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#2449208 - 02/09/18 04:47 PM Re: Would pushrod length make this much difference? [Re: EV2Bird]
BradH Online   content
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Probably nothing you'd ever notice.
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#2449215 - 02/09/18 04:53 PM Re: Would pushrod length make this much difference? [Re: madscientist]
BradH Online   content
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Originally Posted By madscientist
Originally Posted By Cab_Burge
I wonder if these instructions apply to stud mounted rockers only? shruggy


Nope. Adjuster position affects geometry on stud and shaft rockers.

Adjuster position on a shaft system has no effect on geometry; that's determined by the rocker fulcrum location with respect to the valve.
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#2449253 - 02/09/18 06:19 PM Re: Would pushrod length make this much difference? [Re: BradH]
sixpackgut Offline
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Registered: 06/08/03
Posts: 9066
Loc: Charleston
Geez, and I'm just happy when the pushrods stay where they belong
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#2451846 - 02/14/18 06:13 PM Re: Would pushrod length make this much difference? [Re: sixpackgut]
BradH Online   content
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Originally Posted By sixpackgut
Geez, and I'm just happy when the pushrods stay where they belong

Ain't that true. IIRC, my first trip to Dwayne's dyno we ended up bending a couple because I hadn't noticed there were clearance issues w/ the heads. I'm an idiot. eyes
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#2451863 - 02/14/18 06:59 PM Re: Would pushrod length make this much difference? [Re: BradH]
AndyF Offline
Too Many Posts

Registered: 01/20/03
Posts: 24382
Loc: Oregon
You aren't an idiot, you just haven't learned everything the hard way yet. Once you learn everything the hard way you'll be a bitter, grumpy old man with no patience for whipersnappers who haven't learned everything yet.

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#2451869 - 02/14/18 07:11 PM Re: Would pushrod length make this much difference? [Re: AndyF]
WHITEDART Offline
top fuel

Registered: 10/06/11
Posts: 2367
Loc: bean town
Pushrod length was one of the things we explored when I went to competition engine building school.. by adding .050 a pushrod length we gained about .06 at Max lift.But the early and mid numbers suffered slightly... made absolutely no difference on back-to-back on the dyno.. I would say picking a pushrod length with the adjuster set and it's recommended location would be your best bet
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#2452179 - 02/15/18 01:03 PM Re: Would pushrod length make this much difference? [Re: AndyF]
BradH Online   content
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Loc: Valhalla... eventually
Originally Posted By AndyF
You aren't an idiot, you just haven't learned everything the hard way yet. Once you learn everything the hard way you'll be a bitter, grumpy old man with no patience for whipersnappers who haven't learned everything yet.

1. I've told my friends & family for years, I learn EVERYTHING the hard way.

2. I'm already a bitter & grumpy old man with no patience for others... and I still don't know sh!t.
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#2452397 - 02/15/18 09:52 PM Re: Would pushrod length make this much difference? [Re: BradH]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 31079
Loc: Bend,OR USA
I, like Al Aquire, do know that I don't know what I don't know work whistling
I'm willing, and still learning, to learn a little now and then haha
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#2452411 - 02/15/18 10:30 PM Re: Would pushrod length make this much difference? [Re: Cab_Burge]
Greenwood Offline
member

Registered: 09/27/17
Posts: 44
Loc: Red Deer, Alberta
I also don't know what I don't know. Kinda makes sense. I think. One of the things I set about getting a handle on this year was making sure my pushrods were the proper length. Trying to measure actual valve lift with the engine in the car was always a struggle. I was of the opinion I was giving up .030" of lift. After poring over a few treatises on pushrod length and rocker geometry (none of which made acertain light bulb go off like BradH's diagram), I have determined that I'm within .020" of optimum pushrod length. Can't really say that's worth buying new pushrods for my heap. Actual valve lift is within .005 of theoretical so...

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#2452447 - 02/16/18 01:33 AM Re: Would pushrod length make this much difference? [Re: Greenwood]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 31079
Loc: Bend,OR USA
Don't forget that actual valve lift at the retainers with the race valve springs will never be as much as the advertised valve lift or exactly the same as when using light checking valve springs work
I've seen as much as .040 loss due to pushrod and valve train deflection shock
Good thick, stiff, pushrods can make up for a lot of that loss up scope
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#2452546 - 02/16/18 11:11 AM Re: Would pushrod length make this much difference? [Re: Cab_Burge]
BradH Online   content
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Originally Posted By Cab_Burge
...actual valve lift at the retainers with the race valve springs will never be as much as the advertised valve lift...

That's entirely dependent upon how the rocker arm is designed. AndyF's rocker arm articles touched on how some of the brands he checked were "over-ratioed" w/ checking springs, but came in at or above the advertised ratio when checked w/ the actual valve springs.

As far as deflection, I believe it can be in the pushrods, the rocker bodies, and/or the shafts, depending upon the components used. Not sure Joe Average's budget can eliminate it entirely, but I've seen some cases where it certainly went beyond my idea of an "acceptable" amount in terms of lift/ratio loss.


Edited by BradH (02/16/18 11:12 AM)
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#2452556 - 02/16/18 11:28 AM Re: Would pushrod length make this much difference? [Re: BradH]
BradH Online   content
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Registered: 01/30/03
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Loc: Valhalla... eventually
Oh, I came across some pics of "stuff" that Mike at B3RE did w/ some Hughes rockers used on Trick Flow heads that included switching to cup-style adjusters (requires pushrod oiling). I can't say exactly what differences would result from such a mod, but it's pretty obvious the pushrod tip's relation to the rocker fulcrum would change big-time.


Attachments
B3_H_mod.jpg


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#2452890 - 02/16/18 10:15 PM Re: Would pushrod length make this much difference? [Re: BradH]
Brewzer67 Offline
member

Registered: 05/12/17
Posts: 46
Loc: WI
Originally Posted By BradH
Oh, I came across some pics of "stuff" that Mike at B3RE did w/ some Hughes rockers used on Trick Flow heads that included switching to cup-style adjusters (requires pushrod oiling). I can't say exactly what differences would result from such a mod, but it's pretty obvious the pushrod tip's relation to the rocker fulcrum would change big-time.

I'm curious where you found these pictures. These look like my heads and rockers. They came out great with Mike's kit and the change to cup adjusters. The sweep is small and centered and there is minimal lift loss. I am running dual taper 9/16" (.165 wall) oil thru pushrods from Trend and lose less than .008 lift on a .716 lift solid roller. With the change to the cup adjusters there is almost no change in pushrod angle from full closed to full open. Even though the pushrod side doesn't add too much in the way of harmonics issues, I can't help but think this minimal movement goes a long way to promoting valve train stability.

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#2453018 - 02/17/18 10:18 AM Re: Would pushrod length make this much difference? [Re: Brewzer67]
BradH Online   content
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I think there were some pics posted on FABO that I stumbled across. I had a link somewhere, but not at the moment.
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