Solid Lifter Conversion
10-31-2007, 06:25 PM
#17
Drifting
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I take all vendor info with a grain of salt. No doubt the LR solid setup is very good. That said, lots of racers and enthusiasts run over 18psi with factory hyd lifters.
One benefit of solid setup not yet mentioned is weight. The solid setup eliminates a ton of valve-train mass. This alone would make the upgrade beneficial - faster response with better valve control without increasing spring rates, seat pressure, etc.
One downfall (or potential) is in positive vacuum. Typically a hydraulic lifter will produce More vacuum for accessories (power brakes, etc) than solid. This gets particularily noticeable with radical cam profiles. I have not seen it in 944, but expect the same holds true.
One benefit of solid setup not yet mentioned is weight. The solid setup eliminates a ton of valve-train mass. This alone would make the upgrade beneficial - faster response with better valve control without increasing spring rates, seat pressure, etc.
One downfall (or potential) is in positive vacuum. Typically a hydraulic lifter will produce More vacuum for accessories (power brakes, etc) than solid. This gets particularily noticeable with radical cam profiles. I have not seen it in 944, but expect the same holds true.
10-31-2007, 08:57 PM
#18
Hydraulic lifters love spring force. The more the better.
How does a tappet create vacuum? Do you mean the Cam that is used typically with Solid Lifters has more overlap? I think is what you meant to say.
Solids help with Cam profile only. RPM is typically limited to cam profile. Most Cams sold for 944 engines (not all) have harmonics so bad the valve train goes in the trash with any higher RPM. Not usually caused by the Hyd tappet giving up. At very high speeds if the Cam allows the time to pump up goes way down and solids are required.
How does a tappet create vacuum? Do you mean the Cam that is used typically with Solid Lifters has more overlap? I think is what you meant to say.
Solids help with Cam profile only. RPM is typically limited to cam profile. Most Cams sold for 944 engines (not all) have harmonics so bad the valve train goes in the trash with any higher RPM. Not usually caused by the Hyd tappet giving up. At very high speeds if the Cam allows the time to pump up goes way down and solids are required.
10-31-2007, 10:16 PM
#19
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Hydraulic lifters love spring force. The more the better.
How does a tappet create vacuum? Do you mean the Cam that is used typically with Solid Lifters has more overlap? I think is what you meant to say.
Solids help with Cam profile only. RPM is typically limited to cam profile. Most Cams sold for 944 engines (not all) have harmonics so bad the valve train goes in the trash with any higher RPM. Not usually caused by the Hyd tappet giving up. At very high speeds if the Cam allows the time to pump up goes way down and solids are required.
How does a tappet create vacuum? Do you mean the Cam that is used typically with Solid Lifters has more overlap? I think is what you meant to say.
Solids help with Cam profile only. RPM is typically limited to cam profile. Most Cams sold for 944 engines (not all) have harmonics so bad the valve train goes in the trash with any higher RPM. Not usually caused by the Hyd tappet giving up. At very high speeds if the Cam allows the time to pump up goes way down and solids are required.
A Hydraulic lifter bleeds down a bit durring lower oil pressure (like idle and low rpm). This essentially has the effect of lowering the lift and duration. This is how/why a hyd cam will make vaccum for power brakes and a solid may not make enough. This is also why a hyd cam and solid cam of the same duration/lift have completely different idle andlow rpm response characteristics.
10-31-2007, 10:40 PM
#20
Rennlist Member
I don't understand why one would think you will have better spool-up characteristics with a more aggressive cam (which is the only reason one would consider solid). Generally aggressive cam shifts the powerband up the rpm scale, therefore less exhaust energy for early rpm spool-up.
11-01-2007, 01:26 AM
#21
""oh boy..... Ok I am not going to explain at length but here is the quickie overview.
A Hydraulic lifter bleeds down a bit durring lower oil pressure (like idle and low rpm). This essentially has the effect of lowering the lift and duration. This is how/why a hyd cam will make vaccum for power brakes and a solid may not make enough. This is also why a hyd cam and solid cam of the same duration/lift have completely different idle andlow rpm response characteristics"""
Oh oh boy, and the only quickie that happened here was in my dreams. Unfortuntely.
What are the typical symtoms of a ""bleed down tappet""?? This is why its important to have the correct installed height of the Valve or one reason why the Valve Tip position is important ??
I'm sure we could take 1 engine verses another and see differences in the vacuum levels. Sure some could be from the Valve train, but all things been equal the tappet does not have that much effect. Have you ever seen Valve tests performed on a Spintron machine. The amount of Oil pressure required to pump up a typical street Tappet is less than the bearings require to keep the crank off them at idle. And then the Cam has the cheek to try to collaspe them. Go figure.
Just maybe the differences in idle conditions are from the different Cam profiles between a Solid Cam and a Hydraulic Cam. A very different profile especially as the valve is accelerated off the ramp.
A Hydraulic lifter bleeds down a bit durring lower oil pressure (like idle and low rpm). This essentially has the effect of lowering the lift and duration. This is how/why a hyd cam will make vaccum for power brakes and a solid may not make enough. This is also why a hyd cam and solid cam of the same duration/lift have completely different idle andlow rpm response characteristics"""
Oh oh boy, and the only quickie that happened here was in my dreams. Unfortuntely.
What are the typical symtoms of a ""bleed down tappet""?? This is why its important to have the correct installed height of the Valve or one reason why the Valve Tip position is important ??
I'm sure we could take 1 engine verses another and see differences in the vacuum levels. Sure some could be from the Valve train, but all things been equal the tappet does not have that much effect. Have you ever seen Valve tests performed on a Spintron machine. The amount of Oil pressure required to pump up a typical street Tappet is less than the bearings require to keep the crank off them at idle. And then the Cam has the cheek to try to collaspe them. Go figure.
Just maybe the differences in idle conditions are from the different Cam profiles between a Solid Cam and a Hydraulic Cam. A very different profile especially as the valve is accelerated off the ramp.
