Valve train woes LS3

[trw427ss]

Originally Posted by thahemp

Well now at least we know where lethal is getting their spring advice. To be honest, it makes a little bit of sense. I'd be curious to see what the actual open pressure is that far from coil bind.

Originally Posted by TurboBuick6

If you look at the specs there is not a whole lot of open pressure difference in the 1208 at .620 lift and a lot of the other springs our there.

Here are the specs on 3 of the popular springs used on LS engines.

Springs.............Seat Pressure......Open Pressure @ .620 lift
Pac 1208x...........160lbs...................445lbs

BTR .660.............155lbs...................389lbs

Manley 221436.....155lbs...................390lbs
.660

[thahemp]

Originally Posted by trw427ss @ Futral

Here are the specs on 3 of the popular springs used on LS engines.

Springs.............Seat Pressure......Open Pressure @ .620 lift
Pac 1208x...........160lbs...................445lbs

BTR .660.............155lbs...................389lbs

Manley 221436.....155lbs...................390lbs
.660

Thanks for that! Data is good.

[BplumCrazy-SS]

[vroomapunk]

Originally Posted by BplumCrazy-SS

[Jims Mongoose]

First off I'm a newbie, but I do understand basic valve train operation and I have a few questions.

Isn't it true you only need enough spring pressure(with a little margin) to accelerate the pushrod down the closing ramp of the cam fast enough to keep the roller seated on the ramp. The higher the lift (more or less) you have a higher hill to go down and at any given rpm of the engine it will require more acceleration to do that.
So isn't that a calculateable quantity that GM and all good cam manufacturers must do. I didn't say it was simple but should be available.


Also the spring pressure acts against the roller, pushrods etc on the up ramp and therefore you certainly wouldn't want much more than that to create the needed acceleration above.

Also I really don't understand this coil bind thing. Please help. It seems that you never want coil bind, period, the system becomes non linear at that point and who knows what will happen. Aside from valve train requirements dimensionally, why cant it be set to make sure there is no possibility of coil bind, whats wrong with a little more clearance for good measure?

I am not trying to be smart here, just asking

Jim

[thahemp]

Here's a good reason to get the spring closer to coil bind. Dampen spring surge.

[Jims Mongoose]

Originally Posted by thahemp

Here's a good reason to get the spring closer to coil bind. Dampen spring surge.

Okay so when you say coil bind you mean the deliberate touching of variable rate spring coils to dampen out overall valve train vibrations that can occur at high rpms various cam and valve train mass. This is an engineered system with much engineering and testing behind it. This deliberate touching of some of the variable rate springs is designed to occur at higher RPMs and is often used to control valve surge do to inherent resonances in the whole system often caused by light valve train components with too much spring.

I think the coil bind spoken of for installation refers to the static coil bind or clearance to prevent it during an install. To make sure that at low rpms you don't have it.

My problem is that from what I have read it's really in and engineers purview to figure this out and even they resort to much testing to actually see what works and doesn't.

A well known cam company that does much testing and has much experience at what works is the way we should go. Messing and experimenting with their recommendations gets us in trouble because the system is so complex

jim

[axis]

Originally Posted by Jims Mongoose

A well known cam company that does much testing and has much experience at what works is the way we should go. Messing and experimenting with their recommendations gets us in trouble because the system is so complex

jim

Then what happens when you have several companies that do a lot of testing on this very subject that have differing opinions?

We have Manley putting it on their box of springs (post 73), and BT also with the same recommendation. I believe both of those companies do lots of testing with their springs as well.

[TurboBuick6]

Originally Posted by trw427ss @ Futral

Here are the specs on 3 of the popular springs used on LS engines.

Springs.............Seat Pressure......Open Pressure @ .620 lift
Pac 1208x...........160lbs...................445lbs

BTR .660.............155lbs...................389lbs

Manley 221436.....155lbs...................390lbs
.660

You got me there. If I recall correctly the patriots had 410 open. If you want to chaulk a cam and rocker failure to that you can but I don't see that. There is an underlying cause to the problem. Such as a failed lifter shocking the system. There are enough out there with more open than 440 that do not have this issue.

[TurboBuick6]

Originally Posted by thahemp

Here's a good reason to get the spring closer to coil bind. Dampen spring surge.

The title says a cup engine. that is .800 range lift at 9,500 RPM, different application but does show a good example of spring surge.

[TurboBuick6]

Originally Posted by axis

Then what happens when you have several companies that do a lot of testing on this very subject that have differing opinions?

We have Manley putting it on their box of springs (post 73), and BT also with the same recommendation. I believe both of those companies do lots of testing with their springs as well.

And of all the people giving thier recomendation, who are the actual manufactures that have thier hands in every aspect of an engine such as drag, endurrance and O.E.?

[Jims Mongoose]

Originally Posted by TurboBuick6

And of all the people giving thier recomendation, who are the actual manufactures that have thier hands in every aspect of an engine such as drag, endurrance and O.E.?

All I'm saying is that we are not going to solve it here.

Go with the setups that have worked. There will always be someone that does not do exactly what the cam manufacturer recommended. There will be something a little different in the build especially if someone does it themselves. It takes many installs to know all the little idiosyncrasies that can make an install fail.

I believe that we are always spending a lot of time trying to unravel all this stuff on just a few examples of installs that didn't work.

When I see many installations done by Lethal racing and Jannetty and such that work it leads me to believe that the ones that don't are just because someone did not all they should to do the job correctly.

Everyone of us has tackled a 'simple' home repair job that we pulled out our hair because of the unexpected stuff. These car engines are far more complex than that.

I will admit I'm philosophizing here, but it comes from a great deal of experience designing and over seeing our techs building turbine engines for commercial and military aviation.

Jim

[Ject]

Subscribed for the hilarity factor that has come about seeing as how any reputable builder or shop I've talked to say it's not suggested to go over 400lbs of open pressure.... even some with spin tron testing and results. maybe they are all stupid

[thahemp]

Originally Posted by Jims Mongoose

Okay so when you say coil bind you mean the deliberate touching of variable rate spring coils to dampen out overall valve train vibrations that can occur at high rpms various cam and valve train mass. This is an engineered system with much engineering and testing behind it. This deliberate touching of some of the variable rate springs is designed to occur at higher RPMs and is often used to control valve surge do to inherent resonances in the whole system often caused by light valve train components with too much spring.

I think the coil bind spoken of for installation refers to the static coil bind or clearance to prevent it during an install. To make sure that at low rpms you don't have it.

My problem is that from what I have read it's really in and engineers purview to figure this out and even they resort to much testing to actually see what works and doesn't.

A well known cam company that does much testing and has much experience at what works is the way we should go. Messing and experimenting with their recommendations gets us in trouble because the system is so complex

jim

I mean you use the approach to coil bind to dampen spring surge. That's all.

Originally Posted by TurboBuick6

The title says a cup engine. that is .800 range lift at 9,500 RPM, different application but does show a good example of spring surge.

Yeah I saw it is a race engine, but it's a great visual for people to understand what we're talking about.

I agree that you should go with what you know works unless you can prove another way is better. I haven't seen any proof that running further away from coil bind for spring longevity is a good idea on our run of the mill LS3 cam installs. Data doesn't lie. Is there data we can see that proves your point? Or are we going to argue about this forever?