No Lifter Preload? Problems with Pushrods LQ4
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Teching In
Joined: Dec 2011
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No Lifter Preload? Problems with Pushrods LQ4 80K mile LQ4. Swapped a comp cams XER281hr-12 cam, new timing chain, new oil pump, new comp cam springs 26918. Bought a comp cams checker and here's the problem:
With cam on the base circle my checker is telling me 12.5 to 12.75 turns out. So at 12.5 x.050 per turn that's .625 x 6.8 = 7.425. Now if i add for lifter preload of .060 I would need a pushrod that is 7.485?
Seemed wrong to me so called comp cams - they said something is wrong and to try to pump up the lifter. I get no movement when I stick a stock pushrod into the lift? I tried all the lifters and i get no movement - did they all bleed down? Motor has been apart for about a month. When i install the stock pushrod when the cam is on the base circle the rocker doesn't touch the valve stem. I hear the lifter touching the cam and when i cycle the motor the pushrod does eventually touch the rocker to move the valve but back on the base circle the rocker doesn't touch the valve.
Any thoughts?
With cam on the base circle my checker is telling me 12.5 to 12.75 turns out. So at 12.5 x.050 per turn that's .625 x 6.8 = 7.425. Now if i add for lifter preload of .060 I would need a pushrod that is 7.485?
Seemed wrong to me so called comp cams - they said something is wrong and to try to pump up the lifter. I get no movement when I stick a stock pushrod into the lift? I tried all the lifters and i get no movement - did they all bleed down? Motor has been apart for about a month. When i install the stock pushrod when the cam is on the base circle the rocker doesn't touch the valve stem. I hear the lifter touching the cam and when i cycle the motor the pushrod does eventually touch the rocker to move the valve but back on the base circle the rocker doesn't touch the valve.
Any thoughts?
Thread Starter
Teching In
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I initially installed the rockers and stock pushrods until the exhaust started to open and then checked the intake and vis versa for the exhaust. I also put my thumb over the spark plug hole to verify on the compression stroke.
TECH Addict
Joined: Aug 2005
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From: Monroe,NY
When i installed my 5315 lifters you could not push down the plunger by hand. When you take the pressure off the lifter it will spring back up. If it doesn't there is something wrong.
What heads and what lifters do you have? If you measure the base circle of both cams you will see the difference.
What heads and what lifters do you have? If you measure the base circle of both cams you will see the difference.
Thread Starter
Teching In
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stock lifters (lq4) - stock rockers. Just seems strange that all the lifters have zero movement and there is 1/8th gap between the rocker and valve on the base circle. When I was changes the springs the motor was trying to turn over (presumably due to the air pressure in the cylinder and maybe forced air into each lifter and bleed them down?
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Look down the pushrod hole with a strong flashlight. You will be able to see if the plunger is not at the top.
Also, are the Scorpion rockers shimmed? They may be the reason for the pushrod length. Retry the measurement with the stock rocker and see what you get.
Also, are the Scorpion rockers shimmed? They may be the reason for the pushrod length. Retry the measurement with the stock rocker and see what you get.
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Teching In
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Not using scorpion rockers - stock rockers. I filled motor with oil and engaged starter not building enough oil pressure - rockers are all still loose. I really don't want to take the heads off - I might just put 4.725 pushrods in and cross my fingers that everything will pump once I fire the motor.
On The Tree
Joined: Jun 2012
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I ran a lq4 about 5 miles with zero oil pressure and if the rockers would have gotten as loose as yours they would have totally came off the push rods you would think huh, but they didn't, though it was CRAZY NOISY LOUD....
Not using scorpion rockers - stock rockers. I filled motor with oil and engaged starter not building enough oil pressure - rockers are all still loose. I really don't want to take the heads off - I might just put 4.725 pushrods in and cross my fingers that everything will pump once I fire the motor.
You should still be able to see the plungers on the lifters. If this is a straight cam swap, something is unknown. The plunger will not typically stay down even if compressed unless the valve spring is pushing on it.
Do you know the base circle of the cam, if you do you can run a few numbers to see if the additional length makes any sense. If you don't, not sure if you can measure with the valley cover off. I looked at my photos and it would be tight through the casting where the cam is visible.
Last edited by vettenuts; Feb 13, 2016 at 06:32 AM.
TECH Fanatic
Joined: Jul 2007
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From: Wilmington, De
I would quit counting turns and buy an 8" digital caliper. Then find zero lash on the base circle of the cam at 22 ft/lbs, and once you do, carefully remove the checker and measure its length.
Hell yes! If you really want your preload accurate this is the way. Why cheap out on a $50 tool on a $800 project?