While I wait for my pushrod length checker to come I took some time today to try to get an idea what my rocker arms were doing when they were pressing on the top of the valve stem. Let me start out by saying I've just had my rocker arm assembly rebuilt by Rocker Arms Unlimited (http://www.rockerarms.com/index.html) which included a new hard chromed shaft, new bushings and tips re-radiused so I'm hoping that its in good shape. Also, the valve stem heights are all the same.
I loosened all the rocker arms and marked the tips of the valve stems with a black magic marker (I'm pretty sure a dry erase marker would be better but I don't have one of them). I then rotated the crankshaft and set each rocker arm tight against the valve stem (i.e., no clearance) so I could (hopefully) get a pattern on the stem.
The following is what I got -
Rocker Arm/Valve stem interface
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Gene Gillam
- Posts: 1275
- Joined: Wed Jan 02, 2013 4:52 pm
- Location: Saucier, MS
Rocker Arm/Valve stem interface
- Attachments
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- Valve stem #8 - Not sure what this shows - there's very little contact even though the rocker arm was hard against the stem. It does start more to the center and end up closer to the outside edge of the tip.
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- Valve stem #7 - Starts just short of the middle then moves across to the outside of the stem.
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- Valve stem #6 - Again, not showing a lot of contact but starts just short of the middle then moves across to the outside of the stem.
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- Valve stem #5 - Starts just short of the middle then moves across to the outside of the stem.
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- Valve stem #4 - Poor contact again but it starts just short of the middle then moves across to the outside of the stem.
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Gene Gillam
- Posts: 1275
- Joined: Wed Jan 02, 2013 4:52 pm
- Location: Saucier, MS
Re: Rocker Arm/Valve stem interface
Based on what I'm seeing here I believe I need longer pushrods (I'm running a supercharger on an engine with domed pistons (originally carbureted) so I have two (2) solid copper head gaskets to lower the compression). Do the valve train geometry gurus agree?
Thanks,
Gene
Thanks,
Gene
- Attachments
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- Valve stem #3 - Poor contact again but it starts just short of the middle then moves across to the outside of the stem.
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- Valve stem #2 - Poor contact again but it starts just short of the middle then moves across to the outside of the stem.
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- Valve stem #1 - Again poor contact but it starts just short of the middle then moves across to the outside of the stem.
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- Lastly, this is typical of where the adjusters are - this is #8.