Gun drilled AAH cams...
06-08-2004, 05:14 AM
#22
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You removed about 170g per cam....
or 0.375lb, using 12" x 9.5mm
Though I questioned the claimed increase in rigidity with gun drilling and countered with a theoretical loss in strength, I didn't mean to imply that the racing community is wrong. I simply want to know why. The loss in torsional strength and stiffness is only about 15% in this case. I guessing that these are not the driving factors in cam failures. The static loads on a cam are nowhere near high enough to fail a steel bar of that thickness. I think the success of hollow cams must have to do with increased resistance to fatigue and vibrational loads which will be helped by reduced mass.
On another note, from what I've read, most OEM hollow cams use the bore to deliver oil to the bearings. Is there any advantage of trying to do this?
Though I questioned the claimed increase in rigidity with gun drilling and countered with a theoretical loss in strength, I didn't mean to imply that the racing community is wrong. I simply want to know why. The loss in torsional strength and stiffness is only about 15% in this case. I guessing that these are not the driving factors in cam failures. The static loads on a cam are nowhere near high enough to fail a steel bar of that thickness. I think the success of hollow cams must have to do with increased resistance to fatigue and vibrational loads which will be helped by reduced mass.
On another note, from what I've read, most OEM hollow cams use the bore to deliver oil to the bearings. Is there any advantage of trying to do this?
06-08-2004, 07:12 AM
#26
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170g X 2= 12ozs. 3/4 lb is a totally acceptable weight loss...
Almost sure to blow past the 1lb mark with any measure of regrinding. And I'm with you on wanting to know "why." While the racing community is quick to laud gun drilling's weight savings and subsequent benefits it's totally void of any explanations as to how it accomplishes it, often time with stock, drilled cams and noticeably absent of breakage or even worries or concerns regarding them failing (how's that donut guy for a run-on sentence?).
Due to the size bore and remaining wall thicknesses I wasn't and am still not concerned with any kind of incidental/consequential breakage associated with failure but I was concerned if I crunched a valve into a piston and stacked a valve assembly solid that the cam might fail. But now that I've seen the even larger stemmed valves of the AAH en masse that have done just that in salvage yards and no signs of cam breakage I'm much less concerned. That action just "lunches" the valves but leaves the cams unscathed. And since the valves I'm using will have a 31% smaller undercut diameter to yield in the event of piston contact I'm pretty certain it's a war the cams would continue to win... likely even if I made a dramatically larger bore.
I actually considered trying to adapt a way to use the cam bore for positive pressure oil feed but seems our cars are already adequately oiled up top as-is. No sense guilding that lily. In fact they are so well lubricated as to have oil pressure regulator/relief valves in each cylinder head assembly to bypass/relieve pressure in the event of over-pressurization. Then there's the addtional hassles of a rotational seal assembly I would've had to engineer at the front/rear of each cam and risk thread locker being compromised on the front/rear of both cams or it leaking out the pulley bolts or Hall sender (CPS).
And from the looks of both high-mileage AAH head sets I have in here (over 1/4 million miles between them) the cams and cam bearings (journals) are in such good shape as to have "zero" measureable wear. Hard to improve on that kind of success. I am replacing those pressure relief valves but thats about it for any planned oil delivery enhancements on these heads.
Due to the size bore and remaining wall thicknesses I wasn't and am still not concerned with any kind of incidental/consequential breakage associated with failure but I was concerned if I crunched a valve into a piston and stacked a valve assembly solid that the cam might fail. But now that I've seen the even larger stemmed valves of the AAH en masse that have done just that in salvage yards and no signs of cam breakage I'm much less concerned. That action just "lunches" the valves but leaves the cams unscathed. And since the valves I'm using will have a 31% smaller undercut diameter to yield in the event of piston contact I'm pretty certain it's a war the cams would continue to win... likely even if I made a dramatically larger bore.
I actually considered trying to adapt a way to use the cam bore for positive pressure oil feed but seems our cars are already adequately oiled up top as-is. No sense guilding that lily. In fact they are so well lubricated as to have oil pressure regulator/relief valves in each cylinder head assembly to bypass/relieve pressure in the event of over-pressurization. Then there's the addtional hassles of a rotational seal assembly I would've had to engineer at the front/rear of each cam and risk thread locker being compromised on the front/rear of both cams or it leaking out the pulley bolts or Hall sender (CPS).
And from the looks of both high-mileage AAH head sets I have in here (over 1/4 million miles between them) the cams and cam bearings (journals) are in such good shape as to have "zero" measureable wear. Hard to improve on that kind of success. I am replacing those pressure relief valves but thats about it for any planned oil delivery enhancements on these heads.
06-08-2004, 11:16 AM
#28
Density of forged VS hot rolled steel, reference
A quick scan of physical properties for the two materials indicates Both have a density of
.283 #/in^3
Alloys can be heavier.
Data tables may be wrong, just one reference for each.
CalG
.283 #/in^3
Alloys can be heavier.
Data tables may be wrong, just one reference for each.
CalG
06-08-2004, 11:19 AM
#29
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If you want to call him on "it's" and "its" go to the root of the problem . . .
Contractions should not exist in the English language; they simply legitimize improper and lazy pronunciation and spelling.
Reserve apostrophes for indicating possession.
If you use contractions, "your mother was a hamster and your father smelt of elderberries." :-p
P.S. What is your favorite color?
P.P.S. What ... is the air-speed velocity of an unladen swallow?
Reserve apostrophes for indicating possession.
If you use contractions, "your mother was a hamster and your father smelt of elderberries." :-p
P.S. What is your favorite color?
P.P.S. What ... is the air-speed velocity of an unladen swallow?