Hydraulic lifters and how they work on DSMs???

[Groomz]

I've been thinking about how 4G63T engines have hydraulic lifters for the camshaft followers. I understand how a Chevy or Ford lifter works, and would assume that they operate on the same basic principles. I know that there is the rocker arm that has a follower for the camshaft ( 4G63T ) which is attached at one end to the valve and the other to the hydraulic lifter. What I don't understand is its purpose. I would assume the basic geometry of a rocker would have one point fixed and have the camshaft lobe pass over it, exchanging that motion to the valve and valve spring. My question is that do the hydraulic lifters change height based on oil pressure or are their heights fixed? If oil pressure is not present, do the hydraulic lifters shrink back into the head and not allow the camshaft to act on the rocker?

I hope this makes sense to someone. Obviously the design works and is capable of very high RPMs, but I would still like to understand this part of my engine. I have had very bad phantom knock and this is why I have been thinking about the lifters. When replacing the lifters with 3G ones that have the larger oil passages, are the only benefits better oiling and reduced noise? I only ask this because I don't understand how the lifters work. Thanks for reading this far if you have, and any thoughts you have are most appreciated.

Merry Christmas!

 

[Defiant]

Originally posted by Groomz
I know that there is the rocker arm that has a follower for the camshaft ( 4G63T ) which is attached at one end to the valve and the other to the hydraulic lifter. What I don't understand is its purpose. I would assume the basic geometry of a rocker would have one point fixed and have the camshaft lobe pass over it, exchanging that motion to the valve and valve spring. My question is that do the hydraulic lifters change height based on oil pressure or are their heights fixed?

Their running height is fixed by the internal valving and the distance between the valve seat and the cam follower on the camshaft face. Hydraulic lifters adjust themselves almost to zero, and stay there.

If oil pressure is not present, do the hydraulic lifters shrink back into the head and not allow the camshaft to act on the rocker?

Kind of, but more like "if oil SUPPLY is not present". The lifters generate their own internal pressure, but must have an oil supply to generate it. When you shut off a hydraulic-liftered engine, some will bleed partway down and clatter a bit on startup until they have re-filled themselves. But oil supply pressure has minimal effect on this until there is no supply.

Obviously the design works and is capable of very high RPMs, but I would still like to understand this part of my engine.

The main purpose of hydraulic lifters is to keep valve lash at or near zero to keep valve timing more accurate, and to reduce noise and eliminate the need to adjust valve clearances with wear.

I have had very bad phantom knock and this is why I have been thinking about the lifters.

You might want to start with a new knock sensor.

When replacing the lifters with 3G ones that have the larger oil passages, are the only benefits better oiling and reduced noise?

Better oil _control_, I'd say, to better eliminate DSM valve train clatter.

I only ask this because I don't understand how the lifters work.

Oil goes into them to extend the valve follower against the cam base circle, then slightly bleeds down as the cam applies pressure to it until by the design of its bores and check valving the lifter stops [almost] losing oil and becomes [for all intents and purposes] a "solid" structure which transfers the lift of the cam grind to the valve stem.

 

[Groomz]

Thanks! That was exactly what I was looking for. Happy Holidays to Defiant and everyone else!!!

 

[Defiant]

I was kinda hoping GTM was going to correct the parts I got wrong~~

 

[bigjangin]

I have a question to add to this. I was talking to someone selling regrind cams, and I asked "wont there be less lift since the cam is reground?."

He couldn't really answer me, all he said is "the lifters can more than compensate."
I decided that im going to get hks when the time comes, but I still would like to know, what would happen with reground cams and stock lifters(without shimming).

 

[Groomz]

From what I understand, the lifters would pump-up and make up for the smaller camshaft lobe. The geometry would change though, so I don't know if you can make an apples to apples comparison. The best thing to do is to buy new camshafts, regrinds sound a little backdoor mechanic to me.

 

[Defiant]

Originally posted by bigjangin
I have a question to add to this. I was talking to someone selling regrind cams, and I asked "wont there be less lift since the cam is reground?."

He couldn't really answer me, all he said is "the lifters can more than compensate."
I decided that im going to get hks when the time comes, but I still would like to know, what would happen with reground cams and stock lifters(without shimming).

Well, don't buy from him. When a cam is ground, the base circle is also ground, so the effective lift is changed, usually increased. The lifters will take up the "space" (which you have to remember is wee-tiny, like 1/64th of an inch or so), just as you'd adjust solid lifters or rockers to take it up. The danger point of regrinds is how well they re-harden the new surface- regrounds used to be famous for mushrooming because the grinding had cut deeply enough through the original hardening to let the lobe mush out. I'm not up on this week's technology in this, they probably have laser hardening devices or the like by now... which probably cost all of two-hundred bucks. You guys have no idea how incredibly tools have improved in the last twenty years.