Lifters

[Cool_The_Slain]

I feel incredibly stupid for having to ask this. What is the difference between mechanical and hydraulic lifters. I think it is that they use oil pressure or something to become the correct length instead of being fixed to the length that they were last set at, but I don't know for sure. Also how do the hydraulic ones work?

[SappySE107]

Hydraulic lifters have a spring inside them, and a check valve. Once the engine is started, the oil pressure pumps them up, but they have a bit of give to them, so the time the valve is open isn't precisely when the cam was telling it to open. The makes it much easier to run the motor within a tolerance range, instead of being exactly dead on for valve lash. Mechanical lifters are also called solid lifters. THey have non of that crap, and are a direct link between cam lobe and pushrod (or valve on the DOHC). Hydraulic lifters have less give though at WOT because the oil pressure is higher. You can get lifters with less pump up, which means they are more like solid lifters with the higher oil pressure. Drawbacks of hydraulic lifters are the weight, and the RPM they work till. Solid lifters will spin to 1,000,000 RPM theoretically. Most hydraulics don't make it to 8k though some DOHC lifters will go to at least 8500 (I dont know what the max out there is).

[Cool_The_Slain]

Thanks a lot. So the TDC Lifters are hydraulic?

[SappySE107]

Yup. Fitting solid lifters in would be quite an ordeal for valve lash checking. I have though about it but it would require me to cut up a set of cam carriers to use for figuring out the lash cap sizes.

[Cool_The_Slain]

Why would you have to cut up the cam carriers? Couldn't you just put in the lifters and adjust them to be the right length? And why do you need lash caps, or am I really missing something?

[Cool_The_Slain]

And I guess while I am asking stupid questions, what is the difference between hydraulic, solid, hydraulic roller, solid roller, and mushroom tappet cams. I didn't even know you could have a cam that was anything besides solid metal.

[SappySE107]

You can have hollow cams with press on lobes, but thats really not the point with those labels. They refer to the lifter type, not the cam. Well, roller cams have a different lobe shape for the roller part on the lifter but thats about it. Flat tappet (what 3.1s have) ride on the cam lobe and spin around in the lifter bore. Roller lifters (3100s have this)don't spin, and are paired up to keep each other in perfect alignment with the cam. This reduces friction and generally gives more duration. No clue what mushroom tappet is.

[v6h.o.]

No clue what mushroom tappet is.

thats a worn to shit lifter that is "mushroomed" from a poor cam lobe or a bad material selection which wears the lifter and mushrooms the end out.

[geoffinbc]

Here is a nice pic of a hydraulic roller lifter

[Anonymous]

Ben will you back up your lifters to 8,000rpm?

[SappySE107]

no. I don't know what RPM they will go to given a specific cam spec, valvetrain weight, and springs. I know they have gone to 8k in other applications but thats hardly relevant to this one.

[RednBlack]

Mushroomed lifters were available, (at about 60,000 miles, or less), on 350s in the early 80s. Back 2 cylinders were notorious for crapping a cam and lifters, due to bad oiling. (The 231 V6 did the same, since it was a 350 at birth) True solid lifters in an overhead cam would be a bad idea. Only way to adjust would be surface grinding the lifters. Which is also bad since grinding more than a few thousandths would cut through the hardness. You can't change the cam carrier size to adjust valves individually. Cams don't adjust to line bore changes. Changing cam size would be a nightmare. The roller hydraulics might be the best bet for any real gains as far as lifters go. Are they even available for the DOHC? Dunno. I doubt it. Tighter springs would help, a little. Another way would be a high pressure oil pump, not high volume. Would keep the stock lifters tighter. But, I don't know if those are available. Remember, we have a bastard engine that everyone, including GM forgot about. (The 3.4) And I really don't know why. But I guess that is why we are here.

[SappySE107]

Plenty of DOHC motors are solid lifters. Basically, your reasoning is wrong for saying its a bad idea. Read my post about doing solid lifters...lash caps on the valve stem, or shims that go on top of the lifter. Yes, I know where to get solid lifters that could work in our motors with some work, and I also can get better lifters for higher RPM and less valvetrain mass. Solid lifters weigh damn near nothing and would awesome for a high RPM motor, but its no small task to adjust lash.

[Anonymous]

no. I don't know what RPM they will go to given a specific cam spec, valvetrain weight, and springs. I know they have gone to 8k in other applications but thats hardly relevant to this one.

Give me a while to get you a valvetrain weight on my valves and springs. They will be drilled hollow Ferrea valves, and Ferrea springs, but I am not sure on their weight or their specs just yet. As for cam specs, I'll be using stock for now, in the stock location at first(just to get it running). Then I am going to play with retarding exhaust/advancing intake, and anythign else with them that will hurt my low end and help my high end

[SappySE107]

That still wont help me. You would have to run the lifters in order to know what they can do.