LS Valve weight VS spring pressure

[Walter R. Malik]

I have mast small bore LS3 heads for my LSX, and the stainless intake valves I have for them are 126g (2.08"x 5/16“ x 5.45" length).
I love these heads, but the long valves are HEAVY!
How much spring pressure am I going to need, in order to control these valves at 8000rpm?
Comp cams HLO SERIES hydraulic roller lobes 13792R intake 13795R exhuast(249*/255* .613/.613 lift 116lsa)
Johnson ST2126 hydraulic lifters.
1 shop has told me I need titanium valves, along with their super light weight rockers, in order to make this work, and I think that's bullshit.
My thaughts are a pac 1237x spring set up at ~220lbs installed ~560lbs open should control the valve train, and the Johnson lifters should handle the spring pressure..... Any thoughts, opinions, experience on this would be appreciated.

On an LS3 build for a customer I have used a PAC1238X installed at 1.860" with a large hydraulic roller cam using the good Johnson, (ST2126LSR), lifters with stainless valves but, that engine had .740" valve lift. Went to 8,600 RPM easily.
The PAC 1237X would probably be OK for you at .613" valve lift.

I just looked up the records of this build from 2018. The intake valves weighed 114g.
It was a special designed intake lobe Bullet Cam 312/321 @.006" - 258/267 @.050" - 183/190 @.200" - .4309"/.4176" lobe lift - 109 separation; 1.72/1 rocker ratio.
The engine was 387 cubic inches with a tunnel ram & carburetors; 4.020" bore x 3.8120" stroke

[3pedals]

Thanks Walter. I can definately use that as a point of reference.
I appreciate it
I will definately be looking for some gentler lobes, and I'll try get some mass out of my valve train.

I have mast small bore LS3 heads for my LSX, and the stainless intake valves I have for them are 126g (2.08"x 5/16“ x 5.45" length).
I love these heads, but the long valves are HEAVY!
How much spring pressure am I going to need, in order to control these valves at 8000rpm?
Comp cams HLO SERIES hydraulic roller lobes 13792R intake 13795R exhuast(249*/255* .613/.613 lift 116lsa)
Johnson ST2126 hydraulic lifters.
1 shop has told me I need titanium valves, along with their super light weight rockers, in order to make this work, and I think that's bullshit.
My thaughts are a pac 1237x spring set up at ~220lbs installed ~560lbs open should control the valve train, and the Johnson lifters should handle the spring pressure..... Any thoughts, opinions, experience on this would be appreciated.

On an LS3 build for a customer I have used a PAC1238X installed at 1.860" with a large hydraulic roller cam using the good Johnson, (ST2126LSR), lifters with stainless valves but, that engine had .740" valve lift. Went to 8,600 RPM easily.
The PAC 1237X would probably be OK for you at .613" valve lift.

I just looked up the records of this build from 2018. The intake valves weighed 114g.
It was a special designed intake lobe Bullet Cam 312/321 @.006" - 258/267 @.050" - 183/190 @.200" - .4309"/.4176" lobe lift - 109 separation; 1.72/1 rocker ratio.
The engine was 387 cubic inches with a tunnel ram & carburetors; 4.020" bore x 3.8120" stroke

[hoffman900]

For flat tappet, the Crane Cams F4-F10 NASCAR lobes always worked great for us, with the F5 being our favorite. The F5 family came in 2* @ .050” increments, so you could fine tune and have the same dynamics. Never had them on a Spintron, but the valvetrain was very happy with them where we were running them.

Sadly, I don’t know if these designs are available anymore with the Comp merger.

[Walter R. Malik]

For flat tappet, the Crane Cams F4-F10 NASCAR lobes always worked great for us, with the F5 being our favorite. The F5 family came in 2* @ .050” increments, so you could fine tune and have the same dynamics. Never had them on a Spintron, but the valvetrain was very happy with them where we were running them.

Sadly, I don’t know if these designs are available anymore with the Comp merger.

Personally ... for road race flat tappet cams I used the Reed designs. For all the same reasons.

[nevdos]

IF you are going to use a shelf lobe then HUC lobes from Comp work well for most sub 8k engines ,again assuming the valvetrain is light enough.
Again as I said before ,(and Warp eluded to as well ) adding spring seat PSI is the absolute wrong way to go on a hyd system( most systems really but that hyd plunger for sure doesn't like it ) .
Get the valve weight below 110 grams and run an OEM rocker, and no bigger than a 11/32- 080 wall pushrod with a good Johnson lifter and 8k is easily attainable
Pushrod and lifter weight on a hyd system for sure matter, an anyone who says it doesn't hasn't done the work to prove otherwise
We have 9k + rpm and 2700 rwhp systems in use that prove that !!

[turbo camino]

'No bigger than 11/32' because bigger isn't needed for that level, or bigger than 11/32 hurts stability?

[nevdos]

'No bigger than 11/32' because bigger isn't needed for that level, or bigger than 11/32 hurts stability?

BOTH

[Wetflow]

Pushrod and lifter weight on a hyd system for sure matter, an anyone who says it doesn't hasn't done the work to prove otherwise

What if lifter and pushrod weight COULD be removed from the equation? What general effect would be the result?

What % higher RPM potential if all else remains the same?

Or, what reduction in seat/open spring pressure for the same RPM?

Is there a formula for calculating these values?

[3pedals]

I 100% believe that the BTR recipe WORKS!
I also believe that strategy is specifically tailored around keeping the spring pressure light enough to allow scrub tip OEM LS rockers to survive, and not kill valve tips.
In applications where the valve mass and/or rocker mass cannot be as low as 110g valves and OEM LS rockers, clearly additional spring pressure will be required...
I did order a BTR cam(claimed to be the smoothest lobes around), and the Johnson lifters, and I'm going to try find lighter valves.. so I guess I'll find out what I can get to work, as far as spring pressure.
I'm not downsizing my 3/8 .135 wall push rods tho

IF you are going to use a shelf lobe then HUC lobes from Comp work well for most sub 8k engines ,again assuming the valvetrain is light enough.
Again as I said before ,(and Warp eluded to as well ) adding spring seat PSI is the absolute wrong way to go on a hyd system( most systems really but that hyd plunger for sure doesn't like it ) .
Get the valve weight below 110 grams and run an OEM rocker, and no bigger than a 11/32- 080 wall pushrod with a good Johnson lifter and 8k is easily attainable
Pushrod and lifter weight on a hyd system for sure matter, an anyone who says it doesn't hasn't done the work to prove otherwise
We have 9k + rpm and 2700 rwhp systems in use that prove that !!

[bob460]

IF you are going to use a shelf lobe then HUC lobes from Comp work well for most sub 8k engines ,again assuming the valvetrain is light enough.
Again as I said before ,(and Warp eluded to as well ) adding spring seat PSI is the absolute wrong way to go on a hyd system( most systems really but that hyd plunger for sure doesn't like it ) .
Get the valve weight below 110 grams and run an OEM rocker, and no bigger than a 11/32- 080 wall pushrod with a good Johnson lifter and 8k is easily attainable
Pushrod and lifter weight on a hyd system for sure matter, an anyone who says it doesn't hasn't done the work to prove otherwise
We have 9k + rpm and 2700 rwhp systems in use that prove that !!

So why would the GM Engineer's put a 7/16" pushrod in their hydraulic roller 632 crate engine with only 180/400 seat pressure

[Walter R. Malik]

IF you are going to use a shelf lobe then HUC lobes from Comp work well for most sub 8k engines ,again assuming the valvetrain is light enough.
Again as I said before ,(and Warp eluded to as well ) adding spring seat PSI is the absolute wrong way to go on a hyd system( most systems really but that hyd plunger for sure doesn't like it ) .
Get the valve weight below 110 grams and run an OEM rocker, and no bigger than a 11/32- 080 wall pushrod with a good Johnson lifter and 8k is easily attainable
Pushrod and lifter weight on a hyd system for sure matter, an anyone who says it doesn't hasn't done the work to prove otherwise
We have 9k + rpm and 2700 rwhp systems in use that prove that !!

So why would the GM Engineer's put a 7/16" pushrod in their hydraulic roller 632 crate engine with only 180/400 seat pressure

The pushrod needs to fit within the aloted space; sometimes a larger diameter pushrod is simply not feasible.

[Warp Speed]

'No bigger than 11/32' because bigger isn't needed for that level, or bigger than 11/32 hurts stability?

BOTH

At 8k, an 11/32 pushrod will look like a slinky! Lol

[Warp Speed]

So why would the GM Engineer's put a 7/16" pushrod in their hydraulic roller 632 crate engine with only 180/400 seat pressure

The pushrod needs to fit within the aloted space; sometimes a larger diameter pushrod is simply not feasible.

Plenty of room in even a stock ls for 3/8. Minor work for a 7/16.

[Walter R. Malik]

So why would the GM Engineer's put a 7/16" pushrod in their hydraulic roller 632 crate engine with only 180/400 seat pressure

The pushrod needs to fit within the aloted space; sometimes a larger diameter pushrod is simply not feasible.

Plenty of room in even a stock ls for 3/8. Minor work for a 7/16.

A 3/8" diameter pushrod will not fit correctly through the head when using an O.E.M. L92/LS3 head, without enlarging the pushrod holes.
Trend and others make special 11/32" diameter pushrods just for that reason.
They worked fine when going to 8,600 RPM in my customer's application; some rubbing on the head can even help to stabilize the pushrod.

[Eroy]

The pushrod needs to fit within the aloted space; sometimes a larger diameter pushrod is simply not feasible.

Plenty of room in even a stock ls for 3/8. Minor work for a 7/16.

A 3/8" diameter pushrod will not fit correctly through the head when using an O.E.M. L92/LS3 head, without enlarging the pushrod holes.
Trend and others make special 11/32" diameter pushrods just for that reason.
They worked fine when going to 8,600 RPM in my customer's application; some rubbing on the head can even help to stabilize the pushrod.

With stock rockers I have not had to clearance any LS3 for 3/8 pushrods. Aftermarket rockers may change that though.