Pushrod length help
Pushrod length help I got my motor on the stand and I'm trying to figure out what length I need, I have a length checker I used on the number 1 cyl and it came out to be 7.35 as the best fit. I got a set off btr 7.35 and after I put them in my motor I torqued dwn the rockers and some where loose, what did I do wrong? This is my first time messing with pushrod length I'm used to old school ajustable rockers ha, its 4.8 with 243's and a .623 lift cam
Sounds like you may not have been on the base circle of the cam when you took your initial measurement. Or you may have miss counted the turns in your pushrod checker. That is most likely the reason your new pushrods now seem to be short.
1. To re-measure make sure the lifter is on the base circle of the cam
2. Since you know your 7.350” pushrods are too short, turn your pushrod checker an extra ½ turn past the 7.350” length, your checker will now be at 7.375” length.
3. Install the checker and tighten down the rocker until it is snug (you do not need to torque it down)
4. Lift the rocker tip up and down, if you get movement up and down and it “ticks” then the pushrod is too short, if the rocker is solid and firm with no movement then the pushrod is too long. You want to find the point where the pushrod is not depressing the lifter cup and is flush in the rocker arm on the other end, just past the point of having slack. The rocker arm may have slight movement. This is “zero lash”. This may take a few try’s, just keep going in half turn increments on the checker until you find the sweet spot.
5. Once you’ve found zero lash, remove the pushrod length checker carefully and count the number of turns you ended up with. Each full turn equals .050”, so multiply the number of turns by .050, then add that number to the length of your checker (when fully closed). You now have your zero lash length.
6. Now add the preload you want to run, to your “zero lash length” and that is the length pushrod you need to order. (We run .025” to .030” of preload in our motors)
-Hope that helps
1. To re-measure make sure the lifter is on the base circle of the cam
2. Since you know your 7.350” pushrods are too short, turn your pushrod checker an extra ½ turn past the 7.350” length, your checker will now be at 7.375” length.
3. Install the checker and tighten down the rocker until it is snug (you do not need to torque it down)
4. Lift the rocker tip up and down, if you get movement up and down and it “ticks” then the pushrod is too short, if the rocker is solid and firm with no movement then the pushrod is too long. You want to find the point where the pushrod is not depressing the lifter cup and is flush in the rocker arm on the other end, just past the point of having slack. The rocker arm may have slight movement. This is “zero lash”. This may take a few try’s, just keep going in half turn increments on the checker until you find the sweet spot.
5. Once you’ve found zero lash, remove the pushrod length checker carefully and count the number of turns you ended up with. Each full turn equals .050”, so multiply the number of turns by .050, then add that number to the length of your checker (when fully closed). You now have your zero lash length.
6. Now add the preload you want to run, to your “zero lash length” and that is the length pushrod you need to order. (We run .025” to .030” of preload in our motors)
-Hope that helps
I don't think he added the pre-load figure to the length that he got is my guess.
FWIW we've always run .050-.060" as our "optimum" pre-load, but have run as much as .080" with no issues.
FWIW we've always run .050-.060" as our "optimum" pre-load, but have run as much as .080" with no issues.
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