The Cal-look Lounge

As I am reading a lot about valve float spring pressure and things like pitted lifters I can't find good advise on how to determine the correct springpressure in relationship with the rest of the components.

I know that it is best to keep springpressure as low as possible so the whole valvetrain is as light as possible bt on the other hand you want it hard enough to keep the valves from floating.

I used BasMotorsport double springs i my type 4 and it always worked out good.
Now I am adding a turbo so I think I need more springpressure but how much more?Is there something like a golden rule on how to determine what the proper pressure is?


Thanks Michael

I was gonna post the same question ;)

Experience?

think beehive and small diameter stem valves. Type 4?? not sure.Ask joel mohr.. He has done alot of testing. His car (2442)ran 12.50's with radials, belt, muff. Over 200 hundred hp at rear wheels ..I heard his luggage from the hotel stay was even in the car.. He's got it going on.Pump gas driven from the high desert and raced last weekend. Good set of clyde berg head porting always helps.. bill.

Hey Bill, I am not too sure about the beehives.Read some very different stories about them.
As far as I know for now I have the option to go for double gene berg springs or step up to the jpm springs.Really don't know how much pressure they give but I assume they are pretty heavy.

Any one have some more info?

Michael

Michael, me dumb and i would like to go turbo too on the T4 in my Ghia. But do you really need to go stiffer springs ?
I think it's a RPM question... (and yes, in the end you still have to determine the "correct" spring pressure).

info: Kawell, Ugly Duckling ?

It is a combination of factors,yes rpm affects it,the engine will accelerate much quicker and the springs will struggle to keep up,also you have the boost pressure trying to hold the valves open,when i went from a nitrous to turbo engine,apart from lowering the compression nothing else changed but the chevy size springs couldnt keep up and the valve seats were getting beaten into the heads.

I dont have enough experience with type 4 engines to help with what you need,but the best spring you can get in there is a good starting point :)

cheers richie,uk

Nah... you guess or search the www  :D

Hi dudes take your head place a light spring in it and blow 1bar air in the port measure the presurre on the valvehead on a scale ,
add the blowpresurre to the springtension you want to drive and your safe

gr henri

There is no Golden rule for Spring Pressure. It depends on a few factors.

The rate of attack the cam has. lifter, pushrod and valve wight. and the amount of energy the rockers need to control them. the pressure acting on the rear of the valves ie, boost and back pressure.

Your better going a little over the top than under, as if you go under then you'll just beat the crap out of the valves and seats.

If you run the springs too far off bind then they will resonate and beat the crap out of the rockers.

First place to look for spring info is the cam manufacture, as they will be able to tell you a starting point, then add the boost / back pressure which ever is highest. and i'd go just a 10-20lbs more than that to be on the safe side.

Ultimately you would put the motor on a Spintron machine. This machine measures what the valves are doing right though the rev range, enabling you to select the correct springs for the job.

Do a search on youtube for valve float and see what happens at hi rpm!!!!


Hope this helps
 

Martin.

That`s an pretty interesting question.Experince is the safest way.

Or you can do some math to get the needed spring pressure for your wanted max rpm. A self project I have sadly never finnished, but some day I will...

The real hard nuts in that formula are the cam acceleration and the moment of inertia of the rocker.The first thing I have, ONLY need the second.
Then you need to know what rev`s you want to go and add a secure factor to get to the dynamic side. Mr. Apfelbeck has some good advices in his book but only for non blown...

Sorry only in german:

It's easier than that.
Calculate the area of the valve.  Multiply that by the boost pressure you plan on running.  The result is how much more spring pressure you need.