[Dragncar]

Originally Posted by Stan Weiss

So just how is spring pressure related to HP?

Stan

He has a Pontiac 468 that is under 600 HP and you know where these engines make max power. Relatively low RPM. He is not going to need a lot of spring pressure for his situation. So IMO if he runs a good SS rocker with stud girdle and sft cam he will not be in a high maintenance position as long as he runs the right oil.
I have seen a person break a lifter bore with a SR cam that should not have simply by running way too much spring pressure for his intended RPM. Pontiacs have weak lifter bores and attention needs to be paid to that fact.
Pretty sure people knew where I was going.
Stop trying to start a argument Stan.

[Stan Weiss]

Originally Posted by Dragncar

He has a Pontiac 468 that is under 600 HP and you know where these engines make max power. Relatively low RPM. He is not going to need a lot of spring pressure for his situation. So IMO if he runs a good SS rocker with stud girdle and sft cam he will not be in a high maintenance position as long as he runs the right oil.
I have seen a person break a lifter bore with a SR cam that should not have simply by running way too much spring pressure for his intended RPM. Pontiacs have weak lifter bores and attention needs to be paid to that fact.
Pretty sure people knew where I was going.
Stop trying to start a argument Stan.

So that is what you call it when I ask you to explain a statement you made.

I have some questions about this post but I will not ask them because I don't what to start an argument.

Stan

[78w72]

is this roller lifter set up something that would work for the OP's situation & be more reliable than the current average HR lifters?

https://forums.maxperformanceinc.com...25#post6289725

[Steve C.]

I will suggest there is more to choosing spring pressure that the horsepower involved and/or RPM involved.

"If we were to sum up the role that the valve spring plays in regard to its function as part of the overall valve train with one word, that word would be control. Considering that it is the predominant part responsible for keeping all of the valve train components in constant contact with the camshaft lobe, it’s easy to see how important getting the correct amount of spring pressure can be. Insufficient or excessive pressure will cause engine performance to suffer, along with the possibility of damage occurring, which can be severe. In conjunction with getting the correct pressure, there are other areas to address that will make sure you’re getting the best spring for the application."

https://www.enginebuildermag.com/201...ring-pressure/


"The valvetrain is one of the areas where properly matched parts are vital to ensure that the engine functions properly and the valvesprings are the key to this.

https://www.dragzine.com/tech-storie...ring-pressure/





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[RUDOLFSSON]

Flat faced follower will also side load the lifter into the block!
Nothing to the extremes of the roller follower combination though…. But worth looking into IMO.


Look up the force diagrams from Nortons book.


Extreme SFT combinations can double or triple that load through their much higher Normal force, the lever arm is always the same (lifter radius).


With that in mind.. put a safety factor from PMD engineers at 2-3 on their lifter valley design and you’re knocking at the gate … (in extreme appl. btw)





Kris.


Sent from my iPhone using Tapatalk

[Stan Weiss]

Originally Posted by RUDOLFSSON

Flat faced follower will also side load the lifter into the block!
Nothing to the extremes of the roller follower combination though…. But worth looking into IMO.


Look up the force diagrams from Nortons book.


Extreme SFT combinations can double or triple that load through their much higher Normal force, the lever arm is always the same (lifter radius).


With that in mind.. put a safety factor from PMD engineers at 2-3 on their lifter valley design and you’re knocking at the gate … (in extreme appl. btw)





Kris.


Sent from my iPhone using Tapatalk

I don't have the Norton book but do have a couple of other books on cam design. I would be interested in seeing that diagram. Everything I have read says that the cam against a flat tappet causes no side loading. Now I can see lifter side loading being cause by the push rod.

Stan

[RUDOLFSSON]

It's called the overturning moment..


http://mechdesigner.support/cam-desi...0&printWindow&

[Steve C.]

From the OP....

"For reference this is a combo street/road race application 468. Certainly not a race engine at under 600 hp but a hydraulic roller lifter will be stressed in this form of racing."

Not mentioned, he has intentions for boost with this application. And as mentioned a road race application at extended RPMs.

For discussion.....

"Consider the fact that when the engine is in a "boosted" condition, the supercharger (or turbocharger) is trying to blow the intake valve open. The boost pressure actually reduces the intake valve spring seat pressure. This is extremely critical on engines with hydraulic lash adjustment."

https://www.yellowbullet.com/threads...essure.239727/
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Now, if you plan on pushing a lot of boost into your engine, things get a little more complicated when it comes to valve spring pressures.

“In a boosted application with very high boost numbers, you should take into consideration that the backside of the inlet valve is under constant static pressure, which does indeed diminish the seat pressure."

https://www.dragzine.com/tech-storie...ring-pressure/


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[rod cole]

Why is a nitrided sft cam better than a nitrided hyd flat tappet cam? And are the new hyd flat lifters with the welded hard bottom better than the fully one piece ones? What is the cost of nitriding Steve linked it but asking if anyone knows. Thanks Rod