The Stovebolt Site Forums The Shop Area Engine Shop Hydraulic vs Mechanial lifters

Ok can you install hydraulic lifters in a mechanical lifter 235?

Joe

Depends on what year 235. The block has to be bored for hydraulic lifters.

Cams designed for hyd lifters have a very different profile from a cam meant for mechanical lifters.
Mechanical lifters work better on a hyd cam than the other way around if you set the valve clearance at almost zero but the valve timing can become very different when the cam/lifters are mis matched.
This is all due to a thing called clearance ramps which the mechanical cam has to manage the clearance in the valve train before and after the actual designed valve action.
The performance would likely be worse if hydraulics were used on a mechanical cam.
Just learn the art of adjusting the valves.A valve train in good condition with mechanical lifters at the proper clearances will be almost as quiet as the hydraulic fitted engines and the clearances won't need correction before 10,000 miles, probably longer.
MOST performance and hard working engines are still fitted with mechanical lifters/clearance compensators, for several reasons.
I have always been convinced that mechanical cam/lifters experience less wear than the hyd fitted versions because when the lifter is not on the ramp it exerts NO pressure to contact the cam whereas the hyd version is a small hydraulic cylinder- always trying to extend and wiping or thinning the oil film between it and the cam.
Look at a well used camshaft.The hyd cam will show contact all the way around the lobe area while the mechanical cam will appear untouched in the base circle(off the ramp)area.
This all adds up to shorter cam and lifter life for the set that is more in contact.But the machanical valve train must be maintained at proper clearance or wear/noise will result.NO a noisy valve train is not at all desirable and indicates accelerated wear in progress.
Sorry to be so long winded-- it's just hard to find a stopping place sometimes

Joe explained the differences in the solid and hydraulic cam profiles very well. The "acceleration ramp" is an area of slow lift that equals the clearance specification- - -for instance, a cam with a clearance specification of .006" will lift the cam follower slowly to take up the clearance, then the fast opening rate of the valve begins. On the close side of the lobe, the speed of the closing slows down just before the valve touches the seat to prevent battering of the seat, then the clearance gets re-established as the cam lobe transitions to the "base circle" which is ground perfectly round. On a hydraulic cam, the acceleration and deceleration ramps are much shorter since the lifter stays in contact with the lobe all the time.

I don't necessarily agree about wear rates, as the pressure of the lifter on the base circle is minimal, and a properly-preloaded hydraulic lifter eliminates any possibility of the lobe getting battered by an incorrect lash adjustment.

If hydraulic lifters are installed on a solid-lifter cam, the valve begins to lift on the clearance ramps, effectively increasing the lobe duration by a little. That will result in a somewhat rough idle and low intake manifold vacuum at times.
Jerry

My question is why do you not want the solid lifters? For my part the solids are the best in a 235 6 cylinder.

I love hydraulic lifters. I like a quite engine and exhaust. I know a lot of people like the sound of solid lifters and split exhaust.
One other reason I put hydraulics in all of my customers engines is most people are not comfortable adjusting solids.
With hydraulics you set them once and forget them.
Just my two cents.