Just replaced my retainers due to over-rev
06-12-2010, 08:57 AM
#21
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Originally Posted by slipstream444,Jun 12 2010, 09:39 AM
Your clutch slipped at that speed and spared your engine. The AP1 motor will 'grenade' at 10,800 RPM.
Your situation was almost exactly the same as mine. The only difference is I had a Toda FW, Mugen PP and OEM disc at the time and the setup would occasionally slip from time to time during hard acceleration and downshifts to a high RPM. I currently have a CT FW, ACT PP and an OEM disc. It won't slip in that situation.
I estimated my actual RPM to be around 10,000-10,100. Cracked retainers can occur in that range. Any higher they will crack. All but one intake retainer was stretched, but no cracks. ~10,400 RPM your exhaust valves (with stock valve springs) will bend.
The trick to handling the cotters is to use a magnetic pickup. One strong enough to pick up and hold the cotters, but weak enough you don't have to struggle releasing them during the installation.
Your situation was almost exactly the same as mine. The only difference is I had a Toda FW, Mugen PP and OEM disc at the time and the setup would occasionally slip from time to time during hard acceleration and downshifts to a high RPM. I currently have a CT FW, ACT PP and an OEM disc. It won't slip in that situation.
I estimated my actual RPM to be around 10,000-10,100. Cracked retainers can occur in that range. Any higher they will crack. All but one intake retainer was stretched, but no cracks. ~10,400 RPM your exhaust valves (with stock valve springs) will bend.
The trick to handling the cotters is to use a magnetic pickup. One strong enough to pick up and hold the cotters, but weak enough you don't have to struggle releasing them during the installation.
Oh, I have no doubt my clutch must have slipped (even with the Clutchmaster's Stage 3).
Yeah guys, I am doing a valve adjustment today.
Cheers guys,
Jorge
06-13-2010, 01:21 AM
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CourageOO7 Posted on Jun 11 2010, 09:48 PM
Yes I know but I've not seen any stretched retainers.
Are they stretched as in: you can measure the diameter at the base of the retainer and its oval?
As far as I know metallurgy stretching and cracking are opposites.
There are many pictures of stretched/cracked retainers all over S2ki, fyi.
Are they stretched as in: you can measure the diameter at the base of the retainer and its oval?
As far as I know metallurgy stretching and cracking are opposites.
06-13-2010, 10:14 AM
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Originally Posted by SpitfireS,Jun 13 2010, 04:21 AM
CourageOO7 Posted on Jun 11 2010, 09:48 PM
Yes I know but I've not seen any stretched retainers.
Are they stretched as in: you can measure the diameter at the base of the retainer and its oval?
As far as I know metallurgy stretching and cracking are opposites.
Yes I know but I've not seen any stretched retainers.
Are they stretched as in: you can measure the diameter at the base of the retainer and its oval?
As far as I know metallurgy stretching and cracking are opposites.
06-13-2010, 04:36 PM
#25
Originally Posted by SpitfireS,Jun 13 2010, 03:21 AM
CourageOO7 Posted on Jun 11 2010, 09:48 PM
Yes I know but I've not seen any stretched retainers.
Are they stretched as in: you can measure the diameter at the base of the retainer and its oval?
As far as I know metallurgy stretching and cracking are opposites.
Yes I know but I've not seen any stretched retainers.
Are they stretched as in: you can measure the diameter at the base of the retainer and its oval?
As far as I know metallurgy stretching and cracking are opposites.
Take a wire hanger to demonstrate this process. Initially lightly bend the hanger - once you overcome the elastic limits of the material, the initial bending is where the metal feels to have become slightly 'softer' or weaker. Continue to bend and cycle the material and it gets harder to bend - this is strain hardening. Ultimately once you cycle/bend the material to the point where it seems to be the hardest to bend (ultimate strength), cycling the material further will result in it suddenly becoming much weaker and then snapping.
Any stretching evident in a retainer is a precursor to premature failure. The strain hardening process results in a more 'brittle' material that is more prone to cracks/failure. An over-rev of any magnitude that results in measurable stretching may have pushed past the "ultimate strength" region of the plastic deformation mode and will rapidly fail. It's not an 'if' question at that point - it's when it'll happen.
In AP1s, intake valve float during an over-rev results in the cam lobe repeatedly 'hammering' the valve stem end/retainer assembly instead of smoothly maintaining almost continuous contact (minus valve lash at TDC). This results in plastic deformation that will ultimately weaken both the retainer assembly, and the valve stem end (notch near the end) where the cotters seat. There have been a few over-revs documented that have resulted in the valve stem end snapping off. Retainer failure is much more common.
An over-rev in an USDM AP2 (2.2L) of sufficient magnitude to hurt anything will be self-critiquing - there will be no question there was an over-rev because it will result in bent exhaust valves before damaging intake retainers. Really no hidden time-bomb there.
06-14-2010, 07:10 AM
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It would be nitpicking to say "The cam never touches the valve in the F2x as the rocker is in between".
Actually, it makes the converstion a lot easier to see the cam and rocker as one.
Also, there is no difference between being in VTEC or not.
This is what I think happens during an overrev.
Yes, the valve foats but for a different reason.
Ok, your engine is at 10.000 rpm.
The cam pushes the valve down, as normal.
A little faster than at 9000 rpm but IMO that has little impact, it may! push it down a little deeper due to kinetic energy.
Once the highest point of the cam has passed, the valve spring should push the valve up and against the cam to guide the valve back onto its seat, gently.
But.. the cam is now spinning too fast, IOW the spring is not strong/fast enough to keep up.
The cam is still rotating and more and more "valve clearance" appears.
When the valve finally hits its seat it is not guided by the cam but it hit its seat at full speed.
This is when the damage is done.
The valve suddenly stops, the spring and retainer&cotters are at full speed going up and the kinetic energy of the spring and retainer&cotters causes the retainer to get damaged.
This scenario brings the retainer weight into play as well.
That said: as far as I know Honda used "AP2" retainers in all F2x engines after some time as my '05 F20C2 has "AP2" retainers.
And.. as a result of the valve hammering its seat it is IMO very possible that engines that have had damaged retainers also could have damaged valve seats.
A leakdown might confirm that.
Your example of snapped-off valve stems fits perfectly in this valve float scenario as the force is coming from "below".
How is a cam going to snap-off a valve stem hitting it from above?
Back to the stretching & cracking.
At school I also did the material testing class.
You had to cut 3 bars of C60 steel, 10x5mm - 100mm long IIRC.
(I think I still have them somewhere)
One you had to keep as-is, one you had to get cherry red (harden) and cool in water, the 3rd you had to harden and then temper.
The untouched bar stretched the most but also was the weakest, IOW it had the lowest peak load.
The hardened bar stretched the least but cracked the earliest, it did have a higher peak load.
The hardened & tempered one was the strongest, it did stretch and crack but at even higher peak loads.
IOW... sure, stretching is part of cracking IF one takes the load over the threshold.
Of all of the pics of cracked retainers I've seen it looks like (to me) they just cracked, not stretched & cracked.
Ok, lets say it in a Mythbusters way: 15% stretch, 85% cracked.
Actually, it makes the converstion a lot easier to see the cam and rocker as one.
Also, there is no difference between being in VTEC or not.
This is what I think happens during an overrev.
Yes, the valve foats but for a different reason.
Ok, your engine is at 10.000 rpm.
The cam pushes the valve down, as normal.
A little faster than at 9000 rpm but IMO that has little impact, it may! push it down a little deeper due to kinetic energy.
Once the highest point of the cam has passed, the valve spring should push the valve up and against the cam to guide the valve back onto its seat, gently.
But.. the cam is now spinning too fast, IOW the spring is not strong/fast enough to keep up.
The cam is still rotating and more and more "valve clearance" appears.
When the valve finally hits its seat it is not guided by the cam but it hit its seat at full speed.
This is when the damage is done.
The valve suddenly stops, the spring and retainer&cotters are at full speed going up and the kinetic energy of the spring and retainer&cotters causes the retainer to get damaged.
This scenario brings the retainer weight into play as well.
That said: as far as I know Honda used "AP2" retainers in all F2x engines after some time as my '05 F20C2 has "AP2" retainers.
And.. as a result of the valve hammering its seat it is IMO very possible that engines that have had damaged retainers also could have damaged valve seats.
A leakdown might confirm that.
Your example of snapped-off valve stems fits perfectly in this valve float scenario as the force is coming from "below".
How is a cam going to snap-off a valve stem hitting it from above?
Back to the stretching & cracking.
At school I also did the material testing class.
You had to cut 3 bars of C60 steel, 10x5mm - 100mm long IIRC.
(I think I still have them somewhere)
One you had to keep as-is, one you had to get cherry red (harden) and cool in water, the 3rd you had to harden and then temper.
The untouched bar stretched the most but also was the weakest, IOW it had the lowest peak load.
The hardened bar stretched the least but cracked the earliest, it did have a higher peak load.
The hardened & tempered one was the strongest, it did stretch and crack but at even higher peak loads.
IOW... sure, stretching is part of cracking IF one takes the load over the threshold.
Of all of the pics of cracked retainers I've seen it looks like (to me) they just cracked, not stretched & cracked.
Ok, lets say it in a Mythbusters way: 15% stretch, 85% cracked.
06-14-2010, 02:16 PM
#27
A little nit-picking - but that's alright... and expected. I never stated the cam snaps off the valve end. There are a number of forces at play that ultimately cause that failure, and you covered some of them well enough.
Ultimately the floating valve creates the increased distance between cam, follower and retainer/valve end assembly that initiates the process.
It was easier to illustrate the follower as part of the assembly and not discuss it - as it's not a major functional factor in the damage process other than it's there to transmit the force. It would be hard to determine if it actually helps or hurts in the process without seeing it in action (does it accelerate into the retainer assembly because of the distance or does it dampen some of the force??).
Your materials example illustrates how different treatments effect the mechanical properties of steel. Some treatments take a metal component into the strain hardening portion of the plastic deformation in order to achieve the maximum strength, with the cost of creating a brittle component that is unable to flex and recover. When this is done, the component will not respond elastically, but will stretch until the point it ruptures. It will stretch prior to failing, otherwise the component was already past the ultimate strength portion on the stress-strain curve (in the case of most steel alloys).
Since I have no idea how the retainer is specifically manufactured, what alloy its made from, what type of treatment the material has received, it's much simpler to assume the material is still capable of elastic deformation. Unless you have those specifics, it's difficult to accurately nit-pick the basics.
Ultimately the floating valve creates the increased distance between cam, follower and retainer/valve end assembly that initiates the process.
It was easier to illustrate the follower as part of the assembly and not discuss it - as it's not a major functional factor in the damage process other than it's there to transmit the force. It would be hard to determine if it actually helps or hurts in the process without seeing it in action (does it accelerate into the retainer assembly because of the distance or does it dampen some of the force??).
Your materials example illustrates how different treatments effect the mechanical properties of steel. Some treatments take a metal component into the strain hardening portion of the plastic deformation in order to achieve the maximum strength, with the cost of creating a brittle component that is unable to flex and recover. When this is done, the component will not respond elastically, but will stretch until the point it ruptures. It will stretch prior to failing, otherwise the component was already past the ultimate strength portion on the stress-strain curve (in the case of most steel alloys).
Since I have no idea how the retainer is specifically manufactured, what alloy its made from, what type of treatment the material has received, it's much simpler to assume the material is still capable of elastic deformation. Unless you have those specifics, it's difficult to accurately nit-pick the basics.
06-14-2010, 04:46 PM
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Yea, I did the same to mine... well a budy helped... he was driving it, I let him take it on a B run, and tried to down shift from 5th to 4th hit 2nd. Bent every one of the intake side valves and four on the other side cracked six guides... I got the head re done 3 de. port and pollish farrara Ti valves double springs Ti ritaners and bronze guides with skunk 2 stage 2 cams... Dose any body think there should be any thing else done... so this crap dont happen agen...
06-14-2010, 07:26 PM
#29
Originally Posted by S2K&CBR,Jun 14 2010, 04:46 PM
Yea, I did the same to mine... well a budy helped... he was driving it, I let him take it on a B run, and tried to down shift from 5th to 4th hit 2nd. Bent every one of the intake side valves and four on the other side cracked six guides... I got the head re done 3 de. port and pollish farrara Ti valves double springs Ti ritaners and bronze guides with skunk 2 stage 2 cams... Dose any body think there should be any thing else done... so this crap dont happen agen...
jk
06-15-2010, 01:10 PM
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slipstream444 Posted on Jun 14 2010, 11:16 PM
Hmm....
Yes you did.
I guess.
* This looks like it is stil in the line of thought that the cam is giving the valve a "hammer" during an overrev.
IMO is doesn't (at all)
In a 4-stroke engine it takes an extra piston stroke before a set of valves is pushed down again.
That gives them enough time to close, even during an ovverrev, as long as they are not hit by the piston at TDC.
When the cam starts to push the valve down it is closed, as normal.
At any rpm.
I never stated the cam snaps off the valve end.
In AP1s, intake valve float during an over-rev results in the cam lobe repeatedly 'hammering' the valve stem end/retainer assembly instead of smoothly maintaining almost continuous contact (minus valve lash at TDC). This results in plastic deformation that will ultimately weaken both the retainer assembly, and the valve stem end (notch near the end) where the cotters seat. There have been a few over-revs documented that have resulted in the valve stem end snapping off. Retainer failure is much more common.
I guess.
It was easier to illustrate the follower as part of the assembly and not discuss it - as it's not a major functional factor in the damage process other than it's there to transmit the force *It would be hard to determine if it actually helps or hurts in the process without seeing it in action (does it accelerate into the retainer assembly because of the distance or does it dampen some of the force??).
.
.
IMO is doesn't (at all)
In a 4-stroke engine it takes an extra piston stroke before a set of valves is pushed down again.
That gives them enough time to close, even during an ovverrev, as long as they are not hit by the piston at TDC.
When the cam starts to push the valve down it is closed, as normal.
At any rpm.