Shaved 317 heads, shim rockers, or shorter pushrod
08-31-2010, 10:43 PM
#1
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Shaved 317 heads, shim rockers, or shorter pushrod If I am not mistaken, they should accomplish the same thing, but which is the best solution to keep pressures in check?
They are shaved .030
They are shaved .030
Last edited by transsam; 08-31-2010 at 10:52 PM.
09-01-2010, 05:52 AM
#2
Not sure I understand what pressures you are referring to. If the cam is stock the the rockers should have the correct height unless some valve work was done on the head. You may need short pushrods though. Not enough information to answer your question.
09-01-2010, 01:27 PM
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Cam is going to be: " CheaTR v.3" - 219/230 .607/.604 117 LSA
Heads, as stated, are shaved .030.
Heads are well worked and are running 2.02/1.57
Rotating assembly runs a 4" crank to bring CI to 384 with 2cc valve reliefs.
Current pushrods are 7.400
I am looking to make sure the geometry and pressure is correct. Would I be better off placing shims under the rockers, or shortening the pushrod to accomplish correct geometry?
I hope that is enough info,
Thanks again.
Heads, as stated, are shaved .030.
Heads are well worked and are running 2.02/1.57
Rotating assembly runs a 4" crank to bring CI to 384 with 2cc valve reliefs.
Current pushrods are 7.400
I am looking to make sure the geometry and pressure is correct. Would I be better off placing shims under the rockers, or shortening the pushrod to accomplish correct geometry?
I hope that is enough info,
Thanks again.
09-01-2010, 06:19 PM
#4
shimmnig changes rocker sweep, so pushrod is usually the way to go, unless you've got longer valves.
However, in your case, measure. Depending on where you want to be in your lifter travel, you might get away with your 7.4, or maybe longer. On a 5.3 we went from a stock cam to a TFs228/230 cam, and the base circle change was .088, so .044 change in pushrod length longer. We milled the head .050 and used a thinner gasket, so we ended up with ~.011 extra preload with stock length pushrods.
However, in your case, measure. Depending on where you want to be in your lifter travel, you might get away with your 7.4, or maybe longer. On a 5.3 we went from a stock cam to a TFs228/230 cam, and the base circle change was .088, so .044 change in pushrod length longer. We milled the head .050 and used a thinner gasket, so we ended up with ~.011 extra preload with stock length pushrods.
09-01-2010, 06:42 PM
#5
shimmnig changes rocker sweep, so pushrod is usually the way to go, unless you've got longer valves.
However, in your case, measure. Depending on where you want to be in your lifter travel, you might get away with your 7.4, or maybe longer. On a 5.3 we went from a stock cam to a TFs228/230 cam, and the base circle change was .088, so .044 change in pushrod length longer. We milled the head .050 and used a thinner gasket, so we ended up with ~.011 extra preload with stock length pushrods.
However, in your case, measure. Depending on where you want to be in your lifter travel, you might get away with your 7.4, or maybe longer. On a 5.3 we went from a stock cam to a TFs228/230 cam, and the base circle change was .088, so .044 change in pushrod length longer. We milled the head .050 and used a thinner gasket, so we ended up with ~.011 extra preload with stock length pushrods.
Agree with the above if you still have stock length valves & stock rockers no shims needed with those heads ... Even when you shim the rockers for correct geometry (wipe) like a lot of guys are now doing on TFS heads you still measure PR length for correct preload AFTER wipe is set.... So measure for PR length and you should be golden...
