Another pushrod length question
05-09-2010, 05:03 PM
#1
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Another pushrod length question ok i know measuring is the only way to be sure but im chasing down a valvetrain tick that i cant seem to get right. i m running just a thunder racing tr224 cam and i have switched to ls7 lifters. thought my ls1 stock lifters were bad so i replaced them. still getting the same sound. im running a hardened 7.4 pushrod. Also replaced my oil pump o ring and installed a new ls6 oil pump. when i seat my pushrods in, and after tightening to 22ft lbs. there are several pushrods i can spin and some rocker arms almost seem loose. am i running the right size pushrod? i have inspected them and none seem to be bent. the ticking is present mainly above 2500rpms only. by the way, i running stock thickness fel pro head gaskets. Any one running a similar setup? 243 heads also. a few have sugguested a 7.35 pushrod. if i can freely spin some of them, wouldnt i need a longer pr
05-09-2010, 05:17 PM
#2
Best way is to measure. Alternate check would be to pull the driver's valve cover, set the motor at TDC, then loosen the #1 rocker and snug to zero lash and count turns to reach 22 lb-ft. This will let you know if it is way out. Also, if stock rockers, are you sure all the bearings are in place or there isn't some other mechanical issues that could be the source of the noise?
05-09-2010, 06:07 PM
#4
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Here is a thread that explains it pretty good.
https://ls1tech.com/forums/generatio...od-length.html
I like to measure it's just easier and makes more sense to me.
.
https://ls1tech.com/forums/generatio...od-length.html
I like to measure it's just easier and makes more sense to me.
.
05-09-2010, 11:56 PM
#5
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I just reinstalled my lifters and 7.400 pushrods with my new PRC ls6 heads and a .040 cometic gasket. It was a hair less than 1-1/2 turns from zero lash to 22lbs, right in the sweet spot. Glad I don't need to buy another set.
05-10-2010, 07:20 AM
#7
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If the pushrods/rockers are loose when the bolts are torqued then the pushrods are too short. If you're using the bolt method then all lash should be out and the rocker should be tight at 1 to 1 1/2 turns before full torque. The most accurate way is using a PR length checker and adding your desired preload once you find the zero-lash length.
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05-10-2010, 04:44 PM
#8
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see thats what i was thinking/ i think i need a longer pushrod? anyone got a pushrod length checker they could loan me? ill pay shipping to and from. whats the next length of pushrod after 7.40?
05-10-2010, 07:39 PM
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should give you the preload you need. Those will .025 longer that stock push rods.
If you are using dual springs those can be a little noisy sometimes, especially when hot.
.
05-11-2010, 04:39 AM
#12
Define what you calling "loose rockers". Can you move them side to side or up and down (i.e., you get a "tick" "tick" when you lift the rocker tip). If the valve spring is not compressed, the rocker will easily move side to side a small amount. If you truly measured 1-1/2 turns from zero lash (and had zero lash correctly set up), I am coming up with 0.088" of preload. If you are unsure, get an adjustable pushrod and measure.
05-14-2010, 04:53 AM
#20
If the valve is closed the rockers will move side to side a small amount. If that is what you are seeing then that is normal. If they are moving a large amount, something is wrong.
You really need to buy an adjustable pushrod. They are less then $20 and will answer all the questions. It will be money well spent if you endup buying the wrong pushrods because you didn't measure. The problem with borrowing one is that shipping costs alone will pay for half the cost of the tool and in the end you have the tool you can use or sell if you want.
Also, how are you determining you are at zero lash?
You really need to buy an adjustable pushrod. They are less then $20 and will answer all the questions. It will be money well spent if you endup buying the wrong pushrods because you didn't measure. The problem with borrowing one is that shipping costs alone will pay for half the cost of the tool and in the end you have the tool you can use or sell if you want.
Also, how are you determining you are at zero lash?