Welcome! Please use the navigational links to explore our website.
PartsASAP LogoCompany Logo (800) 853-2651

Shop Now

   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver

Attention Forum Users: On the 28th of December 2023 at 9:00am Central Time, we will be taking the forums down for maintenance while we prepare the new forums for your use. Please click here for more information.

Tractor Pulling Discussion Forum

Rocker Arm Crap Again

Welcome Guest, Log in or Register
Author 
Tyler Neff

02-05-2004 19:35:48




Report to Moderator

My puller is currantly torn apart and I was wondering if there was any way of telling what ratio my rockers are. They have been cut so Im not sure . Thanx




[Log in to Reply]   [No Email]
ToddF

02-07-2004 17:19:51




Report to Moderator
 Re: Rocker Arm Crap Again in reply to Tyler Neff, 02-05-2004 19:35:48  
Another thing I haven't seen mentioned in this discussion is that the opening and closing of the valves are often measured at the point in time when the valve has moved .050" off the seat. I have no experience with it but in theory a larger rocker arm ratio would advance the valve open timing and retard the valve close with respect to the crankshaft, in essance increasing the duration. Both of these effects may be rather small, but you might see gains in Hp by indexing the cam to optimize the rocker arm ratio change.

[Log in to Reply]  [No Email]
Buzzman72

02-06-2004 06:49:41




Report to Moderator
 Re: Rocker Arm Crap Again in reply to Tyler Neff, 02-05-2004 19:35:48  
With your rocker arms apart, measure from the center pivot point to the valve end, at the point where the rocker arm contacts the valve. Then measure from the same center pivot point to the point where the arm contacts the pushrod. The realtionship between these two numbers is your rocker arm ratio, and most are numerically reduced to a "__": 1 ratio in order to easily compare rocker arms of different leverage (ratio).

Hope this helps explain things a little...better yet, I hope it makes the water clearer instead of murkier for you!

[Log in to Reply]  [No Email]
Flogger

02-06-2004 06:03:24




Report to Moderator
 Re: Rocker Arm Crap Again in reply to Tyler Neff, 02-05-2004 19:35:48  
The way I understand it a higher ratio rocker works similar to stroking a crankshaft. It opens and closes the valve higher and quicker than the stock rocker in the same amount of time. I would think you could measure the actual lift at the pushrod and also at the valve and be able to roughly determine the ratio.



[Log in to Reply]  [No Email]
Jd Puller

02-06-2004 07:21:17




Report to Moderator
 Re: Re: Rocker Arm Crap Again in reply to Flogger, 02-06-2004 06:03:24  
A higher Ratio rocker arm will open the valves farther but not faster or shut them faster infact it takes the same longer because you are opening the valves farther. as for measuring them just go from the center pivot to the center of the valve stem and from the same point back to the center of the push rod it will be close enough.



[Log in to Reply]  [No Email]
Flogger

02-06-2004 07:45:12




Report to Moderator
 Re: Re: Re: Rocker Arm Crap Again in reply to Jd Puller, 02-06-2004 07:21:17  
If the valve is opening and closing further in the same amount of time is has be be doing it faster doesn't it?



[Log in to Reply]  [No Email]
Wild Horses

02-06-2004 08:13:49




Report to Moderator
 Re: Re: Re: Re: Rocker Arm Crap Again in reply to Flogger, 02-06-2004 07:45:12  
Think of it this way. The camshaft actuates the rocker by way of the push rods. One rotation of the camshaft (360 deg) opens and closes the valve. You only have 360 deg regardless of lift. The rocker is a lever. Say it takes 10 deg of rotation to open the valve and 3 deg duration to hold it open. The higher ratio means that the tip moves farther up and down, but in the same 10 deg as it would in a lower ratio. So the rocker is moving faster, but the valve is still fully open and fully closed at the same time, the 3 deg.

[Log in to Reply]  [No Email]
Bob

02-06-2004 08:03:03




Report to Moderator
 Re: Re: Re: Re: Rocker Arm Crap Again in reply to Flogger, 02-06-2004 07:45:12  
The valve is moving faster, but the total elapsed time is the same from start of open to end of close. So it moves faster, but doesn't happen faster.



[Log in to Reply]  [No Email]
Flogger

02-06-2004 08:17:23




Report to Moderator
 Re: Re: Re: Re: Re: Rocker Arm Crap Again in reply to Bob, 02-06-2004 08:03:03  
I agree. You're wanting to open that valve further, and close it but you've got a pre-determined amount of time or degrees of rotation to do it in so it has to happen faster.



[Log in to Reply]  [No Email]
ChadS

02-06-2004 09:20:31




Report to Moderator
 Re: Re: Re: Re: Re: Re: Rocker Arm Crap Again in reply to Flogger, 02-06-2004 08:17:23  
On messing around with chevys, and the rocker ratios, It opens the valve more, kinda like puting in a bigger cam with out puting in a bigger lift cam. The lift and duration on the cam still stays the same, just opens the valve more. the valves do not open faster or slower, just more travel. Now in my opinion, if you had a long duration cam, this is a great idea, duration is the amount of time the valve is opened off of the seat during a 360 degree revolution. say it is a 225 deg, it will be open for 225 degrees out of 360 degrees. Lift is how far the cam move the push rod and how far the valve is opened. .500 lift is a half inch movement. Rocker ratios, change the lift on the valves, not the cam timing. Chad

[Log in to Reply]  [No Email]
Drew

02-06-2004 09:41:45




Report to Moderator
 Re: Re: Re: Re: Re: Re: Re: Rocker Arm Crap Again in reply to ChadS, 02-06-2004 09:20:31  
With a higher ratio rocker arm, the valve does move faster. The valve is moving a longer distance in the same amount of time. The seat timing of the valves will be the same, but duration at .050" lift will increase a few degrees.

This is copied straight from the Crane Cams website (http://www.cranecams.com/?show=camQuestions)

How does an increase in Rocker Arm Ratio improve the engine's performance?

The lobe lift of the cam is increased by the ratio of the rocker arm to produce the final amount of valve lift. A cam with a .320" lobe lift using a 1.50:1 ratio rocker arm will have a .480" valve lift (.320" x 1.50 = .480"). If you install rocker arms with an increased ratio of 1.60:1, with the same cam, the lift would increase to .512" (.320" x 1.60 = .512"). The engine reacts to the movement of the valve. It doesn't know how the increased lift was generated. It responds the same way it would as if a slightly larger lift cam had been installed. In fact, since the speed of the valve is increased with the higher rocker arm ratio, the engine thinks it has also gained 2� to 4� of camshaft duration.

Check out the link to Murphys website that has a graph of what a high ratio rocker does.

[Log in to Reply]  [No Email]
BILL

02-06-2004 11:50:38




Report to Moderator
 Re: Re: Re: Re: Re: Re: Re: Re: Rocker Arm Crap Ag in reply to Drew, 02-06-2004 09:41:45  
WHATS THE HP GAIN ON THEM LIKE IN A JD A OR G THANKS BILL



[Log in to Reply]  [No Email]
Tyler Neff

02-06-2004 10:36:30




Report to Moderator
 Re: Re: Re: Re: Re: Re: Re: Re: Rocker Arm Crap Ag in reply to Drew, 02-06-2004 09:41:45  
Thanx for all the info guys. The reason for the guestion was to determine if its possible to have to high of a ratio on the rocker arms. I have put the stock cam back in the tractor (JD 70). The one I had reground looked like a nitro dragster cam (thanx Keith). The combination of the cam being that big and the rockers being cut to the point that they are almost binding up cant be a good thing. I would like to put a whole new set up in the tractor but Im very nervous about who does it. I would like to run some roller rockers but trying to figure out wich cam to put in it and getting the right info is like trying to pull teeth out of a p@#s ant. Thanx for all the replys and info

[Log in to Reply]  [No Email]
Proredpuller

02-06-2004 12:22:21




Report to Moderator
 Re: Re: Re: Re: Re: Re: Re: Re: Re: Rocker Arm Cra in reply to Tyler Neff, 02-06-2004 10:36:30  
Although most everyone is aware of this I thought it would be worth mentioning. Watch your geometry as you increase rocker arm ratio. Note the contact patch between the rocker arm and the valve stem. Also, speaking from experience, depending upon the type of engine you are working, note the pushrod hole size and location when installing the new rockers... otherwise you might have contact where you don't want it.

Good luck.

[Log in to Reply]  [No Email]
Flogger

02-06-2004 10:41:51




Report to Moderator
 Re: Re: Re: Re: Re: Re: Re: Re: Re: Rocker Arm Cra in reply to Tyler Neff, 02-06-2004 10:36:30  
Hey Tyler,

Not a deere man but I have some buddies that are. Word is that Alan Schooler has something figured out on rocker arms. I'd check with him before I did anything. Pretty sure his # is in the Hook.



[Log in to Reply]  [No Email]
[Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:


TRACTOR PARTS TRACTOR MANUALS
We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

Home  |  Forums


Copyright © 1997-2023 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters

Website Accessibility Policy