Big Block Rocker Shaft Shims

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JGC403

JGC403

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At Carlisle last year there was someone selling shims for Big Block Mopar to correct the valvetrain geometry. I remember him claiming that it is incorrect from the factory. Anyone know what I'm talking about? What is it supposed to be correcting? I'm at the point in my 383 BB build that I'm going to be getting new rocker arms soon and I want to make sure I'm getting what I need.
 
I think Dan Dvorak sells what you're talkin about. But first, not ALL Mopar engines have incorrect valve train geometry. That's the stupidest thing I ever heard. Yeah, I am sure a lot of them ain't perfect, but for the most part, they are Purdy dang close. Close enough to run for 100K or more miles. I think the shims you're talkin about actually relocate the rocker shafts either toward or away from the valves to get the pad or roller in the right spot on the valve tip. There was a guy on Ebay that sold them to whatever thickness you needed, but I don't see him on there now. Maybe Dvorak can help you out.
 
RustyRatRod said:
I think Dan Dvorak sells what you're talkin about. But first, not ALL Mopar engines have incorrect valve train geometry. That's the stupidest thing I ever heard. Yeah, I am sure a lot of them ain't perfect, but for the most part, they are Purdy dang close. Close enough to run for 100K or more miles. I think the shims you're talkin about actually relocate the rocker shafts either toward or away from the valves to get the pad or roller in the right spot on the valve tip. There was a guy on Ebay that sold them to whatever thickness you needed, but I don't see him on there now. Maybe Dvorak can help you out.
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I'm not saying all of them. But I just remember seeing them at that guys stand. I didn't make it back to ask more questions about it at the time. maybe I'll see him there this year.
 
You wouldnt need any shims until after the motor has been built/rebuilt and or heads surfaced, block decked etc etc. At that point developing push rod length is the last thing to do before setting up the rocker arm geometry. One of these days I will post a pic of how to vastly improve oil flow thru the shims into the shafts, neat little trick I dreamed up.
 
The shims are for setting lifter preload correctly, like stated above after head resurface or block decking, on a non adjustable valve train.
 
I got mine from Mancini and yes they do work. With milled heads, different valves, and different lifters, the angles on my solid lifter 273 were all wrong. Special length pushrods and shims corrected the problem. I think the new valves were longer than the stockers. Here's a link:

http://chucker54.stores.yahoo.net/rocshafshim.html
 
I have used the shims to get the valve train geometry exactly were it needs to be. You need to move the rocker shafts up off the rocker stands to move tip of the rocker arm so that it meets the tip of the valve a little off center to the outside. As the rocker arms pushes down on the valve the tip of the rocker arm moves back toward center of the valve tip This lets the valve move straighter in the guide with less friction and less wear and tear on the guide, and that means more HP and a longer life for the valve train components. Maybe this will help answer your question. You can get a shim pack from 440 Source
 
one bad 440 said:
The shims are for setting lifter preload correctly, like stated above after head resurface or block decking, on a non adjustable valve train.
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The shims I was talking about are not used for preload. They are used to relocate the rocker shaft. I had some made for my slant six head. They are thicker on one side to allow the rocker shaft to be moved either towards or away from the valve stems.
 
RustyRatRod said:
The shims I was talking about are not used for preload. They are used to relocate the rocker shaft. I had some made for my slant six head. They are thicker on one side to allow the rocker shaft to be moved either towards or away from the valve stems.
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Arent slant six a pedestal type rocker assy? I was thinking of a typical BBM rocker shaft that sits in the concave of the cast-in stand in the head.
 
hemi446 said:
I have used the shims to get the valve train geometry exactly were it needs to be. You need to move the rocker shafts up off the rocker stands to move tip of the rocker arm so that it meets the tip of the valve a little off center to the outside. As the rocker arms pushes down on the valve the tip of the rocker arm moves back toward center of the valve tip This lets the valve move straighter in the guide with less friction and less wear and tear on the guide, and that means more HP and a longer life for the valve train components. Maybe this will help answer your question. You can get a shim pack from 440 Source
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Exactly!
 

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one bad 440 said:
Arent slant six a pedestal type rocker assy? I was thinking of a typical BBM rocker shaft that sits in the concave of the cast-in stand in the head.
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No. They are just like big blocks and LA small blocks. Why would I have said that when it is something I have had in my HAND and know about?
 
RustyRatRod said:
No. They are just like big blocks and LA small blocks. Why would I have said that when it is something I have had in my HAND and know about?
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I wasnt saying you were wrong just saying I have never seen them plain and simple, was mearly looking for the explanation and got it.
 
one bad 440 said:
I wasnt saying you were wrong just saying I have never seen them plain and simple, was mearly looking for the explanation and got it.
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If you do a search in the slant section, "ported head" I posted some pictures of the shims when I installed them. They are pretty trick.
 
The block has been square decked, but the heads haven't been milled. I'm using a solid lifter cam, so I need to get adjustable rockers.

So I just need to mock it all up and go from there.


What are your guys opinions on roller tipped rocker arms? Are they worth the extra expense? I just found these on Mancini's site, they are cheaper than other adjustable steel rockers. Is this an instance that you get what you pay for? http://chucker54.stores.yahoo.net/prmstshroarm1.html
 
Those look good. I would not use needle bearing rockers. Too much small stuff to come apart with a failure, plus, the bronze bushed rockers have more surface area for better support for the rocker. There are no real power benefits to speak of with a roller rocker, but they offer fantastic valve guide and stem wear resistance. I would imagine you can see the difference on a dyno, but IMO you'd never feel the difference. But to me, if you can spring for them, they are great addition to help keep wear down and that's always a good thAng.
 
JGC403 said:
At Carlisle last year there was someone selling shims for Big Block Mopar to correct the valvetrain geometry. I remember him claiming that it is incorrect from the factory. Anyone know what I'm talking about? What is it supposed to be correcting? I'm at the point in my 383 BB build that I'm going to be getting new rocker arms soon and I want to make sure I'm getting what I need.
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Is this him ?

http://board.moparts.org/ubbthreads...218&Words=B3RE&topic=&Search=true#Post7923244
 
You'll likely need to get some custom length pushrods if you are using the shims to optimize your valve train geometry. You would be wise to measure for the correct length at any rate.
 
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