During valve float a piston can actually smack a valve on some engines. This usually results in a bent valve or worse.
Valve Float
Pro
Joined: Oct 2004
Posts: 510
Likes: 5
From: Pipe Creek TX
Over the years , I have had and seen, many engines that suffered from pre-mature valve float. Marginal springs will cause power loss from lifters not following the lobe correctly. Extreme float will bang pistons with the valves ; sometimes spitting a keeper or breaking a retainer. I have never seen a keeper come out in one piece; they have always been broken.
I curious why you asked?
I curious why you asked?
Thread Starter
Le Mans Master
Joined: Mar 2010
Posts: 7,049
Likes: 944
From: DFW TX
Over the years , I have had and seen, many engines that suffered from pre-mature valve float. Marginal springs will cause power loss from lifters not following the lobe correctly. Extreme float will bang pistons with the valves ; sometimes spitting a keeper or breaking a retainer. I have never seen a keeper come out in one piece; they have always been broken.
I curious why you asked?
I curious why you asked?
The car was on the dyno and we did 3 pulls. Car ran great everything fine. Turned it off to cool.
Then we started it up and backed it off the dyno and the car sounded terrible. Almost a sound like the belt had some off. After about 10 seconds (and at idle) we killed the car. Pushed it back into the shop and pulled the valve covers. What we saw was the intake valve keeper on the number 2 cylinder just came out completely. It was not broken it was just laying in the head. Of course the valve fell a bit but stayed in the guide and just moved with the piston. Compression check and leak down showed perfect results. The valve was not bent and moves in the guide just fine.
We replaced all the keepers and retainers with brand new hardware and the car is running fine. The keepers and retainers were about 6 months old and were brought brand new on a set of AFR215 heads.
It was scary to say the least, I am just still searching for maybe a reason it could have happened.
Last edited by C7&7; Feb 28, 2012 at 01:21 PM.
Racer
Joined: Dec 2010
Posts: 418
Likes: 0
From: South Central Kansas
The other day I had a strange situation happen to me.
The car was on the dyno and we did 3 pulls. Car ran great everything fine. Turned it off to cool.
Then we started it up and backed it off the dyno and the car sounded terrible. Almost a sound like the belt had some off. After about 10 seconds (and at idle) we killed the car. Pushed it back into the shop and pulled the valve covers. What we saw was the intake valve keeper on the number 2 cylinder just came out completely. It was not broken it was just laying in the head. Of course the valve fell a bit but stayed in the guide and just moved with the piston. Compression check and leak down showed perfect results. The valve was not bent and moves in the guide just fine.
We replaced all the keepers and retainers with brand new hardware and the car is running fine. The keepers and retainers were about 6 months old and were brought brand new on a set of AFR215 heads.
It was scary to say the least, I am just still searching for maybe a reason it could have happened.
The car was on the dyno and we did 3 pulls. Car ran great everything fine. Turned it off to cool.
Then we started it up and backed it off the dyno and the car sounded terrible. Almost a sound like the belt had some off. After about 10 seconds (and at idle) we killed the car. Pushed it back into the shop and pulled the valve covers. What we saw was the intake valve keeper on the number 2 cylinder just came out completely. It was not broken it was just laying in the head. Of course the valve fell a bit but stayed in the guide and just moved with the piston. Compression check and leak down showed perfect results. The valve was not bent and moves in the guide just fine.
We replaced all the keepers and retainers with brand new hardware and the car is running fine. The keepers and retainers were about 6 months old and were brought brand new on a set of AFR215 heads.
It was scary to say the least, I am just still searching for maybe a reason it could have happened.
Keep us posted.
Bob
Thread Starter
Le Mans Master
Joined: Mar 2010
Posts: 7,049
Likes: 944
From: DFW TX
Yeah what is weird is the car ran great for about a month after we just did the heads and cam. Then I went back in for some minor tuning tweaks is why the car was on the dyno again. This situation happened 2 weeks ago Saturday and I have put about 100 miles on it since. However this past Saturday we pulled the valve cover back off along with the valve spring just to look at things. Valve had no abnormal wear, retainer looked great, and the keeper had no strange wear on it either.
So this doesn't sound like I floated a valve?? Just something really bizarre?
So this doesn't sound like I floated a valve?? Just something really bizarre?
Racer
Joined: Dec 2010
Posts: 418
Likes: 0
From: South Central Kansas
Yeah what is weird is the car ran great for about a month after we just did the heads and cam. Then I went back in for some minor tuning tweaks is why the car was on the dyno again. This situation happened 2 weeks ago Saturday and I have put about 100 miles on it since. However this past Saturday we pulled the valve cover back off along with the valve spring just to look at things. Valve had no abnormal wear, retainer looked great, and the keeper had no strange wear on it either.
So this doesn't sound like I floated a valve?? Just something really bizarre?
So this doesn't sound like I floated a valve?? Just something really bizarre?
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Thread Starter
Le Mans Master
Joined: Mar 2010
Posts: 7,049
Likes: 944
From: DFW TX
Drifting
Joined: Feb 2012
Posts: 1,796
Likes: 37
From: skiatook oklahoma
You must be living correct to have not destroyed that engine. WOW Some years ago, i blew a souped up 327, top of value ate a hole in the rocker, rocker pressed down on keepers/spring, keepers popped out, value dropped. Needless to say, it doesnt sound pretty when you try to compress a valve at 10:1 compression at 6K+ rpm.
Last edited by ChevyDave; Feb 28, 2012 at 07:46 PM.
Pro
Joined: Oct 2004
Posts: 510
Likes: 5
From: Pipe Creek TX
Just thinking out-loud ; during valve float ; a correctly seated keeper on a weak spring will usually let the valve hit the piston and the lifter will hammer the lobe and then you bend or break a push rod. If the keepers are too hard ;they will fracture at some point during the process.
You only spit a keeper out of the retainer. Chalk this one up to; you never have seen it all.
You only spit a keeper out of the retainer. Chalk this one up to; you never have seen it all.
