Is it normal? Help (Rocker arm install)
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Teching In
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Is it normal? Help (Rocker arm install) So I was installing the (stock) rocker arms and made sure the lifters was on base circle (valve should be closed) when I tightened them to 22 ftlb and noticed the spring/valve compressed down slightly. Is it normal for it to compress a little? I was going to do a leak down test this weekend to see if it holds pressure cuz if it does hold then I'm not gonna worry about it. Cuz what I'm thinking if it moved a little then that means the valve is slightly open all the time.
Staging Lane
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Just wait a bit as the lifter may not have bled down all the way. If it always holds the valves open its too long. How many turns down did it take to tighten once you felt it compressing the lifters or opening the valve?
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Teching In
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I can't remember but that's true about the lifters. I'll just recheck them tomorrow if I have time. I'll take all of them off and redo them one by one again to see if they move
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Teching In
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I've read where people do it like that with no problems with stock rockers but I feel like the tension on the rockers when tightening can affect torque.
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From: Dickinson, Tx
On my car I always put the bolts on hand tight and then torque them down to 15lbs then 22lbs. I never spin the engine over for each one to torque down. Yeah yeah, I live dangerously.
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Thread Starter
Teching In
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So I just checked them and redid the rockers. the valves/springs didn't move!!! Yay yay!!! So I guess the lifters didn't bleed when I was tightening them the first time that's why they move a little. Now I'm ready to attack the wiring for my swap
Maybe not a good thing. What's going to happen when you have 60-70psi of oil pressure? Will it hold the valve open?
Well if you don't do the correct method you might only be hitting 15-18 ft lbs even though its clicking @ 22 ft lbs
And it's not something you can recheck with the torque wrench and click them all at 22 ft lbs to double check and make sure "you" got it!
Might as well not use a torque wrench and just tighten it down if you want to skip an important step like that.
And it's not something you can recheck with the torque wrench and click them all at 22 ft lbs to double check and make sure "you" got it!
Might as well not use a torque wrench and just tighten it down if you want to skip an important step like that.
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It will hold the valve open cuz if it took that long to bleed to were the valve didn't close right away when I tightened them then with oil pressure it will hold
With a stud mounted rocker, you tighten the nut to zero lash, and then add 1/2 turn. That compresses the lifter plunger a little bit and gives it room to operate, but doesn't compress the spring or hold the valve open. If the valve is open, it's too tight, and the engine will back fire. If you tighten it enough to hold the valve open, the plunger is bottomed out.
As I understand it (and haven't done it yet), you tighten the nut to 22 ft/lbs, which is zero lash. Then add the required number of turns, which depresses the lifter plunger the required amount. Oil pressure is about 70psi, and valve spring pressure is >100psi. So oil/hydraulic pressure shouldn't overwhelm valve spring pressure.
What am I missing here?
You're not missing a thing. With pedestal rockers its just a little more crucial to have the correct pushrod length because you dont have the same fudge factor you do with adjustable stud mounted rockers (even though yes pushrod length is still important)
If pushrod length is correct you simply tighten all the bolts down to the 22 ft/lbs, if you have a lifter high in its bore where the oil supply orifice is blocked you will notice it compressing the spring slightly, this is nothing to worry about if you have the correct pushrod length because when the lifter does bleed down its no different than going 1/2 turn past zero lash on a stud mounted setup.
Once again if you have the correct pushrod length dont worry about oil pressure opening the valves because consider this:
lifter diameter is .842", now lets assume the internal piston is half of that at .421"
Compute the area 2R*pi .421*.421*3.1415= .557 sq/inches .557*70psi = 38.99
39 LBS acting on the pushrod with 70 psi oil pressure, now consider the mechanical
DIS-advantage at the rocker 1.7 ratio probably in this case, so 39/1.7 = 22.94 lbs acting on the valve stem. In other words dont worry about it as long as you have adequate springs for your cam and not expecting to run over 7000 rpm
If pushrod length is correct you simply tighten all the bolts down to the 22 ft/lbs, if you have a lifter high in its bore where the oil supply orifice is blocked you will notice it compressing the spring slightly, this is nothing to worry about if you have the correct pushrod length because when the lifter does bleed down its no different than going 1/2 turn past zero lash on a stud mounted setup.
Once again if you have the correct pushrod length dont worry about oil pressure opening the valves because consider this:
lifter diameter is .842", now lets assume the internal piston is half of that at .421"
Compute the area 2R*pi .421*.421*3.1415= .557 sq/inches .557*70psi = 38.99
39 LBS acting on the pushrod with 70 psi oil pressure, now consider the mechanical
DIS-advantage at the rocker 1.7 ratio probably in this case, so 39/1.7 = 22.94 lbs acting on the valve stem. In other words dont worry about it as long as you have adequate springs for your cam and not expecting to run over 7000 rpm