First my apologies to everyone for my dumb statement about cops in an earlier thread. I've run into some bad ones and beer and the internet don't mix and I got carried away. I even have a good cop in my family! Sorry.

My question is about hydraulic roller lifters. I have heard here that they are rpm limited to about low 6000 rpm. The 08 LS7 now has a 7000 rpm redline with hydraulic rollers and was wondering how they achieve it.

"The LS7’s CNC-ported aluminum cylinder heads are designed to meet the high airflow demands of the engine’s 7.0-liter displacement. A hydraulic roller camshaft with 0.588/0.593-inch valve lift is used to allow plenty of air to circulate in and out of the engine. To ensure optimal, uninterrupted airflow, the LS7’s heads have straight, tunnel-like intake runners. Very large by production-vehicle standards – even racing standards – they are designed to maintain fast airflow velocity, providing excellent torque at low rpm and exhilarating horsepower at high rpm. The heads feature 70-cc combustion chambers that are fed by huge, 56-mm-diameter titanium intake valves. They are complemented by 41-mm sodium-filled exhaust valves. "

Are these different from what you can buy from the perfomance aftermarket?

Thin stemmed titanium valves and good springs. The valve side of the fulcrum is where weight savings is most important.

If your talking about 23deg heads I can say that my hyd roller lifter cam will rev well past 6k.Some people say that the hyd rev kits don't work but ..... the 6800 chip in my msd says otherwise.:D

Chris

I think most of the trouble with hydraulic rollers and high rpm's is the ones used to retrofit older motors. It requires rather large and heavy lifters with cross bars and thus they must use heavier springs and greater spring pressures. Modern rollers are smaller don't have a cross bar. With less lifter weight you can use a lighter bee-hive spring and less spring seat pressure.

More of a problem with big block motors.

The rev kit spring goes on the lifter body and the the head. the add spring pressure is put on the body of the lifter not the plunger as with stronger springs. The down side is it will only work on comps and I think speed pro lifters.

Morel Hyd rollers, both retro and drop ins have been in the market now since arround '02. These hyd roller have gone through extensive testing and have proven themselves to 6600 to 6800 rpm range in marine, street, and drag race applications. Morel's valving and tolerance control makes this a better piece along with a larger nose roller and better materials used in mfg.

Another reason for limited rpm on hyd roller is the amount of spring pressure you could put on the lifter. The Morels consistantly see 170# to 200# on the seat with open loads of around 550#'s depending on application. Morel also has an HLT lifter (hyd. limited travel) which is a "0" lash hyd that is treated like a solid with no lash. The special valve design has a built in .030". This allows for clearance during opening and closing.

Oil Band location. Aftermarket cams have smaller base circles. This can allow for improper location of the oil band of the lifter in the lifter bore causing spauling resulting in loss of cam and lifters. Morel has properly located the oil band on the hyd rollers to be used with aftermarket cam profiles.

Morels are available from Wolfie/Olandi Motorsports/ and CNC on the board...

I have a 396 with a comp cam hyd roller cam and it revs up to 6000 pretty easy.It makes lots of power up there.I wouldnt want to go higher though.

The LS-1,2, 6 and 7 all have different method of retaining the lifters that let them get away with more RPM on a hydraulic roller lifter setup. They also have a very large cam core, something along the lines of a 55-60 mm which makes the ramps more gradual and the cam itself stiffer. My son bought a new LS-2 powered Trailblazer SS and it has a 6500 redline from the factory. The valves are fairly light in these motors and they can run the redline RPM without major problems. New lifters and springs stuff is coming out all the time so the RPM limits should continue to rise.

I've got a hydraulic LT4 that turns ~7000 rpm...beehives and AFR Hydra Rev kit got me past 6200 nose over with the GM 847 cam (.575/.595 lift).

It seems possible to get some decent rpm...

The LS-1,2, 6 and 7 all have different method of retaining the lifters that let them get away with more RPM on a hydraulic roller lifter setup. They also have a very large cam core, something along the lines of a 55-60 mm which makes the ramps more gradual and the cam itself stiffer. My son bought a new LS-2 powered Trailblazer SS and it has a 6500 redline from the factory. The valves are fairly light in these motors and they can run the redline RPM without major problems. New lifters and springs stuff is coming out all the time so the RPM limits should continue to rise.

The lighter weight valves really help extend the RPM band over the 2.19s and 2.25s you see in most BBCs. My C5 ran 2.02 valves, Comp 987 springs, stock hydraulic lifters, and a now mild cam. The rev limiter was set at 7k and I shifted at 6,800. I sold the car and an inner spring cracked after ~30k miles after the heads and cam. If you change the springs every 25k with the way we drove the car, fairly hard for no track time, it should be good to go.

The LS-1,2, 6 and 7 have a very large cam core, something along the lines of a 55-60 mm which makes the cam itself stiffer.

Stick diameter (cam stiffness) is a key element to the rpm limit of a roller hydraulic lifter. I've done extensive testing of hydraulic rollers in spin fixtures and always see the rpm limit relate to cam deflections. This assumes you have enough valve spring to control the valve train inertia. So for the correct spring on a SBC, the little stick is going to dance, and the poor hydraulic lifter tries to adjust for this perceived "lash". Then the lift profile comes around and the lifter is maladjusted to handle the event.

With less cam deflection you can run a heavier spring for more rpm.

Stick diameter (cam stiffness) is a key element to the rpm limit of a roller hydraulic lifter. I've done extensive testing of hydraulic rollers in spin fixtures and always see the rpm limit relate to cam deflections. This assumes you have enough valve spring to control the valve train inertia. So for the correct spring on a SBC, the little stick is going to dance, and the poor hydraulic lifter tries to adjust for this perceived "lash". Then the lift profile comes around and the lifter is maladjusted to handle the event.

With less cam deflection you can run a heavier spring for more rpm. I think the new LSX race block comes with a cam tunnel made for a 60 mm cam and located high enough in the block to clear a long stroke crank.

I believe its in the cam profile, lifter brand and spring pressure.
My 502 rattles at 7000K and I shift 6700-6800.
My 383 needed beehives to go 6500 with a mild but aggresive Comp lobe.

67rs502, Looking at your sig 502 motor. That must be one bad mo. Are you turning that thing to 6700 + with those heads and cam, 3.73. What tire are you running at the track. Do you got a little spray on it.

Shift it pretty much on the rev limiter 6700-6800.
I've run ET streets, QTPs, and 28x10.5 slicks which work the best - its nose heavy. Dont believe in sprey - it just aint my thing, its fun to do it on motor.
You could put a 500shot on a 305 and run 9s, but it just dont seam right to me;) More details on my webpage.