Do I have enough lifter preload?
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Do I have enough lifter preload? I just installed some TFS 215s on my SS tonight with the included 7.5 inch Trickflow pushrods & some new Yella Terra 1.7s, & GM MLS gaskets. Following YTs instructions, I finger tightened both #1 cyl rockers at TDC, then from there torqued them to 25 ft lbs, without shims. From finger tight to 25 ft lb it only took 1/4 turn. Their instructions say 1/4-1/2 turn is ideal, if more than 1 full turn use the shims. If I rock the rockers back & forth theres prolly .020 play. Now the heads were milled .010, & the LS7 lifters are new & submerged in fresh oil for a few days. Do you think its just the new lifters not being pumped up or should I get longer pushrods?
YT's instructions are garbage and incorrect. I'm too lazy to type it all out, but do a search and you'll find tons of info on this subject. User "vettesnuts" (I think thats his name) has posted this info a million times.
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After doing a search I found the LS7 lifters like a lot of preload, like .060, & from what I did tonight I only have .012 preload. From that, a 7.550 pushrod sounds about right. I do have a pushrod length checker tool & may play around with it tomorrow after work. Thanks though for the info.
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I went ahead & got the pushrod length checker tool out tonight & tried that. With the 7.5 pushrod it takes 1/4 turn to 22 ft lbs after finger tight. With the pushrod tool turned out 15 times(=7.550 inch) it takes almost 1 full turn to 22 ft lb from finger tight so I am gonna go with 7.550. I dont know why Trickflow recommends this 7.5 pushrod for their heads when theres so many variables.
Note that the shims are to adjust the wipe pattern and not the preload. You need to set the wipe pattern first before measuring for the pushrod length. The YT instructions are confusing. Also, LS1howto is not correct either so don't follow the instructions there.
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From: Fayetteville, NC
hydraulic lifters need to be preloaded .045" to .075" to operate correctly however many racers in hydraulic classes will run as little as .010" with a hydraulic lifter that has a very stout retaining device to keep the plunger from pushing out the top of the lifter
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Well YTs instructions make it appear that the shims are used if there is too much preload without them. I would imagine setting the wipe pattern consists of making sure the roller tip is centered on the valve tip correct?
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You would be correct. Do a search and you should get some good pics and directions on the wipe pattern. PR lenght will give you the preload.
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The 7.550 pushrods did the trick. That gave me around .050 preload & a fairly quiet valvetrain after I let it warm up. The wipe pattern appeared to be good as well. After working on it for the last 4 days after work, I was anxious to get this thing fired up so I had them overnighted from Summit.
