I have been thinking lately, it appears that Chevrolet hydraulic lifters are much weaker than Fords. I see plenty of guys with 5 liters turning 6500+ rpms with stock lifters. An engine builder I trust (Ed Curtis) says they take 7500 with no problems, and can go to 8500 with lightweight valvetrain components without running them collapsed. I do think the majority of the classes limit lift, so is that the issue? It seems the LTx crowd doesn't run high lift cams tho, compared to most Fords.
Is there any aftermarket chevrolet lifters that you would be fine to 7000+ rpms, or do you still need a rev kit? If so, why the need for the rev kit? Wouldn't it be easier and most likely cheaper to simply run a good hydraulic lifter?
Last, would it be possible to have the lifter bores bored out to accept a ford lifter, or would there be other issues? The only difference I can see is that the ford lifter has a larger diameter, and they are roughly the same height, which I would presume a different pushrod could correct. Also, could that be the difference? The diameter of the lifter? Presumably it would hold more fluid, so have a better tolerance for high rpms?


Mods- if this doesn't belong in advanced, please move to LT1 tech! Thanks

 

I'm assuming you are referring to hydraulic flat lifters?
What motor/year are you asking about?

Lash setting / preload will have a major effect on how much RPM you can get from a hydraulic lifter. I don't think I'd want to spin a flat tappet to over 6000 RPM and feel good about it.

Setting a zero lash with about 0.020" preload will get a little more RPM out of the lifter. It will make it function "more like" a solid lifter. The down side is having to check your lash more often to ensure the preload hasn't expired from worn valve train components.

If you're looking to rev a motor that high, I would suggest a roller setup, or at the very least a solid cam/lifter kit. Proper seat pressure and spring height will also make a huge difference in the cam's power production.

 

No, I'm referring to a stock 93+ roller lifter from the LT1/4. Also, it was my understanding that all hydraulic lifters would be set at "zero lash" as the hydraulics prevent you from setting lash. How do you set preload on a hydraulic lifter? Wouldn't the lifter bleed down during the process?

I think we're getting somewhere with your last statement. Is the limitation most people have with stock lifters due to improper seat pressure and spring height? I see you recommend going to a solid, that is exactly my question. 6500 rpms is too much for stock lifters? What gives? How can Fords turn 7500 without incident and chevy's can't?

 

A roller lifter is good for more than 6000 RPM, I don't know what the limits are, but again it's going to rely heavily on proper springs and preload.

With a full roller setup, you can get away with much less preload as the breakdown is dramatically reduced due to less friction.

Setting preload on a roller lifter is done pretty much the same as a flat lifter. You don't want any oil in the lifters to begin with. Hydraulics are easier on the valvetrain, but don't yield as much RPM or power. The pros and cons will vary depending on your application.

A full race only motor will likely have solid components and the engine techs will check lash after every run. A street setup will benefit from hydraulic as it will adjust and take up slack as the valvetrain wears down.

I wouldn't say that Chevy's can't turn 7500 RPM on the rollers, I think the motors are not tuned to run that high. It's all about the power range of the camshaft and where it's making power.

If you were to match proper spring weight and height along with a high band camshaft, the lifters will support a more frequent 7500 RPM zone.

The idea about zero lash is to take up any play in the rod between the lifter and rocker arm. Solid lifters don't allow for preload...there is a different procedure to set a solid cam. However, a hydraulic lifter is designed to 'self adjust' and that's the idea of pre-load. After setting "Zero-lash", you can tighten down the rocker and set the push rod to descend into the lifter.

That amount can be argued, but nonetheless, the plunger inside the lifter along with oil pressure will keep the pushrod sandwiched tightly against the rocker arm.

As the cam lobe wears down, the plunger will rise keeping the entire assembly tight...whereas a solid roller will become noisy and start to click - resulting in damage if not reset for zero-lash.

 

just go solid roller and rev as high as you want

 

Before the IHRA and NHRA allowed "cheater" lifters in Stock Eliminator I ran the factory hydraulic rollers. I set the lash according to the factory shop manual, zero plus one full turn. I never had a problem running them past 7000 rpm.

Best Regards,

Daren

 

A solid lifter is not really needed on a LT1 with a stock PCM 7,000-7,200 PCM shut down and all.

I am running my stock Lifters to 7,000.

The biggest advantage of zero lash for some is that the lifters will not pump up at high RPMs and hold the valves open all the time. At least that is what I was taught years ago.

I am sure there are a few here that can cover this stuff better then me

 

Let me try this one...

The lifters will only "pump up" if valve float occurs. The plunger is set at a predetermined pre-load and wont pump up as long as the pushrod maintains spring pressure of the lifter seat.

The oil pressure is not strong enough to drive the lifter seat to overcome the spring pressure...and the spring pressure cannot compress a fluid...therefore the pre-load is maintained.

Excessive pre-load on a hydraulic roller lifter is not necessary because cam lobe breakdown, lifter roller wear or pushrod wear is minimized from reduced friction.

Solid cams are set hot to account for thermal expansion and set to zero lash. Resetting lash on solid cams is frequent because there is no pre-load to adjust for the valve train wear....which results in "play" from the components beween the cam lobe to the rocker arm.

You could get away with as little as 0.010" pre-load on a hydraulic and might not have to reset lash/pre-load for several thousands of miles....whereas solid cams are checked every couple of months (or more frequently for street/strip motors).

How's that for a rookie reply?

 

I take flat tappet hydraulic lifters to 6500 on a regular basis WITH PROPER VALVESPRINGS AND VALVETRAIN COMPONENTS. And I have done this many times even on cheap parts store lifters. Like everyting else in an engine, it's the COMBINATION of parts that matters. That's why they call it a valveTRAIN. If one thing in the line isn't right the whole train won't go down the tracks like it should.

I set my hydraulic lifters at about 3/4 turn down from zero lash and I pay attention to proper rocker arm geometry as well.

If you DO float the valves the lifter will "pump up" and fill with oil, holding the valve off it's seat. You'll run like crap for a while until you let the RPMs down, give the lifters a few seconds to slowly "bleed down" the excess oil and let the valves back down on their seats again. Of course, if your piston/valve clearance was tight to begin with you can easily have a piston smack a valve during this time. So you obviously DON'T want this to occur.

If you run at zero lash with hydraulic lifters there is no where left for them to "pump up" TO. They're already at the top of their travel. You will STILL be floating the valves at the same RPM but you won't have to worry about the bad effects of getting a lifter "pumped up."

Regarding valve float.... it can happen 2 different ways, basically. The more rare one in my opinion, but the one everyone thinks about, happens if the cam lobe basically "throws" the lifter off the tip of the lobe at high RPMs (usually inadequate OPEN spring pressure). The one that never gets it's due is when the valve BOUNCES off the seat as it closes (usually inadequate SEAT spring pressure). Either one is bad, obviously. Not just becuase you can pump up the lifters but because the cam profile is no longer determining the location of the valve. Bad bad bad. You can STILL have a piston smack the valve crooked, not to mention giving up boatloads of horsepower.

In my experience with flat tappet hydraulic cams the second form of valve float is more common (bouncing the valve off the seat due to inadequate spring seat pressure). This is common if you stab in a more aggressive cam but leave the stock (weak) springs in place. Stock springs on a (wimpy) stock cam that would rev to 5800 suddenly encounter valve float at only 5200 with a more aggressive cam!! The springs jsut aren't strong enough to deal with the more aggressive cam lobes.

Interesting tidbit..... Many stock SBC valve springs often have only about 60-70 lbs seat pressure (especially after they spend a decade or two in an engine!). Even a very MILD set of performance replacement springs for a hydraulic flat tappet cam will have about 100 lbs on the seat.

So stab in the biggest hariest springs you can find, right??? No. You can flatten a cam lobe with too high a spring pressure on a flat tappet cam. It's a BALANCE of control vs. killing the cam. Not to mention that excessive pressures can "collapse" a lifter's internal guts. You really don't run into that too much with flat tappet hydraulic cams if you use the right springs, but a hydraulic roller cam that's more of a concern. They can require much stronger springs than a flat tappet cam, but I'm not going to try to go into roller cams. Lots of people smarter than me about roller cams on this board.

Anyways, the only thing you can do to help this "balance" situation regardless of lifter or cam type is to LIGHTEN the valvetrain ANYWHERE you can take weight out. Weight in a valvetrain is death. The lighter the better. You can make the same valve springs rev higher with less weight or you can use lower tension springs and still achieve the same RPM with less weight. Lightweight valvetrain components are the "holy grail" of making a stable valvetrain at extremely high RPMs.

 

Ok, so 7000 is no problem. Then why the need for REV kits? Whats the point? Or are you running your lifters collapsed?

 

Point is someone wants to make a buck!

 

I think I'll disagree...the Rev Kits are installed between the head and lifters. The rev kit uses the lip of the head exposed to the lifter valley to exert force onto the lifters only.

The rods fit down the middle of the springs. The valve springs work less to control valve bounce and keep the entire assembly tight.

I would imagine this would also reduce vibrations/harmonics in the valve train as well?

 

Lets see.. If you use the RIGHT compmonents and valve springs there really is no need for a rev kit either.

The only time I ran a rev kit was when I was running a solid roller cam with bar style lifters. I shattered a Crane gold rocker arm and pitched a lifter sideways. After that I installed the rev kit. Only reason was to keep lifters in bore if I broke some thing else and save the rest of the motor. Spring pressure was 340 closed and 710 open at .690 lift.

I am running K-Motion springs on my current setup. after two years they were all sitting with in 5Psi closed at 140 and all at 320ish open.

it is VERY true. Run the combination of Valve train parts you can. they are 90% of what keeps you going

Later

Ellis
18* Monster car under way!

 

Don't you hate it when the site eats your post. Ughhh


Anyways, yes valve bounce is probably more important than valve toss in the problems of maintainging high RPM control of the valve train.

One reason why guys have XE cams in their LT1's and no matter how much duration they crank into the cam it still peaks at 6K and dies after that is because they have the wrong supporting cast to control the valve how it needs to be controlled.

Valve control is done with 4 things. Stiffness (lack of Deflection), Mass (or lack of), Force (spring pressure) and lobe design.

Mass and Force are hand in hand because the more mass you have to control the more force you need to control it.

The cam lobe determines the amount of force and lack of mass in combination that you need. The more agressive the lobe the more aggressive the spring and weight savings you need.

Stiffness is more important the more pressure we have to deal with. So an agressive HR or a SR need to pay more attention to the stiffness of the parts. Pushrods, Rockers and Studs are all areas where stiffness is key. In these areas stiffness is more important than mass.

Today there are alot of advancements in component weight and in stiffness. Mostly due to the more agressive lobes that are coming out right now. I use alot of these new parts in motors and cam kits to take advantage of what's out there right now. I have to say that there are alot of good little tricks out there that help alot.

I can't stress Damon's and OneFlyn95z28's point on the SYSTEM of parts. Be it a full motor, or a valve train the components and how they work together are abosolutely key to making HP and going fast.

The high RPM Mustang guys you see with HR cams are probably running Morell lifters. At $525 a pop they are not cheap but they take a hell of alot of spring pressure. The Comp R's will take about everything you need for a street car as far as spring pressure is concerned. The only real reason for upgraded lifters is so the plungers don't colapse, and the rollers can usually handle the extra pressure too.

As for Rev Kits there is one motor out there that uses them and it's a good arguement for them
Joe Shermans Engine Masters Small Block With 155lbs on the seat and a Isky Rev Kit and a 234/234 108LSA cam that thing made peak HP at over 6500rpm with a single plane intake and a Hyd Roller cam. That's pretty impressive, not to mention the 530 ftlbs and 600hp.

BTW You rarely get something for nothing. Cams should come in a kit, that's always been my opinion and one reason why I don't sell just camshafts. The good parts that are needed to run with agressive camshafts cost money. Now there are bargan parts out there and there are guys with extra high mark ups and I'm not really sure either one is the way to go. Getting a fair price for high quality parts is the best way to go, and usually what you find in a setup that works properly too.

Bret