Does this look like valve float?

[Brewzer67]

I hurt the motor last year and am finally able to start tearing things down to fix it. While trying to figure out what went wrong I am seeing signs that lead me to believe the valves were either floating or bouncing off their seats. I am running the Trickflow 270's with the springs for the big roller cam. Bullet ground the cam (.700 lift and [email protected]) and said they should be ok but I suspect they were either light over the nose or too soft of seat pressure for the grind. I did check their pressures and clearances before running them and everything spec'd out with what their published numbers were (and were actually a smidge stiffer). Here is a picture of the tops of the stems that leads me to think it was float. I don't believe it was float though as the intakes and exhaust both look the same and I know it's not as likely to float an exhaust valve. The other reason I lean away from float is that the motor only saw the high side of 6500 a few times and was just street and freeway driven the rest of the time. Nothing else shows any sign of issues (no odd chafing of retainers, no signs of coil bind, no beat up pushrod cups or bent pushrods). The only other odd thing was that the shaft hold down nuts had backed off on the one head that resulted in the failure. This is what leads me to think it was some other harmonic thing that caused the ultimate failure.

Any thoughts?

 

[Kraig Jorgensen]

Would be a tough diagnosis until the head is off and you can look at piston tops and valves. Lift at 50 sounds pretty strong.

 

[Jerry Hall]

I'm going to make my guess. I think you described what went wrong in your post. If the hold downs were not torqued correctly to start with and loosened wouldn't that cause what you are looking at?

 

[Brewzer67]

I'm going to make my guess. I think you described what went wrong in your post. If the hold downs were not torqued correctly to start with and loosened wouldn't that cause what you are looking at?

It would, and that might have been the case but I looked at my notes and I see that checked it off 3 times that I torqued all the hold down bolts. I do three check marks because i usually torque them in two steps and then do a "one more time" double-check to satisfy my OCD. I also have a check I do to make sure that every pushrod is centered in its respective cup on the rockers once the shaft is tightened to make sure nothing shifted while I was snugging things down. I took things down a little further and don't see any indication that anything else was damaged. Pushrods are all straight (7/16 taper .165 wall so I didn't think they would bend), no signs of any valve to piston contact, lifters look good and roll smooth with no measurable spread at the axle, and the cam looks good from what I can see as well. I also did a quick check with some lighter fluid to see if there was any leakage past the intake valve from the port side and that came out clean as well with no leaks. So other than the damage to two rockers and some minor scuffing of a few valve tops I dodged a bullet. I still would like to know the "why" because it just doesn't make sense. Hopefully someone else can weigh in on the pattern on the valves. Here are pic's:

P.S. Happy Birthday!

 

[cryplydog]

How far did the lock nuts back off when you first looked. is your shaft bent now. What happened? did you spit out a few push rods or? All t/f fact. parts, and what is that wear pattern on the lifter.

 

[fbs63]

Disassemble the heads and look at the seating areas on the retainers and keepers. If there is scuffing or metal transfer you have valve float.

 

[Brewzer67]

How far did the lock nuts back off when you first looked. is your shaft bent now. What happened? did you spit out a few push rods or? All t/f fact. parts, and what is that wear pattern on the lifter.

The 2nd nut from the back backed off completely and the center one backed off halfway.

 

[Brewzer67]

How far did the lock nuts back off when you first looked. is your shaft bent now. What happened? did you spit out a few push rods or? All t/f fact. parts, and what is that wear pattern on the lifter.

No pushrods got spit out as it got trapped under the rocker. The lifter looked fine as you can see from the earlier picture posted.

 

[Brewzer67]

Disassemble the heads and look at the seating areas on the retainers and keepers. If there is scuffing or metal transfer you have valve float.

I did that last night. No scuffing, no metal transfer, nothing unusual. The only potential indicator is that wear pattern on the valve stems.

 

[Brandy]

As I understand valve float you would have to see a bent rod, bent valve stem or dinged piston top. Wear, that isn't 'damage' per say would seem more like a clearance/ fastener torque down issue or either an indication that you are about to have an issue due to that wear because of the above. MHO.

 

[HEMI-ITIS]

The 2nd nut from the back backed off completely and the center one backed off halfway.

View attachment 911773 View attachment 911774

This pic make me think the shaft is slightly bent and the hole is elongated..........

 

[Frustration]

The wear on the roller lifter is not normal. Is the lifter bore the correct diameter? It appears the lifter is rocking back and forth in the bore.

 

[PRHeads]

It’s pretty rare that I tear down some heads used in an application like this and only see a single wear pattern on the valve tip.

There can be odd valvetrain harmonics happening at specific rpm, and if the motor is run steadily within that rpm range, things can move around like that.

Pretty normal looking to me.

What’s actually more normal to see on a “race” motor is basically no wear pattern on the tip....... because the motor isn’t run long enough at rpm low enough to not cause some valve rotation and allow a pattern to develop.

It’s pretty easy to test for,......
If the springs have some paint stripes on them...... arrange them so the stripes are all lined up.

Go run the car hard through the gears a few times, up to your self imposed red line.
Pull the valve covers and see if the stripes are all still lined right up.
On the dyno....... after a few pulls, they’re usually all over the place.
Springs are turning...... valves are turning.

Now....... if the springs are marginal for the particular cam profile, then it’s just going to exacerbate the situation...... and there could be an actual “valve float” situation going on as well.
My point with that is...... the multi-pattern isn’t necessarily “float”....... but it could be.

This is one of the reasons if I build a motor, going to the dyno is mandatory.

If there were an actual “float” problem, within what was determined to be the normal operating range....... it would have been found on the dyno, and remedied before the motor got put into the car.

 

[IQ52]

If that is valve float then nearly every engine I have built has had the valves float. If valves didn't rotate we could use square valves.

 

[Brewzer67]

The wear on the roller lifter is not normal. Is the lifter bore the correct diameter? It appears the lifter is rocking back and forth in the bore.

The lifter bore is within tolerances but not bushed and street driven more than anything. I didn't bush them when I switched to the roller because I knew the short block would be rebuilt within the next few years. This little event just sped that up some. Things still Mic ok and so I should be fine.

 

[Budnicks]

What’s actually more normal to see on a “race” motor is basically no wear pattern on the tip....... because the motor isn’t run long enough at rpm low enough to not cause some valve rotation and allow a pattern to develop.

It’s pretty easy to test for,......
If the springs have some paint stripes on them...... arrange them so the stripes are all lined up.

Go run the car hard through the gears a few times, up to your self imposed red line.
Pull the valve covers and see if the stripes are all still lined right up.
On the dyno....... after a few pulls, they’re usually all over the place.
Springs are turning...... valves are turning.

what he said ^^^^^

my 1st immediate thought was, were the valve guides too tight ?
valves &/or valve springs didn't spin much, 1st

the marks on the valve tips, are not a sign of valve float,
not in my experiences

I've seen them on engines that where relatively new
&/or only run a short time
you can usually tell valve float,
the sounds, fluttering & missing, nosing over usually bigtime too
no mistaking it...
it's over revved for the springs/combo

edited;
and the roller rocker tips, are harder metal alloy, than the valves are

 

[HEMI-ITIS]

What are the spring pressures as assembled???

 

[Cranky]

If valves didn't rotate we could use square valves.

Made me laugh but you're right!!

 

[Extremespeed]

The 2nd nut from the back backed off completely and the center one backed off halfway.

View attachment 911773 View attachment 911774

I have never built an engine with roller rockers before so I have a question. Why in the picture of the head that is still assembled are the rocker arms not centered over the center of the valve stems on the two valves in the center of the picture. That alone looks to me like that would cause a binding problem and cause abnormal wear. Just Curious

 

[oldkimmer]

Some of the hold downs are not on the shaft. Kim