Spring selection Theory
Originally Posted by gun5l1ng3r
Aren't they still quite a bit heavier than equivelant solid lifters?
If you increased the mass on that side of the equation by 50% in a 8000+rpm drag racing motor you could lose 300rpm. In 99% of what we are talking about on here it wouldn't make a difference.
Bret
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From: Laguna Niguel, CA
^ I knew I was forgetting something!
The weight of the valve (post rocker arm) is amplified by the 1.7 ratio of the rocker arm, right?
And the lifter only rises and falls about .350 on a .600 advertised lift cam...
The weight of the valve (post rocker arm) is amplified by the 1.7 ratio of the rocker arm, right?
And the lifter only rises and falls about .350 on a .600 advertised lift cam...
Just thought I would add this quote:
Originally Posted by bg-sdpc
NEW GM Performance Parts Hydraulic Roller Lifter for LS-Engines
#SD8689 $217.85/set
You heard it first from SDPC! This new lifter will work in all LS- engine applications and is specifically suited for race cams and high RPM applications. They can also be used as an upgrade for stock lifters and are suitable for street applications. These lifters were developed for the CTSV Cadillac Race Team that used the “short stroke” LS7 style engines that raced in the Grand Am Cup Series during 2005. If you recall these engines were built using the LS7 block, LS7heads, and LS7 intake but the sanctioning body required the teams to meet the 5.7-liter engine size of 346ci. There were several different combinations tried but most of these engines used a stroke of approximately 3.200”. The demand to make race winning horsepower with a short stroke guarantees the unavoidable element of high RPM’s.
Initial testing, before these new lifters were developed, showed a definite valvetrain stability problem above 7000-rpm’s. Several remedies were tried, but in the end it was determined that the lifter had the biggest contribution to the RPM limit. This new lifter has internal changes made to the hydraulic components which resulted in a significant RPM increase. After installing the new lifters, these engines were now making power at 8000-rpm and they regularly saw 8500-rpm’s without any problems! WOW! The CTSV dominated the first races, not only did the sanctioning body enforce an RPM limit on the short stoke Caddies but they eventually implemented more restrictions to limit the horsepower on these LS7 equipped 346ci engines.
As a reminder, hydraulic roller cam valvetrain stability is a function of many different variables; camshaft design (ramp acceleration), pushrods, valve springs, rocker ratios, spring pressures, valve weight, the weight of all valvetrain components, oil pressure, RPM, etc. It is imperative that you have sufficient spring pressures, quality push rods and lifters, proper lash adjustment, and the lightest valvetrain components you can afford to maintain accurate stability at high RPM’s. Match your components to meet your RPM range!
We recommend a preload setting of 0.060” (cold) with these lifters, in most cases with adjustable rockers this is usually somewhere between 1-full turn and 1-1/2 from the “Zero-Lash” point. This is the same preload as a stock lifter!
Stock lifter on the left in both pictures.
#SD8689 $217.85/set
You heard it first from SDPC! This new lifter will work in all LS- engine applications and is specifically suited for race cams and high RPM applications. They can also be used as an upgrade for stock lifters and are suitable for street applications. These lifters were developed for the CTSV Cadillac Race Team that used the “short stroke” LS7 style engines that raced in the Grand Am Cup Series during 2005. If you recall these engines were built using the LS7 block, LS7heads, and LS7 intake but the sanctioning body required the teams to meet the 5.7-liter engine size of 346ci. There were several different combinations tried but most of these engines used a stroke of approximately 3.200”. The demand to make race winning horsepower with a short stroke guarantees the unavoidable element of high RPM’s.
Initial testing, before these new lifters were developed, showed a definite valvetrain stability problem above 7000-rpm’s. Several remedies were tried, but in the end it was determined that the lifter had the biggest contribution to the RPM limit. This new lifter has internal changes made to the hydraulic components which resulted in a significant RPM increase. After installing the new lifters, these engines were now making power at 8000-rpm and they regularly saw 8500-rpm’s without any problems! WOW! The CTSV dominated the first races, not only did the sanctioning body enforce an RPM limit on the short stoke Caddies but they eventually implemented more restrictions to limit the horsepower on these LS7 equipped 346ci engines.
As a reminder, hydraulic roller cam valvetrain stability is a function of many different variables; camshaft design (ramp acceleration), pushrods, valve springs, rocker ratios, spring pressures, valve weight, the weight of all valvetrain components, oil pressure, RPM, etc. It is imperative that you have sufficient spring pressures, quality push rods and lifters, proper lash adjustment, and the lightest valvetrain components you can afford to maintain accurate stability at high RPM’s. Match your components to meet your RPM range!
We recommend a preload setting of 0.060” (cold) with these lifters, in most cases with adjustable rockers this is usually somewhere between 1-full turn and 1-1/2 from the “Zero-Lash” point. This is the same preload as a stock lifter!
Stock lifter on the left in both pictures.
wow,
it looks like they really limited the oil going into that lifter. The orifice is smaller, so am I to understand that pressure would be up and therefore more stable, or does that higher pressure force it to act like a solid roller?
it looks like they really limited the oil going into that lifter. The orifice is smaller, so am I to understand that pressure would be up and therefore more stable, or does that higher pressure force it to act like a solid roller?
Probably has more to do with the internals of that lifter.
FWIW those early CTS-V race motors were about the only professional hyd roller race motor out there so they were definately trick pieces.
Bret
FWIW those early CTS-V race motors were about the only professional hyd roller race motor out there so they were definately trick pieces.
Bret
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Joined: Jun 2002
Posts: 1,979
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From: Upstate NY
Originally Posted by SStrokerAce
FWIW those early CTS-V race motors were about the only professional hyd roller race motor out there so they were definately trick pieces.
Bret
Bret
Cadillac should have sandbagged the first couple of races, but driving from a back of the pack start to finish second behind the other Caddy sort of exposed what the cars were capable of. They really wanted to win the first race in style. I like the idea that they sold the sanctioning body on the destroked LS7 as a production engine about 2 years before the LS7 was to see any producton, but not even in the CTSV.
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Originally Posted by HataErasa
So how much more stable are destroked motors?
The LS7 (427 cubic inches) was destroked to get back to 346 cubic inches while maintaining the large bore for breathing, and a short stroke to minimize piston speed and inertia loads.
If the 427 stroke, and therefore cubic inches were maintained there would be lots more "horses" available in the "stable", but I don't think that's what you meant.
Valvetrain stability has very little to do with stroke, but lots to do with rpm if that's where you were going.
On the cam side of the rocker, there is also a mass/stiffness trade-off, where stiffer pushrods although heavier will help. Tapered pushrods will help with mass while providing additional bending stiffness. PSI makes a stiff beehive spring that is low mass. Mine are 66 grams for the spring and 6.6 grams for the retainer.
