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Old 04-10-2007, 05:21 AM   #1 (permalink)
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hydraulic lifters and stiff springs

What happens if too stiff a spring is used on a hydraulic flat tappet lifter? I've noticed that they seem to bleed down fairly quick when the engine isn't running, which has made me wonder whats happening with them at say 5k rpm? Can the spring pressure overcome the lifter and 'soak up' a substantial amount of lift? I have no idea what my springs are, they came on the heads when I bought them, they're dual springs and the cam I run is fairly mild. I doubt they are anything special like for a big solid roller or anything, but they may be spec'd for a solid flat cam. I don't know what the threshold of too much spring would be.

I've been considering swapping to a solid cam anyway(Comp 282S), and if I need to go in and replace the lifters or springs, I might as well just change it all.

[ This Message was edited by: indigo66 on 4/10/07 8:23pm ]
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Old 04-10-2007, 06:35 AM   #2 (permalink)
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hydraulic lifters and stiff springs

We're running Isky dual springs on the 302, set at 110 seat pressure. The cam in a hydro 216/228 with right at .5 lift. No problems noted, engine runs as fast as ever. Told my head guy I thought it was overkill, but he runs them all the time and has no problems.

You should always run the recommended spring for the cam, but you might have those checked before you buy new - they may spec in where you need them.

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[ This Message was edited by: ckelly on 4/10/07 9:36pm ]
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Old 04-10-2007, 06:44 AM   #3 (permalink)
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hydraulic lifters and stiff springs

You are not looking at the whole picture.

Sure, the panty waist springs in a hydraulic lifter, at rest, are weak when compared to dual or triple valve springs, but that is not the end of the story. However, if you are using the correct, vendor recommended springs there should not be a functional problem - if you decide you want to use some 400lb open springs because your 'buddy' told you he was using them, then you might have a problem.

What makes hydraulic lifters work is.... wait for it - Hydraulics! Just as when you use a bottle jack to lift a 3 - 4,000 lb car, with very little effort. The hydraulic lifter uses oil pressure, tapped from oil galleys, to fill the lifter and hold it to the correct height. The spring is there mainly to keep things in place.

A lot of science goes into making an hydraulic lifter, especially the many variations that are the basis for high performance hydraulic lifters (anti-pumpup, variable duration, etc). When coupled with proper setup, careful adjustment, proper selection of oil viscosity and block preparation - hydraulic lifters can rev reliably to high 6,000 or low 7,000 rpm. Even if it sounds like more work than just dropping in a set of solid lifters - and it make you go through a little more mental gymnastics - still, personal opinion, hydraulics have an undeserved reputation as being easy and weak. To me, thats like saying you have a bad set of golf clubs or a crappy fishing rod - sometimes its not the tool that is the cause of the problem, it could just as easily be misapplication, wrong tool for the job, poor preparation lifter bores can wear-just like brake cylinders,valve stem passage; or the user really should have looked into roller lifters or solids for what he wanted that engine to do.

Its always funny when some guys only have one answer for lifters, solid lifters. Yet when they go fishing, hunting or work on the car - they have a whole box of different choices available to fit the correct lure, rifle, bow, bullet or arrow or tool to fit the job.
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Old 04-10-2007, 07:21 AM   #4 (permalink)
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hydraulic lifters and stiff springs

nice documentary there Beowolf. The main thing I have issue with is, say I have 50 psi oil pressure, how much spring pressure and/or rpm would it take to bleed hydraulic pressure back into the oil system and collapse (to some extent) the lifter? I know fluids don't compress, but the oil system isn't what I would define as a sealed system. The pressure can be bled back through the system, or so it seems, and I'd guess it would vary from engine to engine, and for matter it would vary within the same engine based on wear, oil viscosity, and temperature. I probably over analyzing this, maybe it only takes a small amount of oil to keep the lifters pumped up. It would still be interesting to know the limits.

I had springs that matched the cam on my old heads, but when I swapped heads I didn't change them over, wonder if I should have.
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Old 04-10-2007, 08:08 AM   #5 (permalink)
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hydraulic lifters and stiff springs

Strange how interest in certain subjects seem to "cluster"... lot of interest in hydraulic lifters lately.
Quote:
"...I probably over analyzing this, maybe it only takes a small amount of oil to keep the lifters pumped up..."
Very true. As you guessed at, in a closed system, a fluid is incompressible. Once the lifter passes the oil galley, the 'bleed down' orifice is closed. The only way oil is going to get out of the lifter is if there is too much clearance in the lifter bore, just like in a brake wheel or master cylinder. The faster the engine revs, the less time the lifter is exposed to an "event window" where it can pick up or lose oil pressure.

Someone could get deeper into this subject, but I've reach my limit. Besides, wouldn't want to start on another documentary.
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Old 04-10-2007, 09:54 AM   #6 (permalink)
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hydraulic lifters and stiff springs

I have successfully run Isky 8005A dual with damper springs on two different 351C motors, one with flat hyd and one with a hyd roller.
No problems yet.


[ This Message was edited by: Mpcoluv on 4/11/07 12:55am ]
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Old 04-10-2007, 11:10 AM   #7 (permalink)
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hydraulic lifters and stiff springs

You could put 26986 beehives in in preparation for the 282S cam. I did during my rebuild because i needed a spring that could handle the extra lift caused by converting to 1.7 shaft rockers (and because of all the positive info I saw about beehives). Engine is running now and the beehives are doing the job with 10% less spring rate than the old springs.

One possible issue with not knowing the spring rate of your existing springs is that if the springs are unnecessarily stiff, you could see accelerated cam lobe wear.
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Old 04-10-2007, 11:13 AM   #8 (permalink)
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hydraulic lifters and stiff springs

single,double,triple,quadtriple what ever,a hydr cant handle the seat or open pressure od a solid spring rate,my personal opnion anything over 150 psi on the seat your asking for trouble.now if you go with solids and a light valve train all bets are off!
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Old 04-10-2007, 09:50 PM   #9 (permalink)
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hydraulic lifters and stiff springs

Before I switched to the modified Sherman hyd roller lifters, I was running the standard, drop in OEM, hyd roller lifters. My springs were Crower units that were 173# installed and 470# open. On the dyno, it peaked hp at 6600 rpms and really started to fall off after that. But just for comparision, I switched to the Sherman lifters, hyd with only 0.025" plunger travel, same springs, engine peaked at 6800-7000 rpms and didn't fall off until it hit the limiter at 7200. That kinda tells ya that the hyd lifters were collapsing, but still, that much spring pressure and rpm on a stock lifter, pretty darn good IMHO.
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Old 04-10-2007, 11:16 PM   #10 (permalink)
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hydraulic lifters and stiff springs

I'm keeping all this inside and going to apply it to the Falcon 200 Dual 2v motor...

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Old 04-11-2007, 04:22 AM   #11 (permalink)
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hydraulic lifters and stiff springs

I thought those 200's had solid lifters? Or was it just the early ones?

[ This Message was edited by: indigo66 on 4/11/07 7:23pm ]
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