lifter preload opinions
05-08-2013, 01:14 PM
#1
Staging Lane
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lifter preload opinions I have comp cams 875-16 reduced travel lifter going into my rebuilt 370. I'd like to adjust it using a dial indicator but I don't think ill be able to do it with the engine in the car. I called comp cams and they said if I install it around .012 cold preload it should be around .002-.004 hot preload. Does that sound about right? Or can you fit all the tools necessary under the cowl of a f body to do it with a dial indicator gauge. Also if someone knew of an engine dyno tat can hook up to an efi engine that'd solve everything. As of right now I'm not having luck finding somewhere. Any opinions on how I could do it will be much appreciated. Thanks for the help in advance.
05-08-2013, 06:25 PM
#2
". Also if someone knew of an engine dyno tat can hook up to an efi engine that'd solve everything" Huh?? You want to put the engine on a dyno to set the preload??
Do you have adj rockers? If not, why would you not set preload like a stock lifter/rocker combo, only use .012 as the desired load, when choosing the pushrod length?
Do you have adj rockers? If not, why would you not set preload like a stock lifter/rocker combo, only use .012 as the desired load, when choosing the pushrod length?
05-08-2013, 07:06 PM
#4
Staging Lane
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I don't have but getting rockers. But with that comes new issues. The range the lifter can be preloaded to is minimal so I wanna go with adjustable rockers instead of shiming the stock rockers or getting custom pushrods. The motor is all stock deck height and head deck wise so I'm using my 7.4 hi tech pushrods from before the rebuild.
05-08-2013, 08:00 PM
#6
Ditch those lifters. Get the 850s or LS7s if you want a pretty much set and forget valvetrain. Otherwise you will need to replace the pushrods. Right now you're probably closer to .060-.080" preload if you're using essentially stock stuff. That's about the total travel area of those lifters. You'll just collapse them.
Btw, most use the 875s with a .030" preload despite what Comp claims to quiet them down and actually use them as a hydraulic lifter.
Btw, most use the 875s with a .030" preload despite what Comp claims to quiet them down and actually use them as a hydraulic lifter.
05-08-2013, 08:09 PM
#7
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It would be cheaper yes but this was my thought. Say I need 7.4" pushrods I wouldn't be able to add .002-.004 to that amount because that's manufacturer tolerances. As for the 850s I heard they max around .600 lift or so. I don't mind forking the dough for adjustable rockers cuz I will just use them later for my next motor. I have thought about returning the lifters but I've had them for over 90 days so idk if I'd get all my money back or if they'd take them
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05-08-2013, 08:16 PM
#8
No, you're not understanding how preload works. Let's say you need a 7.3" pushrod with a solid lifter. You then add preload to that with the length of the pushrod. 7.4" would give you .100" of preload. See the problem? You'd destroy your engine the first time you tried to start it because the lifter would collapse and the valves would hang open and smash into the piston. Let's say you measured and it comes out to 7.35" then you could order custom 7.375" to get .025" preload.
If you don't measure what length you need with a solid lifter (just modify stock) and THEN ADD preload to that, you're pushrod is going to be way off.
If you don't measure what length you need with a solid lifter (just modify stock) and THEN ADD preload to that, you're pushrod is going to be way off.
05-08-2013, 08:27 PM
#9
Staging Lane
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Yes I understand what you're saying. That's the method used when keeping stock rocker. If I buy adjustable rockers then the only thing I need to worry about with the pushrod is if it gives me the correct sweep over the valve tip. I would make zero lash and then tighten for pre load. Sorry if I'm sounding ignorant but I've never dealt with preload in the way. Always did it old school. Buy pushrods for correct sweep, adjustable rockers and run the engine while loosening and tighten 1/4 turn after the tick stops.
05-08-2013, 08:38 PM
#10
Staging Lane
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You know what screw these lifters. They're making thing too complicated. I already have the Trunion upgrade so ill keep my rockers. Ill return or sell them for new ones. What lifters would yall recommend? I'm running .610/.617 lift with 129 lbs of seat pressure and 470 lbs at .675 lift. It'll be my daily spun to 7000 rpm.
05-08-2013, 09:17 PM
#13
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Light as in pressure or light as in physical weight? I wouldbt have been able to run behives due to the cam. I'm running the springs that were designed for the cam.
05-08-2013, 09:39 PM
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Wow, I didn't know someone made beehives that handle that much lift. Well its too late for me now. And if lower spring pressure is the way to go on ls7 lifters then those aren't for me I'd suppose. That leaves the cts v lifters which I know nothing about, the awesome but pricey morels, and the comp r type lifters.
