Maximum valve length

[Newbomb Turk]

If only it worked that way (all the time). Here's a before and after correction. With 'correction' the rocker ratio went down, lift went down, valve speed went down. This is one example. I'm not making a blanket statement.

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I think you’ve posted these numbers before.

You are correct that your numbers show them almost equal off the seat and the corrected numbers start slowing down sooner. But it still looks like around max lift the corrected numbers are slower.

When we get down to the nut cutting the corrected geometry will always produce smoother valve train operation and the engine will rpm higher with the same or even less spring load.

To me, that aspect is far more critical than leaving the geometry uncorrected and having the valve train in distress.

I see a ton, far too much valve train distress on the dyno. Not just Chrysler stuff either.

 

[Newbomb Turk]

A lot of this is relative to what pressures/lift we're talking about. That's the problem with some topics.. they become over generalized.
I wonder how many people on this site are lifting their valve .7 or .800 and wringing it into the red line over 8,ooo rpm ..hard enough and often enough to create the circumstance to break a spring like that.

One thing I see is guys are calculating their open pressures at some arbitrary lift number. Let’s say the cam/rocker should get you a net lift of .600. Then you add in deflection and geometry losses and you may be only netting .560 lift.

.040 doesn’t sound like much but if you are doing the math you may be losing more spring load over the nose than one might think.

 

[PRH]

A lot of this is relative to what pressures/lift we're talking about. That's the problem with some topics.. they become over generalized.
I wonder how many people on this site are lifting their valve .7 or .800 and wringing it into the red line over 8,ooo rpm ..hard enough and often enough to create the circumstance to break a spring like that.

Other than the last sentence of that post, I was referring to the overall thought process on spring set up for performance and racing applications(at the time).
The bulk of work was based on various circle track classes, which ranged from 4cyl 2.3 fords, to 2bbl Hyd cams v8’s, to roller cammed high-ish CR dirt modifides……to hot street/strip and bracket race builds, mud trucks, pullers, etc.

So, a pretty broad range of applications and springs.

Sort of the same as what I work on still.

 

[MOPAROFFICIAL]

One thing I see is guys are calculating their open pressures at some arbitrary lift number. Let’s say the cam/rocker should get you a net lift of .600. Then you add in deflection and geometry losses and you may be only netting .560 lift.

.040 doesn’t sound like much but if you are doing the math you may be losing more spring load over the nose than one might think.

Agreed.
.040 is a lot when it comes to the effect on spring pressure.

 

[Earlie A]

I think you’ve posted these numbers before.

You are correct that your numbers show them almost equal off the seat and the corrected numbers start slowing down sooner. But it still looks like around max lift the corrected numbers are slower.

When we get down to the nut cutting the corrected geometry will always produce smoother valve train operation and the engine will rpm higher with the same or even less spring load.

To me, that aspect is far more critical than leaving the geometry uncorrected and having the valve train in distress.

I see a ton, far too much valve train distress on the dyno. Not just Chrysler stuff either.

There is no 'correct' geometry when it comes to 59 deg mopar heads. The best compromise is all we can hope for. My point is this. Most of the 'bad' stuff is happening on the pushrod side of the rocker arm. Spring force is higher on that side because of multiplication by the rocker ratio. Pushrod angularity makes the load on the pushrod even higher than spring load multiplied by rocker ratio. As a matter of fact, I believe (but I might be wrong) that as pushrod angularity increases, load on the pushrod will increase exponentially, not linearly. And those are just the static loads. As pushrod angularity gets worse, the center of mass of the pushrod travels in a larger arc, increasing dynamic loading and harmonics. This takes more spring load to keep under control, not less.

I agree that the 'correct' geometry is what we want. I disagree that moving the shaft away from the valve will give us the desired result. Picking a rocker arm with the shortest fulcrum arm (distance between center of rocker shaft and center of roller tip) will be a good place to start. Picking a rocker with a long fulcrum arm then moving it away from the valve is not.

 

[MOPAROFFICIAL]

There is no 'correct' geometry when it comes to 59 deg mopar heads. The best compromise is all we can hope for. My point is this. Most of the 'bad' stuff is happening on the pushrod side of the rocker arm. Spring force is higher on that side because of multiplication by the rocker ratio. Pushrod angularity makes the load on the pushrod even higher than spring load multiplied by rocker ratio. As a matter of fact, I believe (but I might be wrong) that as pushrod angularity increases, load on the pushrod will increase exponentially, not linearly. And those are just the static loads. As pushrod angularity gets worse, the center of mass of the pushrod travels in a larger arc, increasing dynamic loading and harmonics. This takes more spring load to keep under control, not less.

I agree that the 'correct' geometry is what we want. I disagree that moving the shaft away from the valve will give us the desired result. Picking a rocker arm with the shortest fulcrum arm (distance between center of rocker shaft and center of roller tip) will be a good place to start. Picking a rocker with a long fulcrum arm then moving it away from the valve is not.

I agree that there is no perfect geometry when it comes to a 59° Mopar. I've always noticed that Chevy could get away using less spring on the small blocks, once I started looking into the issue with the 59° lifter Banks I completely understood why. Change the block for a 48° version and then you can fix that, otherwise you just make the best of it and use plenty of spring or else LOL

 

[Earlie A]

All of this is another reason to use the shortest valve and installed spring height possible. The taller the valve, the shorter the valve tip to rocker shaft centerline distance becomes. This compounds the problems.

 

[GGress]

All of this is another reason to use the shortest valve and installed spring height possible. The taller the valve, the shorter the valve tip to rocker shaft centerline distance becomes. This compounds the problems.

I think I'm getting information overload here, but thanks everyone, I'd prefer too much info as opposed to too little.

I started this thread thinking that a longer valve would increase my spring options for a solid roller cam, the higher rates seem to favor longer springs, not to mention the loss of actually lift with a 59 degree block. If you have a head with max flow at .575 and want to lift your valve .600 to take advantage, you need a cam that, on paper needs .640 lift just to give an actual .600! Higher lift tends to require bigger duration numbers and it becomes a catch 22.

 

[Earlie A]

Sorry for the sidetrack. Spring selection for the SBM with a solid roller can get tricky. There are some pretty stout 1.400" OD springs available.

 

[GGress]

Sorry for the sidetrack. Spring selection for the SBM with a solid roller can get tricky. There are some pretty stout 1.400" OD springs available.

Wasn't really a sidetrack, I'd rather you do all the math than me!

 

[MOPAROFFICIAL]

All of this is another reason to use the shortest valve and installed spring height possible. The taller the valve, the shorter the valve tip to rocker shaft centerline distance becomes. This compounds the problems.

I try to keep it in the 1.907-1.937 as Chrysler already knew this when they did what they could with the old poly to make it an LA. I think for me the nicest centered pattern was @1.917

 

[MOPAROFFICIAL]

I think I'm getting information overload here, but thanks everyone, I'd prefer too much info as opposed to too little.

I started this thread thinking that a longer valve would increase my spring options for a solid roller cam, the higher rates seem to favor longer springs, not to mention the loss of actually lift with a 59 degree block. If you have a head with max flow at .575 and want to lift your valve .600 to take advantage, you need a cam that, on paper needs .640 lift just to give an actual .600! Higher lift tends to require bigger duration numbers and it becomes a catch 22.

You can use the longer valve to get a better spring in there, you'll just have to to face the tips to get them back down to earth 'in the 1.907-1.937 range'.
When I originally responded to this thread I was addressing spring installed height and not stem height. And I am using +.100 longer Chevy valves to get that 1.90 installed height i mentioned.
Just cuz the stem got longer doesn't mean you cant compensate in the valve job end of it.. bring the seat out 1.98 od .

 

[Newbomb Turk]

All of this is another reason to use the shortest valve and installed spring height possible. The taller the valve, the shorter the valve tip to rocker shaft centerline distance becomes. This compounds the problems.

Absolute FACT.