Previous Thread
Next Thread
Print Thread
Page 1 of 2 1 2
Why did Chrysler change to single rockers? #1466239
07/10/13 10:43 PM
07/10/13 10:43 PM
Joined: Mar 2012
Posts: 27
Southern Indiana
R
R/T Lee Offline OP
member
R/T Lee  Offline OP
member
R

Joined: Mar 2012
Posts: 27
Southern Indiana
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
Re: Why did Chrysler change to single rockers? [Re: R/T Lee] #1466240
07/10/13 10:56 PM
07/10/13 10:56 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert Offline
Circle Track
Happy Birthday RapidRobert  Offline
Circle Track

Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
Quote:

Was it a cost saving deal?


Ma (like everyone else) was in business to make a profit


live every 24 hour block of time like it's your last day on earth
Re: Why did Chrysler change to single rockers? [Re: RapidRobert] #1466241
07/10/13 11:01 PM
07/10/13 11:01 PM
Joined: May 2003
Posts: 15,487
Florida
S
scratchnfotraction Offline
I Live Here
scratchnfotraction  Offline
I Live Here
S

Joined: May 2003
Posts: 15,487
Florida
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.

Re: Why did Chrysler change to single rockers? [Re: RapidRobert] #1466242
07/10/13 11:19 PM
07/10/13 11:19 PM
Joined: Apr 2012
Posts: 18,880
-
R
RSNOMO Offline
Moparts Torchbearer
RSNOMO  Offline
Moparts Torchbearer
R

Joined: Apr 2012
Posts: 18,880
-
Quote:

in business to make a profit




A different mindset in the past...

'Profit' and 'cheap' weren't joined at the hip...

Re: Why did Chrysler change to single rockers? [Re: RSNOMO] #1466243
07/10/13 11:32 PM
07/10/13 11:32 PM
Joined: Mar 2012
Posts: 27
Southern Indiana
R
R/T Lee Offline OP
member
R/T Lee  Offline OP
member
R

Joined: Mar 2012
Posts: 27
Southern Indiana
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
Re: Why did Chrysler change to single rockers? [Re: R/T Lee] #1466244
07/11/13 12:15 AM
07/11/13 12:15 AM
Joined: Jan 2007
Posts: 7,664
IN
A
ahy Offline
master
ahy  Offline
master
A

Joined: Jan 2007
Posts: 7,664
IN
FWIW I believe the Magnums with the pedestal rocker are considered to be the longest lasting and best performing stock standard performance SB's. Maybe lowest cost and done right?

Re: Why did Chrysler change to single rockers? [Re: ahy] #1466245
07/11/13 12:49 AM
07/11/13 12:49 AM
Joined: Jan 2003
Posts: 28,063
Irving, TX
feets Offline
Senior Management
feets  Offline
Senior Management

Joined: Jan 2003
Posts: 28,063
Irving, TX
Quote:

FWIW I believe the Magnums with the pedestal rocker are considered to be the longest lasting and best performing stock standard performance SB's. Maybe lowest cost and done right?




Most of the durability comes from the EFI. Those engines don't have carburetors washing down cylinder walls with unburned fuel.


We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
Re: Why did Chrysler change to single rockers? [Re: ahy] #1466246
07/11/13 12:50 AM
07/11/13 12:50 AM
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog Offline
Striving for excellence
Kern Dog  Offline
Striving for excellence

Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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.

Re: Why did Chrysler change to single rockers? [Re: R/T Lee] #1466247
07/11/13 01:17 AM
07/11/13 01:17 AM
Joined: Jan 2003
Posts: 30,947
Oregon
A
AndyF Offline
I Win
AndyF  Offline
I Win
A

Joined: Jan 2003
Posts: 30,947
Oregon
It is an interesting design question. I'd love to see the PowerPoint presentations that the engineers provided pro and con.

I don't know of any obvious advantages either way for a production engine. It isn't clear to me why one or the other should be less expensive or more reliable. Both have been used for decades in various engines and both designs seem to work fairly well.

Re: Why did Chrysler change to single rockers? [Re: Kern Dog] #1466248
07/11/13 02:24 AM
07/11/13 02:24 AM
Joined: Feb 2003
Posts: 4,789
Castlegar, BC, Canada
That AMC Guy Offline
master
That AMC Guy  Offline
master

Joined: Feb 2003
Posts: 4,789
Castlegar, BC, Canada
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....

Re: Why did Chrysler change to single rockers? [Re: That AMC Guy] #1466249
07/11/13 02:17 PM
07/11/13 02:17 PM
Joined: Jan 2003
Posts: 30,947
Oregon
A
AndyF Offline
I Win
AndyF  Offline
I Win
A

Joined: Jan 2003
Posts: 30,947
Oregon
I'm not so sure that it is a cost reduction. It doesn't cost very much money to buy a shaft and some stamped rocker arms. The machining on the head might be a tad more expensive for the shaft since it requires a curved surface, but at the volumes these parts are made I doubt there is much difference. That curved portion is probably made with a large custom mill or broach and I bet it only takes a few moments.

I think the original shaft design is less expensive than the AMC design but without having the quotes in front of me I couldn't say for sure.

The Magnum engine has a bunch of items that cost more than the LA design though so it wouldn't surprise me that they added money in the valve train also. I don't think the Magnum engine was designed as a cost reduction. It seems to me that they were more concerned with warranty reduction and improved service life.

Hyd roller lifters are more expensive, the front belt drive is more expensive, 10 bolt valve covers are more expensive, etc. There are a lot of cost increases in the Magnum engine if you look at it closely and I think the valve train was also a cost increase. I'm not sure why they changed the design, might have just been politics. Some guy who liked that design was put in charge so he changed the design. That stuff happens all the time.

Re: Why did Chrysler change to single rockers? [Re: AndyF] #1466250
07/11/13 02:40 PM
07/11/13 02:40 PM
Joined: Jan 2003
Posts: 27,444
So Cal
autoxcuda Offline
Too Many Posts
autoxcuda  Offline
Too Many Posts

Joined: Jan 2003
Posts: 27,444
So Cal
Another guess...

V-6 valvetrain became interchangeable with V-8 valvetrain. The different V-6 and V-8 rockershaft became eliminated.

Also, maybe there was an production assymbly savings. Maybe it was faster to assemble or automate the assymble of individual rocker vs. shaft??

Re: Why did Chrysler change to single rockers? [Re: autoxcuda] #1466251
07/11/13 05:48 PM
07/11/13 05:48 PM
Joined: Jan 2003
Posts: 30,947
Oregon
A
AndyF Offline
I Win
AndyF  Offline
I Win
A

Joined: Jan 2003
Posts: 30,947
Oregon
Two very good thoughts.

I can imagine that getting the rocker arms assembly correct on the shafts was always a trouble spot on the assembly line. It is a manual assembly job with zero defects allowed so it probably was a constant source of issues.

Re: Why did Chrysler change to single rockers? [Re: feets] #1466252
07/11/13 07:37 PM
07/11/13 07:37 PM
Joined: Mar 2012
Posts: 27
Southern Indiana
R
R/T Lee Offline OP
member
R/T Lee  Offline OP
member
R

Joined: Mar 2012
Posts: 27
Southern Indiana
Quote:

Quote:

FWIW I believe the Magnums with the pedestal rocker are considered to be the longest lasting and best performing stock standard performance SB's. Maybe lowest cost and done right?




Most of the durability comes from the EFI. Those engines don't have carburetors washing down cylinder walls with unburned fuel.




I agree totally with you 100% The EFI being the main source of durability for the magnums. Another thing I thought of, when you look at a INDY cylinder head brochure, all of there SB crate motors are magnums.(might be 1 LA that's supercharged) The 360, 408, 415,440 are all Magnum SBs. Is this just because availability of cores?


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
Re: Why did Chrysler change to single rockers? [Re: Kern Dog] #1466253
07/12/13 08:52 AM
07/12/13 08:52 AM
Joined: Jan 2003
Posts: 16,122
Grand Haven, MI
patrick Offline
I Live Here
patrick  Offline
I Live Here

Joined: Jan 2003
Posts: 16,122
Grand Haven, MI
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.

1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
Re: Why did Chrysler change to single rockers? [Re: R/T Lee] #1466254
07/12/13 09:24 AM
07/12/13 09:24 AM
Joined: Sep 2003
Posts: 1,465
Carson City, NV
B
babarracuda Offline
pro stock
babarracuda  Offline
pro stock
B

Joined: Sep 2003
Posts: 1,465
Carson City, NV
For other then high spring pressure and super high RPM engines I think it was:
1. No spacers R/L to get the rocker aligned with the valve stem.
2. Much easier to get the rocker/valve heigth and they are individually adjustable.

Re: Why did Chrysler change to single rockers? [Re: babarracuda] #1466255
07/12/13 10:05 AM
07/12/13 10:05 AM
Joined: Jan 2003
Posts: 926
MICHIGAN
B
BB65Barracuda Offline
super stock
BB65Barracuda  Offline
super stock
B

Joined: Jan 2003
Posts: 926
MICHIGAN
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
Re: Why did Chrysler change to single rockers? [Re: BB65Barracuda] #1466256
07/12/13 11:31 AM
07/12/13 11:31 AM
Joined: May 2003
Posts: 15,487
Florida
S
scratchnfotraction Offline
I Live Here
scratchnfotraction  Offline
I Live Here
S

Joined: May 2003
Posts: 15,487
Florida
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.


Re: Why did Chrysler change to single rockers? [Re: scratchnfotraction] #1466257
07/12/13 01:09 PM
07/12/13 01:09 PM
Joined: Jul 2004
Posts: 3,799
Arlington, Texas
B
bobby66 Offline
master
bobby66  Offline
master
B

Joined: Jul 2004
Posts: 3,799
Arlington, Texas
Too bad the "ball-stud" Hemi didn't make it into production. Imagine the valvetrain discussions about that one.

Re: Why did Chrysler change to single rockers? [Re: BB65Barracuda] #1466258
07/12/13 01:12 PM
07/12/13 01:12 PM
Joined: Aug 2012
Posts: 1,574
Lakeland FL
F
floridian Offline
pro stock
floridian  Offline
pro stock
F

Joined: Aug 2012
Posts: 1,574
Lakeland FL
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...

Page 1 of 2 1 2






Powered by UBB.threads™ PHP Forum Software 7.7.1