David Vizard's Idea of Almost Bottoming Hyd. ?

[BirdMan]

To Josh, this would be termed a 'Performance Enhancement', right, and any time you change location or position of valvetrain components you need to check for pushrod length and rocker arm/valve contact pattern, at least I would.

[582r10]

S&S has been selling lifter travel limiters since sometime back in the 80s. When Harley came out with the Evo and a modern style hydraulic lifter the heavy springs for hot rod hydraulic cams would pump the lifters down pretty easily. The limiters fit inside the lifter and limit how far the plunger can move. New Harleys use Chevy style rollers so maybe the S&S limiter will fit a Chevy lifter. I don't know for sure. Here's the url for the S&S limiter
http://www.sscycle.com/product/cart.php ... il&p=20361


582R10

Do those travel limiters go in above the plunger and below the clip? Doesn't Comp offer some reduced travel lifters?

I've never used them but my understanding is that the spacer goes in the bottom of the lifter under every thing else.



Roger

582R10

[Buffalobillpatrick]

I think loss of control of the valve train takes pressure off the lifter plunger & allows the lifter to pump up. Not the other way around.

I'm putting on good Lunati (PAC) Beehive valve springs rate = 370#/in. 213# seat & 414# open.

I have Lunati retro hydro roller cam & lifters, Titanium retainers & 10* locks, strong 3/8" chrome-moly pushrods, & Comp Pro Magnum SS roller rockers, & 7/16 ARP studs.

BBP

[LilRacr]

So why not just go to a solid lifter design over bottoming out the lifter?

[Rodz]

So why not just go to a solid lifter design over bottoming out the lifter?

That would be too easy. Some guys like to complicate things.

[CamKing]

So why not just go to a solid lifter design over bottoming out the lifter?

Some racing classes require Hydraulic lifters.

[CamKing]

I think loss of control of the valve train takes pressure off the lifter plunger & allows the lifter to pump up. Not the other way around.

We did a lot of testing on this back in the 80's.
The problem isn't with the lifter pumping up, it's with the lifter bleeding down at higher RPM's.
It's like the lash opening up on a solid lifter cam. Not only does it shrink up the effective duration(hurting the top-end HP), it makes the effective valve seating velocity extremely high(causing seat bounce).

[Rook]

Has anyone ever tested/experimented with almost bottoming out the lifters to see if there is an increase in RPM capability? I know some of the things I have read have been mixed reviews.

Mike, I know you have given some suggestions as to how to get around the hydraulic lifters pumping up but getting caught at it would get me in trouble... LOL!!!

I have been tempted to run hydraulic rollers .006 from being bottomed out but just can't grow the "cohones" to try it. The lifters I am using have .135 of travel and I have .055 of piston to valve clearance. My cam shows some signs of lofting the lifter over the nose. So, you guys can see were I am going with this... I get more than .055 of that .135 of travel "taken up" when the lifter lofts over the nose of the cam and my pistons and valves are going to become more closely acquainted in a bad way...

[levisnteeshirt]

wonder how straight 40 weight or 50 weight oil would change this picture

[Kdub]

That's how the Rhoads VMAX lifters work. You set a lash of sorts, say .010 to .030 from bottoming out the lifter. They seem to work pretty well, a Isky 292 Mega Cam in a 351W and the power brakes work great and it will spin to over 7000 rpm.

[MadBill]

If a 'hydraulic' lifter had very rapid leak down and say 0.030" total travel, wouldn't it be idea for those borderline 'street' engines running 0.800"+ lift solid roller cams and huge spring pressures, by ensuring constant roller contact for better durability and being immune to pump up/leakdown?

[David Vizard]

If a 'hydraulic' lifter had very rapid leak down and say 0.030" total travel, wouldn't it be idea for those borderline 'street' engines running 0.800"+ lift solid roller cams and huge spring pressures, by ensuring constant roller contact for better durability and being immune to pump up/leakdown?

Bill,
That's worth a spintron test if ever -
DV

[tenxal]

I guess it's finally happened. David's run out of things to right about. I think he's gone back to 1980, and started the loop over.
BTW, you don't want to just bottom the lifter out, and back it off a little.
You want to take the lifters apart and put a steel sleeve inside the lifter that limits the travel.

Bottoming the lifter costs you lift at the valve unless you change pushrod length. With a 1.5 rocker, each .050 in length is about .003 on lift.

I just modified a set this way for an NHRA Stock Eliminator Pontiac for a fellow racer....machined a spacer for the bottom. It picked it the car up nicely.

[dynoflo]

I had a solid flat tappet cam ground for .005 lash. Checked it several times hot. It was still .005. It was for a class hydraulic lifter rule. Won alot of races. One night tech guy jiggled one and walked away. If anyone doesnt believe this call Charles at Camcraft. The cam also had 6 more degrees intake duratuion than exhaust. It was a 305 cast iron intake untouched with very small chamber stock heads.

[turbo camino]

If a 'hydraulic' lifter had very rapid leak down and say 0.030" total travel, wouldn't it be idea for those borderline 'street' engines running 0.800"+ lift solid roller cams and huge spring pressures, by ensuring constant roller contact for better durability and being immune to pump up/leakdown?

Bill,
That's worth a spintron test if ever -
DV

I have thought about this concept a lot - check valve removed, 'piddle valve' metering disc still in place, spacers used to limit travel to something like .030" (or some amount greater than the lash setting). I'm still undecided, lots of questions. Is there enough piston area at the plunger to be able to push the lifter body down onto the base circle, especially when things are happening at speed? How much would the effect be affected by oil pressure? How much abuse will the internal spacers see, since the lash would effectively be happening inside the lifter body?

Also curious, how would you set up a Spintron test to see what's happening between the wheel & lobe? Is there a way to measure the lifter body position in real time or would it be high speed video only?