: pushrod and hydraulic lifters



Hammondsix
12-11-06, 07:55 PM
What does it mean that we have "hydraulic lifters" in the LT1. I thought it was a pushrod engine...

N0DIH
12-12-06, 04:30 AM
All pushrod engines have hydraulic lifters. You can replace with with Mechanical lifters, but hydraulic lifters are more tame. The lifter rides on the camshaft that transmits the camshaft motion into lift that pushes the pushrod up and opens the valves. There are also hydraulic lifters with a higher bleeddown (See Rhoades) that make larger cams seem smaller by bleeding off duration at lower oil pressures.

OHC cam engines don't have lifters, they have followers.

joe_padavano
12-12-06, 01:53 PM
All pushrod engines have hydraulic lifters. You can replace with with Mechanical lifters, but hydraulic lifters are more tame. The lifter rides on the camshaft that transmits the camshaft motion into lift that pushes the pushrod up and opens the valves. There are also hydraulic lifters with a higher bleeddown (See Rhoades) that make larger cams seem smaller by bleeding off duration at lower oil pressures.

OHC cam engines don't have lifters, they have followers.

Are you refering to just Caddy engines or all engines, since there were lots of pushrod engines built with mechanical lifters, including a whole bunch high performance small block and big block Chebby motors.

Note that some OHC engines DO have hydraulic "lifters" (OK, that's probably a bad term). Some OHC engines have rocker arms with a hydraulicly adjustable pivot point to self adjust the valve lash, the same way a hydraulic lifter works in a pushrod motor. These are distinct from the followers that ride on the cam.

N0DIH
12-12-06, 06:00 PM
Primarily GM engines seen in Cadillacs. No way to define every engine out there.

Hammondsix
12-12-06, 09:24 PM
what is a hydraulic lifter?

N0DIH
12-16-06, 01:03 AM
The lifter is the small cylinder like piece that connects the camshaft to the pushrod. Engines with roller lifters have roller balls under them, older style do not

joe_padavano
12-16-06, 03:33 PM
what is a hydraulic lifter?

Let me try a little more basic explanation. The valves are opened and closed by a camshaft, which has a series of "bumps" on it. The lifter is a cylindrical part that rides on these bumps and (through a series of other parts) translates this motion into opening and closing the valves. Early engines simply used a solid metal cylinder to ride on the camshaft, however normal wear would eventually result in excess clearance in the valve system and a ticking or clattering noise that may owners found objectionable. The valves would need to be adjusted regularly to eliminate this noise.

Hydraulic lifters use a small piston and spring system inside the cylindrical lifter with oil pressure to automatically make up for this wear and tear. That eliminates the need for regular valve adjustments. Sometimes the mechanism inside the hydraulic lifter will get gummed up, resulting in the clattering noise and an expensive replacement repair.

Finally, newer engines have incorporated rollers on the end of the lifter instead of the metal-to-metal contact where the lifter rides on the camshaft. Racing motors have done this for years to allow more radical camshafts to be used for increased power. On street cars (like the late 1980s 307 motor) this was done to reduce internal friction in the motor and provide a small increase in efficiency and economy.

Hammondsix
12-26-06, 10:58 PM
thank you!

so does the LT1 use rollers? i guess not....

Right!?!