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turbo cam
https://slantsix.org/forum/viewtopic.php?t=51279		 Page 2 of 3
Author:  olafla [ Tue Apr 23, 2013 9:59 pm ]
Post subject: 
Bill, a hydraulic cam for the SL6 could also be an interesting solution for a high-lift cam in a relatively low rpm engine. I know Dolmetsch made a special hydraulic grind for his little dragster.

Olaf.
Author:  69val6 [ Wed Apr 24, 2013 5:35 pm ]
Post subject:  Turbo Cam
I'm happy to see so much interest in this subject. Several good responses. I just need to take some time and make some phone calls. Does anyone know if the cam company in Oregon(I think) that custom grinds cams uses the GM lifter diameter or the Mopar size?

Thanks,

Joel Harris
Author:  billdedman [ Wed Apr 24, 2013 9:40 pm ]
Post subject: 
Quote:
Bill, a hydraulic cam for the SL6 could also be an interesting solution for a high-lift cam in a relatively low rpm engine. I know Dolmetsch made a special hydraulic grind for his little dragster.

Olaf.
Olaf,

Thanks for the response!

Maybe I just don't understand the situation here, but as I remember, it was a matter of the edge of the lifter doing damage to the cam lobe because of too steep an angle of "attack" as the cam rotated to bring the lifter from zero-lift to maximum-lift. The short-duration cams (210-degrees of duration @ .050"-lift) that we use in these turbo motors are grouind that way of necesssirty, to prevent losing boost through the open exhaust valve on the overlap cycle. That short duration reduces the amount of time between no lift and maximum lift, to the point that this angle becomes so steep that the lifter/cam interface becomes a real problem. Add more duration, so you can start the lifter's action earlier, and the angle of attack can become less... and ditto on the down-side as the valve closes. But then you have a cam that wastes your boost...

I fail to understand how a hydraulic lifter's lash-controlling mechanism can affect that troublesome scenario. The hydraulic lifters are the same diameter as the solids., so the troublesome geometry problem is the same...

What am I missing???

Bill
Author:  DusterIdiot [ Wed Apr 24, 2013 10:29 pm ]
Post subject:  Depends...
Quote:
Does anyone know if the cam company in Oregon(I think) that custom grinds cams uses the GM lifter diameter or the Mopar size?
They will check it depending on the stick and engine, or what you request...if you request a grind on a chrysler blank then they check it with a .904 mopar lifter...If you tell them you are running a mopar BB with sleeved lifter bores for a .842 lifter they will check it using that Chevy Lifter...

I will be returning to OCG late next week to pick up two grinds I had them run for me.

Quote:
Maybe I just don't understand the situation here, but as I remember, it was a matter of the edge of the lifter doing damage to the cam lobe because of too steep an angle of "attack" as the cam rotated to bring the lifter from zero-lift to maximum-lift. The short-duration cams (210-degrees of duration @ .050"-lift) that we use in these turbo motors are grouind that way of necesssirty, to prevent losing boost through the open exhaust valve on the overlap cycle. That short duration reduces the amount of time between no lift and maximum lift, to the point that this angle becomes so steep that the lifter/cam interface becomes a real problem. Add more duration, so you can start the lifter's action earlier, and the angle of attack can become less... and ditto on the down-side as the valve closes. But then you have a cam that wastes your boost...
This is all true at lower rpm the juice lifter would make the cam act like the short duration cam at street speed, then at high rpm at the strip the boost would blow through at higher rpm lowering the performance level somewhat. On a NA engine this allows for good street manners and driving, but allowing for good high rpm passes at the strip or while passing. OEM developed the roller to overcome that limitation in lobe profile so they get max lift fast and slam the valve shut again, those cams are really not in the cards for us (although I do have one on my bench that OCG ground with the 828 profile for a mockup for me- 224 duration@.050, .503 lift at 1.5, degree wheel using a mopar lifter showed that it has zero overlap...maybe i should get a blowdryer and see how the cam works since it can't blow the boost out it's ass at any rpm-)

-D.Idiot
Author:  billdedman [ Thu Apr 25, 2013 12:43 am ]
Post subject:  Re: Depends...
This is all true at lower rpm the juice lifter would make the cam act like the short duration cam at street speed, then at high rpm at the strip the boost would blow through at higher rpm lowering the performance level somewhat. On a NA engine this allows for good street manners and driving, but allowing for good high rpm passes at the strip or while passing. OEM developed the roller to overcome that limitation in lobe profile so they get max lift fast and slam the valve shut again, those cams are really not in the cards for us (although I do have one on my bench that OCG ground with the 828 profile for a mockup for me- 224 duration@.050, .503 lift at 1.5, degree wheel using a mopar lifter showed that it has zero overlap...maybe i should get a blowdryer and see how the cam works since it can't blow the boost out it's ass at any rpm-)

-D.Idiot[/quote]

I don't see OEM hydraulic lifters losing oil from their cylinder quickly enough to significantly affect duration at ANY rpm,; That's what Rhoads lifters are designed to do; quick leakdown at low rpm, but not quick enough to affect duration (or, lift) at high rpm. Maybe that's what you meant...

At any rate, you pointed out that that won't work well in a turbo'd engine and I completely agree with you on that!

That cam with zero overlap that you described, might be a really good turbo cam; try it and let us know!

Thanks for your input!

Bill
Author:  olafla [ Thu Apr 25, 2013 10:40 pm ]
Post subject: 
Quote:
the troublesome geometry problem is the same...
What am I missing???
Nothing!

Unless you count torn out strands of hair, and sleep! 8)

Olaf
Author:  CNC-Dude [ Fri Apr 26, 2013 11:53 pm ]
Post subject:  Re: Depends...
I don't see OEM hydraulic lifters losing oil from their cylinder quickly enough to significantly affect duration at ANY rpm,;

100 or so lbs of valve spring pressure pushing back against the lifter will override only 30 or 40 lbs of oil pressure trying to prevent it....
Author:  emsvitil [ Sat Apr 27, 2013 12:43 am ]
Post subject:  Re: Depends...
Quote:
I don't see OEM hydraulic lifters losing oil from their cylinder quickly enough to significantly affect duration at ANY rpm,;

100 or so lbs of valve spring pressure pushing back against the lifter will override only 30 or 40 lbs of oil pressure trying to prevent it....
Lifters have a check-valve internally, so they don't leak back against the oil pressure.

The slight loss is leakage from tolerances.
Author:  Jerame_c [ Fri Jul 19, 2013 10:44 pm ]
Post subject: 
Just a thought on the zero overlap cam grind you mentioned. I read a whitepaper recently on the cam setup for the 2.5 Chrysler turbo and those came stock with a zero overlap cam and were pretty cool.
Author:  terrylittlejohn [ Thu Jul 25, 2013 12:44 pm ]
Post subject: 
I think It was lou that visited cameron tilley in au, what cam profiles was he running on his engines? I'm not running turbo but I just stuck with the best cam I had in my n/a high comp engine and used it in a lower comp bottom end and boosted it. I`m not sure if I am running the optimum cam profile. :?
Author:  Dart270 [ Fri Jul 26, 2013 5:01 am ]
Post subject: 
I asked Cameron about this and he had tried several cams. He really didn't see much difference! The biggest one he tried was the old 228 @ 0.050" 0.460" Crane cam with 108 LSA, but his latest 630 HP and such was with a smaller one.

Lou
Author:  terrylittlejohn [ Fri Jul 26, 2013 1:26 pm ]
Post subject: 
did he use any RDP cams or just same intake/exhaust duration?
Author:  Dart270 [ Sat Jul 27, 2013 3:27 am ]
Post subject: 
He has used many RDPs (4-8 deg more on int) on his NA motors, but he did not tell me about the turbo motor.

FWIW, I ordered a smallish RDP cam (Oregon) for my next turbo Dart motor incarnation, due out in late 2014. 224/219 @ 0.050", 113 LSA, 0.470/0.437" lift.

Lou
Author:  terrylittlejohn [ Sat Jul 27, 2013 6:21 pm ]
Post subject: 
where did you get the dimension ? seem a lot of difference in the lift profile. I have only order one rdp cam but haven`t worked with it yet.
Author:  Dart270 [ Sun Jul 28, 2013 4:00 am ]
Post subject: 
I just picked two lobes from the Oregon Cams list, and focused on duration at 0.050" and their given lash setting so the two lobes are not drastically mismatched on that. I do not care as much about lift.

The Drakes ran all their fast runs on the Simca with the same MP 244, 0.436" cam I have in there now, so I don't expect big gains or differences with a cam - just playing around. They tried a bigger cam (like a 228 @ 0.050") and it shifted their RPM range too high for their comfort so they went back. I will be shifting my new short block at 5000-5200 and I shift the current one at 5400.

Lou
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