ArdWrknTrk Posted April 3 Share Posted April 3 Interesting read https://www.sciencedirect.com/science/article/abs/pii/S0043164821003124 The dimensional tolerance, metallurgy and surface finish was nothing like it is today. Why do you think that cars use 0W20 oil today? It's not just to reduce pumping losses.... 💡 Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 3 Share Posted April 3 Comp definitely had a batch of soft cores years ago. But they could have solved it by checking brinell or Rockwell and sending the batch out for heat treat. But they jumped the shark, got bought out, and won't listen to the guys who had been grinding their cams for decades.... Proper break-in involves plenty of oil, with ZDDP, and varying the rpms for at least 1/2 hour. (Don't let it drop below 2k and you'll be okay) Jim, I have seen a number of pictures of failed cams and lifters including roller lifters. The flat tappets I have seen show what is called "spalling" where the hard surface cracks and then essentially crumbles. Most of the lifters are being outsourced to China and I am sure if I could get one of the Chinese lifters and an older US made one (a) I would bet the US made would be a good alloy steel like 4340 and the Chinese will be a carbon steel (b) the Chinese lifters appear to be case hardened, and once the case hardened layer cracks it starts to flake off and the softer metal underneath just wears rapidly. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 3 Share Posted April 3 Jim, I have seen a number of pictures of failed cams and lifters including roller lifters. The flat tappets I have seen show what is called "spalling" where the hard surface cracks and then essentially crumbles. Most of the lifters are being outsourced to China and I am sure if I could get one of the Chinese lifters and an older US made one (a) I would bet the US made would be a good alloy steel like 4340 and the Chinese will be a carbon steel (b) the Chinese lifters appear to be case hardened, and once the case hardened layer cracks it starts to flake off and the softer metal underneath just wears rapidly. I'm not saying there isn't bad metallurgy. But when you look at something like the old Chevy Berettas, you know, that those cams weren't made in China, and neither were the lifters.... Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 3 Share Posted April 3 I'm not saying there isn't bad metallurgy. But when you look at something like the old Chevy Berettas, you know, that those cams weren't made in China, and neither were the lifters.... Chevy V8s were bad about wiping lobes, usually an exhaust so the engine would pop back through the carburetor. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 3 Share Posted April 3 Chevy V8s were bad about wiping lobes, usually an exhaust so the engine would pop back through the carburetor. Strange things happen when the exhaust has nowhere to go, it's going to find some way out! Link to comment Share on other sites More sharing options...
mat in tn Posted April 3 Share Posted April 3 Strange things happen when the exhaust has nowhere to go, it's going to find some way out! spent gasses seem to retain a little bit of pressure. it's not like it is bled off by the power stroke and a closed exhaust valve, even late opening is going to pop back. there are no points to assume are unimportant. the crown must fit the cam so that the driving surface of the cam is well offset to cause the lifter to rotate as it reciprocates. this rotation allows the cam to polish the lifter and vice versa. if not, then the cam wears a groove into the lifter face and creates a detent and it's all over from there. remember, the cam is rotating and using all of its surface against a spinning disc face. if not spinning then the contact point gets "ground" and super-heated. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 3 Share Posted April 3 spent gasses seem to retain a little bit of pressure. it's not like it is bled off by the power stroke and a closed exhaust valve, even late opening is going to pop back. there are no points to assume are unimportant. the crown must fit the cam so that the driving surface of the cam is well offset to cause the lifter to rotate as it reciprocates. this rotation allows the cam to polish the lifter and vice versa. if not, then the cam wears a groove into the lifter face and creates a detent and it's all over from there. remember, the cam is rotating and using all of its surface against a spinning disc face. if not spinning then the contact point gets "ground" and super-heated. This is why a really fubar cam chain spits back through the carb and can't get out of its own way The charge has multiple times the amount of fuel it really wants, and the valves won't close in time to build decent compression. Link to comment Share on other sites More sharing options...
viven44 Posted April 5 Share Posted April 5 This is why a really fubar cam chain spits back through the carb and can't get out of its own way The charge has multiple times the amount of fuel it really wants, and the valves won't close in time to build decent compression. My boss asked me to differentiate myself at the workplace Link to comment Share on other sites More sharing options...
essmaker Posted April 5 Share Posted April 5 My boss asked me to differentiate myself at the workplace Lol. And backed in like a boss! Link to comment Share on other sites More sharing options...
viven44 Posted April 5 Share Posted April 5 Lol. And backed in like a boss! Yes sir! Proud of the Bullnose! Gotta show it. Link to comment Share on other sites More sharing options...
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