Worn GT Cams - Can they be fixed?
07-25-2015, 01:28 AM
#16
Archive Gatekeeper
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DLC'ed lifters:
Simard cams and DLC'ed lifters in the Turquoise '91:
DLC'ed lifters and re-ground GT cams in my GTS:
After 2500 miles:
Simard cams and DLC'ed lifters in the Turquoise '91:
DLC'ed lifters and re-ground GT cams in my GTS:
After 2500 miles:
07-25-2015, 02:36 AM
#18
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Yup. Intentional.
07-25-2015, 07:31 AM
#20
Pro
OK, but what is it about GT cams in particular that seems to make them so fragile?
Poor OEM metallurgy? Lubrication? Lobe profile causing excessively high acceleration rates and overshoot? Spring design not controlling overshoot? High temp loss of oil viscosity to below that required by the OEM design?
Poor OEM metallurgy? Lubrication? Lobe profile causing excessively high acceleration rates and overshoot? Spring design not controlling overshoot? High temp loss of oil viscosity to below that required by the OEM design?
07-25-2015, 01:19 PM
#21
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OK, but what is it about GT cams in particular that seems to make them so fragile?
Poor OEM metallurgy? Lubrication? Lobe profile causing excessively high acceleration rates and overshoot? Spring design not controlling overshoot? High temp loss of oil viscosity to below that required by the OEM design?
Poor OEM metallurgy? Lubrication? Lobe profile causing excessively high acceleration rates and overshoot? Spring design not controlling overshoot? High temp loss of oil viscosity to below that required by the OEM design?
The wear always starts on the "backside" of the lobe, where the lifter "lands" after loosing contact with the lobe.
GTS models also suffer from this same problem.
Cure with slightly stiffer springs and/or lighter lifters and/or DLC coating on lifters.....after you solve the pitting problems.
07-25-2015, 02:31 PM
#22
Nordschleife Master
DLC and cast iron cams
It's interesting that you guys are getting DLC coated lifters to last with cast iron cams. A couple years back people I spoke to didn't want to coat lifters to run on cast iron cams, only on steel cams. The cast iron somehow risked the coating flaking off and destroying the engine. I guess the technology has advanced in five years.
07-25-2015, 02:58 PM
#23
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It's interesting that you guys are getting DLC coated lifters to last with cast iron cams. A couple years back people I spoke to didn't want to coat lifters to run on cast iron cams, only on steel cams. The cast iron somehow risked the coating flaking off and destroying the engine. I guess the technology has advanced in five years.
Cast iron will not accept and retain DLC. Most steel will. There are several automakers now using DLC lifters with cast iron cams to help with cam wear and internal engine friction.
BTW...DLC isn't a traditional spray on coating that can flake off. It's a process where the carbon is actually impregnated into the surface of the steel. "True DLC" (there are companies "faking it') is very expensive.....the equipment to do it is apparently very costly.....Calico claims that their machine with its 11" cylinder cost over 1 million dollars. And the cost to run that machine is not insignificant. They charge about $2000 for every "batch" of pieces they run through that small cylinder....
Imagine what it costs to fill a transmission full of pieces that look like this:
What I'm doing here isn't "Internet Search Engine" stuff....things actually happen in real life and real time, here. This gives me first hand results of what works and what doesn't work. (Also gives me complete control over what details I choose to reveal.)
__________________
greg brown
714 879 9072
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
07-25-2015, 03:11 PM
#24
Oh man - what piece is that from what trans?
I bet it's cheaper in the UK where f1 lives.
I bet it's cheaper in the UK where f1 lives.
07-25-2015, 04:07 PM
#25
Rennlist Member
Worn GT Cams - Can they be fixed?
Originally Posted by Rob Edwards
DLC'ed lifters:
Simard cams and DLC'ed lifters in the Turquoise '91:
DLC'ed lifters and re-ground GT cams in my GTS:
After 2500 miles:
Simard cams and DLC'ed lifters in the Turquoise '91:
DLC'ed lifters and re-ground GT cams in my GTS:
After 2500 miles:
07-25-2015, 04:35 PM
#26
Archive Gatekeeper
Rennlist Member
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Yes. that's about $6K worth of Simard cams and lifters right there. The **** quotient is high in that motor.
07-25-2015, 04:40 PM
#27
Rennlist Member
Worn GT Cams - Can they be fixed?
Originally Posted by Rob Edwards
Yes. that's about $6K worth of Simard cams and lifters right there. The **** quotient is high in that motor.
07-25-2015, 08:44 PM
#28
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07-25-2015, 08:51 PM
#29
Archive Gatekeeper
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Oh yeah. Forgot about those. OK- more than $6K.
07-25-2015, 11:26 PM
#30
They must have been confused about what you were asking. They must have thought you wanted to treat the cast iron cam itself.
Cast iron will not accept and retain DLC. Most steel will. There are several automakers now using DLC lifters with cast iron cams to help with cam wear and internal engine friction.
BTW...DLC isn't a traditional spray on coating that can flake off. It's a process where the carbon is actually impregnated into the surface of the steel. "True DLC" (there are companies "faking it') is very expensive.....the equipment to do it is apparently very costly.....Calico claims that their machine with its 11" cylinder cost over 1 million dollars. And the cost to run that machine is not insignificant. They charge about $2000 for every "batch" of pieces they run through that small cylinder....
Imagine what it costs to fill a transmission full of pieces that look like this:
What I'm doing here isn't "Internet Search Engine" stuff....things actually happen in real life and real time, here. This gives me first hand results of what works and what doesn't work. (Also gives me complete control over what details I choose to reveal.)
Cast iron will not accept and retain DLC. Most steel will. There are several automakers now using DLC lifters with cast iron cams to help with cam wear and internal engine friction.
BTW...DLC isn't a traditional spray on coating that can flake off. It's a process where the carbon is actually impregnated into the surface of the steel. "True DLC" (there are companies "faking it') is very expensive.....the equipment to do it is apparently very costly.....Calico claims that their machine with its 11" cylinder cost over 1 million dollars. And the cost to run that machine is not insignificant. They charge about $2000 for every "batch" of pieces they run through that small cylinder....
Imagine what it costs to fill a transmission full of pieces that look like this:
What I'm doing here isn't "Internet Search Engine" stuff....things actually happen in real life and real time, here. This gives me first hand results of what works and what doesn't work. (Also gives me complete control over what details I choose to reveal.)