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Why did Chrysler change to single rockers?
#1466239
07/10/13 10:43 PM
07/10/13 10:43 PM
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Joined: Mar 2012
Posts: 27
Southern Indiana
R/T Lee
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OP
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Southern Indiana
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I searched the forums for previous posts, but couldn't find anything. I always wondered, When the Magnum engine came out, why Chrysler went to a single rocker setup and dropped the shaft mount style of LA engines? Was it a cost saving deal? I remember reading an article (couple months ago), about an engine builder that worked for Chrysler in the 70's, His shop was in California. He was, I guess, an R and D/ experimental mechanic that Mopar employed. From the article he worked on everything from /6 to fuel injected 426 Hemis. But I distinctly remember when he was asked by some "penny pincher" from Chrysler in Detroit. The pencil pusher suggested and believed that they should use a single rocker setup like Chevrolet, he thought it would be same performance, and money savings.. The Mechanic(cant remember his name) argued back and forth with them, then agreed to build a 318 with single rocker setup. He told them he would do it, but he would personally deliver the engine! They asked him why, and he replied: Because I want to be in the dyno room when it fails, not if, when.. And sure enough the engine failed. I have always wondered why they changed when the magnums came out, then after reading that article, I was more confused!! Any Ideas?
NO!! It's not a Nova...
72' Demon 340-727-8 3/4 3.55
69' Charger 440-727-8 3/4
78 Powerwagon 318-727
99' Dakota R/T 5.9
74' Scamp (project)
96' Cherokee 4.0 4x4
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Re: Why did Chrysler change to single rockers?
[Re: RapidRobert]
#1466241
07/10/13 11:01 PM
07/10/13 11:01 PM
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Joined: May 2003
Posts: 15,487
Florida
scratchnfotraction
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I Live Here
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Quote:
Quote:
Was it a cost saving deal?
Ma (like everyone else) was in business to make a profit
look at the cost to replace the shafts and HD rockers compaired to the cheap magnum pedistal mount rockers.
less & cheaper metals also.
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Re: Why did Chrysler change to single rockers?
[Re: RapidRobert]
#1466242
07/10/13 11:19 PM
07/10/13 11:19 PM
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Joined: Apr 2012
Posts: 18,880
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RSNOMO
Moparts Torchbearer
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Moparts Torchbearer
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Quote:
in business to make a profit
A different mindset in the past...
'Profit' and 'cheap' weren't joined at the hip...
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Re: Why did Chrysler change to single rockers?
[Re: RSNOMO]
#1466243
07/10/13 11:32 PM
07/10/13 11:32 PM
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Joined: Mar 2012
Posts: 27
Southern Indiana
R/T Lee
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I was thinking it was all about cheaper production costs.. I was just being optimistic I guess, hoping there was something else that I wasn't picking up on.
NO!! It's not a Nova...
72' Demon 340-727-8 3/4 3.55
69' Charger 440-727-8 3/4
78 Powerwagon 318-727
99' Dakota R/T 5.9
74' Scamp (project)
96' Cherokee 4.0 4x4
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Re: Why did Chrysler change to single rockers?
[Re: Kern Dog]
#1466248
07/11/13 02:24 AM
07/11/13 02:24 AM
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Joined: Feb 2003
Posts: 4,793
Castlegar, BC, Canada
That AMC Guy
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Quote:
Rick Ehrenberg says it was from the consolidation of the AMC engineers when Chrysler bought AMC/Jeep in the 80s. When the 5.2/5.9 magnum was being developed, the AMC guys insisted on the pedestal mount design.
That could make sense. AMC sixes used shaft-mount rockers through 1972 and the first-generation V8 (250/287/327) also had shaft mounted rockers. So, AMC was no stranger to using them. The reason the second-gen V8 and the '73-and-up sixes use individual (then later, "bridged") rockers was two-fold: cost & weight.
I'd still be willing to bet it was more of a decision based on cost than anything else.
And also, the later aluminum bridged rockers used in '74 thru '80 AMC V8's were prone to failure. Even today, you can still buy hardened steel replacements to get rid of those ridiculous aluminum bridges.
Leave it to the AMC boys to think outside the box.
Bloody Mary, Full of Vodka, Blessed art thou among cocktails....
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Re: Why did Chrysler change to single rockers?
[Re: Kern Dog]
#1466253
07/12/13 08:52 AM
07/12/13 08:52 AM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
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Quote:
Rick Ehrenberg says it was from the consolidation of the AMC engineers when Chrysler bought AMC/Jeep in the 80s. When the 5.2/5.9 magnum was being developed, the AMC guys insisted on the pedestal mount design.
in fact, the pedestal mount rocker arm and pedestal is a DIRECT CARRY OVER PART from the AMC 290-401 series engines....
haven't heard of too many AMC rocker failures, so I wouldn't be concerned with durability until you get into completely nutso solid roller cam spring pressures...
and it definitely could have been an assembly line issue--I could see how it would be very easy for the shaft mount rockers to be installed incorrectly, since the intake and exhaust rockers have unique offsets, and there really is no easy way to poka yoke the assembly to eliminate those errors. the intake and exhaust pedestal mount AMC rocker is the same part. no way to f that up....
and from an inventory standpoint, it's a bit of an advantage....you have V6 shaft, V8 shaft, LH offset rocker, RH offset rocker....with the magnum assembly you have pedestal, rocker, base/guide plate.....1 less part, and cheaper to manufacture parts--I'm assuming the shafts are precision parts, that have to have some sort of secondary op to grind to precise tolerance.....and have to have 2 different sized holes drilled in them, and plugs pressed into the end. also, I've never seen an OEM stamped shaft rocker new, only used, where the bearing surface looks polished....are they as stamped new, or do they have some secondary machining on the bearing surface to true them up and polish the bearing surface?
Last edited by patrick; 07/12/13 09:01 AM.
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Re: Why did Chrysler change to single rockers?
[Re: babarracuda]
#1466255
07/12/13 10:05 AM
07/12/13 10:05 AM
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Joined: Jan 2003
Posts: 926
MICHIGAN
BB65Barracuda
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super stock
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MICHIGAN
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Im Pretty sure it had nothing to do with the pedestal type set up being a better design.  If that was the case they would not make shaft mounted conversion kits for Chevrolet race applications. Press in rocker studs and Girdles that are the alternative for the Bow-Tie should say it all. Cost Savings not Quality.  
1957 Power wagon wm300 original 10.000 mile truck, 1964 dodge Polara Convertible numbers matching
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Re: Why did Chrysler change to single rockers?
[Re: BB65Barracuda]
#1466256
07/12/13 11:31 AM
07/12/13 11:31 AM
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Joined: May 2003
Posts: 15,487
Florida
scratchnfotraction
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I Live Here
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Quote:
Im Pretty sure it had nothing to do with the pedestal type set up being a better design. If that was the case they would not make shaft mounted conversion kits for Chevrolet race applications.
Press in rocker studs and Girdles that are the alternative for the Bow-Tie should say it all.
Cost Savings not Quality.
the shaft mount rockers and pedestal rockers share the same low friction 1/2 barrel fulcrum design and are a reliable set up either way for a non-adjustable rockers. less friction,less wear,longevity
the pedestal mount is just cheaper overall in production with less materials used, with the same reliabilty/longevity as the old tried and true shaft rockers.
savings would then be seen coming down the line as the 1 part fits all. there is no need to check/recheck/sign off before it goes out the door. less work, less workers, more profit..
I thought about this back when i worked on a 3.8 ferd engine with the pedestal mount non-adjustable rockers... owner thought they were adjustable and snaped the bolt off in the head and I removed it and replace 1 bolt/rocker/alum fulcrum to stop the ticking lifter.
since then I have fixed 2 318 magnums from ticking by replacing the pedestll mount rockers as a set for a givin cyl. (biggest issue I find for ticking is clogged roller lifters)
parts bill 58$ try that with a LA shaft mount rockers I never have had luck swaping rockers around on shafts for lifter ticks from worn mech parts.
plus the old mopar engineers are all gone and a lot of younger chebby guys work there now. they know after market will be upgrading to screw in studs and roller rockers that are chebby cheap to use on the new magnum heads.
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Re: Why did Chrysler change to single rockers?
[Re: BB65Barracuda]
#1466258
07/12/13 01:12 PM
07/12/13 01:12 PM
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Joined: Aug 2012
Posts: 1,574
Lakeland FL
floridian
pro stock
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pro stock
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Lakeland FL
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Quote:
conversion kits for Chevrolet race applications.
Last time I checked the cars coming off the assembly line were not made for racing.. While yes I understand the need for different, stronger pars in Nascar, and drag racing, these type of rockers perform pretty well in millions of small and big block chevys...
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Re: Why did Chrysler change to single rockers?
[Re: Kern Dog]
#1466260
07/12/13 03:47 PM
07/12/13 03:47 PM
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Joined: Jan 2003
Posts: 5,387
Pikes Peak Country
TC@HP2
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Quote:
Rick Ehrenberg says it was from the consolidation of the AMC engineers when Chrysler bought AMC/Jeep in the 80s. When the 5.2/5.9 magnum was being developed, the AMC guys insisted on the pedestal mount design.
This is probably the closest to the truth of it all. The Magnum head incorporates some runner designs that are more closely related to the AMC heads than traditional Chrysler small block heads. How else do you think they improved flow, swirl, tumble, and reduced chamber volume. The original Mopar small blocks heads were pretty crappy to begin with so why not clean sheet design them with the ideas form the AMC group. The icing on the cake was now they have a greater parts interchange with other engine families as well, so while the cost per engine may not be significantly less than the shaft system, the cost of ordering ten of thousands of rockers for engine builds over a decade adds up quite a bit.
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Re: Why did Chrysler change to single rockers?
[Re: a12superbee]
#1466265
07/12/13 07:57 PM
07/12/13 07:57 PM
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Joined: Aug 2003
Posts: 6,301
colorado
a12superbee
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To stay on topic, I agree, money money money. It's what corporations do.
I can't afford this.
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