SB cam lift/dur, how much net is lost by 59 degree?
#1346326
12/05/12 09:57 AM
12/05/12 09:57 AM
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Joined: Jan 2003
Posts: 9,866 Weddington, N.C.
Streetwize
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Weddington, N.C.
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I could probably Trig this out but I figured AndyF or Polyspheric already figured it out.
Everybody knows the 59 degree LA lifter bank was a cost saving carry-over from the 318 Poly. My question is, has anybody figured out the lift/duration effects of the offset lifter angle?
Every time I do a sb (especially a roller) I'm amazed how much the pushrod arc has to oscillate compared to other motors.
I also know the arc gets worse the further the base of the lifter cup is from the cam centerline.
Last edited by Streetwize; 12/05/12 10:10 AM.
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Re: SB cam lift/dur, how much net is lost by 59 degree?
[Re: one bad fish]
#1346329
12/05/12 10:46 AM
12/05/12 10:46 AM
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Joined: Sep 2004
Posts: 2,091 oberlin, Ohio
Rapid340
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top fuel
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oberlin, Ohio
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If you place a dial indicator at 45 degrees at the end of a long pushrod, you will loose close to three percent. The loss will increase with shorter pushrods and increase thru the lift cycle. But how it affects actual valve lift is much more complex and will depend on the rocker stud angular position, rocker dimentions, lifter and pushrod length as well as the rocker tip design. I suspect the designers added the lifter angle offset to allow the pushrod to move with the rocker stud relative to the rocker shaft (pivot) centerline on the original design but that is just a guess. If someone knows firsthand, please let me/us know.
Last edited by Rapid340; 12/05/12 11:29 AM.
1971 Factory Appearing Duster 340 11.000 @ 122 mph
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Re: SB cam lift/dur, how much net is lost by 59 degree?
[Re: S/ST 3040]
#1346332
12/05/12 02:56 PM
12/05/12 02:56 PM
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Joined: Jan 2003
Posts: 9,866 Weddington, N.C.
Streetwize
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Vic, Thought you might show up Thanks, buddy! I knew a builder who angle clearanced the pushrod passages in Aluminum heads so that they'll just slightly "kiss" the pushrod at the base of the deck surface (at HIGH RPM or Peak of pushrod deflection) ; He claimed it acted a as a guideplate by limiting the side to side motion and dampened the harmonics in the pushrod. claimed the valvetrain stayed more stable at High RPM and the 'friction' was minimal. Never gave it much thought but on a small block mopar I can sort of see the logic in it.
Last edited by Streetwize; 12/05/12 03:14 PM.
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Re: SB cam lift/dur, how much net is lost by 59 degree?
[Re: S/ST 3040]
#1346334
12/05/12 06:57 PM
12/05/12 06:57 PM
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Joined: Jan 2004
Posts: 8,193 fredericksburg,va
cudaman1969
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Quote:
Roughly .012" @ valve, with a 1.5 rocker..........IIRC.
Roughly same thing I got with the 360-380 crate motor cam. First time I worked with a small block, very bad push rod angle. This was the first thing Glidden fixed in the pro stock 79 Arrow, he was unbeatable.
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Re: SB cam lift/dur, how much net is lost by 59 degree?
[Re: Streetwize]
#1346335
12/05/12 07:01 PM
12/05/12 07:01 PM
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Joined: Feb 2007
Posts: 2,578 sweden
1Fast340
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sweden
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Quote:
Vic,
Thought you might show up
Thanks, buddy!
I knew a builder who angle clearanced the pushrod passages in Aluminum heads so that they'll just slightly "kiss" the pushrod at the base of the deck surface (at HIGH RPM or Peak of pushrod deflection) ; He claimed it acted a as a guideplate by limiting the side to side motion and dampened the harmonics in the pushrod. claimed the valvetrain stayed more stable at High RPM and the 'friction' was minimal. Never gave it much thought but on a small block mopar I can sort of see the logic in it.
im not sure i like his way of thinking,my moly pushrods slightly touch the heads in a very few spots and they have lost some material there. at first i would have suspected that the aluminum heads should have been eaten first but this does not seem to be the case, however i have never measured the wear on the pushrods but its defenitly there by just fingertip precision measuring device metod. also keep in mind that these pushrods have been beaten on with a variety of solidroller cams since noone knows how long and might have started flexing more than they should,and the wear started after the instalation of aluminum heads in 2005 i would gues.
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Re: SB cam lift/dur, how much net is lost by 59 degree?
[Re: Streetwize]
#1346337
12/05/12 08:19 PM
12/05/12 08:19 PM
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Joined: Feb 2009
Posts: 1,019 Finland
mafo
super stock
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super stock
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Finland
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It gets worse with more rocker offset , on my w2 engine it was bad, 1 inch offset rockers... we put one dial indicator on the lifter and an other on the valve, and it was to bad I never wrote it down, but my theoretical .750 lift was more like .700
-65 Valiant,420", all motor,2700#, dot tires, 8,42 @ 160,2
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Re: SB cam lift/dur, how much net is lost by 59 degree?
[Re: Streetwize]
#1346340
12/06/12 12:03 PM
12/06/12 12:03 PM
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Joined: Nov 2004
Posts: 3,544 Syracuse,NY
CompWedgeEngines
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Quote:
Vic,
Thought you might show up
Thanks, buddy!
I knew a builder who angle clearanced the pushrod passages in Aluminum heads so that they'll just slightly "kiss" the pushrod at the base of the deck surface (at HIGH RPM or Peak of pushrod deflection) ; He claimed it acted a as a guideplate by limiting the side to side motion and dampened the harmonics in the pushrod. claimed the valvetrain stayed more stable at High RPM and the 'friction' was minimal. Never gave it much thought but on a small block mopar I can sort of see the logic in it.
This man was a smart man.
When you get into blown alky stuff, you learn a lot about pushrods, as well as when you talk to Pro Stock and ADRL guys....you'd be amazed.
RIP Monte Smith
Your work is a reflection of yourself, autograph it with quality.
WD for Diamond Pistons,Sidewinder cylinder heads, Wiseco, K1 rods and cranks,BAM lifters, Morel lifters, Molnar Technologies, Harland Sharp, Pro Gear, Cometic, King Engine Bearings and many others.
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