LS Hydraulic lifter limitations

[e vassar]

I am running the GM perf LS7 hydraulic lifters in my stocker. It hits a wall in high gear at 7K which occurs between 1000ft and the finish line. Just stops pulling and sometimes has 2-3 light misfires ( banging) . I know the lifters should easily handle 7K ..but is that the limitation? I am running 10-30 oil so staying pumped shouldn't be a problem. I am going to do compression,leak down test and valve spring test as part of off season maintenance. Should I just go ahead and change to solid lifters?... Thanks!

[GUMP]

Originally Posted by e vassar

I am running the GM perf LS7 hydraulic lifters in my stocker. It hits a wall in high gear at 7K which occurs between 1000ft and the finish line. Just stops pulling and sometimes has 2-3 light misfires ( banging) . I know the lifters should easily handle 7K ..but is that the limitation? I am running 10-30 oil so staying pumped shouldn't be a problem. I am going to do compression,leak down test and valve spring test as part of off season maintenance. Should I just go ahead and change to solid lifters?... Thanks!

I can't speak for the LS7 lifter, but I wouldn't even try them in a Stocker motor.

I have had good success with the racing hydraulic rollers (88958689) to 8,000 rpm with a beehive valve spring. Currently, I am running a Johnson hydraulic roller lifter in my 302 and turning it to 8,600 rpm without issues. Both are full hydraulic, not limited travel.

[SSDiv6]

Originally Posted by e vassar

I am running the GM perf LS7 hydraulic lifters in my stocker. It hits a wall in high gear at 7K which occurs between 1000ft and the finish line. Just stops pulling and sometimes has 2-3 light misfires ( banging) . I know the lifters should easily handle 7K ..but is that the limitation? I am running 10-30 oil so staying pumped shouldn't be a problem. I am going to do compression,leak down test and valve spring test as part of off season maintenance. Should I just go ahead and change to solid lifters?... Thanks!

The best guy to field your question is Robin Wright and he is a member here.
He was the guy in charge of the COPO program, a valvetrain expert and also in charge of the engine development for the Corvette and Cadillac LS road racing engines.

[e vassar]

Originally Posted by SSDiv6

The best guy to field your question is Robin Wright and he is a member here.
He was the guy in charge of the COPO program, a valvetrain expert and also in charge of the engine development for the Corvette and Cadillac LS road racing engines.

Yes .I have heard Darren speak of him . Thanks!

[JRyan]

I currently have LS7's in my bracket 6 liter that we drove with a turbo on the street for 4 years. I've run them up to 72-7300 and haven't run into any issues as of yet. That being said I have two other engines we are doing that have the Johnson hydraulics like Darren along with one that is a low lash solid roller setup.

Rick Ryan

[Rob Wright]

Stock LS7 lifters have the best dynamic stability out of any I've tested, and the earlier-version LS7 lifters with circlip axle retention are the ones to have.

Differences in stability of stock vs aftermarket brand "M" and aftermarket brand "J" is not incredibly significant.....Best to worst (stability-wise) is listed in order and again, they are not vastly different. All of this assumes plunger at mid-travel for preload.

Actually in my experience the WORST performing hydraulics (stability, , on a given cam/spring/rocker/pushrod combination) were limited travel units.

If you're hitting a wall at 7000 RPM, you should look at whether you have TOO MUCH spring force (compressing the lifter plunger isn't necessarily the problem.....), too heavy retainer, spring, rocker, or all three, and more often than not the cam lobe geometry itself.

Proper lobe geometry shouldn't require tons of spring force to run well past 8K RPM if it is packaged with light valves (like stock LS) a light rocker (like the stock LS), retainer (again, stock LS), and spring (like beehive or well thought out dual like PSI LS 1512 ML), along with a pushrod that is stiff enough to avoid deflection/energy storage/energy release. This sequence causes bounce at closing and that's when stuff breaks.

[Rob Wright]

Originally Posted by SSDiv6

also in charge of the engine development for the Corvette and Cadillac LS road racing engines.

Mmmmm........to be fair & honest, not really true for those specific programs.

[Mark Lewis]

ON the short travel hydraulic roller lifters what is the best valve adjustment to get the best performance out of the lifter. Assuming not too much spring rate or valve train weight

[SSDiv6]

Originally Posted by Rob Wright

Mmmmm........to be fair & honest, not really true for those specific programs.

The GM Performance marketing video seem to imply so when "Bad" Robin was pulling the dyno lever...

[Rob Wright]

Originally Posted by SSDiv6

The GM Performance marketing video seem to imply so when "Bad" Robin was pulling the dyno lever...

Yo've got that backwards amigo. I'm the good one, the other guy is the evil one, according to his own staff.

But - after a week with me they did say the lines between good & evil were very blurry.