Detecting Valve Bounce

la360 · Post by **la360** » Sat Dec 11, 2004 6:56 am

What signs should I be looking for when examining a valve train for valve bounce? A few things I have noticed upon dissambly of my heads is a great differance in the free heights of the outer springs, some varying by close to an 1/8" of an inch. The heads have 3/8" stem Manley Pro Flow Stainless valves, 2.08"/1.60" , I have notices the heads are not falt across the faces, the exhausts aren't too bad, the intakes are worse. Some of the valve faces are not worn evenly, some of which show short patterns of wear, that apose one another. What Should I be looking for?
AL...

speedtalk · Post by **speedtalk** » Sat Dec 11, 2004 10:37 am

I've always looked at the valve's keeper groove to see how happy the valvetrain is. If you have to debur the groove to get the valve out of the guide, it's not good.

Walline · Post by **Walline** » Sat Dec 11, 2004 12:22 pm

I agree Don. I built a engine and after 4 weekends of drag racing it was dissasembled, and found that the springs had lost 30-45 lbs on the seat. the keeper grooves on the valves were terrible! Very scary. I am going to change spring supplier.

bill jones · Post by **bill jones** » Sat Dec 11, 2004 12:38 pm

-First thing I'd do is check the valve faces and the seat faces for runout, using gauging that reads to the ten thousandths of an inch.
-Once you find out what you have there then you can get onto something else but if the seats and valves are ground poorly you need to get that under control very first thing.
-It is very common to find well over .0015" to as much as .004" on either or both faces with sloppy valve jobs, and what you want is something on the order of .0005" (or less if you can get it) on either face.

MaxCFM · Post by **MaxCFM** » Sat Dec 11, 2004 1:58 pm

Walline wrote:I agree Don. I built a engine and after 4 weekends of drag racing it was dissasembled, and found that the springs had lost 30-45 lbs on the seat. the keeper grooves on the valves were terrible! Very scary. I am going to change spring supplier.

Just curious, your valve springs are made of what material? Chrome silicon,h-11 or titanium?

la360 · Post by **la360** » Sat Dec 11, 2004 4:53 pm

To be perfectly honest, I have no idea what brand the springs are , let alone what material they are made from. I don't imagine they would be Pacalloy or anything exotic, what materials were they using in Roller valve springs in 1981? At a guess I would say that they were something like Mopar Performance springs, as they have basically been set up as per their recommendations.
The valve locks and the grooves in the valves are like new, so could it be a case of just a bad valve job??? I will have to check out the seat and valve runout this week.
Thanks for the replies
AL....

Walline · Post by **Walline** » Sat Dec 11, 2004 5:11 pm

Just curious, your valve springs are made of what material? Chrome silicon,h-11 or titanium?

Max CFM

They were chrome silicon. I was told sometimes the heat treat isnt perfect. I am unsure about that, but for the money I might beleive it. I am going to run H-11 this year! What was strange, was the car never slowed down.

bill jones · Post by **bill jones** » Sat Dec 11, 2004 5:51 pm

-One other sign of valve bounce is when the flat ends of the springs are shiny from pounding against the shims and the retainers.
-AND-if you see any visible signs of the coils touching each other liek what would happen at coil bind.
---------------------------------
-I have witnessed a home brewed spin test that we did on a handcrafted flathead Ford roller cam that we made for a saltflats car.
-When we ran that to the bounce or float point (we could chase the motion with a strobe light) the valve spring ends up all compressed and it just sits there inbetween the retainer and the shim pad and there's a clearance of the spring to the retainer and to the shim pad that is 1/2 the valve lift on both ends of the spring.
-When that happens the noise (which is already like a machine gun) changes up to such a horrendous noise level it's damned scary.
-Within the same moments of all of this happening and we are trying to dial in the strobe and look at the valve spring and components, and get the thing shut back down, the spring goes to cherry red, all within just a few seconds like maybe the most we ever held that at bounce was about 8 t0 12 seconds.

la360 · Post by **la360** » Sat Dec 11, 2004 7:55 pm

The springs look fine, but I am unsure as to how much work these have done. I know the original owner tried a few different camshafts, before running the General Kinetics camshaft that was in the engine when it was imported.
Appart from an uneven wear pattern on some of the valve faces, and what appears to be the begining of the valve heads starting to pull through, the valves are in very good condition. There is little to no scuffing of the valve stems, and the guides still seem to be ok , the guides are cast iron .
I have put a few engines together over the time, but have never really had to analyze one after tearing it down, so this is all a little new to me.
Thanks
AL...

ChrisU · Post by **ChrisU** » Sat Dec 11, 2004 9:33 pm

Another clue to valve bounce is when the keeper face(angled part) is polished or galled up...... that's a pretty quick sign that things are really dancing.

tk · Post by tk » Sun Dec 12, 2004 10:06 am

Walline wrote:I agree Don. I built a engine and after 4 weekends of drag racing it was dissasembled, and found that the springs had lost 30-45 lbs on the seat. the keeper grooves on the valves were terrible! Very scary. I am going to change spring supplier.

I've found that using Pacaloy springs on my race car would last at least 2 seasons of racing compaired to Chrome Silicon and even H11 springs.

Last time I checked I think Pacaloy was used in Nascar engines

I know the Prostock used them and now use Titainium on the intakes.

In Superstock the Pacaloy has improved reliability.