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#2448178 - 02/07/18 05:28 PM Would pushrod length make this much difference?
BradH Offline
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Registered: 01/30/03
Posts: 13699
Loc: Valhalla... eventually
A couple of diagrams I did trying to get a sense for how much difference might result from running the shortest possible pushrod vs. one at the max exposed adjuster length.

Seems like -- on paper, at least -- there's a significant ratio difference... and not something I'd given much thought to before.

Oh, the reason why the tip of the adjuster ball in the first picture isn't the actual point of measurement is that I was trying to account for my using that same style of rocker with a brand of adjuster screw that's noticeably shorter than what's pictured.


Attachments
Rocker geo 1.jpg

Rocker geo 2.jpg


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#2448191 - 02/07/18 06:01 PM Re: Would pushrod length make this much difference? [Re: BradH]
AndyF Offline
Too Many Posts

Registered: 01/20/03
Posts: 23928
Loc: Oregon
Yep, using a pushrod that is as long as possible will give you more valve lift. But you have to watch out for the gotchas. For example, with Harland rocker arms on my 470 I toasted the pushrod ends since the long pushrod puts the cup out of reach of the oil squirt. Pushrod oiling solved that problem. With T&D rocker arms you have to have the adjuster in the correct location or else they won't oil. So you can't screw the adjuster all the way in or all the way out, it has to be in the middle of the range or else you'll kill the rocker arms.

This trick is also dependent on the design of the rocker arm. If you get a bunch of different Mopar rocker arms and put them on the same shaft you'll see that everyone designs their rocker arm differently. So the angle of the backside of the rocker arm is different. The pushrod to rocker arm angle can vary a lot between different rocker arms so the long pushrod trick may or may not work.

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#2448199 - 02/07/18 06:13 PM Re: Would pushrod length make this much difference? [Re: BradH]
hemi-itis Offline
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Registered: 12/29/07
Posts: 10493
Loc: Great Neck,LI,new york
Pushrod oiling is the answer to anything that has an issue with burnt cups.
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#2448274 - 02/07/18 08:55 PM Re: Would pushrod length make this much difference? [Re: AndyF]
mopar dave Offline
master

Registered: 01/04/07
Posts: 5573
Loc: flint michigan
Yep, turn your adjuster all the way up, then 1 turn down. From there you only have 1 turn either way. The closer you get to 1 full turn either way the less oil you get.

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#2448280 - 02/07/18 09:35 PM Re: Would pushrod length make this much difference? [Re: BradH]
Sport440 Offline
master

Registered: 01/20/03
Posts: 6553
Loc: Canton, Ohio
Your pics don't give the minute differences justice.

Longer pushrod equals more max lift while a shorter pushrod gives quicker more mid lift but with less max lift.


Significant difference??, in the scheme of the whole overall lift event, either way, long/short pushrod, doesn't make any significant difference in performance on the engine involved. The valve train, does like the longer pushrod though, less stress on the rocker arm because of the lesser angles involved. IMO

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#2448310 - 02/07/18 10:47 PM Re: Would pushrod length make this much difference? [Re: BradH]
polyspheric Offline
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Registered: 10/10/07
Posts: 2562
Loc: New York
The minimum adjuster length isn't a specific number of turns. What matters:
1. no contact throughout the range of travel
2. enough adjustment to get lash
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#2448348 - 02/08/18 01:37 AM Re: Would pushrod length make this much difference? [Re: BradH]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 30717
Loc: Bend,OR USA
I've seen adjusters and pushrod cups broken off due to using to short of pushrods, way to short work
To long can and may beat up the bottom of the rockers also so my choice is to see between 1/8 of a thread to three complete threads max exposed under the rocker arms up
As already mention on the single shaft T&D system they like 1 1/2 turns out to three turns out max on their adjusters for oiling the push rods properly shruggy
I think I have 1 1/2 threads exposed on my 440-1 with the Jesel pair shaft system with pushrod and spray bar oiling up
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#2448496 - 02/08/18 10:50 AM Re: Would pushrod length make this much difference? [Re: Cab_Burge]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13699
Loc: Valhalla... eventually
I've read where both Jesel and T&D say to set their cup adjusters to one turn out from seated in order to limit the exposed (unsupported) amount of the adjuster, and to keep the oiling passages aligned.

Seems like part of the cup-style pushrod-to-rocker clearance concerns could be addressed by converting to cup-style adjusters. Is going from ball-type to cup-type adjusters as simple as changing to hollow pushrods, as long as the lifters support pushrod oiling?
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#2448499 - 02/08/18 10:56 AM Re: Would pushrod length make this much difference? [Re: polyspheric]
mopar dave Offline
master

Registered: 01/04/07
Posts: 5573
Loc: flint michigan
My point on the on the 1 turn from seated up was to get enough oil to the pr tip. With TD rockers i always seat lash from that 1 turn down from seated position. I latter added spray bars and it didnt matter.

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#2448543 - 02/08/18 12:27 PM Re: Would pushrod length make this much difference? [Re: BradH]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 30717
Loc: Bend,OR USA
Brad, the Jesel adjusters are hollow and don't have any provisions for oiling the axles or valve tips shock shruggy
I called them about this and they said that splash oiling was good enough confused
So I added the spray bar valve covers luck
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#2448623 - 02/08/18 03:03 PM Re: Would pushrod length make this much difference? [Re: BradH]
Stanton Offline
master

Registered: 10/13/05
Posts: 6532
Loc: Ontario, Canada
I'm curious as to why pushrod length affected the lobe lift.

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#2448629 - 02/08/18 03:13 PM Re: Would pushrod length make this much difference? [Re: Stanton]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13699
Loc: Valhalla... eventually
The lobe lift only changed because I reversed-engineered the lobe lift for the same valve lift to account for the ratio change. If I'd left the lobe lift the same, then I'd have had to increase the lift curve on the valve side. It was simpler to leave the rest of the rocker diagram the same and only tweak the pushrod adjuster arc to match the ratio difference.


Edited by BradH (02/08/18 03:16 PM)
_________________________
"Do what you can, with what you have, where you are." - Theodore Roosevelt

“Money talks. Sometimes all it says is ‘Goodbye’.” - Unknown

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#2448661 - 02/08/18 04:42 PM Re: Would pushrod length make this much difference? [Re: Stanton]
fast68plymouth Offline
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Registered: 01/20/03
Posts: 10728
Loc: So. Burlington, Vt.
Be a good excercise with the rocker on the head, an adjustable pushrod, a checking spring, and a dial indicator.
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#2448664 - 02/08/18 04:53 PM Re: Would pushrod length make this much difference? [Re: fast68plymouth]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13699
Loc: Valhalla... eventually
Originally Posted By fast68plymouth
Be a good excercise with the rocker on the head, an adjustable pushrod, a checking spring, and a dial indicator.

Yep. scope
_________________________
"Do what you can, with what you have, where you are." - Theodore Roosevelt

“Money talks. Sometimes all it says is ‘Goodbye’.” - Unknown

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#2448675 - 02/08/18 05:21 PM Re: Would pushrod length make this much difference? [Re: BradH]
Sport440 Offline
master

Registered: 01/20/03
Posts: 6553
Loc: Canton, Ohio
Originally Posted By BradH
Originally Posted By fast68plymouth
Be a good excercise with the rocker on the head, an adjustable pushrod, a checking spring, and a dial indicator.

Yep. scope



Yep, and Your just the right kind of guy to do it. Put the car on hold for just a little bit longer. laugh2 up

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#2449055 - 02/09/18 09:51 AM Re: Would pushrod length make this much difference? [Re: BradH]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13699
Loc: Valhalla... eventually
More "stuff" to think about... the location of the pushrod contact point w/ respect to the rocker arm fulcrum also affects whether the lift curve translated by the rocker arm from the cam lobe is linear or regressive. The diagram below came from an old Crane Cams presentation that shows an example of how the leverage ratio actually decreases across the lift curve as the valve is opened.



Attachments
Regressive ratio diagram.jpg


_________________________
"Do what you can, with what you have, where you are." - Theodore Roosevelt

“Money talks. Sometimes all it says is ‘Goodbye’.” - Unknown

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#2449070 - 02/09/18 10:08 AM Re: Would pushrod length make this much difference? [Re: BradH]
WedgeFED Offline
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Registered: 01/03/16
Posts: 171
Loc: America

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#2449119 - 02/09/18 12:29 PM Re: Would pushrod length make this much difference? [Re: BradH]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 30717
Loc: Bend,OR USA
I wonder if these instructions apply to stud mounted rockers only? shruggy
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Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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#2449182 - 02/09/18 03:41 PM Re: Would pushrod length make this much difference? [Re: Cab_Burge]
madscientist Offline


Registered: 09/17/14
Posts: 1953
Loc: Washington
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.
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#2449197 - 02/09/18 04:28 PM Re: Would pushrod length make this much difference? [Re: BradH]
EV2Bird Offline
No more politics

Registered: 06/23/14
Posts: 3667
Loc: Kansas Roads Between 0 and 140...
Interesting info posted.

Folks mention the cup oiling window of setting, so when also taking into account possible rubbing issues, scrub pattern at the end of the day what, say does .050 off give or take just for an example in terms of usable power/rpm amount to?

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