lifter crash ?

I am useing a camshaft with 226* / 240* .505" /.484" ground on a 113 LSA , adv dur. is 270* / 290* this makes for a somewhat fast profile angle . My heads are to spec ,valve tip ht. valve spring inst ht ,etc They flow .258/.189 . The valvetrain has some noise at idle, on the road the preformance is outstanding the powerband hits hard & never stops pulling untill 5100 rpm then it goes flat up to 5500. I am running stock 1.55 stamped steel rockers with adj pushrods & I have tried the Delphi & Johnson style lifters. Well after several changes to timing ,jetting lifter preload it still preformed the same .. 12.78 @ 106 mph 1-2 shift @ 4800 rpm & 2-3 shift @ 4900 rpm & pulls to 5100 @ the finish line.
The lack of rpm made me do some digging & I was told by some that they turned 5300 , 5500 rpm shifts. After checking my valve spring specs I saw where they were coming up short & went the shim route .030 was placed under all the springs & waited for a good day to test (clean roads) The lifters being used are the "Good" Delphi style that were being used before the shiming . I started the engine & I thought it made less noise @ idle (good deal) Onto the test shifts @ 4800 seemed fine & it pulled hard @5000 same thing but @ 5100 & it did not go flate anymore it broke up & floated the valves to the MAX ..... all valve control was lost after 5000 rpm.

The increases in spring pressures were within the camshafts specs , by increasing the pressure I think this might be a good example of LIFTER CRASH . Do you think a new set of Mech lifters would live on a camshaft with around 50 miles run time ?

More spring pressure reduced my rpm range & the condition went from flat to float.


ick

 

Larry, the part that sticks in my mind is before adding shims to the springs this engine would pull hard to 5100 with power & flatten out on its way to 5500rpm . Now with the added shims it pulls hard to 5000 rpm & then goes into valve float big time ! The added spring pressure may have been just enough to cause the lifter to bleed down & send it into valve float ! Years ago it was the other way around more spring ,more rpm ! I think it all boils down the dynamics between the lobes & lifters.

Mark

 

Yep, either a different cam, or solid lifters on that one.. get roller rockers and run about .005 clearance hot with iron heads.

Considering the cost of roller rockers, I would put a cam and lifters in it, and be done with it.

JW

 

Jim ,I have adjustable pushrods & would be going with the TA 1410 solid lifters. I guess it's a 50/50 chance it will break in & have a long life . With this camshaft I have went from the Johnson style (bleed down) to (Delphi) more noise but better overall. Last but not least adding more seat & open spring pressure has caused premature valve float @ 5000rpm & before the spring change the valvetrain just went flat @5100 but no noticible float . I think all in all the best route is to install a new cam & lifters , @ this time it will have to be a grind that uses 1.55 stock rockers .. in a word the most bang for the buck with a stock valvetrain.

Thanks Jim & Larry

 

Interesting point about too much valve spring pressure aggravating the problem.

The best luck I've had running the fast ramp cams is with the Comp Pro Magnum lifters which allow you to run basically 0 preload. I usually run them at 1/8-1/4 turn on the adjustable pushrods which gives about .004"-.008" preload because I run it on the street and I want it to be reasonably quiet. That allowed my cams to rev to 5700 and at that point it ran into a wall but up to there it pulled strong. Probably could have run even less because I set mine when the engine is cold.

http://www.compcams.com/Products/CC-'Hydraulic Lifters'-0.aspx

You could probably try lowering your preload to the 1/8-1/4 turn minimal cold preload setting and see what happens. You don't want to go too low on the preload unless your lifters have heavier duty retaining clips. The stock type wire ones won't hold the cup in if it comes up against it with such little preload. Easy to try before pulling the intake again and may do just what you need. I'd back up on the spring shims also because of your earlier results.

 

Anybody ever try to compress a lifter plunger by hand (with oil inside of course)? It's nearly impossible, even with a large screwdriver and bearing down with all your weight. It would take many hundreds of pounds of force, if the plunger-to-lifter-body clearance is within reason. Oil (or any hydraulic fluid) is incompressible. In the short amount of time the lifter is on the lobe nose, there is not a lot of time for the plunger to bleed down appreciably. An increase of just a few pounds of spring force does not seem like enough to cause the oil to now be squeezed out. To me, the lifter pumping up due to loss of contact is a much more plausable reason.

I understand your testing results. Were the springs running solid (stacked)?

As mentioned, solid lifters would definitely tell the story...

Zero preload test will also go along way in explaining

 

Tested and observed the exact same thing.

Add spring pressure, reduce rpm range.

comp cam magnum lifters, .010 preload, 30wt oil, springs from 125/310 to 135/330

5400 to 5200

JW

 

Can't argue with test results...I'm just surprised.

With the engine on the stand, am wondering if anyone has tried to fill a lifter with oil and turn the engine till a lifter is on the lobe peak and watch the actual plunger/pushrod/rocker motion as it bleeds down. I'm pretty sure that motion would be very slow and take 10-30 seconds ....o No:

Then add 20 lbs of spring force and repeat...probly shorten the time by a few seconds

 

Scott,

Your thinking of a lifter in a static environment. Yes, they are hard to push down, and take a while to bleed.

On the other hand, try opening a valve by pushing down on it.. then do it 500 times a minute. Then 2500 times a minute.

Forces on that little lifter and it's valving are astronomical, it's no wonder that we have located the limit of function.

IN all the testing we did, I found only one thing that eliminated it, beyond changing the cam.

I replaced the 1.6 ratio roller rockers with 1.55 ratio stockers. The reduction in actual force on the lifters allowed them to function properly. Subsequently I have done that several times with the same results, on engines with "questionable" ramp rates on the cams.


___________________

Recently, Ron Quarnstrom, my dyno guy, related a story of a situation he had come across.

He had one of his other engine builder/dyno customers like me in the shop, with a BBC on the pump. H/D roller suffering rpm limitations around 5600.

Builder had him unhook the motor and took it back to the shop.. in consult with the cam company, they went from 5/16 to 3/8 pushrods.

Cam company claimed the push rods were flexing causing the issue. Push rod acting like another spring.

Ron said that motor came back and would rev to 7500 rpm.

I am skeptical, due to the fact that it was not at the dyno shop the whole time.. if they had popped the covers and the rockers and changed the push rods on the spot, then that's one thing, but I bet there was more to it than that.

Although I can't recall ever trying such a thing with a BBB.

But I am using the same pushrods we have used successfully on 7000+ rpm solid roller cam motors, with 800psi of open spring pressure.

Logic dictates they would be fine in this application, but it is something I heard recently, and will pass it on.

Maybe Mark needs to measure up his pushrods, and call up Smith Brothers and have them whip up a set of HD 3/8 units.

JW

 

I too have heard about the 3/8" vs 5/16" pushrod difference varying RPM potential. If the angle of the pushrod was different it could potentially put more strain in different applications and thereby cause them to flex and give a springing effect.

Also, reducing the rocker arm ratio will give the lifters more time to bleed down, raising RPM potential. Lifter crash is not uncommon with fast ramp profiles and hydraulic lifters around 5200 RPM.

Am I missing something here? I feel like this is supposed to be common knowledge, and maybe I'm just overlooking something obvious that this thread is addressing.

I wonder if running thinner oil might help too, since faster lifter bleeddown is what's needed here. Perhaps Johnson's or even Rhodes?


G

 

It's got nothing to do with bleed down.

So that got me thinking. What is different in a (highly) dynamic environment? And I believe I have the answer. It has to do with mass and inertia, and specifically how it relates to the check valve. I recall some years ago the advent of the flat disc check valve as an evolution of the steel ball check valve. The disc is supposedly faster (lighter, lower inertia) allowing for more rpm potential, via quicker seating.

As the cam lobe starts to push up on the lifter body, everything with mass (and inertia) resists this motion. The pushrod is pushing down on the plunger cup, and the check valve needs to seat now to trap the oil to allow full valve lift. But the ball's inertia wants it to stay "down" not sealing the orifice. The oil squeezing into the bottom of the plunger (plus the little spring) is what is supposed to carry the ball with it against it's seat, sealing the check valve. The super fast lobe motion is so fast with a faster action cam lobe that the ball inertia overwhelms the little tiny ball spring and flow of oil rushing past, resulting in lost valve motion (less duration and lift) before it finally seats and operates as normal.

Stronger valve spring force compounds the problem because more plunger motion is lost as even more oil is squeezed out before the time delay allows the check valve to seat.

This triggered my remembering reading somewhere about a similar problem and the solution. Some 4-cylinder GM guys (Z24 or Z34 can't remember) were bemoaning loss of rpm and performance using a fast ramp hyd roller cam. One of them did some research and found out GM engineers discovered the same thing when developing new cam profiles for the ZR-1 corvette. This new fast-action high-lift camshaft had the same issues we are seeing. They did some research and found out the check ball inertia and it's delay in seating was the cause. The solution was a new light-weight ceramic check ball and special higher tension check ball spring, now standard equipment in all new vette hyd roller lifters. The ambitious Z24/Z34 guys bought new sets of GM ZR-1 lifters, swapped out the check ball and spring into their stock lifters and their problems were solved!

So all we need are ceramic check balls and higher tension check ball springs

http://www.lingenfelter.com/mm5/merchant.mvc?Screen=PROD&Product_Code=88958689&Category_Code=C158
http://xtremecarzone.com.au/index.php?showtopic=539
http://www.ls1gto.com/forums/showthread.php?t=227012
http://60degreev6.com/forum/showthread.php/50206-lifters/page2

Edit: So I knew I remember it wrong, it was the GM 60 deg V6 and the new Caddy CTS V racing program in the story.

 

Fast lobe profiles leave rpm on the table & if some type of lifter design could allow them to reach those levels is there still enough unused area under the lift cuve of the flat tappet to make it worth the effort & will the lobes & lifters run into premature failure?
Mark

 

How did you engine perform during regular driving around town in traffic, merging into freeway traffic, etc? I'm asking because I have a Lunati Voodoo 268/276 cam I'm itching to include in an 455 engine build for my Skylark convertible street-performance cruiser. However, this thread is making me rethink my cam choice.

The reason I even thinking about that cam is my engine should never exceed low-5000 RPM range on the street, anyway.

 

Very interesting about the ceramic check balls in the lifters

 

Dan , The 226/240H13 camshaft from Scott Brown idles @ 14'' vac @ 750 rpm ,from off idle to 5100 rpm it is outstanding & has great torque through out the power band. My issue is my valvetrain set up may be leaving a few rpm on the table (400).As for the Voodoo ..... Do a search on the board for more info the words spoken here are kind compared to what you will read from a couple dyno test on the VooDoo lineage.

Mark

 

Mark, Im running a Scott Brown 226/239H12 with the Edelbrock heads and that cam will rev past 5800 easily. The spring set up is his own blueprint set up when you buy the heads from him so I am not sure of the exact spring pressures. Full weight 72 Skylark is running high 11's now with that cam.

 

Steve what are the flow #'s for those heads ? What are you running for a fuel pump & line dia?


Thanks for your reply that you run the 226/239H12

Mark

 

The heads flow 320 intake, 215 exhaust at .500 lift. My fuel pump is an electric Holley 12-125 as a pusher running to an Autozone airtex stage 1 pump. fuel lines are the stock 3/8". Intake is an untouched B4B