Why valves do not float - what cracks retainers
Thread Starter
Joined: Jan 2006
Posts: 4,953
Likes: 25
From: 17 ft below sea level.
You've mentioned the head-on-a-bench test before.
I wish I could have seen it with my own eyes.
If that happened I would not have to ask this: what was the temperature of the head?
Was there oil flow to the cam journals?
Just to make things clear without a doubt: this was an F20/F22 head?
Still..
At 4500 rpm everything is fine, I think we all agree on that, 9k-all-day.
Talk us through what happens between 4500 and 5350 rpm in your opinion.
Do valves keep up with the cam up to a certain rpm, just like they do at 4500 rpm?
A few rpm extra and they suddenly move slower than before to not close during the following 180 degree cam rotation - where there is no lobe?
And where is this cross-over rpm point?
A valve pushed up by a spring does not slow down half way, the spring keeps accelerating the valve.
It doesn't make sense.
I wish I could have seen it with my own eyes.
If that happened I would not have to ask this: what was the temperature of the head?
Was there oil flow to the cam journals?
Just to make things clear without a doubt: this was an F20/F22 head?
Still..
At 4500 rpm everything is fine, I think we all agree on that, 9k-all-day.
Talk us through what happens between 4500 and 5350 rpm in your opinion.
Do valves keep up with the cam up to a certain rpm, just like they do at 4500 rpm?
A few rpm extra and they suddenly move slower than before to not close during the following 180 degree cam rotation - where there is no lobe?
And where is this cross-over rpm point?
A valve pushed up by a spring does not slow down half way, the spring keeps accelerating the valve.
It doesn't make sense.
Moderator
Joined: Jul 2002
Posts: 22,386
Likes: 1,838
From: Long Island, New York
Head temp was about 180. It was an all original 2001 AP1 head with 100k miles. The cam caps were blemmed up so we used them for the test. We enlarged the holes and gravity fed them.
I'll try to word out some more later tonight...
I'll try to word out some more later tonight...
Banned
Joined: Dec 2003
Posts: 7,662
Likes: 1
From: Long Beach, CA
So it is float? The spring isn't strong enough to follow the cam back up and hits hard? It makes sense that a springs spring rate can be overpowered and a small delay on return will be added from inertia. I'm surprised people would think the valve could float an entire revolution though.
^ Ive always wondered just how much would make the spring overpowered in the aspect that many mfgrs. sell their springs as the increased spring rates give some resistance to the mentioned float concept.
Im running the BC Duals with Steel retainers and according to BCs spec sheets, they are 84lbs at the seat
Banned
Joined: Dec 2003
Posts: 7,662
Likes: 1
From: Long Beach, CA
My findings differ...maybe there are characteristics or factors that cause differnt scenarios.
Here is my finding..not on the web, but my own in house test conducted with a local marine racing engine builder of 45 years experience:
When spinning a camshaft at 5500 rpms (the crankshaft speed it takes to split retainers, plus a few hundred) and using other controls...
We were able to reproduce splitting retainers. The noise it makes sounds like a large electric transformer buzzing. I jumped because I though the light above us shorted out
At this RPM, we were able to place a .030 plastic stint between the valve and the head at 5350rpm ...The valve did not cut the stint, it didnt leave a blemish.
The valve did not close. It was opened again by the cam before it would close all the way.
Here is my finding..not on the web, but my own in house test conducted with a local marine racing engine builder of 45 years experience:
When spinning a camshaft at 5500 rpms (the crankshaft speed it takes to split retainers, plus a few hundred) and using other controls...
We were able to reproduce splitting retainers. The noise it makes sounds like a large electric transformer buzzing. I jumped because I though the light above us shorted out
At this RPM, we were able to place a .030 plastic stint between the valve and the head at 5350rpm ...The valve did not cut the stint, it didnt leave a blemish.
The valve did not close. It was opened again by the cam before it would close all the way.
This was on an ap1 head?! Thats scary, is that what honda had intended?
Joined: Jun 2010
Posts: 5,539
Likes: 6
From: McKinney, TX
I agree with Bill....and I disagree with the OP. Valve's DO float. It has already been proven that they do. So why the whole "reason for cracked retainers" argument comes up over and over again is beyond me. It's pretty plain and simple. Valves float, cam comes back around and slams down on the valve. Simple as that.
Joined: Jan 2011
Posts: 2,207
Likes: 7
From: Long Island
Originally Posted by Billman250' timestamp='1349060910' post='22048725
My findings differ...maybe there are characteristics or factors that cause differnt scenarios.
Here is my finding..not on the web, but my own in house test conducted with a local marine racing engine builder of 45 years experience:
When spinning a camshaft at 5500 rpms (the crankshaft speed it takes to split retainers, plus a few hundred) and using other controls...
We were able to reproduce splitting retainers. The noise it makes sounds like a large electric transformer buzzing. I jumped because I though the light above us shorted out
At this RPM, we were able to place a .030 plastic stint between the valve and the head at 5350rpm ...The valve did not cut the stint, it didnt leave a blemish.
The valve did not close. It was opened again by the cam before it would close all the way.
Here is my finding..not on the web, but my own in house test conducted with a local marine racing engine builder of 45 years experience:
When spinning a camshaft at 5500 rpms (the crankshaft speed it takes to split retainers, plus a few hundred) and using other controls...
We were able to reproduce splitting retainers. The noise it makes sounds like a large electric transformer buzzing. I jumped because I though the light above us shorted out
At this RPM, we were able to place a .030 plastic stint between the valve and the head at 5350rpm ...The valve did not cut the stint, it didnt leave a blemish.
The valve did not close. It was opened again by the cam before it would close all the way.
This was on an ap1 head?! Thats scary, is that what honda had intended?
Joined: Jun 2009
Posts: 3,689
Likes: 21
I thought they were Belgian as well! But, not so!
Registered User
Joined: Jun 2010
Posts: 2,807
Likes: 0
From: Melbourne
I agree with Bill....and I disagree with the OP. Valve's DO float. It has already been proven that they do. So why the whole "reason for cracked retainers" argument comes up over and over again is beyond me. It's pretty plain and simple. Valves float, cam comes back around and slams down on the valve. Simple as that.
Joined: Jun 2010
Posts: 5,539
Likes: 6
From: McKinney, TX
Originally Posted by jordanksartell' timestamp='1349123983' post='22050621
I agree with Bill....and I disagree with the OP. Valve's DO float. It has already been proven that they do. So why the whole "reason for cracked retainers" argument comes up over and over again is beyond me. It's pretty plain and simple. Valves float, cam comes back around and slams down on the valve. Simple as that.
Joined: Apr 2008
Posts: 306
Likes: 1
From: Orange County, California
My findings differ...maybe there are characteristics or factors that cause differnt scenarios.
Here is my finding..not on the web, but my own in house test conducted with a local marine racing engine builder of 45 years experience:
When spinning a camshaft at 5500 rpms (the crankshaft speed it takes to split retainers, plus a few hundred) and using other controls...
We were able to reproduce splitting retainers. The noise it makes sounds like a large electric transformer buzzing. I jumped because I though the light above us shorted out
At this RPM, we were able to place a .030 plastic stint between the valve and the head at 5350rpm ...The valve did not cut the stint, it didnt leave a blemish.
The valve did not close. It was opened again by the cam before it would close all the way.
Here is my finding..not on the web, but my own in house test conducted with a local marine racing engine builder of 45 years experience:
When spinning a camshaft at 5500 rpms (the crankshaft speed it takes to split retainers, plus a few hundred) and using other controls...
We were able to reproduce splitting retainers. The noise it makes sounds like a large electric transformer buzzing. I jumped because I though the light above us shorted out
At this RPM, we were able to place a .030 plastic stint between the valve and the head at 5350rpm ...The valve did not cut the stint, it didnt leave a blemish.
The valve did not close. It was opened again by the cam before it would close all the way.