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TR6 Cam and Lifter failure in TR6's
- Thread starter TheSearcherMan
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The original Stanpart drawing states
"If required to test hardness of cams, this to be done before machining.
Brinell hardness to be 235 to 285 on non-chilled surfaces"
If you send me a PM, I can send you a scan of the cam drawing. It does have dimensions. It takes a bit of work to read it.
Bryan
"If required to test hardness of cams, this to be done before machining.
Brinell hardness to be 235 to 285 on non-chilled surfaces"
If you send me a PM, I can send you a scan of the cam drawing. It does have dimensions. It takes a bit of work to read it.
Bryan
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What the web site says about Triumph cam & lifter hardness is probably still true though.Brosky said:
D
OP
TheSearcherMan
Jedi Trainee
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Everyone I have talked to has said nitride does not work on camshafts, however, maybe they didn't know what they were talking about. If I remember right, it don't go deep enough. The answer is a USA made blank, and knowledgeable grinder. Also, everyone SAYS, Triumph didn't crown their lifters, or taper their lobes. It would be interesting to find out if this is really the case. I do not like using a regrind. However, what I am being told is, if it is being reground to the original profile, the hardness is still there. The part number is cast on the stanpart camshaft. If you regrind to a different profile, you will most likely grind thru the hardness. In other words, you don't want to take a CR PI camshaft, and have it re ground to a CP PI camshaft. As I said before, the hardened part of the camshaft is only the part the lifter hits, not the whole lobe, or camshaft. Apparently it is somewhat of a tediouus process. I think it is becoming a lost art due to roller cams. Also, if Triumph cams had the part number cast onto them, and you can't change the profile without grinding thru the chill hardened part, how can someone make a blank nowadays, that can be ground to any profile, without grinding thru the hardened part. What one US supplier told me, they had the blank tested BEFORE it was ground. This is not the way to do it. How do you know you are not grinding thru the hardened part if you don't test one after you grind it? It would have to be done to every profile you grind. However, Rockwell destroys the cam, so they say. I see how small that punch mark is, and have to wonder if it is really destroyed. The way I see it, the suppliers don't want to spend the money for the testing, and destroy a couple cams, let us do their R&D for them, its free.
tomshobby
Yoda
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When Triumph was having cams made the cams would have been subject to quality testing. This would have consisted of pulling a predetermined number of pieces from different phases of production and testing them. Those would then have either been stored in the event there might be problems later or just scrapped. The cams from each batch that were used would have been certified by the testing of those that were pulled and not used.
That little crater from the testing upsets the molecular structure to 7 times the size of the crater. Sure the effect is less as it nears the farthest reaches of the effect but it still causes change. It also would cause a small mushroom effect around the crater. Think of it this way, the metal that was in the crater had to go somewhere. The question is what will the effect be and what will that cause over time as the cam runs.
That little crater from the testing upsets the molecular structure to 7 times the size of the crater. Sure the effect is less as it nears the farthest reaches of the effect but it still causes change. It also would cause a small mushroom effect around the crater. Think of it this way, the metal that was in the crater had to go somewhere. The question is what will the effect be and what will that cause over time as the cam runs.
OP
TheSearcherMan
Jedi Trainee
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You are right Tom. But, here is how I look at it. Is there more risk in having the little mushroom that testing leaves, or, is the greater risk using a camshaft that is soft?
Searcherman,
Just to see if I am following along... I suppose the cam you just sent back appeared to have the lobes and dist. gear in the right place but for some reason the lifters didn't spin - Is that correct? Does that suggest it was from one of the Turkish blanks but perhaps there was an issue with that particular grind?
Thanks,
Bryan
Just to see if I am following along... I suppose the cam you just sent back appeared to have the lobes and dist. gear in the right place but for some reason the lifters didn't spin - Is that correct? Does that suggest it was from one of the Turkish blanks but perhaps there was an issue with that particular grind?
Thanks,
Bryan
This has been interseting and disappointing. I have a rebuilt Spitfire engine that I am getting close to trying to start. I fianlly wnet witha reground cam from BPNW. I researched this for a good while, but searcherman has gone above and beyond.
I noticed APT claims to have good Spitfire cams. Do they have TR6 stuff as well and do they use the same blaks as searcheman described? They also list some special new lifters that are very expensive.
Seems to my simple mind that its time for somebody to mnake roller lifters for these cars. It can't be that darn hard.
I noticed APT claims to have good Spitfire cams. Do they have TR6 stuff as well and do they use the same blaks as searcheman described? They also list some special new lifters that are very expensive.
Seems to my simple mind that its time for somebody to mnake roller lifters for these cars. It can't be that darn hard.
vettedog72
Jedi Knight
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Dr. Brown may have the answer to the circle of TR6 cam development. The circle is "Back to the Future". If the cam fails, its because you did not break it in correctly using 1.21 Jigowatts at precisely 88 MPH.
On the other hand, I predict the "lost art" of making hard steel as well as finding the OEM TR6 lobe profiles will be found. Its hard to believe the spec's for lobe placement on the shaft are lost too. Will it take Germany to make it with quality? Maybe Crane will do it.
On the other hand, I predict the "lost art" of making hard steel as well as finding the OEM TR6 lobe profiles will be found. Its hard to believe the spec's for lobe placement on the shaft are lost too. Will it take Germany to make it with quality? Maybe Crane will do it.
TR6oldtimer
Darth Vader
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I think the old process of heating the entire blank, then quenching it and repeating the process until the desired hardness is reached, then grind to spec has gone away.
Today, they grind the blank to spec then with the use of electro induction to heat the lobes and bearing surfaces and quench until desired hardness is reached. This process use less power and can be done much more rapidly.
Who knows.
Today, they grind the blank to spec then with the use of electro induction to heat the lobes and bearing surfaces and quench until desired hardness is reached. This process use less power and can be done much more rapidly.
Who knows.
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I believe the typical nitride process, there are several variations, will harden the wear surfaces to a depth of about 0.010". Obviously, this would be done after final grinding. As Ray points out, there are several processes that achieve similar results.
You don't want the entire cam to be hardened all of the way through which would make it very brittle. Only the major wear surfaces should be hardened.
It's not hard to track cam/lifter wear during & after break in. If the valve lash is carefully set to start with, the gaps should increase no more than about 0.002". You should be able to reset lash back to spec & have it stay at this setting for a long period of time.
Do make sure that all lifters/push rods continue to have rotation.
If frequent lash checks show continuing increases, something is wearing that shouldn't be, & the cam/lifters are headed for failure.
Someone mentioned that Rockwell hardness testing raises a perimiter area that is above the surface. The raised area can be flattened by careful use of an oil stone so that only a tiny harmless dimple remains. Standard practice, I believe.
D
You don't want the entire cam to be hardened all of the way through which would make it very brittle. Only the major wear surfaces should be hardened.
It's not hard to track cam/lifter wear during & after break in. If the valve lash is carefully set to start with, the gaps should increase no more than about 0.002". You should be able to reset lash back to spec & have it stay at this setting for a long period of time.
Do make sure that all lifters/push rods continue to have rotation.
If frequent lash checks show continuing increases, something is wearing that shouldn't be, & the cam/lifters are headed for failure.
Someone mentioned that Rockwell hardness testing raises a perimiter area that is above the surface. The raised area can be flattened by careful use of an oil stone so that only a tiny harmless dimple remains. Standard practice, I believe.
D
G
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DNK said:
I <span style="font-weight: bold">really</span> don't want to get in this conversation.
martx-5
Yoda
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DNK said:
Don't lose any sleep over this. Whatever will be will be. Just make sure that the oil you're using has enough of the ZDDP stuff in it and that you observe that proper start up and break in procedure. That's all you can do at this point in time. Keep the fingers crossed and hopefully everything will be OK.
I had my original TR3 cam reground, and sometimes think the worst, as I haven't started mine up yet either. I decided that I will do what I should do on start up and let the chips fall where they may. I had Ken Gillanders do the regrind and got the lifters from him (all of them had the Rockwell dimples on them), so hopefully his gazillion years of TR experience will prove to be OK in this matter. But, I still have freted over this. Now is the time to just say whatever happens, happens.
Brosky
Great Pumpkin
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<div class="ubbcode-block"><div class="ubbcode-header">Quote:]All this talk of cam failures sure scares me. Installed Ted's cam about 5 years ago and I still haven't started it yet. What will happen when it does????[/QUOTE]
Good News Don!!!
If you continue with the exact same break in procedure that you are currently using, I can GUARANTEE another five, maybe even ten trouble free years for your cam. :lol:
Good News Don!!!
If you continue with the exact same break in procedure that you are currently using, I can GUARANTEE another five, maybe even ten trouble free years for your cam. :lol: