Preload help!
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TECH Apprentice
Joined: Sep 2011
Posts: 344
Likes: 1
From: La Porte, TX
Preload help! Question: Since I'm using the Morel "street" link-bar lifters how much preload do those have? I did a search and came up with 0.050 in an aluminum block with aluminum heads and 0.030 - 0.034 in a iron block with aluminum heads (which I have a LQ4 block with 317s). Do I subtract the preload of the lifters from over all length of the pushrods after I check the preload using the EO/IC method??
Joined: Nov 2001
Posts: 3,043
Likes: 0
From: Texas and Qatar
Those specs you found are what you set the preload to, its not a built-in value. Preload is the measurement the pushrod pushes the lifter plunger down when the lifter is on the base circle of the camshaft and the intake or exhaust valve closed. I find it best to use a dial indicator along with an adjustable pushrod when you are dealing with such stringent specifications (like your .030-.034" range)
Scenario: Let's say when you measure pushrod length with a length checker... that the closest value (with no preload) is 7.350". Well with a non-adjustable valvetrain you then take that value and add your desired lifter preload to it: 7.350" + .030" = 7.380" ideal pushrod length. Now depending on how close your 7.350" measurement was, you have a few choices... you could either run a 7.375" (for .025" preload) or bump up to the 7.400" (for .050" preload). Finally you can always get custom pushrods in your exact length but you'll pay $$$.
One other heads-up: Check an intake and exhaust valve on each engine bank for pushrod length, often they can vary a few thousandths. Last one I checked with low-lash lifters had a variance of .010" bank to bank. Just makes it all the more complicated. Sometimes you will have 2 different pushrod lengths due to intake/exhaust variances from valve tip height or camshaft lobe design, but then if you have a bank to bank discrepancy you can need 4 different lengths!
Scenario: Let's say when you measure pushrod length with a length checker... that the closest value (with no preload) is 7.350". Well with a non-adjustable valvetrain you then take that value and add your desired lifter preload to it: 7.350" + .030" = 7.380" ideal pushrod length. Now depending on how close your 7.350" measurement was, you have a few choices... you could either run a 7.375" (for .025" preload) or bump up to the 7.400" (for .050" preload). Finally you can always get custom pushrods in your exact length but you'll pay $$$.
One other heads-up: Check an intake and exhaust valve on each engine bank for pushrod length, often they can vary a few thousandths. Last one I checked with low-lash lifters had a variance of .010" bank to bank. Just makes it all the more complicated. Sometimes you will have 2 different pushrod lengths due to intake/exhaust variances from valve tip height or camshaft lobe design, but then if you have a bank to bank discrepancy you can need 4 different lengths!
I checked every valve on every cylinder several times and ordered 4 different lengths to cover the 25 thou of total variation across the motor. My lifters are short travel as well. Custom prods are not expensive, look at manton's site. Like $12ea.
My cam is 227r with 617 lift, so pretty fast ramps and my valvetrain is much quieter than stock thus far.
My cam is 227r with 617 lift, so pretty fast ramps and my valvetrain is much quieter than stock thus far.
