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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Thats exactly what i didnt understand. Perfectly answered man thank you Ive been doing this years and that actually made it click in my head. And another thing. When the lifter is pumped up, After the motor runs. Why would it not be opening the valve too far when full of oil. Is the pressure from the valve springs not letting it over fill and push the valve out too far. I still dont get that
The lifter is actually not pumped up by oil pressure, there is an internal spring that extends the plunger in the lifter, and a check valve that lets oil get sucked in to fill the chamber below the plunger. And when the cam lobe arrives the check valve closes and the lifter basically hydrolocks to a solid unit.
The purpose of this is as stated already is to take up the added clearance from cylinders growing taller with heat. The force of the plunger spring is much less than the valve springs so it can only extend the lifter to zero lash, it can not compress the valve springs.
Interestingly thought they don't pump up from oil pressure.
Why do they need the bleed?
Maybe of course so there is an opening for oil to enter side hole.
So the bleed is not for keeping the lifter from overriding the valve springs.
The obvious need for lifter bleed down is when you stop riding and the engine cools down, the lifter must be able to retract again to make it possible to run the engine cold again.
It would take an oil pressure in excess of 1000 psi for a lifter to compress a valve spring, typical pressure in our engines is around 50 psi.
I guess a micro amount of bleeding during each cycle would make the lifter act as a cushion, absorbing some of the force from when the cam ramp hits the roller, reducing some noise, but this is pure speculation on my part. I kind of doubt that would have any real effect.
Last edited by user 7209823083; Jun 24, 2024 at 07:33 AM.
The obvious need for lifter bleed down is when you stop riding and the engine cools down, the lifter must be able to retract again to make it possible to run the engine cold again.
It would take an oil pressure in excess of 1000 psi for a lifter to compress a valve spring, typical pressure in our engines is around 50 psi.
I guess a micro amount of bleeding during each cycle would make the lifter act as a cushion, absorbing some of the force from when the cam ramp hits the roller, reducing some noise, but this is pure speculation on my part. I kind of doubt that would have any real effect.
Actually on a TC, it's 35 pressure relief.
We are going to have to get that user on here that programs AI to fix Google.
must correct an error.
the example of the rocker ratio of 1.7 at .001 lifter would be .0017 NOT .017
be careful if you grind on the rocker as most are NOT harden through out. harley is not.
on a very high mileage solid lifter, the rocker will actually groove, been there done that. hd says you can re-arch them.
this could be a bummer on a manual foot. had a valve stem hang at random and when it did, the kick would be a free wheel trip, not good on the knee.
why hd never went roller rocker is a mystery but i guess $$$$$ had its say in things.
On my 2002 95" TC with Daytona oil pump pressure is 25 psi at idle and 40 to 50 psi at speed. But 35 or 50 is kind of moot when 1000 is required
I have no idea what the AI part means
There's a user on here that programs what Artificial Intelligence says when you do a search. He has a resent thread going. He's also an oil specialist. Think it's Brandon?
That 35 is stock oil pump pressure relief, there all kinds of modifications to change it. Including just a Beastly (spelling )spring.
TCs have pressure releases on cooling oil injectors. They don't spray at idle so Harleys don’t cook the oil in hot climates. They open at 12.
Engine can take brief red light sits better then oil.
Last edited by Jackie Paper; Jun 24, 2024 at 09:08 AM.
There's a user on here that programs what Artificial Intelligence says when you do a search. He has a resent thread going. He's also an oil specialist. Think it's Brandon?
That 35 is stock oil pump pressure relief, there all kinds of modifications to change it. Including just a Beastly (spelling )spring.
TCs have pressure releases on cooling oil injectors. They don't spray at idle so Harleys dont cook the oil in hot climates. They open at 12.
Engine can take brief red light sits better then oil.
I have not done any mods to the relief valve, except checking that it is in good shape and moving freely. I think its just the higher capacity oil pump that provides the extra pressure. I doubt any aftermarket pump like S&S or Feuling, or even the 06 up SE version will give less than 12 psi at idle. Fortunately I spend very little time idling at red lights so hopefully I will be fine.
Still have no idea what the AI stuff has to do with any of this. Maybe its some kind of joke that I'm not getting. Just in case I will add a smiley to make it appear like I got the joke
The lifter is actually not pumped up by oil pressure, there is an internal spring that extends the plunger in the lifter, and a check valve that lets oil get sucked in to fill the chamber below the plunger. And when the cam lobe arrives the check valve closes and the lifter basically hydrolocks to a solid unit.
The purpose of this is as stated already is to take up the added clearance from cylinders growing taller with heat. The force of the plunger spring is much less than the valve springs so it can only extend the lifter to zero lash, it can not compress the valve springs.
Wrong. That's not how a lifter works & they do rely on oil pressure not suction.
Where do you guys get this stuff from?
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