Engine and Transmission Tech

Can valve spring rates be determined from valvetrain component weights vs. rpm vs. closing rates? Formulas? Charts?

The short answer is yes. All the charts and calculators are available on line. ( comp cams, crane etc.)
The better question is should you?
The cam companies spend a huge amount of time, equipment and expertise determining what works with what.
They are your best ally in your valve spring quest.
Given all the variables in a modern valve train. Trying to roll your own might not be the best idea.
All hail the mighty "B" cam
Fred

I once heard the "B" cam didn't need no stinkin' valve springs! It is so enormous it SCARES the valves closed.

All Hail the Mighty "B" cam!

Jim

Little known is the fact, that the leader of a secretive musical groupe, from Liverpool, "Desmo and the Dromics", invented the B-cam-Almighty. He is quoted as saying...." valve springs...we doan need no stinkin valve springs", and thusly, in and out was first accomplished, without springs........ roverman exhausted.

Yeah, I used to be a Ducati dealer. What I had in mind was spring requirements changing because of custom cam profiles and lighter than normal components. Small valve stems, hollow stems, titanium valves, beehive springs, titanium retainers, should allow less spring pressure. Current oils certainly favor lower spring rates. I am hoping some of you cam experts can help me come up with a superlative cam design for this eclectic little engine I'm building. Desmo valve gear would be too far out even for me.

That's cool Larry.
Ive got an old ST2 that I'll never let go of.
What is this "ecelectic little engine" and what does it need to do?

All hail the mighty "B" cam.

Fred

Well, I've been accumulating parts for about 40 years, and I'm going to build something with them. The original plan was an American BOP 215 TR7. Then I bought a Fiero. [still have the TR7] So, sleeve the block for 305 TRW forged pistons, use sbc small journal h-beam 6" rods, 215 crank, 3/4" alum. girdle, 3.9l TPI manifold with twin throttle bodies, 3.9l heads ported with larger valves, custom roller cam with GM 3.4l roller lifters, GM 3800 front cover and oil pump, twin 996 Porsche turbos, and GM LS type computer. All the parts are in hand, so I have a little machinework to do.

I built some heads today with real springs. Seat pressure 320lbs., open pressure 900 lbs. @ .800 lift! Can't help but believe that could be reduced significantly with titanium components. Valve weight alone drops from 173.8 to 109.0 g. Some guys use more spring pressure when using higher boost turbo setups. Any thoughts on that?

Larry, Sounds like a race only, roller cam motor. For street I like about 100lbs seat pressure and 300lbs @.500 lift.



Edited 1 time(s). Last edit at 02/27/2014 08:50PM by mgb260.

Holy cow Larry!
Those springs will hold up your whole car.
Nothing in your valvetrain will survive that kind of pressure. In particular the 3.4 hydraulic lifters. They're gonna say adios before the starter stops turning.
The best ported late model heads that I've seen, stall out at 0.480" or so.
So 0.800'' valve lift is just wasted.
Jim is in the ball park with his #s
Re; running boost. There are several schools of thought. Some say crank up the spring pressure to counteract boost.
I'm from another school that say's you could probably get away with less spring pressure under boost.
If you consider that the biggest intake valve that will fit into your heads has an effective area of 2.4 square inches.
Then at 10 lbs of boost you only have an extra 24 lbs of pressure trying to open the valve.
Conversely if we pick a nice round # of 1000 psi for peak cylinder pressure unboosted.
Then multiply that by 0.7 ( 10 psi divided by 1 atmosphere) to account for the boost pressure.
With losses let's call it a 500 psi increase.
That gets you another 1200 lbs trying to close the valve.
It's not really that simple, but you get my point.

All hail the mighty "B" cam
Fred

there are a lot of factors to consider In Valve springs Hydraulic cams Solid cams run differently roller cams versus flat tappet cams all require different spring pressures one thing to keep in mind are you running it on the street those really high pressure springs 500 to 900 pound open load pressures will destroy parts on the street springs like that will put 4 or 5000 pounds Of download On the camshaft plus it takes a lot of horsepower to turn the camshaft with springs like that the bottom line you need to run the latest spring pressures you can get away with it makes the motor faster and live longer most cam companies just tell you to run heavy springs they don't care how long it lasts they want to sell you more parts plus heavy springs will cover their mistakes in crappy cam lobe design you can buy camshafts cut with very smooth ramp design on the camshaft

I just ordered a new camshaft for my new 347 motor it is solid roller around 600 lift and it will turn over 8000 RPMs duration is 248 256 at 50 the cam is, Street capable With close pressure of 150 pounds open pressure 400 pounds the people at CAM research told me they are constantly working on coming up with better ramp designs on their camshafts that will work with lighter springs

In some things bigger is just not better

There is another factor that comes into play with hydraulic camshafts it takes a certain amount valve spring to compensate for the hydraulic pressure in the lifter to keep it from pumping up mechanical camshafts do not have that problem

Quote:

What I had in mind was spring requirements changing because of custom cam profiles and lighter than normal components. Small valve stems, hollow stems, titanium valves, beehive springs, titanium retainers, should allow less spring pressure. Current oils certainly favor lower spring rates.

Larry, what happened to your original idea?

Sorry, I neglected to mention these numbers are for a drag only BBC with 2.300" int. and 1.900" ex. valves. Lift is .820". Cam by John Reed. (not my favorite) + 150hp shot of nitrous. My intent was to show the perfect example of ridiculous valve spring setup. I didn't think about someone thinking I would use anything like this. Since I don't like valve springs anyway, smaller is better.

Larry, as others have stated, between the cam grinders tech., and the calculators out there, I suspect an adequate ovate wire/beehive , will prove adequate. Smaller/lighter retainer, with more rocker clearance, reduced harmonics/un-sprung weight, and better gravity oiling, of the spring, are sound reasons, to consider. I'm using a set, on a 540" HR, bbm., so big rates, are available. Cheers, roverman.

Good to hear Larry.
I was scared for you.
Cheers
Fred