Facts about the dreaded sticking bucket

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cannondale27
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#11 Post by cannondale27 »

Yes. Soft cams or soft buckets.

wistech
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#12 Post by wistech »

What were hardness of the cams and buckets that caused your failures? What spring pressures did you have? What model of cam was it? Were they the newer buckets, the older short chrome buckets or aftermarket? What type of oil was used?

cannondale27
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#13 Post by cannondale27 »

How about your Speed? Didn't that drop a valve? Cam was shot also? Does spring pressure matter? Doesn't seem to matter since we are using single valve springs which cut pressure by almost half. Maybe it's not spring pressure that is most important, could be frequency and reaction time. That cannot be tested with a spring pressure tester. Who is going to check hardness of cams and buckets? What I am trying to convey here is there is no consitancy and alot of factors. They all need to be eliminated.

wistech
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#14 Post by wistech »

QUOTE (cannondale27 @ Feb 23 2008, 07:51 PM) <{POST_SNAPBACK}>
How about your Speed?Didnt that drop a valve?Cam was shot also?Does spring pressure matter?Doesnt seem to matter since we are using single valvesprings which cut pressure by almost half.Maybe its not spring pressure that is most important could be frequency and reaction time.That cannot be tested with a spring pressure tester.Who is going to check hardness of cams and buckets?What I am trying to convey here is there is no consitancy and alot of factors.They all need to be eliminated.

Many years ago my original unupdated 300 hour speed engine did indeed drop a valve from a worn cam lobe which was one of the reasons I started into the whole R@D program. Did it have soft cams weak springs ..I have no idea. Those cams have been rewelded and reused. I can check the bucket bores for warpage though. I do know that the intake lobe by the water pump and the exhaust lobe by the decomp were both shot but the others 2 were like new. Not the common one.
From the evidence I have seen from engines that come in tight buckets are the number one cause of cam lobe failure and dropped valves. As far as repairing the bucket issues Tim insists that the high spots can not be sanded down and rehoned to smooth out. Well Ive been doing it from day one and guess how many cam lobes have failed (other than the high lift unhardened rough test cam)Ive had go bad regardless of any other factor . Zero Thats well over 160 bucket bores that should have according to Tims "facts" thread here should have dropped valves many years ago.
You just stated that there are a lot of factors yet conclude that your failures must have been because of "soft cams or buckets"
Did you ever consider that maybe just maybe machining the buckets bores and leaving them so tight oil cannot get through them may be at least a factor in why you Tim and others have had so many cam issues? Maybe they are sticking as engine temps warp the head at operating temps. Ive never checked that and Ill bet nobody else has either.
When Tim is boring the buckets is he doing it with the head bolted down and the parts at operating temps?
I know how much some absolutely loath my not doing things the way in their minds are the ONLY way to do it right but hey I know what works and have proved it many times.
We should be trying to do R@D according to results and not preconcieved ideas. I have been seeing way to many assumptions being made lately and it worries me. Lets stick to what we can prove or disprove.
If you cant answer the questions I asked in the last post then just say you dont know or remember . Redirecting the questions gives us no data to use so if you could please share what you know.

wistech
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#15 Post by wistech »

Data please

cannondale27
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#16 Post by cannondale27 »

I have never had a bad cam maybe my use of SG rated Amsoil from day one is reason.I was answering for Timbo who was on phone with me.I think we all agree that sticky buckets is no 1 root cause of worn cams.What we dont agree on is practice of shimming worn springs and boring bucket bores so far they dont hold oil.Show me a manufacturer who bores bucket bores so big they dont hold oil.Show me any other builder who would reuse old springs shimmed to spec.To me it is just common sense that both those practices should not be done.A simple search of the internet will confirm this.Also a search of the Machinists Handbook will tell you what is the standard for hardness of both buckets and cams.Coatings help tremendously but are not a long term solution.Some things dont have to be proven since they are accepted as fact.No need to remake the wheel as they say.

SlOoT
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#17 Post by SlOoT »

I did 2 heads today. Neither of them had sticking buckets, one has about 10 hours, the other a lot more. I did work on the bores a bit so that when put in DRY they fall to the botom and with oil on them they stay in place.

I will also put a 10k RPM rev limit on the engines.

timbomoose
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#18 Post by timbomoose »

Wistech "Tim insists that the high spots can not be sanded down and rehoned to smooth out"

Yes that is a fact a hone distorts the bore have a video to prove from a head that was honed.

Wistech "Did you ever consider that maybe just maybe machining the buckets bores and leaving them so tight oil cannot get through them may be at least a factor in why you Tim and others have had so many cam issues? Maybe they are sticking as engine temps warp the head at operating temps. I've never checked that and I'll bet nobody else has either."

Been tested years ago in an oven bore and became looser when heated and also aluminum expands faster than steel.

Wistech "When Tim is boring the buckets is he doing it with the head bolted down and the parts at operating temps?"

Machining at temps is not necesary oil only needs to hold when the engine is not running. Check any head on any machine clearances on buckets are the same as a Cannondale from steel bucket to the aluminum bore with the same wear limits.
Wistech "I know how much some absolutely loath my not doing things the way in their minds are the ONLY way to do it right but hey I know what works and have proved it many times."

Yes, there is only one correcet way of doing it. That is taking material off only the high spot. When honing you are removing material from the rest of the bore and distorting it. That is a fact.

timbomoose
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#19 Post by timbomoose »

Hardness and metal material facts...
2 sliding materials cannot be the same hardness or gauling or metal mixing will occur. Not hard enough and the metals will wear fast. Different materials hold up better than other ones. Two sliding materials should not be made from the same material. Even at different hardnesses the metals are more likely to mix. Disimilar metals should be used.
How does this affect our cams?
Many, many new cams are not hardened within spec. Good made cams should be cams 58-60 rc and bucket 54-56 rc on the c scale. Alot of new replacement cams are at best 54-56 rc. Which is acceptable for holding up on its own but when mating with a bucket that is the same hardness will still wear because the metals will mix. This will not happen right away because the coating on the cams. Once the coating wears bye bye cam. The cams are not consistant in hardness either. I have checked probably about 40% of the new cams at upper 40's rc which is not strong enough too hold up and have even found a couple in the high 30's which is not even heat treated. Average buckets check from 48-52 which is borderline too soft highest seen 56. Between the sticking buckets poorly hardened cams, and similar overlapping hardness long term survival is unlikely.

For all the borderline hardness cams and buckets and overlapping hardnesses a coated bucket can prevent failure from preventing galling and mixing metals. Earlier Cannondale cams were made from a different material and the buckets had a chrome plating. These cams hold up much better than the later ones. Hardness is almost always in spec on these cams. The only times you see these cams worn is from a sticking bucket, a very weak valve spring, or a section of chrome flaked off on the buckets. These cams usually hold up very well compared to the later ones.

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