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Will Solid Lifters Work on a Hydraulic Cam?

It is possible to run solid flat tappets on a hydraulic flat-tappet cam and even mechanical roller lifters on a hydraulic-roller cam. Putting solid lifters on a hydraulic cam will gain about 500 rpm on the top-end over hydraulic lifters due to the solid lifters’ improved valvetrain control—unlike the hydraulic, solids have no bleed-down/pump-up problems. Some hydraulic-roller cams—particularly smaller grinds with 220–240 degrees duration at 0.050—are quick off the seat, but this tends to cause more instability on top. Using solid lifters, even with the existing hydraulic springs, enhances top-end stability and fights the onset of valve float.

Successfully running solid lifters on a hydraulic profile requires some amount of valve lash (a solid lifter cannot run at zero lash or be preloaded). This lash effectively reduces cam duration, especially at low lift off the valve seat (see table below). With less duration, peak torque and power occur at lower rpm than would normally be the case for the given combo when running a hydraulic lifter. In other words, the cam acts smaller.

DURATION VS. LASH
This table shows the change in effective duration at the valve from different valve-lash settings on a Comp Cams Xtreme Energy No. 3315 hydraulic-roller lobe profile. It assumes a 1.5:1 rocker arm ratio.
VALVE DURATION AT LASH
LIFT0.0040.0080.012
0.006″279.7°273.6°268.6°
0.020″262.5°258.9°255.6°
0.050″240.9°238.6°236.5°
0.200″183.2°181.9°180.6°
, Will Solid Lifters Work on a Hydraulic Cam?
Run solid lifters on a hydraulic cam? Yes, but you’ll need to experiment with specific lash settings as explained in the text.

Exactly how much lash is necessary varies with the specific cam profile, as well as the material used to make the block and heads. Too little lash and you could burn a valve; too much and the valvetrain gets very noisy. Generally, the amount of hot lash will vary between 0.004 and 0.015 inch. These tight hot-lash settings may cause problems with aluminum blocks and heads, which see considerable thermal expansion between cold-start and normal operating temperature, so running solids on a hydraulic profile is problematic with all-alloy engines. Aluminum heads on an iron block usually work out OK, with lash expanding about 0.012 inch from cold to hot. With iron heads, expect about 0.008-inch growth.

The more aggressive the lobe, the tighter the lash needs to be. The tighter the lash, the more you need to pay attention to thermal expansion problems. For example, Comp Cam’s classic Magnum hydraulic-roller grinds usually run fine with solid lifters at 0.012–0.014-inch hot lash. But its newer, more aggressive Xtreme Energy hydraulic rollers get very noisy over 0.010–0.012 hot lash, so for them Comp recommends tightening up the lash to 0.006–0.010 hot.

One way to home in on what lash your combo likes is to first set the valves at 0.004-inch cold, warm up the engine, and recheck the lash hot. Fine-tune lash settings within the preceding recommendations if the valvetrain is too noisy. Once satisfied, let the engine cool down again and recheck the lash. In the future you can accurately cold lash the motor. —Marlan Davis

, Will Solid Lifters Work on a Hydraulic Cam?
, Will Solid Lifters Work on a Hydraulic Cam?
Mechanical roller lifter on hydraulic roller cam? With care, it’s possible!

Contact

Comp Cams; Memphis, TN; 800.999.0853 or 901.795.2400; CompCams.com

The post Will Solid Lifters Work on a Hydraulic Cam? appeared first on Hot Rod Network.

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