WTF is a..

What the **** IS a "Hydraulic Lash Adjuster???"

The illustration in my FSM shows it to be INSIDE the little nub that the cam pushes down on to open a valve.... what does it do?!?!? the illustration makes no sense to me..

-a

[svx_commuter]

The CAM lobes pushs the valve down and a spring returns it. Between the cam lobe and the valve there is usually a follower. The cam lobe pushes the follower and tha pushes the valve. Every thing is in metal to metal contact and this is called a solid set-up or solid lifters. There has to be clearance between the cam lobe and follower to let the oil in. This set-up can also be noisy because the the cam lobe can smack the follower. Solid followers/lifters also need to be adjusted as the valves and lifter parts wear.

Soooooo........... Along came the hydraulic lifter. Needs no adjustment but limits the maximum engine rpm because the valve can't keep up. They are quieter because there is no clearance. The oil from the engine is forced into a chamber that is a small hydraulic piston. The piston takes up the clearance in the valve train. When the hydraulic lifters go bad they make a lot of noise. I do not know about other cars but I think the Subaru hydraulic lifter is very small by comparison.

so if it's in fact possible to replace the hydraulic lash adjusters and run a "solid setup," it would be possible to run the engine to higher rpm? I mean, running the engine faster obviously requires a lot of rebalancing, but switching to a solid setup would make it all the more possible?

[svx_commuter]

I don't know what is involved on the SVX to get the lifters out. The engine may have to come out of the car. I also don't know if solid ligters are available. My 97 OutBackSport has sloid lifters. Have to be adjusted every 100K miles. I have done them personaly once. I had to get under the car to do some of them. The dealer did not even know of this change as they were hydraulic up to that year.

You would have to ask around to find out if it would gain you anything in the SVX. There is an RPM limit by electronics on the engine.

[MoreIBNR]

The maximum rpm is governed by the valve springs (among, probably other things). If the valve springs are too weak, they don't respond fast enough at high rpms and the valves "float." If the springs are too strong, they put too much stress on the valves an the valve seats. My advice (for what it's worth), don't f*** around with it!

[Beav]

The main thing to remember is if it's cheap, easy, high-yield, reliable, yadda, yadda the factory would have beat you to it. Why wouldn't they, don'tcha think they'd rather say "The new 400hp SVX"?

Beav