Farm Equipment - Murphy's rocker arms

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Murphy's rocker arms

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=12001
Printed Date: 30 Jan 2025 at 6:25pm
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Topic: Murphy's rocker arms

Posted By: OrangeFever
Subject: Murphy's rocker arms
Date Posted: 05 May 2010 at 9:32pm

Anyone out there have 1st hand experience with the murphy's rocker arm assembly on a d17 bone stock head. I think there might be come coil bind if someone doesnt do their homework. The reason I ask is I want to but a set if it doesnt require changing springs and install heights... Thank you.

Replies:

Posted By: mlpankey
Date Posted: 06 May 2010 at 7:27am

Anytime you deviate from stock engineering to a performance upgrade . Stress on factory engineered materials needs to be considered. You increase the net valve lift by cam regrind or increased rocker ratio. spring opening rates closing rates and coil bind need serious consideration.

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: Hudsonator
Date Posted: 06 May 2010 at 7:50am

What are the ratios of the murphy rocker arms?

And, what spring pressures are you guys running? I ask this because in my youth I exceeded the spring pressure the late model, stock rocker shaft would withstand. I had no problem with any part of the shaft except the ends, they would bend upward or snap clean off. I could only run an early WC, non-rolled, rocker shaft.

I couldn't tell you how much pressure it was, I made that mistake 25 years ago. I do know I removed the inner springs from the spring set I was using at the time. I believe they were BB chevy.

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There isn't much a WC can't do.

WD's just do it better.

Posted By: mlpankey
Date Posted: 06 May 2010 at 9:24am

murphys rocker ratio is 1.85 . Stock ratio is 1.46 . people have different thoughts on spring rates cause the cam is hollow. All I can say is that I personally havent damaged a cam with comp.brand or z28 solid lift factory springs set up on 120lbs seat.

http://www.allischalmers.com/new/forum/forum_posts.asp?TID=11768&title=pankys-hi-perf-distributor - http://www.allischalmers.com/new/forum/forum_posts.asp?TID=11768&title=pankys-hi-perf-distributor

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: Hudsonator
Date Posted: 06 May 2010 at 5:54pm

You wouldn't happen to know how the increased ratio changes the numbers on a stock cam, would ya?

Looking over some old catalogs I have, I believe the spring pressure snapping off the rocker shaft would be 328 lbs. By the time I took out the inner springs and got down to the outers only, about 160-175lbs.

I noticed in your pic that the shaft doesn't have (or I can't see it) a seam at the bottom like a stock WD/WD45. Does murphy have a shaft machined from solid stock?

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There isn't much a WC can't do.

WD's just do it better.

Posted By: mlpankey
Date Posted: 06 May 2010 at 6:04pm

The shaft doesnt come with the murphy rockers . the rockers, stands and spacers is all he provides . My shaft is a factory allis shaft . Its brand new though I just couldnt see putting the new rockers on a worn shaft. I wouldnt want to have that on the seat of a mechanical lift cam with a install spring height of 1.550 or more. jmho Remember a spring with 110lbs seat at a install height of 1.688 will have a open pressure of 320 lbs at 1.208 and have a spring rate around 437 pounds per inch.

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: DrAllis
Date Posted: 06 May 2010 at 6:50pm

When I ran a 175 cam (pressed on gear) that had been reground for more lift (.550") at open RPM (probably never over 4000) I would have the cam gear try to slide off of the end of the cam when using springs with only 45 lbs of seat pressure. I had to design a new way to retain the gear using the threaded hole in the end of the camshaft and by grinding away material from the thrust bolt in the timing cover. Had no trouble with push rods or lifter/lobe wear. Big block Chevy valves were used.

Posted By: mlpankey
Date Posted: 06 May 2010 at 6:57pm

yet another reason to use the bolt on gear . I dont know how 45 lbs on seat with heavy bbc valves could have run over 3000 rpms without floating . I would also think at.550 lift the exhaust valve would tend to tulip from the harmonics of bouncing on the seat.

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: DrAllis
Date Posted: 06 May 2010 at 7:01pm

Never floated any valves and used stock rocker arms and never had any valve problems. Have run the same set-up now for 10 years at stock rpms....gave up the "open" rpm thing when there got to be too many 6 cyl Farmalls and Olivers to whip.

Posted By: mlpankey
Date Posted: 06 May 2010 at 7:31pm

Thats good we pulled a set of stock springs off our first pulling motor that checked 37lbs on the seat . Engine popped at rpms above 1600 in the exhaust and beat the exhaust seats up into the head . We normally see springs fall off as much as 10 lbs after 3 heat cycles also . I know Tarbills engine when we purchased it had verry light springs but the Scooter brothers ground cam was relatively low lift for the amount of duration it ran in the rpm classes that cam is setting in the shop corner. DrAllis I would assume that the 45 lbs seat was at 1 13/16 also?

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: DrAllis
Date Posted: 06 May 2010 at 8:55pm

Don't remember the height....springs I use are off of a Dodge 2.4?? engine in a car.

Posted By: mlpankey
Date Posted: 06 May 2010 at 8:59pm

I sent you a private message. I think you might laugh?

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: Hudsonator
Date Posted: 06 May 2010 at 9:09pm

Stock valve springs are too weak even for farming engines. That's the skip n' jump they do when not under load. I think the power stroke pulls the exhaust valves off their seats. The in-cylinder pressure rise as you put it under load ceases that little phenomena. Or, use stronger springs.

I never did keep track of the optimum spring size/pressure. Wish I had now.

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There isn't much a WC can't do.

WD's just do it better.