Lifters / Valvetrain - not just Hyd VS Solid

[Route666]

Hi all, I've been reading up on lifters, solid, hyd, cam profiles for both, with and without rollers.

Now it got me thinking about people recommending higher ratio rockers - now my theory is this:

Say you want .5 lift on your valve. If you use a 1.5 ratio rocker, the lifter and pushrod have to move further, in the same amount of time, thus also faster. This is more inertia. If you up the ratio of the rocker, and want to maintain the lift, you'll have to use a smaller cam profile which moves the lifter and pushrod less - less inertia.

Now for higher rpms in a hydraulic roller setup is it better to have less lifter / pushrod movement and more ratio which would impart more pressure on the plunger but be easier to control for the spring (as it has more leverage, and the lifter / pushrod is moving slower)

OR

To have the lifter and pushrod moving faster with less pressure on the plunger but giving the spring less leverage to control that part of the valvetrain while it moves faster?


My guess is the first one as the lifter and pushrod would make up a very big majority of the valvetrain mass, so controlling it is a major factor.

Then again, the extra spring pressure would have a greater impact on the plunger in that there is more pressure to push the plunger down, and the amount that the plunger moves is a bigger proportion of the total cam lift over what it would be with the lesser ratio rockers.

Hmm so what say all ye tech heads out there?


EDIT: I would definitely pick the first one IF the plunger spring was replaced with one with a greater RATE - same (almost) seat / preload pressure but stronger rate to combat the extra leverage against it.

Is it possible to get better springs for the plunger??

 

[D.Hearne]

You can tell it's getting to be winter time down under......... I asked this question to a friend that builds race motors. He prefers the higher ratio rocker route. I thought a larger cam profile with less ratio would have been better. I think to find which is better you'd have to build a test mule motor and try each on a dyno. Otherwise the difference probably would never register on the seat-of-the-pants meter.

 

[Route666]

Yeh winter's getting here, but I don't have anything to do that winter will stop me doing anyway lol.

Besides, it gets to maybe 10C (50F) at VERY coldest here, in Brissy anyway.

What I was asking about, although not well stated I guess, is rpm capability - which way would allow hydraulics more rpms. I suppose also general valvetrain rpms too, with the total inertia, etc.

 

[Route666]

Oh and why do people reccomend higher ratio rockers? Is it just for more lift?

 

[D.Hearne]

Yea, that's why I use em. Your winters are like mine sounds like. Only gets reelly cold occasionally. gettin to be summer here.

 

[Route666]

Don't like summer eh? I hate winter because it's too cold and summer because it's too hot lol. You miss what you don't have. Oh that's right you're in Louisiana, it probably gets hotter and steamier than here. But damn, up in the north of QLD, where I used to live, tropical paradise, but HOLY BLEEP it gets soooo hot and steamy (rainforest / tropics area) in summer.

Man I might just get some stronger rate plunger springs MADE if I feel the need. I'm in the biz now where I'm gaining a lot of contacts in fabrication, so building things from scratch is not as far out of reach to the common man as I think most people think it is. Heck, where I work I / we design and cut exhaust header flanges for almost every engine built - for a couple of big exhaust companies. Just yesterday I drew up a flange for a CBR600. I can't wait to get my custom headers made, the flanges won't be 10mm mild steel like the ones we make, oh no, they'll be from 10mm 316 SS - Number 8 finish if posible (mirror)

I'll be able to cut my own fuel tank pieces, walls, baffles, etc, and get them welded, for an arm and a leg saving over what a fuel safe cell would cost me. Oh and perhaps a grille for the 69 made from 316 #8 stainless too. Mmmm classy...

Anyways, hopefully someone else has thought about the original topic of the thread and can bring me some more insight.

 

[Route666]

Hmm ok, since I'm now thinking of eventually making my own plunger springs of greater rate, what's needed now is the pressure they give at the preloaded (1/4 turn) setting, and how far does a quarter turn compress the spring? Also I assume the springs are compressed a little when the plunger is fully extended as well, so I'll need to know how much.

 

[65ShelbyClone]

Before you go to the trouble of making your own sprngs, you might try measuring the length, width, turns, and rate of the factory lifter parts. Then you may be able to cross ref a similarly shaped spring with more rate. I dont think a stonger spring will help very much, though. There are racers in some of the 5.0 classes that are turning up around 7800 on stock hydraulic roller lifters. Alot of that probably comes from the cam profile, though.

 

[Route666]

Damn, and I was thinking beehive springs for their ultralight retainers, and spring characteristics like no single natural harmonic frequency and thus the ability to use lighter spring pressures and still would need to go to extremes with lifters to get to a 7krpm absolute limit.

Excellent - I've read a lot that supports hydraulics going to high rpms, still not as high as solids, and perhaps never will be, but high enough for me.

Thanks for the idea of just trying to match the spring, sounds like a good one, too simple for me to have thought of lol. I'll give that a go first I guess, if necessary, but for myself, I know that getting some springs made wouldn't astronomically expensive, expensive yes, but not overly, and I'd rather get a spring with the right height, od, id, and rate and not compromise with a similar height, rate, etc. Close enough is good enough is a phrase that would make me say "Get out" in the driest voice possible whilst pointing at the door lol. Perfect is good enough is closer to my belief.

I believe hydraulic lifter rpms is in the cam too, and the spring pressure. Reduce the spring pressure and the severity of the lobe ramps and the lifters will be good for big rpms, however lower spring pressure usually aren't. That's where my interest in beehive springs springs from. They themselves are slightly lighter than standard dual springs, they are also progressively wound making them compress from the bottom up so that they stack and move less and less of the spring mass the more the valve is lifted, and it also gives them a self-damping effect - requiring less pressure to stop valve bounce - not the launched off the lobe kind, the spring and valve vibrating and lifting off the seat again kind. However, having said that, their reduced overall mass (spring, valve and retainer) makes less spring pressure more effective against that kind too. The other big factor with these springs is because the top of the spring is so much smaller, and there is only one spring is that the retainer is a lot smaller, and even a hard steel one is lighter than a titanium dual spring retainer, and a titanium one...

And before someone asks why not solid - I want to use a knock sensor with EFI - apparently the lash will set it off.

EDIT: Oh and this guy Shaun Tiede knows his stuff (he thinks like I do) in regards to cams, he's from Ultradyne http://www.ultradyne.com/

I read this thread http://www.eng-tips.com/viewthread.cfm?qid=47381&page=4 on cam design and he had some interesting stuff to say, praising solid lifters though, but I see that it could benefit hydraulics but in different ways. Basically his theory is for solids to open slowly at first to eliminate reversion, then open quick, and close slowly, to allow ram effect to be fully utilised. I can see the slow start up helping hydraulics to not squeeze the plunger so much, and the slow closing helping with valve bounce - both kinds.

 

[D.Hearne]

On the built 5.0 I had in my Ranger last year, I was turning it up to 7500 before the lifters would float, using Crane replacement factory style rollers. They were riding on a B303 cam. Rockers were 1.7's.

 

[brianj5600]

The hydraulic lifter works on hydraulic pressure, not spring pressure. The only reason is to hold tension when there is no oil pressure.
I've heard more than one cam designer say they prefer higher rocker ratios.

 

[Route666]

Yeh I've read about how they work, and I guess I was just thinking about the oil as a dampener, but you're right, as the lifter lifts it blocks off and "locks" the oil in, or so I've read.

So at high rpms they pump up and hold the valves open too long, I'm guessing they hold them open just a little for the full 360 degrees.

Well at least I understand more about how things work, thanks all!

So what would happen if one were to set less preload on the lifter? Say you set enough so the lifter had zero preload / zero lash when hot, so has a little when cold, as the aluminium head would expand more than the pushrod right? This would make them act like a solid at high rpm right? You could even leave a tiny amount of preload as the lifters are still going to bleed down a tiny bit, and the extra height may actually make the cam slightly bigger at higher rpms. There would come a point again where they would stay pumped up though, but it would be higher, and not as overpumped.

 

[Route666]

One more question: How are the camshaft lobes oiled? I've heard it's from oil slung off the crank. Are there any mods you can do to increase oiling to the lobes?

 

[brianj5600]

I have seen mechanical lifters with oiling hole, but they are only usefull if you are running a class that require flat tappets. Roller lifters are the answer to friction. I believe that if you plan on spinning much over 6000 you are better off with a solid lifter. There are hydraulic cams that will rev more than 6500, but IMO you are giving up hp for convenience. Ask a cam grinder if a hydraulic lifter is the best choice on a motor meant to rev over 6500.

 

[Route666]

(Hopefully I can reply now)

It wouldn't be a choice if I were set on 100% power and high revs, I want a street motor that will handle some zinging stuff once in a while, and to this end it should have a cam that's a little easier on lifters too, not as severe - more low down than an all out power cam. There's that and I want to use a knock sensor with the EFI, and they don't like solid noise or so I've heard, distracts them and fools them.

Are there no "Hi-Rev" kits for Ford motors like the chev ones? They look like a fantastic idea, use a spring to take work away from the valvespring but still leave the plunger function.

As for lobes on cams, rollers still need some oil too right? How are the rollers and lobes oiled? Just by splash?

 

[65ShelbyClone]

I want a street motor that will handle some zinging stuff once in a while, and to this end it should have a cam that's a little easier on lifters too, not as severe - more low down than an all out power cam.

That just screams hydraulic. Dont get me wrong, going as light and durable as you can afford is not bad, but assessing your realistic goals will make the decision for you. If your applicain really demands a solid roller, its not a big deal. They arent that bad on regular maintainence.

As far as oiling the lifters, they get some splash/sling from the crank and some leakdown from their own bores in the block. Rollers dont need alot of oil.

 

[Route666]

Alright, thanks for the help!

 

[84convertablegt]

while on the topic here, not to steal this thread or anything, but are there higher ration rockers available for a stock 289 with basically stock heads, stock everything. and what is the ratio of the stock rockers? any problems with piston to valve clearance when using higher ratio rockers on a stock 289? hoping i can squeeze just a little more out of my edelbrock performer cam here!

 

[SoCalCruising]

Regarding beehives, remember that one broken spring = dropped valve. It won't be common, but it does happen, as attested by an engine builder I spoke to. n a low-lift, moderate RPM application, they should be quite safe, but you are pushing teh envelop when you go to high-lift, high RPM applications. Just something to ponder.

 

[D.Hearne]

while on the topic here, not to steal this thread or anything, but are there higher ration rockers available for a stock 289 with basically stock heads, stock everything. and what is the ratio of the stock rockers? any problems with piston to valve clearance when using higher ratio rockers on a stock 289? hoping i can squeeze just a little more out of my edelbrock performer cam here!

The difference in lift at the valve with 1.7 rockers over the stock 1.6's is only .030. Not enough to cause any problems with stock cams. Only with the very largest cams, might there be issues.