Keep Breaking Retainers

[radracr]

Keep breaking retainers...any ideas? Thanks

 

Just rebuilt the heads...ran the both practices and the heat...no problem.

 

About 10 laps into the main...I heard a different exhaust note and immediately shut it down. When I opened the valve covers there was a retainer broke in half...with several others cracked! What gives?!

[HiTech]

ill take along shot here .but happened to me many many years ago ..valve guides sticking just alittle tp high ... when the springs would heat up they lost some tenstion or start to float and let the retainers bottom out onto the guide ....sounds far fetched ..but it happend /////

[jwmbishop]

They are not just breaking - they are floating loose, stressing and then breaking. Spring frequency sends a rebound down the coil stack when the valve slams shut and bounces off the seat. As the rebound runs down the coil the keepers fall loose. Common when using an over rated spring with tall installed height (ie a 145 @ 1.750 installed to 1.775 to lower pressure to 125).

 

Picture this - to disassemble the valves we used a wrist pin that fit the outer edge of the retainer - a sharp rap on the pin sent the keepers flying! 8 quick raps and the valves were all un assembled! Doing this I can "strip" a head and have small parts in the tumbler basket and the head on an oven rack in under 2 minutes per head.

 

Increase your seat pressure with .015 shims on all springs - but measure carefully to make sure you are not binding over the nose. What is your current seat pressure and installed height? On most apps you can go to .750 installed with a 125 seat pressure. The actual problem is ramp speed on closing. The faster it closes the more bounce you get. Get with cam manufacturer and see what they recommend as a faster closing ramp speed will cause this - as this is why they reco specific seat and nose pressures!

 

Also check to make sure you are using the correct keeper for the retainer! There are two different angles and they do not mix and match! And also verify that at full lift you have at least .050 between theretainer and guide top.

 

Valve Float causes* Valvetrain too heavy for the valvesprings

* Worn or weak valve-springs

* Valvesprings mismatched to camshaft profile

* A high rocker-arm ratio that produces excessive valve accelerations

* Incorrect hyd lifter preload

* Rocker contacting retainer

[radracr]

I dropped off my head (and affected parts) to my machine shop this AM. (The machine shop is a very reputable shop in the NW Houston area.) He knows my application inside and out. As a result originally they spec'd out the Comp 926s installed at 1.750". This is yielding ~125# closed, and 330# open. After seeing the damage this AM he identified the Retainers as being the "bad parts". (Enpro's) He also noted that we'll be changing form the stamped keepers to machined keepers as it was clear that they are wearing.

 

I also spoke with cam manufacturer (not related to the spring mfr) and they also stated that the springs were installed "right on the money."

 

The setup is 10* retainers / keepers.

 

There was no indication, either from the sound of the motor going down the back straight, or visually on the springs that it's valve float. It appears that it is the mating surfaces between the keepers and retainers.

[jwmbishop]

It appears that it is the mating surfaces between the keepers and retainers.

With his eyes being the ones on the problem I can agree very easily with this. the stamped keepers are not reliable for spreading the heat load across the entire piece, and the retainers themselves will brinell very easily once the wear starts. Once that happens cracks and splits are the next logical progression as the two (or rather three) pieces start work hardening at different rates. As e sounds like he is on top I am sure he knows to dress the edges of the keeper groove should not be "sharp" to the touch.

 

As for hearing float - if you can hear it it's already way into damaging zone! I have seen float show up on the dyno (indicators of rapid increase of exh temp, vacuum dropping or fluctuating with out a corelating load change, intake charge temp increase or fluctuations in torque at steady rpm and throttle) well before the operator or booth tech actually hears the note change or stumble - which is a crossing of the cylinder charges. Float also shows up on a scope - but very few folks use them any more.

[radracr]

The hits keep coming...

 

I just got the head with the bent valve back rebuilt and ready to go with a new valve, new retainers and valve locks. The retainers and keepers are an improvement. The other head was still on the motor and they informed me which shims went where so it was a plug-and-play. Everything was going fairly smooth...I did have to use the wrist pin and hammer to loosen the locks as they were wedged in...2 cylinders done 2 to go...when I went to the install the spring and remove the spring compressor on the third cylinder I noticed that the spring / retainer assembly was loose. Closer inspection revealed that the exhaust valve height had raised significantly...Off came the head...and there in the combustion space was the...........head of the valve...looking at the fracture pattern its as if the head had sheared off! And these valves are Ferrea 5000s!

 

Called the machine shop and to say the least he was stunned. The question now is how many other valves are on the verge.

 

There were no indications on the piston of any contact before, during or after the install.

 

One more chapter in the book.

 

Its clear, based upon the wear marks on the locks that the load was being unevenly distributed between the lock and retainer - mainly along the bottom 50% of the assembly. This leads me to believe the the crack originated on the bottom on the retainer and propagated to the top and then across.

[4cylfordz]

my first question is how old are the valves, I usually recomend to peoplle to replace them at least every two seasons for the exhaust depending on the circuit and sometimes every season, and ferra valves are no exception, I've broke plenty of them on my bench removing the retainers and it appears that the heads just shear off. over time valves fatigue creating a weakend spot on the stem where they are narrowed for improved flow, the cause for the fatigue is the valve to seat contact area and guide is not completely perfect. not saying that your machinist didn't do a great valvejob it is because of the clearance that must be given to the valve guide it will let it hit slightly offcenter in the seat bending the valve ( because they are really hot and fragile especially the exhaust) and the pulling it straight when it reaches the closed position. take any head run it for one night then pull any valve out of that head and put it in a valve grinder and it will chatter just a little bit befor it smoothes out.

[jwmbishop]

rad - those are two piece valves. Not being funny, they are made by spinning the stem stock in one direction and the valve head in another - and literally welding the two pieces together via friction. And if I recall these are tulip shaped valves (aka cupped) - the only time I like using tulips are when the head is over milled and we need the extra cc's in the chamber to meet rules AND they are undercut. Yes these shave weight - but at the cost of longevity. No problem if you are a big budget and throw em away (or hand em down) every year.

 

It is quite normal to see the keeper retainer contact in the lower (usually about 70% though) part of the angle. this is because they are made to contact low and as the loads increase and cause the retainer to want to cup the contact load moves upwards. Its when you see the brinelling up top of the angle that the keepers are toast. man I can't tell you how often I have literally yelled at my clients - bring me BOTH heads!

 

Why do two piece valves break? # 1 - overheating. NOT the cooling system - valve overheat from the exhaust gasses. Lots of timing and running lean are an example. If you are jet checking in the afternoon and hitting right on the money, by main event you may be on the lean side (as the air temp drops the relative humidity does too - both effecting afr) #2 too narrow a face/seat contact - not enough heat transfers off the valve - especially when using aggressive cam profile (reducing the time on seat). This also includes a mis match in the grinds (worn or inaccurate truing fixtures for seat grinder, and or worn or inaccurate indicator on valve grinder)! #3 too narrow a margin - in other words it saw the the grinder once too often. #4 float. Bouncing off the seat doubles the number of high temp impacts to the seat surface and reduces the time for heat transfer. #5 fuel - Lead additives don't just lube the seat - the lead flowing out with the gas carries a bit of heat with it and cools the valve! This is one of the reasons pipe color is not a reliable indicator of mixture when running unleaded fuels.

 

Sounds to me like you have worn valves and pushed the envelope a little too far - heat could also be a factor in the retainer breakage! Maybe a slight stick from and overheated stem growing into the clearance. I would have to look at the guides with a very high magnifier and bright light to tell. the signs are subtle and can only be explained with a comparison with your eyes on them to see the differences. One good indicator of high combustion temp would be the head gasket flame ring - the edge exposed to the flame looks like a micro hammer peened it (and has a stressed white color i the metal itself after cleaning any carbon off with brakleen)!

 

4cyl - yep you are all over that one! that .0015 stem clearance lets that valve go all over the place! they usually find their own relative sweet spot - but as they rotate (which we hope they are!) you get walk all over. And its always a trade off - loosen the guide and more heat stays on the valve, tighten the guide and more guide/stem wear or seizure occurs.

 

I STRONGLY recommend one piece valves - they last as much as 4 seasons when properly maintained and tuned! (and only lapped in between full guide/valve jobs). But the question is do your rules allow it? Often times tracks think by outlawing the high end valves that costs are reduced when I have seen just the opposite be the result in cylinder head small parts when failures take out something else (and the true cause can be missed in the tear down inspection.

[Boernebullet]

Ferrea 5000 series valves are a one piece forging and a very durable valve for the price. The valve may have broke when hit with a hammer if the piston was up.

 

Greg Spreen