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Valve Adjustment, Flat Tappet Cam Break-In - Hydraulic Lifters
Although hydraulic lifters shouldn't require any adjustments during normal
service, it is important to check the lifter pre-load when lifters are installed.
Adjust as necessary. Lifter pre-load is the distance between the retaining
snap ring and the push rod seat in the lifter when the lifter is on the heel
of the cam lobe with the valve closed. A number of things can affect lifter
pre-load:
1.Resurfacing the heads and/or
block deck
2.Changes in camshaft diameter
3.Changes in push rod length
4.Changes in valve length
5.Changes in rocker arm length
or geometry
6.Changes in head gasket thickness
7.Changes in lifter height
8.Valve job
9.Different rocker arm stands
or shafts
Be sure and check the valve geometry and use either longer or shorter
push rods to correct the geometry.
In some cases on shaft systems a shim under the rocker shaft may be required to maintain
correct geometry.
When installing new hydraulic lifters, follow the proper OEM procedures
for checking and
adjusting lifter pre-load.
Initial settings on Hydraulic lifters-PRELOAD
Presuming that your using an aftermarket QUALITY set of hydraulic lifters
this procedure should be right for your application. It is your responsibility
to assure that this tutorial applies to your specific application.
This procedure is what we use for a Racer Brown Cam and Lifter set
with adjustable rocker arms.
Install the push rods and rocker shafts, backing the
adjusters all the way out to be sure you don't jam a valve.
While priming the engine with a drill motor and priming
tool we rotate the engine 360* X 2 to rotate the cam.
This will bring oil to the lifters and support the
push rod seat during adjustment.
With the intake manifold off you can see the cam lobes
and easily determine when the lifter is on the backside of the cam and the valve
is in the closed position.
This part requires the gentle touch of a brain surgeon,
once you have determined that the lifter is on the backside or heel of the
cam start tightening the adjuster on
the rocker arm, gently take up the slack while rotating and moving the pushrod
up and down until the rocker arm forces the pushrod to
JUST TOUCH the cup in the lifter. The pushrod should rotate in your
fingers easily with zero up and down movement.
Don't make the mistake of forcing the push rod
up and down as the hydraulic lifter cup is supported by a tiny spring and
you can collapse the lifter if you
push hard enough and force the push rod to the bottom of the main body of the
lifter. This will give you excessive valve train load
and probably kill your cam, bend a pushrod or ruin a good lifter or a variety
of other catastrophic results that we can discuss at some other time...bottom line,
be gentle and don't over tighten.
After you set the valve you should be able to force
the rocker arm down on the push rod and it will give slightly....the amount
of force is going to depend on how much oil pressure you pumped up into the lifter
during the priming procedure and how much it held.
Once you rotate the cam to the next valve you may
have some slack in the lifter as the spring pressure will try and bleed off
the oil in the lifter and bottom out the push rod, this
of course is normal.
Once you have determined zero lash tighten the rocker
arm adjuster bolt 1/2 turn, this is the preload we use, check with your cam
and or lifter manufacturer to confirm
preload settings.
Now on to the other 15, try to rotate the engine as
little as possible, go in both directions to minimize rotation of the cam
after your all done. Use a break-in oil of your choice and pour some
over the cam lobes, install the manifold and try and fire the engine within
24 hours. We usually leave the
lifter adjustment until the engine ready to install and we're ready to fire it
off.
Initial Start-Up
It is important that the engine starts immediately.
Prolonged cranking may damage the camshaft, lifters and/or followers.
Before starting the engine, top off the coolant level and make sure the
ignition timing is properly set. After starting the engine, DO NOT let it
idle. It is essential to run the engine at 1800-2200 RPM for at least
20 minutes.
Because the camshaft and lifters are primarily lubricated by the splash
of oil from the crankshaft, any RPM below 1,800 may result in insufficient
lubrication and may cause cam lobe failure.
The high RPM also allows the lifters to rotate quicker and seat properly
to the camshaft during this critical break-in procedure. During the first
20 minutes, carefully monitor oil pressure and temperature, if any problems arise, shut down
the engine immediately.
Remember, DO NOT allow the engine to idle.
Typically, whenever a bigger valve spring is used, greater precision is
required to maintain reliability. Cleanliness, alignment, clearances, journal
surface finishes and lubrication must all be controlled more closely.
Here are some tips to help maximize performance and longevity when using
aluminum alloy camshaft bearings.
There’s many things that can cause a cam to go flat here are a few
of the most common.
Not following the camshafts
manufactures instructions to the letter.
Not using enough break-in
lube
At least 15 minutes of engine run
in at a minimum of 2000 rpm.
Improper valve adjustment during
break-in
Valve train interference: check retainer to
guide, rocker arm to retainer, rocker arm slot to stud, valve to piston,
valve spring coil binding
or weak springs allowing lifter to bounce on lobe and a sticky valve
in the guide from incorrect clearances. Most Common... Too much spring pressure.
Not using a break-in oil
Not priming the oil system before
startup. Using a priming shaft and drill you should prime until you get oil up
to the rockers.
Having to crank engine over for
say 30 seconds or more before it fires or if your not able to keep running
at the required rpm immediately after
it fires, cam failure is very possible.
Dirt or blast media left in engine.
Rule of thumb….whatever Oil
pressure you get with the drill during priming is what you’ll have at idle,
if you can only crank 20# with the
drill it is likely that’s all you’ll have at idle and something may
be wrong.
This is only a guide and a few tips to help with break-in and nothing here
guaranty's that your break-in will be successful. The only way that we
know of to guaranty a successful break-in with any flat tappet Hydraulic or
Solid lifter cam is to use a ceramic tipped lifter by SM Machine. These
require NO Break-in and NO special oils, however even with Ceramic type
lifters Manufacturers recommendations MUST be followed to the letter.
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