Help I need advise bad head work

[coop]

yeah it couldn't hurt to get a few more opinions I will take them on a field trip next week. I did have another shop look at them they didn't think it could of been the cam or springs. What he thought might of caused it was the guide clearances to big or small. Also he said maybe there was some machining compound left in the guides. The valve stems do have traces of what looks like metal deposits on them. Here is a great link with a article on what can cause valve damage


http://www.aa1car.com/library/ar1192.htm

[Rockerdog]

Here's a few examples of valve float done with high speed cameras.
The top one shows it the best.
The bottom two are FE SOHC 427
http://www.youtube.com/watch?v=i_NpzU4p ... re=related
http://www.youtube.com/watch?v=yVwzXeAtEHg
http://www.youtube.com/watch?v=MXrQw8cXEiI&NR=1

[fordman]

in those video's i can see the spring vibratign. that is all i really see. except in the second video you can see the spring spin. so from what i seen. explain to me valve float.

[Rockerdog]

in those video's i can see the spring vibratign. that is all i really see. except in the second video you can see the spring spin. so from what i seen. explain to me valve float.

If the spring has room to vibrate then it is no longer pushing up on the retainer thus allowing the valve to "flutter" The whole point of the spring is to slam the valve closed and hold it there. If the valve can slam shut and bounce back open (vibrating the spring) then the "installed height" spring pressure isn't high enough to hold the valve closed. That's my understanding anyway.

[fordman]

ok i was thinking that was the answer to the question. thank you.

[DuckRyder]

Also, one of the car rags did a test quite a few years back and each time it was floated, it floated at a slightly lower RPM the next time.

[Rockerdog]

Also, one of the car rags did a test quite a few years back and each time it was floated, it floated at a slightly lower RPM the next time.

Probably because it all happens so fast, the spring doesn't have a chance to stabilize from the previous event. I'm in the process of selecting all the components and setting up a 390 build. Finding a spring with the right pressures at "installed height" and "full open" and then making sure that "full open" was far enough away from coil bind was a fairly time consuming process.

[DuckRyder]

Also, one of the car rags did a test quite a few years back and each time it was floated, it floated at a slightly lower RPM the next time.

Probably because it all happens so fast, the spring doesn't have a chance to stabilize from the previous event.

No, the times could be hours or days apart, the oscillation fatigues the spring... at least that is what the rag said...

[fordman]

yes that was what i figured was happening. so the spring was getting weaker.

[Rockerdog]

Wow that's really rapid wear. Didn't realize it could ruin a spring that fast!
All of this goes back to the original point of this topic to show how carefully things need to be set up!

[70_F100]

I'm just sitting around bored tonite, and decided to stir the pot.

Any update on this thread?

[bb429power]

don't let the heads leave your site. he may trash them saying you never gave them to him and then you lost your eviedence. talk to a lawyer before you give him the heads for examination.

X2, get them quickly.