Re: Pushrod length/adjuster threads
[Re: 540DUSTER]
#775622
08/17/10 05:47 PM
08/17/10 05:47 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
If you don't believe the geometry changes,then how about rocker arm ratio?
Its changing the ratio... why is the geometry changing
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Re: Pushrod length/adjuster threads
[Re: 540DUSTER]
#775625
08/17/10 06:46 PM
08/17/10 06:46 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Mr P, You are right it doesn't change the relationship of the valve tip to the rocker;But if the adjuster ball is closer to the rocker,lift will increace.
Yes you are correct that it will change the ratio due to the distance of the contact point on the adjuster up to a point... if you take a straight edge and go from the contact point of the rocker/valve point through the center of the shaft then continue to the push rod side that point is where it would be at the optimum for the adjuster to be at(point of contact for the push rod and rocker)
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Re: Pushrod length/adjuster threads
[Re: Von]
#775626
08/17/10 09:07 PM
08/17/10 09:07 PM
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Joined: Jun 2009
Posts: 705 Michigan
Hemiroid
super stock
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super stock
Joined: Jun 2009
Posts: 705
Michigan
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Quote:
Quote:
Hey PVP......I've got a few extra sets of pushrods laying around.....Bring by what you have and we can see if I have something that'll work better........
I may take you up on that!! Ive got some rough measurements. Depending on which adjusters I use I need either 9.040 effective length or 9.140.
Got anything close?
Thanks, you big
That's too funny. My crappy Crane rockers I bought for my hydraulic cam in my GTX has EXACTLY those same push rod dimensions. Half of the rockers were of a fairly new batch and the others were antiques with different adjusters. That being said, the distance from the beginning of the threads and the tip of the ball are different, so simply using thread exposure isn't always accurate.
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Re: Pushrod length/adjuster threads
[Re: ahy]
#775628
08/17/10 11:26 PM
08/17/10 11:26 PM
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Joined: Jul 2010
Posts: 2,091 Delray beach, Florida
Performance Only
top fuel
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top fuel
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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technically speaking, adding lash caps does change the geometry. it doesn't change the fulcrum point, but it does change the sweep of the rocker tip over the valve tip. also, moving the adjuster farther or closer to the fulcrum to change the ratio, also changes the geometry since the force applied from the pushrod needs to be greater since it is closer to the fulcrum on that side. think of a teeter totter for a reference. it's all basic geometry. now replace the kid at either end with a valve tip and a rocker adjuster at either end. any time you change the position of any of the three pieces, your changing the "geometry", regardless of how much and regardless of the effect.
machine shop owner and engine builder
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Re: Pushrod length/adjuster threads
[Re: MR_P_BODY]
#775629
08/17/10 11:57 PM
08/17/10 11:57 PM
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Joined: Nov 2003
Posts: 6,293 Rock Springs
Bob_Coomer
master
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master
Joined: Nov 2003
Posts: 6,293
Rock Springs
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LOL, You guys would argue over the color of a black board. I dont understand why were talking and even arguing about stuff that is irrelevant, doesnt matter and cant change LOL -Push rod length doesnt effect geometry -how much adjuster is hanging out doesnt affect geometry How far the adjuster is located from the cup does change the ratio, how else would one change it? It cant be changed unless you buy another rocker arm so why bring it up? also with little to no thread protruding from the rocker arm can cause problems with push rod interference where the cup actually contacts the rocker body. This isnt a problem with cup adjusters and ball end/ball end push rods... I have no proof or hard evidence but I truly believe that cup adjusters and ball end/ball end push rods are better than cup style push rods from burning up etc. But thats another story and doesnt matter here either. Lash caps will effect geometry a little. I have used lash caps on diff projects and engines over the years maybe a half dozen times. To be honest I it has really never made any significant changes either way. Some engine builders avoid lash caps like a plague, but why? I think they definitely serve a purpose, and in some cases save the engine builder a bunch of money. i have heard horror stories about guys trashing engine or loosing lash caps, but IMO thats not the lash caps fault. If the lash cap is to deep and it pushes against the valve lock, its not the lash caps fault. Bottom line if these are Isky, or Crane type Ductile type rockers anything from 1 to 3 threads showing will be just fine.... IMO 1 /2 thread is pretty idea...
[color:"red"]65 Hemi Belvedere coming soon [/color] [color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]
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Re: Pushrod length/adjuster threads
[Re: Bob_Coomer]
#775631
08/18/10 07:09 PM
08/18/10 07:09 PM
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Joined: Oct 2007
Posts: 4,213 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,213
New York
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I'd like to make a clear distinction in terms. "irrelevant" (meaning, nothing to do with it) isn't true, all those dimensions affect geometry, lift, wear etc. - the question is in what way, and how much?
"doesn't matter" is actually true in many cases, you get an error but the effect is very small, or 2 errors almost cancel each other out. Sometimes an accidental change corrects an unseen error.
"Push rod length doesnt effect geometry": well, not directly (a fixed length hydraulic pushrod is always "right"), but will if you need more adjuster to make it up.
"how much adjuster is hanging out doesnt affect geometry": it not only changes the ratio (more threads = lower ratio), it changes the angle between the 2 rocker levers (pushrod side and valve side), which is part of the basic rocker design. The rocker's inter-lever angle is the total of the pushrod angle (not the tappet bank angle) and the valve stem angle (15°, 18°, etc.). If the pushrod is 0° (parallel to the cylinder) the angle is just the stem axis. If the lever total changes (as with too many threads), the arc of either the pushrod side, the valve side, or both cannot be centered, and the sweep and scrub increase.
Yes, it's a complicated subject.
Boffin Emeritus
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