Lifter preload and valvetrain noise?
Thread Starter
Staging Lane
Joined: Apr 2004
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Lifter preload and valvetrain noise? I've mocked up my new engine parts, and as far as I can tell I need a longer pushrod than stock (my stock LS1 parts measure 7.400). With the new LPE cam, AFR heads milled .024", and the stock pushrods, I'm getting around .030" preload. The stock cam gave .060, way different. Anybody know how the reduced preload will effect the noise situation? I'm thinking about ordering 7.425 pushrods to get the lifter plunger back to it's stock location, since the extra oil would make the already heavy lifter much heavier.
I have two aftermarket cams here, the LPE GT2-3 and a Comp 220/224 XER. The LPE base circle is .050" smaller than stock, and the Comp is .040" smaller. I ran a few searches, and most seem to think that aftermarket cams have a .030" reduced base circle, but that doesn't seem right to me.
I have two aftermarket cams here, the LPE GT2-3 and a Comp 220/224 XER. The LPE base circle is .050" smaller than stock, and the Comp is .040" smaller. I ran a few searches, and most seem to think that aftermarket cams have a .030" reduced base circle, but that doesn't seem right to me.
Last edited by Flareside; Feb 17, 2005 at 07:43 PM.
Recommend replace stock pushrods. I am running pp ls6 style heads, Vinci Boss II cam with 1.89 crane rocker kit with 7.250 pushrods on my 04 C5 A4. Donaldson, dyantechss header kit with magnaflow exhaust. Higher lift cams increase top end noise in LS1's. Adjusted rockers one turn past zero, about .041 preload, noisy, tightened 4- 1/4 more turns, about .080 preload, what crane recommends still noisy, but runs great.
I believe the stock pushrods are 7.385". Since it always good insurance to replace the stock pushrods when doing a head/cam job you can probably go with some 7.4" and be fine. These cars have valvetrain noise anyway. You ad an aftermarket cam with a more aggresive lobe and it makes it worse. Mine sounds like a sewing machine. But my exhaust system helps to cover up the sound.. 
Thread Starter
Staging Lane
Joined: Apr 2004
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Originally Posted by smask04C5
you are correct flareside, 7.400 length stock. Consider jesel or t&d shaft rockers?
Mainly, I'm wondering if you can hear or feel the difference between .080 and .030 preload in an LS1...
Teching In
Joined: Jul 2004
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Too low of preload will make noise as well as be harder on valvetrain components, and too much will kill power. For the street you want to be somewhere in the middle. On our race applications that require hydraulics...We run as LITTLE preload as possible (And where allowable, actually limit plunger travel). If you tend to overev the engine at all, too much preload will pump them up, and can in some cases cause V/P interference, and too little in that situation can over-extend the plunger...Given the high rocker ratio of the LS1 and if you have an aggresive lobe profile, combined with low viscosity oil that everyone runs in them.....They're gonna be noisy no matter what you do. But as a general rule of thumb, I try to hover in the middle of the lifter manufacturer's specs for street apps..Just my $.02
Felber
Felber
