Questions - Solid lifters - Duke and others

[Jerome P.]

[Don H.]

Re: Questions - Solid lifters - Duke and others

Jerry,
I am not an engine expert but my understanding is solid lifters could turn higher RPM's than hydraulic lifters. Hydraulics would "float out" when solids would not. Newer hydraulics did not do that so solid lifters became obsolete.
Don H.

[Duke W.]

Re: Questions - Solid lifters - Duke and others

Mechanical lifters usually allow higher revs before significant false valve motion occurs than hydraulics. That's why high revving SHP/FI engines have them. Also bear in mind that camshaft design is different for both, particularly at the beginning and end of the lobes. Mechanical lifter cams have long (duration-wise) "constant velocity" clearance ramps to take up clearance that changes with component temperatures so that the valve doesn't hang open. Clearance should be adjusted so this lash is taken up at "clearance ramp velocity" before the valve opens and closes so it is gently lifted off the seat and, in particular, gently seats the valve to minimize the chance that the seat will be eroded or pounded in. Sometimes the closing clearance ramp velocity is lower than the opening clearance ramp velocity.

Hydraulic lifters use engine oil pressure to maintain zero lash under all conditions. They have very short clearance ramps that can be constant velocity, constant acceleration, or a combination of the two. As soon a the valve begins to lift a valve inside the lifter closes or the lifter closes off the inlet oil passage causing the lifter to hydraulically lock and lift the valve.

Hydraulic lifters generally require no maintenance for the life of the engine and are quieter than mechanical lifter engines, so they are favored on passenger cars where low noise is preferred and the emphasis is on high low end torque rather than peak power, so they are favored on engines with relatively low duration/overlap cams.

For highest specific output and revs, which is the objective of SHP/FI engines the mechanical lifter is favored for their relatively long duration high overlap cams.

During the sixties GM learned a lot about valve train dynamics and were able to design cams that would rev higher with hydraulic lifters. Also, exhaust emission requirements favored relatively low overlap cams since high overlap cams generate higher emissions, which is why that were last used in 1972.

Later, hydraulic roller lifters gained favor as they are lower friction and allow more aggressive lobe dynamics. Modern Corvette cams are relatively low duration and overlap compared to the most aggressive vintage cams, but have significantly more lift, and the LS7 revved to 7000.

Duke

[Jerome P.]

Re: Questions - Solid lifters - Duke and others

Thanks guys.

Duke, your very detailed and complete explanation is appreciated.

[Michael J.]

Re: Questions - Solid lifters - Duke and others

I love solid lifters, nothing sounds as sweet........

[Terry M.]

Re: Questions - Solid lifters - Duke and others

I love solid lifters, nothing sounds as sweet........

You mean that sewing machine sound? I love it too.

[Patrick C.]

Re: Questions - Solid lifters - Duke and others

I love high compression mechanically cammed 327s

https://www.amazon.com/photos/shared...m9t3r2Yjf24p7S

[Michael J.]

Re: Questions - Solid lifters - Duke and others

You mean that sewing machine sound? I love it too.

Yep, that's it: https://www.youtube.com/watch?v=g1CTpDGoPgg

[Ray K.]

Re: Questions - Solid lifters - Duke and others

And also 425 and 435 HP big blocks !!

Ray