong all the time though, so feel free to educate me if you see an error.

Sorry I skipped a step in the math in the pic, it was to save space on the page so I could get a picture. X (actually 1/X) disappears from both sides of the equation because it was on both sides of the equation. Note that all I rely on is the 1.7:1 ratio of the rocker and while I used one turn of the bolt (0.049) you can use whatever # of turns you want.

To measure your preload by counting turns you just use (# turns-1/3)*1.59*0.049. It's not the most accurate way, but it is a good sanity check on final install.

1 turn is 0.052"
3/4 turn is 0.033"
1/2 turn is 0.013"

The only way the rocker multiplies motion by 1.7 is if the fulcrum is at the bolt, and in the preloading situation it is not.

soundengineer

iTrader: (16)

I dont know what is wrong with your math....
but let me show you simple geometry...


Valve to Bolt = 1.7
Bolt to Pushrod = 1.0
1 turn of Bolt = .0492

Known value of Valve to bolt being 1.7 and a height of .0492
using opposite over Hypotenuse we get a sin of .028941176...or 1.658438837 degrees of angle
extend to total length of 2.7(1.7 +1.0) using the same value of 1.658438837 degrees (sin of .028941176...we can find our opposite side that is an unknown
so.. Sin x Hypotenuse = opposite
.028941176 *2.7(total length) = .078141176

or we can do it with an arc of a circle since it isnt a right angle exactly....and it travels in an arc...
(2*(pi)*Radius)*(Degrees/360)
Radius = 2.7, Degrees = 1.658438837

which in our case = .077834309



again.. either way you look at it... one turn of the Rocker Bolt = .078