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Re: Hemi Rocker Arm Deflection
[Re: mr_340]
#1120709
12/05/11 10:36 PM
12/05/11 10:36 PM
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Joined: Mar 2007
Posts: 314
Manitoba, Canada
Big Wedge
enthusiast
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enthusiast
Joined: Mar 2007
Posts: 314
Manitoba, Canada
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Hi Wayne, We couldn't see anything really visible. Just for the heck of it, I place the dial gage on the rocker shaft with the 600 lb springs in place. The shaft moved .002". The deflection graph is about what I expected to see. At the start, the parts are taking up clearances in all of the associated parts. Once the valve is being lifted off of the seat, it is encountering the seat load of the valve spring. I am not sure what that is, but let’s say for arguments sake that it is 300 lbs. That may account for the start of the graph. With the spring having a constant rate of X lbs/inch, the deflection goes up until it peaks out at maximum lift. The curve that is shown in the deflection portion of the graph may be a result of the ramp on the camshaft lobes not being linear. We tried to keep one thing constant while doing this which was using crankshaft angle. We ran into this quite by accident. The light checked springs we started with were having a difficult time returning the valve on the closing event. We did get the maximum lift however. We threw back on the 600 springs to check all the events and were amazed by the loss of total valve lift. Then we had more questions than answers. I have a 440 engine and I have never taken the time to measure this. I have always used checker springs. This is new territory for us. We were hoping some of the more “seasoned veterans” might chime in and offer some feedback. I, for one, find this very interesting. I am trying to reverse Engineer the exhaust rocker arm in my CAD software and run and FE analysis. Now that I have real world data, I would like to see if the analytical matches. Stay tuned. Garth 
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Re: Hemi Rocker Arm Deflection
[Re: astjp2]
#1120712
12/06/11 09:46 AM
12/06/11 09:46 AM
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Joined: Mar 2007
Posts: 314
Manitoba, Canada
Big Wedge
enthusiast
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enthusiast
Joined: Mar 2007
Posts: 314
Manitoba, Canada
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Quote:
I just pulled my rockers this morning to send them off for inspection and blueprinting. I have Dvorak style stands and when I pulled the exhaust hardware on the even numbered bank, it sprung like a coil spring getting loose. The center rocker stand is out of alignment compared to the rest of the them. It put the .180 wall shaft in a .062 bind. How much do you think that the stands and shafts are flexing? How would you measure the flex in the stands? Tim
Tim, I put a dial gage on the rocker shaft adjacent to the exhaust rocker arm. We measured .002" deflection.
Garth
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Re: Hemi Rocker Arm Deflection
[Re: astjp2]
#1120713
12/06/11 11:45 AM
12/06/11 11:45 AM
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Joined: Oct 2005
Posts: 290
Manitoba, Canada
liteweight
OP
enthusiast
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OP
enthusiast
Joined: Oct 2005
Posts: 290
Manitoba, Canada
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Quote:
I just pulled my rockers this morning to send them off for inspection and blueprinting. I have Dvorak style stands and when I pulled the exhaust hardware on the even numbered bank, it sprung like a coil spring getting loose. The center rocker stand is out of alignment compared to the rest of the them. It put the .180 wall shaft in a .062 bind. How much do you think that the stands and shafts are flexing? How would you measure the flex in the stands? Tim
Hi Tim
First time I've heard of this . How are you aligning the shafts durring assembly? So, all the stands are in alignment, they should be loose on the head bolt down, you tighten the shafts, & finally tighten the stands.
If this is the way you've done it, then you either have a stand that is off register or the dowel register on the head is wrong. TYry swapping stands around to see if it corrects your problem or remains with the same alignment on the same area. If it remains in the same area, your dowel register is wrong on the head, if the alignment issues follow that stand-------.
liteweight
68 Hurst LO Hemi Dart
70 hemicuda 4 spd. R code owned since 76
70 GTX 4 spd. 21,000 orig. miles
55 Ford F100 chopped,slammed,bagged & supercharged
96 Ram 2500 4X4 Twin turbo'd Cummins 550hp 1200 ft. lbs tow vehicle
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Re: Hemi Rocker Arm Deflection *DELETED*
[Re: liteweight]
#1120714
12/06/11 12:51 PM
12/06/11 12:51 PM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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Post deleted by polyspheric
Boffin Emeritus
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Re: Hemi Rocker Arm Deflection
[Re: polyspheric]
#1120716
12/06/11 03:40 PM
12/06/11 03:40 PM
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Joined: Jan 2003
Posts: 3,504
DFW
mr_340
master
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master
Joined: Jan 2003
Posts: 3,504
DFW
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Poly, I did a similar calculation on piston pins a while back and HemiFred told me I was wasting my time polishing a block. I got similar results to you. The fourth power of the diameter on the moment of inertia makes a big difference in the stiffness of a bar (same as a torsion bar in relative stiffness). Here is some of the results of my calculations if anyone had an interest.
Piston pin strength
Pin OD 0.990 1.031 0.984 0.929
Pin ID 0.610 0.721 0.674 0.489
Mom.In. 0.822 0.860 0.731 0.688
Pin Lg. 2.930 2.930 2.750 2.750
Areas 0.152 0.136 0.128 0.156
Density 0.283 0.283 0.283 0.283
Weight 180 161 143 173
Wall Th 0.190 0.155 0.155 0.220
C (max) 0.495 0.516 0.492 0.465
Rel Str 0.602 0.600 0.673 0.675
Shorter and larger diameter is the lightest. I imagine the T&D/Jesel small diameter rocker shafts work since they are short in length.
Floyd Lippencott IV
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Re: Hemi Rocker Arm Deflection *DELETED*
[Re: mr_340]
#1120718
12/06/11 09:46 PM
12/06/11 09:46 PM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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Post deleted by polyspheric
Boffin Emeritus
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I won't go into the longer and thicker versus the shorter and thinner debates 
