What spring preassure for blown alky...

Valve sizes are 2.20 and 1.625 and boost 55 pounds. Suggestions on over the nose preassure are appreciated.

 

Valve weight, rpm, valvetrain parts. Those are the questions we need answered.
The most important being the rpms. Are the valves Ti, Stainless, etc.?
Cuz the difference between a 7,000 engine and a 10,400 engine is almost double in spring pressure closed.
So, with some more info, we can sure give you some starting points.

 

i would use around 380 on intakes and 340-360 on exhaust with only what you gave us

 

Spring perssure

I NEED TO KNOW THE MAXINUM ENGINE SPEED AND THE QUALITY OF THE COMPONENTS.

WITH THAT SAID, THE BASIC RULE OF THUMB IS BOOST TIMES THE SQUARE INCHES OF AREA OF THE VALVE IN QUESTION. SUPERCHARGED THE INTAKE SIDE IS IN QUESTION. TURBO CHARGED BOTH SIDES MUST BE LOOKED AT.
IN THIS CASE THE MATH IS 1.1 X 1.1 X 3.1416=3.801336 X 55= 209.07 POUNDS OF NEGATIVE VALVE SPRING SEAT PRESSURE.
IF WE ONLY USE 360 POUNDS OF SEAT PRESSURE, THE EFFECTIVE SEAT PRESSURE WILL BE 360 lbs-209 lbs = 151 POUNDS OF VALVE SPRING SEAT PRESSURE.
THE VALVE TRAIN DOES NOT KNOW THAT IT IS IN A SB CHEVROLET, SB FORD OR A 519 CUBIC CHRYSLER. IT ONLY KNOWS VALVE, WEIGHT, BOOST AND ABOVE ALL THE CAMSHAFTS ABILITY TO PRODUCE THE VALVE CLOSING FUNCTION WITHOUT CAUSING SURGE.
WITH ALL OF THIS SAID,THE ACTUAL REQUIREMENT WILL BE IN THE AREA OF 500 POUNDS IF THE ENGINE SPEED IS GOING TO BE ABOVE 10,000 RPM.
THE WORST THING WE CAN EVER DO IS TO ATTEMPT TO PROVIDE TO LITTLE SPRING PRESSURE. IF WE DO THIS WE WILL NOW HAVE TO DEAL WITH SOME IMPACT LOADING THAT WILL BE IN THE 60,000 PSI AREA. THIS WILL GREATLY DAMAGE ALL OF YOUR REAL NEAT STUFF, DROP VALVES, BLOW YOUR SUPERCHARGER OFF, ETC.

Noel Manton 951 674-2212
www.mantonrockerarms.com
Al Perkins 951 245-6565
www.mantonpushrods.com
Terry Manton 951 245-6565
www.mantonpushrods.com

WE ARE HERE TO ANSWER YOUR QUESTIONS FROM 8:00am UNTIL 7:00PM MONDAY - FRIDAY.

 

Well there you have it !!!

 

thanks guys, 8500rpm titanium intake valve stainless exhaust t&d rockers screw blower.

 

Just ring noel we dropped a valve early on in our racing lives (many moons ago now) and we spoke to noel and he gave us great advice now we have rock solid valvetrain and get more life out of our parts than 90% of the other racers around us . If noel says jump i say how high

 

Is the number 55 a constant or is it derived from something? Thanks for the very informative post.

 

55 is the boost number in the equation if i get it right. then my question is to Noel: in a 8500rpm n/a ti valved motor, what would the preffered spring preassure be? my motor builder is asking for the "over the nose preassure".

 

"IF WE ONLY USE 360 POUNDS OF SEAT PRESSURE, THE EFFECTIVE SEAT PRESSURE WILL BE 360 lbs-209 lbs = 151 POUNDS OF VALVE SPRING SEAT PRESSURE."

In a static condition that would be the case, minus seat facing and valve stem. But there is dynamics going on on both sides of the valve. I personally don't think the effective seat pressure is 100% affected this straight forward. Should you add some spring pressure to account for the boost, sure...! But I think it would be substantially less than the full figure of -209 lbs in this case.

That's my thoughts and seems to prove out in my own case.

Blessings.........Ron Clevenger.

 

My thoughts also and seems to prove out in my own case also.

 

it is simple hydraulics
force = pressure x area
but i did say 380
so that giving, this is what a lot of people ran years ago
how much is nessacary to maintain stability above static
i would think it has a lot to do with cam ramp angles and lift as much as boost
and weight of the moving parts, valve, lifter, pushrod, rocker

 

I think we are missing another large piece of this equation, that being the weight of the valve. I would love to here Manton chime in on how the weight effects the amount of spring pressure required at 10k. I'm sure grams become lbs at that speed.

 

It sounds like you you have a small block chevy by the valve sizes so I think the prefered spring would be the new lightwieght 1.5 diameter dual manley's or pac's. Im sure you want well over 1200 open. They want you to push them to .070 to .120" of coil bind so figuring out the best spring without your valve lift and est. installed hieght is impossible.Your best bet is to have your engine builder call Noel.

Noel,
Do you still have a valve spring website? I cant find it.

Marty