G Atsma

Yep! Gettin' GOOD!

TrendSetter

im late to the thread and what i would normally have said has already been posted, so all i am going to say is when you get into class racing and real competition, every gram absolutely matters, and valvetrains are complex beasts. the exception that i am aware of is pushrods. stiffness is king even at the expense of weight.

IGN-1A

The Pushrod is "low weight" , before the Rocker Arm ratio has effected valve train speed.

There is also a benifet of a LARGER Cam Lobe and a LOWER rocker arm ratio.

Corona

This and the post above Lance...each professional head guy has a weigh used that they have Experience with in setting up the valve train and it's components at certain rpm and lift points.

Lance is on point with the:

👍 Cam core size and rocker ratio also a YB thread and conversation

ddnspider

iTrader: (26)

Care to elaborate on that? Higher cam lobe lift/lower RR ratio vs. lower cam lobe lift/high RR ratio.

Corona

Cam Core and Rocker ratio.... I think there's a thread with a similar question about weight of the valve train and each Head porter having a Baseline Weight for a Particular RPM° from Experience°. Nah, I don't think it was a thread I know it was now thinking about it...

G you like technical and I just try to keep it basic
😁
(Look above) as long as we get the Principal's correct 👍

https://www.yellowbullet.com/threads...-lift.2664069/

Kawboom

I think the advantages are that for a given valvespring pressure, higher lobe lift and lower rocker ratio means that there is more movements but less pressure placed on the lifter, pushrod, and rocker than a lower lift lobe with a higher ratio rocker arm. This gives better stiffness and valvetrain control.

If I recall correctly, this control is why pro-stock engines run huge lift cam lobes and relatively low ratio rocker arms.

TrendSetter

larger cam lobe gives you more flexibility in lobe design, you can do inverse radius stuff and also run larger diameter lifters which are stronger/better.
i am not sure about the lower rocker ratio part. I know with higher ratios you can get more area under the curve.
Maybe lance means with equal area under the curve with a more aggressive lobe but less ratio its easier on parts?

TrendSetter

do you know what ratio they are running these days?

Kawboom

I can only take an educated guess, probably 1.7:1, with about 1.125" valve lift. Since they implemented the rev-limiter the valve lift they run has actually gone up.

Remember that their camshaft tunnel diameter is 70mm. They can have a lot of lobe lift.

IGN-1A

The larger cam lobe has INCREASED "contact area" , good for lobe life !

Corona

With the Ls 55mm cam core
I was stuck on Ratio and lobe lift a wk or 2 ago for a future top end swap.


​​​​​​.430 lobe with a 1.8 ratio
or
.420 lobe with a 1.9 ratio

Using a .750 lifter wheel. The Rocker Ratio changes are Free.. but the Larger lobe is/was sounding better. Also the reason for the call for a part number about a wk or 2 ago...

I still don't know about the choice ..😂🤣 I laugh at myself a lot

I'm gonna find the time to ask a few people one day 😏
Hey Bipolar & ADD, who's laughing now 🤣

Kawboom

why.... does... everything... you... write... end with an ellipsis?

(An elipsis is three dots. (...) used to signify the omission of one or more words that are obviously understood but that must be supplied to make a construction grammatically complete, to signify that there is additional information that could not fit in the space allotted, or to trail off without completing your sentence giving an implication. It is not a replacement for a period, or a semicolon.)
wrong...
use...
makes...
everything...
read...
like...

Corona

I just love emojis .. It looks a little bit better now.

Btw I love Brian Griffin... The Coolest MF'er Ever on Cartoons

Kawboom

I swear I just facepalmed through the back of my own skull.

IGN-1A

I have fit Titanium valve springs, sure they cost more but last THREE times longer.
The ones I have used will allow a valve lift of 1".

spanks13

iTrader: (5)

We still don't have anywhere near an answer to the question of when do you use hollow vs solid vs Ti, and spring choices etc.

I have beat the ever living **** out of a stock LS3 hollow stem intake valve engine for ~25k miles with 600 lift cams and comp dual springs on it to a 7400 rpm limiter many times.

I have also had a Manley solid stainless intake valve drop after 750 runs on an ls3 that used to turn 7500+ rpm every pass (that or the stock flycut cast piston failed and broke the intake valve when everything exploded...chicken or the egg).

You're building a new engine - New set of ls3 heads - stock ls3 hollow valves, solid stainless, hollow stainless, Ti? What springs? Why - budget, performance, risk vs investment etc?

1. Stock bottom end ls3 including stock lifters, stage 2 off the shelf cam. Will be run day in and out until something breaks, hopefully never does.
2. Rowdy street car w/ forged 416 ls3 with short travel slow leakdown lifters, slaps harder than your mom last night stage 4 cam...will go on car show cruises, Mexico roll racing, and hits the track 10 times a year. Took the stock heads off for porting - still has the stock LS3 hollow valves. Do you change them?
3. LY6 junkyard motor (iron 6.0 w/ L92 heads), hydraulic roller with a sloppy stage 2 cam and an ebay turbo making 1000 hp turning 6500 rpm or less - Gas pedal has two positions, 0 and 30psi, but is just a daily driver.
4. Super clean ls3 grand sport corvette with 10k miles - medium sized LLSR will turn up to 7500, likely won't drive past 7000 much, and probably will just show off the dyno sheet and drive 100 miles a year. Just bought M311 heads and needs to pick valves. Has all other premium bolt-ons like carbon clutch, fast intake, 2" headers etc etc.

Bonus round:

• 14:1 compression drag engine and street race machine SBE ls7, LLSR cam but not too crazy - endurance type lobes for good stability and life, 7500+ rpm expected with a single plane, runs mid 8's in a fox body, but the motor only cost $10k to piece together - Might do race week, probably just a race car. The heads are off for porting - do you leave the stock Ti valves? Install Solid, hollow stainless, or expensive aftermarket Ti? Which springs?

As the teacher used to say - justify and explain your answers lol.

DualQuadDave

iTrader: (6)

You are going to have to FedEx me a cold 12 pack to answer that many specific combos...lol. Later tonight when I am insomniac, will shoot some opinions on those. Spoiler alert, the whole hollow stainless vs Ti is more cost driven than applied preference for the situation about 90% of the time give/take.

Corona

Spanks you as well as others who've done other higher rpm builds or type of engines, Know this:

If it's set up correctly not Dependant on valve material used it will hold up.. being lighter just allows more rpm & less maintenance , which is HP without the extra weight which hinders Rpm. At which Rpm point does a Valve switch needed to be considered?

Budget decides that. As you listed a Hollow stem which Weighs more than a Titanium valve and a Solid valve Weights more than Either...

Springs Control all listed @ any giving Rpm. Losing weight is only a benefit to the point of a person's budget. 👍 If we've got great springs would it not be possible to get 9000 rpm with a Solid stem valve using a Shaft mounted system with a larger type push rod?

Budget and or rules. + A seen valve out of Control from testing.

spanks13

iTrader: (5)

Just stirring the pot with some talking points

Answer one or all lol I know it is a lot of questions just some common scenarios we see these days.