hydraulic lifter pre-load, why?
- Thread starter 388dart
- Start date
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demon seed
The Original Demon Seed
To make sure that the hydraulic piston is not against the stop (cir clip). Therefore it can make the minute adjustments to maintain a zero valve lash.
The lifter pre-load must be there. Amount in your choice not withstanding.
The reason there must be some, as stated above, is the retaining clip for the inner workings of the lifter are held in by that clip. Should it fail, then there a bunch of little parts running around the engine. The pushrod falls into the lifter which is much more than the total travel of the lifter by design, the pushrod falls out because theres nothing holding it up into the rocker. Next revolution of the cam will send the P-rod up and out of the valve cover.
(It's cool when they glow. Like a bottle rocket)
The the rest of the lifter pops out of its hole causing a total lose of oil pressure while the remains of the lifterbody bounce around the somewhere. If it made it passed the cam, (Fell through the valley) thens theres the crank and parts whipping around knocking this empty body around like a pinball causing how knows what damage.
The .040- .060 is a nominal area. The total amount of adjustabiloty is .100 with the last .010 being a bad area to gamble. So say the manufactures.
However, your not going to lose any lift. The Hyd. lifter is design to work under pressure. At idle, theres less. So when you start up the engine, it is easy. Just what the manufactuer wants. A nice and complyent easy to start car. The reduction in lift makes it so.
Once you start to motor on down the hwy. the oil pressure picks up some, surplying the presure needed to pump up the lifter and restore it so the engine see the valve lifting up to it's max.
Depending on lifter design, the unit will get pumped up from idle to just off idle or be designed to get to a fully pumped up position after a few hundered or thousand RPM. Like Rhoads lifters. There slow to pump up. By making use of them, you can restore a bit of low end torque lost due to a larger cam.
Some race rules require a vaccum rule to be inplace in an attempt to limit very large cams from the comp. feild.
If you adjust your set up to having the pushrod depress the lifter only a (Just for say) .001, your then reaping full bennifit of reduced valve lift at start up and possibly passed idle. In effect, losing lift at low RPM.
By having the pushrod depress the lifter at max, (Just for say) .090 your in effect, getting rid of any lose at low lift. Theres less area to pump up.
The factory gives the .050 idle setting for intended operation. In there opion, I guess, the best of both extreme settings.
MoPar Muscle did a dyno test on this sometime back. Anybody have this around? I think theres was a few pounds of extra torque with a shallow setting.
(Sorry about the spelling, I just got up, wheres my coffee. But thats how it works)
The reason there must be some, as stated above, is the retaining clip for the inner workings of the lifter are held in by that clip. Should it fail, then there a bunch of little parts running around the engine. The pushrod falls into the lifter which is much more than the total travel of the lifter by design, the pushrod falls out because theres nothing holding it up into the rocker. Next revolution of the cam will send the P-rod up and out of the valve cover.
(It's cool when they glow. Like a bottle rocket)
The the rest of the lifter pops out of its hole causing a total lose of oil pressure while the remains of the lifterbody bounce around the somewhere. If it made it passed the cam, (Fell through the valley) thens theres the crank and parts whipping around knocking this empty body around like a pinball causing how knows what damage.
The .040- .060 is a nominal area. The total amount of adjustabiloty is .100 with the last .010 being a bad area to gamble. So say the manufactures.
However, your not going to lose any lift. The Hyd. lifter is design to work under pressure. At idle, theres less. So when you start up the engine, it is easy. Just what the manufactuer wants. A nice and complyent easy to start car. The reduction in lift makes it so.
Once you start to motor on down the hwy. the oil pressure picks up some, surplying the presure needed to pump up the lifter and restore it so the engine see the valve lifting up to it's max.
Depending on lifter design, the unit will get pumped up from idle to just off idle or be designed to get to a fully pumped up position after a few hundered or thousand RPM. Like Rhoads lifters. There slow to pump up. By making use of them, you can restore a bit of low end torque lost due to a larger cam.
Some race rules require a vaccum rule to be inplace in an attempt to limit very large cams from the comp. feild.
If you adjust your set up to having the pushrod depress the lifter only a (Just for say) .001, your then reaping full bennifit of reduced valve lift at start up and possibly passed idle. In effect, losing lift at low RPM.
By having the pushrod depress the lifter at max, (Just for say) .090 your in effect, getting rid of any lose at low lift. Theres less area to pump up.
The factory gives the .050 idle setting for intended operation. In there opion, I guess, the best of both extreme settings.
MoPar Muscle did a dyno test on this sometime back. Anybody have this around? I think theres was a few pounds of extra torque with a shallow setting.
(Sorry about the spelling, I just got up, wheres my coffee. But thats how it works)
well Rumble just for the sake of all you typing effort I am going to reset the pre-load to .040 to see if it makes any differnce in starting or idle operation.
As for the wozzy wire clip in most lifters I have the snap ring type so prone to failure is less - not impossible, bust less.
thanks
As for the wozzy wire clip in most lifters I have the snap ring type so prone to failure is less - not impossible, bust less.
thanks
LOL, Keep in mind the answer is a factory engineer driven type answer.
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