Rocker pushes down spring when torquing them down?
03-08-2009, 01:40 PM
#1
Rocker pushes down spring when torquing them down? Trying to solve a tuning issue with the new carb today, i decided i would go back and threadlock my rockers since i didnt when i installed them. Tehy are stock rockers, when i was loosing them i could wiggle them slighlty side to side which i know is normal. When i loosened them the spring did not move (no pressure on them). When i cleaned them off, put the red thread locker on and started to torque them down i could see then spring being pushed down slightly as i tightened it down. I didnt measure exactly how much but the car runs perfectly fine asside from very rich with the new carb. Is this normal? I figured it was due to the hydraulic lifters uncompressing without the weight of the rocker pushing against the plunger.
I am running 7.450" pushrods, unmilled cylinder heads. I measured for what size pushrod i needed when i put the cam in and i came up with 7.450 with .080" preload.
I am running 7.450" pushrods, unmilled cylinder heads. I measured for what size pushrod i needed when i put the cam in and i came up with 7.450 with .080" preload.
03-08-2009, 04:59 PM
#4
Thanks guys! I am running very tight PTVC so i just wanted to be sure haha. Valve train seems a little noiser since i adjsuted them. I know i had them way too tight since i didnt use a torque wrench the first time. I'll pull the valve covers in a few miles and double check the torque again. Runs great though.
03-08-2009, 07:40 PM
#5
There is no adjustment. Over tightening does nothing but potentially strip the threads. That slight movement of the valve was due to the oil in the lifter, which should have bled down so the valve came back up. If done by the GM procedure, even with tight PTV you should still have room since the procedure calls for only tightening the rockers on the base circle. You just need to tighten them down slowly to allow them to bleed. If you follow LS1howto, then all bets are off since the rocker installation procedure on there is wrong.
03-08-2009, 07:46 PM
#6
I just followed my own metho haha. turned the engine over by hand watching the valve springs compress and release and removed and torqued them down accordingly. I cranked the engine over about 5 rotations with the starter then torqued them down again (which didnt change), then waited a few minutes and started it. I figured the red threadlocker should be fine even if its still wet. I didnt run it for but 5 minutes for a test run.
03-08-2009, 07:55 PM
#7
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Not every lifter is able to be on the base circle of the cam at the same time. Some lifters will be up on the cam lobe and some will be on the base circle. You want to tighten the rockers when the lifters are on the base circle. You can tighten them all at the same time but then you need to spin the engine over 180* and retighten them so that you get the ones that were not on the base circle the first time. Some of the rockers will push the valves down when you tighten them because the lifter is up on the lobe and not down on the base circle.
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03-13-2009, 04:22 PM
#10
Re-checking is pointless. The required torque is a running torque based on the dynamic friction. When you re-tighten, then you have to over come static friction, which is great so even though your bolts may not actually be tightened correctly the torque wrench won't tell you because of the difference in friction characteristics.
03-13-2009, 06:54 PM
#11
The reason i am running such long pushrods is because i am running LSK lobes which have .651" lift on them. They grind them on a smaller base circle so the lobes will clear the cam bearings when sliding the cam through the block.
Yeah that makes sense about rechecking them. I am just very careful with rockers and such. I think i checked my Duramax rocker clearnce and adjsutment nut about 5 times each just to be sure when i swapped the heads on it.
Yeah that makes sense about rechecking them. I am just very careful with rockers and such. I think i checked my Duramax rocker clearnce and adjsutment nut about 5 times each just to be sure when i swapped the heads on it.
