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Old 11-04-2009, 05:56 PM   #1
green70
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Default Lifter pump up or collapsing??

I'll start this by stating that I've not had but a few experiences with trying to use hydraulic lifters in a somewhat race type situation with none being very successful. Been trying to find the missing upper rpm power in my ls-2 combo for a couple months now. Have checked everything and nothing is obviously wrong. Cam timing, head flow, valve springs, etc. Combo that this setup was copied from made peak power at 6200 while my starts trailing off at 5700-5800 and is down a solid 50hp over 6000. Since everything has checked out fine, it's looking like I'm seeing some type of lifter/ and or valve float issues but from all the opinions out there it getting impossible to determine whether or not it could be the lifters pumping up or collapsing. I know there's guys out there making ls motors fly that are still using hydraulic lifters so could someone please enlighten me? Will excessive upper rpm oil pressure cause pump up? This I've wondered since I've replaced the pan and oil pump. My oil pressure is pretty stout now at high rpm where it was only seeing around 50psi stock. Sorry bout the long winded questions but I really need some input from people who have dealt with hydraulic lifters...
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Old 11-04-2009, 06:10 PM   #2
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Default Re: Lifter pump up or collapsing??

Copied from shubeck's site...

After putting the cam wear problem behind us, you get to enjoy two additional benefits with Schubeck “Zero Lash” Hydraulic lifter technology:

1. An RPM increase, because they will not pump-up. We all know that lifters pump up, causing the valves to hang open, which in turn, puts a lid on the engine's rev ability. The Rev limit usually starts around 6,000 RPM.

Schubeck “Zero Lash” Hydraulic drag racing lifters are a drop-in prevention for the pump-up problem because Zero Lash means no preloading of the hydraulic travel. Preloading sets the stage for lifters to pump up, which is like an RPM governor. You set the them as you would a solid lifter, but as close to "0" lash as you can get with a tight a tight .002 feeler gage. The engines' rpm limit will be higher, just like having solid lifters.

2. A power increase, because they will not leak down. Valves lose lift when leakdown occurs.

Loss of power from "Leak down” occurs when the valves lose lift because the lifters fail to support the open valve under the spring pressure. This is caused by oil bleeding past the hydraulic piston in the lifter. When multiplied by the rocker arm ratio, as much as .100 or more in valve lift can be lost. You never know when it occurs or how bad you may have this power robbing engine cancer, but we do know how it can be prevented. Schubeck "Zero Lash Technology lifters restrict plunger travel, limiting the leak down to between .012-.015; if it occurs at all.
So could that be any more confusing? That's the same thing I'm reading everywhere. Could it really be that much on the edge? I know there's guys having no problem whatsoever getting 6500 out of hydraulic rollers so what gives??? Thanks..
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Old 11-04-2009, 07:01 PM   #3
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Default Re: Lifter pump up or collapsing??

I have one customer that uses hyd lifters in a race type car, it is a turbocharged LSX 447. I used the Morel lifters without link bars, a double spring with 200 on the seat and 500 open pressure, Harland Sharp rockers with a stud girdle I made to keep the rockers stable. It has a SS ex valve and Ti intake. He normally shifts around 7600rpm, but has been 8100 a few times. I have never ran the engine on the dyno, but the engine looks to peak around 7000-7200 and drift off over that.

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Old 11-04-2009, 09:43 PM   #4
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Default Re: Lifter pump up or collapsing??

Thanks for the reply. Is the morel you used the zero lash race lifter or the standard lash version? I've got a set of morels on the way. Hope it fixes the problem. What kind of oil pressures did this engine have? Thanks...

Edit: just saw you said without link bars so I would assume that's the morel drop in lifter for use with the factory buckets.
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Old 11-04-2009, 10:07 PM   #5
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Default Re: Lifter pump up or collapsing??

Which rockers are you using?
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Old 11-04-2009, 10:09 PM   #6
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Default Re: Lifter pump up or collapsing??

Comp ultra gold. Your the second person to ask me that today. Why you ask?
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Old 11-04-2009, 10:14 PM   #7
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Default Re: Lifter pump up or collapsing??

I have a set of Comp shaft rockers that gave me a fit for adjusting and they were doing the same thing. I was using the comp "r" lifters. I finally set them at zero lash with the engine warm, and let it go. Before I did that it would only rpm to around 5800rpm. It seemed/sounded like it was hitting the rev limiter.

Also, I had restricted tip push rods in it and pulled them as well.
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Old 11-04-2009, 11:11 PM   #8
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Default Re: Lifter pump up or collapsing??

Are you still using the Comp shaft rockers? I just bought the set that was listed in the classifieds, and I was planning to use them with regular LS7 lifters in my 408. It's going to be a turbo build, so I don't plan on needing rpm higher than 6,500.
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Old 11-04-2009, 11:37 PM   #9
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Default Re: Lifter pump up or collapsing??

Quote:
Originally Posted by green70 View Post
Will excessive upper rpm oil pressure cause pump up? This I've wondered since I've replaced the pan and oil pump. My oil pressure is pretty stout now at high rpm where it was only seeing around 50psi stock.
Virtually all our wet sump engines peak around 70-75psi oil pressure--street and race--with hydraulic lifters spinning anywhere from 6500-7500.

What does your dyno graph look like at around 5700? Even on a chassis dyno, weak valve springs or just valve trouble period will cause the graph line to go from somewhat smooth to what appears to be graphed "static" in a phone line or some shit.
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Old 11-05-2009, 12:29 AM   #10
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Default Re: Lifter pump up or collapsing??

Heavy rockers and stock lifters do not play nice with each other. Especially if you have alot of spring pressure. All kinds of hell can break loose.
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Old 11-05-2009, 07:35 AM   #11
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Default Re: Lifter pump up or collapsing??

Yes standard Morel lifter.
Oil pressure is 85-90 at high rpm.

Kurt
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Thanks for the reply. Is the morel you used the zero lash race lifter or the standard lash version? I've got a set of morels on the way. Hope it fixes the problem. What kind of oil pressures did this engine have? Thanks...

Edit: just saw you said without link bars so I would assume that's the morel drop in lifter for use with the factory buckets.
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Old 11-05-2009, 07:48 AM   #12
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Default Re: Lifter pump up or collapsing??

Quote:
Originally Posted by Billyman View Post
Virtually all our wet sump engines peak around 70-75psi oil pressure--street and race--with hydraulic lifters spinning anywhere from 6500-7500.

What does your dyno graph look like at around 5700? Even on a chassis dyno, weak valve springs or just valve trouble period will cause the graph line to go from somewhat smooth to what appears to be graphed "static" in a phone line or some shit.
Graph trails off real smooth. No real signs of valve float. I checked the springs when I pulled it apart the other day. They had 145-150 on the seat and 425-430 open. They were brand new, the ones that come on the tfs heads.
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Old 11-05-2009, 07:51 AM   #13
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Default Re: Lifter pump up or collapsing??

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Originally Posted by Collinsautomotive View Post
Heavy rockers and stock lifters do not play nice with each other. Especially if you have alot of spring pressure. All kinds of hell can break loose.
This is what I've been thinking. That's why the switch to morels. Still waiting on them to arrive. Also thinking about switching to an adjustable rocker setup so I can dial in the pre-load which might be the only way to determine if they are pumping up or bleeding off.
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Old 11-05-2009, 09:54 AM   #14
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Default Re: Lifter pump up or collapsing??

What's your combo?
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Old 11-05-2009, 09:56 AM   #15
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Default Re: Lifter pump up or collapsing??

Quote:
Originally Posted by Chevy406 View Post
Are you still using the Comp shaft rockers? I just bought the set that was listed in the classifieds, and I was planning to use them with regular LS7 lifters in my 408. It's going to be a turbo build, so I don't plan on needing rpm higher than 6,500.
No I pulled them off. They were something I was talked into buying and did not really need. I put the stockers on them with correct preload and push rod length. I have not looked back.
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