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Why did Chrysler change to single rockers?

Posted By: R/T Lee

Why did Chrysler change to single rockers? - 07/11/13 02:43 AM

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?
Posted By: RapidRobert

Re: Why did Chrysler change to single rockers? - 07/11/13 02:56 AM

Quote:

Was it a cost saving deal?

Ma (like everyone else) was in business to make a profit
Posted By: scratchnfotraction

Re: Why did Chrysler change to single rockers? - 07/11/13 03:01 AM

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.
Posted By: RSNOMO

Re: Why did Chrysler change to single rockers? - 07/11/13 03:19 AM

Quote:

in business to make a profit



A different mindset in the past...

'Profit' and 'cheap' weren't joined at the hip...
Posted By: R/T Lee

Re: Why did Chrysler change to single rockers? - 07/11/13 03:32 AM

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.
Posted By: ahy

Re: Why did Chrysler change to single rockers? - 07/11/13 04:15 AM

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?
Posted By: feets

Re: Why did Chrysler change to single rockers? - 07/11/13 04:49 AM

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.
Posted By: Kern Dog

Re: Why did Chrysler change to single rockers? - 07/11/13 04:50 AM

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.
Posted By: AndyF

Re: Why did Chrysler change to single rockers? - 07/11/13 05:17 AM

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.
Posted By: That AMC Guy

Re: Why did Chrysler change to single rockers? - 07/11/13 06:24 AM

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.
Posted By: AndyF

Re: Why did Chrysler change to single rockers? - 07/11/13 06:17 PM

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.
Posted By: autoxcuda

Re: Why did Chrysler change to single rockers? - 07/11/13 06:40 PM

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??
Posted By: AndyF

Re: Why did Chrysler change to single rockers? - 07/11/13 09:48 PM

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.
Posted By: R/T Lee

Re: Why did Chrysler change to single rockers? - 07/11/13 11:37 PM

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?
Posted By: patrick

Re: Why did Chrysler change to single rockers? - 07/12/13 12:52 PM

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?
Posted By: babarracuda

Re: Why did Chrysler change to single rockers? - 07/12/13 01:24 PM

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.
Posted By: BB65Barracuda

Re: Why did Chrysler change to single rockers? - 07/12/13 02:05 PM

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.

Posted By: scratchnfotraction

Re: Why did Chrysler change to single rockers? - 07/12/13 03:31 PM

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.

Posted By: bobby66

Re: Why did Chrysler change to single rockers? - 07/12/13 05:09 PM

Too bad the "ball-stud" Hemi didn't make it into production. Imagine the valvetrain discussions about that one.
Posted By: floridian

Re: Why did Chrysler change to single rockers? - 07/12/13 05:12 PM

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...
Posted By: BB65Barracuda

Re: Why did Chrysler change to single rockers? - 07/12/13 05:49 PM

Quote:

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...



Its all about money, Not durability or whats good for the consumer.
I had an Escort that had 250K on it, so whats your point?
You can ride a bike for all that matters.
Isnt this thread Why did Chrysler change to single rockers?
Posted By: TC@HP2

Re: Why did Chrysler change to single rockers? - 07/12/13 07:47 PM

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.
Posted By: patrick

Re: Why did Chrysler change to single rockers? - 07/12/13 08:34 PM

Quote:

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.



actually the magnum pedestal mount (and AMC pedestal mount) ARE NOT adjustable
Posted By: TooMany62s

Re: Why did Chrysler change to single rockers? - 07/12/13 08:56 PM

Take a look to see what Honda, Toyota, MB and BMW use. There you will find the clue to what's cheap and it isn't what they're using.
Posted By: BB65Barracuda

Re: Why did Chrysler change to single rockers? - 07/12/13 09:22 PM

Quote:

Take a look to see what Honda, Toyota, MB and BMW use. There you will find the clue to what's cheap and it isn't what they're using.



Posted By: a12superbee

Re: Why did Chrysler change to single rockers? - 07/12/13 11:55 PM

Quote:

Quote:

Take a look to see what Honda, Toyota, MB and BMW use. There you will find the clue to what's cheap and it isn't what they're using.







This? So the arrogant XXXXX that just cut me off has clothes pins in the engine of his 80k car?
Nice. I feel a bit better now.

Attached picture 7774498-bmw_valvetronic.jpg
Posted By: a12superbee

Re: Why did Chrysler change to single rockers? - 07/12/13 11:57 PM

To stay on topic, I agree, money money money. It's what corporations do.
Posted By: R/T Lee

Re: Why did Chrysler change to single rockers? - 07/14/13 02:45 AM

The theory of AMC and some of their "guys" coming over after the buyout is something I didn't think of. The more I think about it, the more it makes since. I know AMC had a large influence with the 4.0 six. So if Chrysler was looking to lower costs, and the AMC guys was pitching the idea to them to drop the shaft mounts style, they figured they could appease the AMC group, and still get a cost savings...? I love R and D history, thanks for your ideas
Posted By: Bad340fish

Re: Why did Chrysler change to single rockers? - 07/14/13 07:13 PM

Quote:

The theory of AMC and some of their "guys" coming over after the buyout is something I didn't think of. The more I think about it, the more it makes since. I know AMC had a large influence with the 4.0 six. So if Chrysler was looking to lower costs, and the AMC guys was pitching the idea to them to drop the shaft mounts style, they figured they could appease the AMC group, and still get a cost savings...? I love R and D history, thanks for your ideas



I would say AMC did the whole 4.0 six and it was ready to go when the buyout happened.

I agree with the guys saying its a cost issue. The pedestal mouns are cheaper, and were a proven idea long before.
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