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 Post subject: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 6:59 am 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3564
Location: Indianapolis
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I bought a set of roller rockers, probably five years ago from Jim Cox. I installed the roller rockers on the built slant in the 68 B and I wanted to get the rocker arm roller to valve tip interface as good as possible, to maximize any possible gains and to minimize any wear issues.
The valves I have in the head are Ford 289 valves and they are .096 longer than stock slant six valves.

I found a company called B3 Racing that specializes in Mopar shaft mounted rocker systems.
A link to their Tech web page is below

http://www.b3racingengines.com/techcorner.asp

I went through the process with B3, they have a list of measurements they use to size the shims that they say will reduce the travel of the rocker across the valve tip.
A part of the selling pitch from B3 is that rocker motion across the valve tip is wasted motion. When the rocker is moving across the valve tip it is not pushing down on the valve, nor is the pressure on the valve tip as centered as it could be.

Photos of the roller movement without the B3 shims and with the B3 shims are posted below.
I was surprised, roller travel was reduced at least 50%, and I am being cautious with the reduction reported. The photographs capture a good representation, in person with good lighting the reduction in travel across the valve stem tip is significant. All the travel is centered on the valve tip.


Attachments:
B3 Shims 021822.jpg
B3 Shims 021822.jpg [ 122.5 KiB | Viewed 743 times ]
Shims on pedistals 021822.jpg
Shims on pedistals 021822.jpg [ 121.35 KiB | Viewed 743 times ]
no shims 021822.jpg
no shims 021822.jpg [ 90.65 KiB | Viewed 743 times ]
with shims 021822.jpg
with shims 021822.jpg [ 91.41 KiB | Viewed 743 times ]

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 Post subject: Re: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 7:10 am 
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Joined: Mon Oct 21, 2002 11:08 am
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Location: Blacksburg, VA
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Very cool. Thanks for posting. I will likely spring (haha) for a set of those shims and do some measuring. A few of my heads are Chev valves that are 0.100" longer than stock.

Lou

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 Post subject: Re: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 7:29 am 
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Turbo Slant 6

Joined: Sun Jul 20, 2008 10:20 am
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Location: St. Louis Park, MN
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Be careful that the shims won't crack your rocker stands in the head.

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 Post subject: Re: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 8:19 am 
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Supercharged
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Joined: Sat Nov 27, 2004 8:03 pm
Posts: 7716
Location: IRWIN PA
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Can the adjustment for using those shims be taken up in the lash settings or would new pushrods need to be sourced as well?


Good work John!

Greg

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 Post subject: Re: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 9:22 am 
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Joined: Sat Oct 19, 2002 12:06 pm
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Location: Silver Springs, Fl.
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I haven't done it on a slant, Yet. I do have a head that I milled off the rocker stands. I did a set of 440 heads, back in the '80's. Milled off the cast rocker stands, and used the old 413 bolt on stands, to adjust the geometry. On the 440 I did gain lift. I don't remember how much.
PS: the big block and slant six use the same dia shaft.
PPS: I remember several years ago, a company that would make rocker stands, based on your info, to get the optimum geometry.

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 Post subject: Re: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 11:26 am 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3564
Location: Indianapolis
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* The shims are aluminum and a nice fit into the rocker stands, not saying they could not crack the tapered tips of the stands, they seem to be a good fit.

* I used a dab of red M1 synthetic grease, it's really sticky to hold the shims in place while putting the shaft and rockers in place, I also stuffed paper towels into the push rod passages.

* The shims I got were about .220 thick, that moved the rocker shaft up that amount, so to get the adjusters back to a normal position I ordered new longer push rods from Smith Brothers.

* With the rocker shaft moving up I had a concern over valve cover clearance, I put modeling clay on both end of all the rocker arms and by hand turned the engine a revolution. The adjusters right below the internal baffels in the valve cover fully compressed the clay, the two most outboard adjusters hit hard on the valve cover. This is a hydraulic head and valve cover, I am modifying the valve cover to add clearance, I'll post on that in the 68 Barracuda build thread.

* I got the few measurements needed using a dial caliper. The cylinder head was on the engine in the car, but still not too difficult to get. There is one measurement, the distance from the valve stem to the rocker shaft IIRC, that can be got with the valve springs on, but is more accurate with the valve spring removed, I used the rope in the cylinder and the valve spring removal tool I built and got it.

* I am a bit of a nerd when it comes to getting measurements right, so I measured the features as requested and wrote the dimensions down and set that piece of paper aside. The next day I went out and remeasured without looking at what I done the previous day. When I compared the two data sets they were within a thou or two on all the readings. Figuring if the measurements are repeatable it is probably right, I went with it and the shims seem to be right.

* I emailed and spoke with Michael B the owner of B3 a couple of times. He patiently listened to my questions and concerns and responded promptly and professionally. Was a nice guy to talk to and he came through with what he promised.

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 Post subject: Re: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 2:38 pm 
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EFI Slant 6

Joined: Mon May 26, 2014 4:02 pm
Posts: 339
Location: Vermont
Car Model: Slant Six powered M37
Charrlie_S wrote:
the old 413 bolt on stands, to adjust the geometry. On the 440 I did gain lift. I don't remember how much.
PS: the big block and slant six use the same dia shaft.
PPS: I remember several years ago, a company that would make rocker stands, based on your info, to get the optimum geometry.


Did all 413's have the bolt on stands, or only the heavy duty truck ones?


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 Post subject: Re: Rocker Arm Geometery
PostPosted: Fri Feb 18, 2022 4:10 pm 
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Board Sponsor & SL6 Racer

Joined: Wed Oct 23, 2002 7:57 pm
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Location: Waynesboro, Pa.
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Certainly good info John! I would be interested in total lift numbers before and after. :D :D

How do you go about knowing what to order? I did not see anything on their web site that explained that. Or do you have to call them and talk to someone.

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 Post subject: Re: Rocker Arm Geometery
PostPosted: Sat Feb 19, 2022 6:32 am 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3564
Location: Indianapolis
Car Model:
I called and we discussed the valve train set up that I had and then Michael offered what he could do and he quoted a price. Then I was sent an e mail with instructions on the measurements needed.

Concerning the changes in lift, I wish I had thought of that, the roller rockers and spacers are in place, I already did an install and remove and re install and remove again to get the valve tip to roller travel photos. I am satisfied with seeing the reduction in roller travel and knowing the pressure on the valve stem is centered. It would be interesting to see the change in lift and I would do that if I have the rockers out of the head in the future.

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