Valvefloat is usually a problem with not enough valvespring or in the case of hydraulic lifters they can pump up at higher rpms. Restrictor pushrods allow less oil to make it to the rockers.

 

When I talked with a guy at Crane he told me that a restricted pushrod
can help, but it depends on the situation, if the lifter is bleeding down.
If its not its not going to help. I still hear a lot of different opinions on these,
but I dont think you'll need them. 1st make sure you have good lifters,
right springs, and right installed ht. is correct. How high does it rev now?

 

Less oil in the pushrods = less overall weight associated with the pushrods.

Anything you can do to make the valvetrain lighter like with restrictor pushrods will help when it comes to valve float caused by v/spring issues.

But i would not think the small amount of weight saved with the restrictor pushrods may not be much of a factor unless the pushrods themselves are much lighter too. Then collectively less oil and less material in the pusrods themslves may add up to enough of a weight reduction to help avoid v/float.

Scott

 

Less oil in the pushrods = less overall weight associated with the pushrods.

Anything you can do to make the valvetrain lighter like with restrictor pushrods will help when it comes to valve float caused by v/spring issues.

But i would not think the small amount of weight saved with the restrictor pushrods may not be much of a factor unless the pushrods themselves are much lighter too. Then collectively less oil and less material in the pusrods themslves may add up to enough of a weight reduction to help avoid v/float.

Scott

If the pushrods restrict oil flow by means of an orifice, that will in no way affect the mass of oil in a hollow push rod, it's still hollow and filled with oil. What ever means you use to reduce the volume of oil in a push rod is going to increase the mass of the push rod. Am I missing something here?

The problem with most hydraulic rollers is the mass of the lifter itself. Do a side by side comparison of a mechanical roller vs. a hydraulic roller and see the difference!

 

Myself and a customer of mine along with Smith Brothers were the first to mass produce restrictor pushrods. Various methods over the years had been used to restrict pushrod oil flow. Smith used an EDM machine to blow at .030 to .040" orfice (half the normal size of a pushrod hole) into one swedged in of the pushrod. We used these on high rpm Renegade class engines that were lift limited and had to run hyd roller cams. After a year exclusive we began selling these to other people for many applications. They are safe to run on the street and yes they do help keep the lifter from pumping up.

 

Dave,i realize that,i was under the impression the restrictor pushrods were mfg with a smaller diameter hole thruout the entire/complete length of the pushrod,not just resticted with inserts that had the smaller holes which in that case would result in approx same amount of oil in pushrods thus same weight of oil in the unrestricted p/rods.

But if the mfg didnt also reduced the o/d of the p/rods when using the smaller oil hole along entire lenght of rod then there would be more metal in the rod making them a little heavier which would not be good when it comes to high rpm & valve float,i guess thats why they used the light wt restrictor inserts .

Scott

 

I hadnt heard anything about making the pushrod lighter... the idea I had heard was that in the case where the lifters were pumping up, the restricted pushrod in theory keeps the oil "trapped" in the lifter and keep the hydrailic lifter from pumping up.

Hopefully my valve float issues are solved with the recent change to morel lifters and Pacaloy beehive springs/ titanium retainers with 175lbs seat pressure. I have a small HR cam, but I need the seat pressure to keep the high boost (I am at 15 lbs now) from blowing the intakes open and causing a kaboom in the intake. I was only asking for my own knowledge as I continue to ponder the issue. I make peak power at about ~6000-6100rpm. shift at ~6200-6300rpm and have my rev limiter set at 6400rpm. I fixed it for a while last year when I increased the seat pressure to 145lbs with Manely dual pricings and titanium retainers & locks to control 14 lbs of boost, but eventually I floated her again and that usually blows the intake gaskets right out of the engine. Doesnt happen often but when it does it is not nice so I wanted to increase my safety margin. I have 12 more degrees of exhaust than intake duration and she is very happy to rev well past peak power, were it not for the valve float.

 

I make peak power at about ~6000-6100rpm. shift at ~6200-6300rpm and have my rev limiter set at 6400rpm.

I think you need to move your rev limiter up a couple of hundred rpm. If you are shifting at 6200 rpm and the rev limiter is at 6400, you are likely already getting into the rev limiter control. Almost certainly are at 6300 rpm.

Maybe the "valve float" you are experiencing is actually the rev limiter starting to come into play.

IMO rev limiter needs to be 500 rpm above shift points. They don't just cut out at the specified rpm, they usually seem to start dropping spark a bit before.

Just a thought, and an easy idea to test.

 

The restrictor pushrod has 1 end with a smaller hole. This end goes to the lifter. This restricts the flow of oil from the lifter to the pushrod preventing the lifter from "pumping up".

Mass reduction on the valve side of the fulcrum is more critical then on the lifter/pushrod size. SBC in Cup are running .500" or 1/2" diameter pushrods.

 

Mass reduction on the valve side of the fulcrum is more critical then on the lifter/pushrod size.

If this was the case, why are soild rollers rpm'ing alot higher than HR's? Everything is just about the same on the valve side of all motors yet the SR motor way out rpm the HR's. Killer sping pressure?

 

That was my understanding is to take the weight off the valve side. The pushrod side has smaller effect.

 

I think the answer is titanium HR lifters. Some people will say they will be too expensive, but I dont think they will need to be priced at crazy levels. I have many titanium parts on my dirt bike.. rear shock spring, foor pegs, valves, etc.... I dont think they would be too expensive for my car. Of course they would be more expensive, but I honestly have spent over $3K in trying to get my tiny HR cam to work with my combo, with rev kits, trying different HR lifters and springs and titanium retainers, etc. I would consider titanium HR lifters for $700 or $800 bucks, if they made it rev to 6800pm with modest spring pressures. Short of that, increasing spring seat pressure has shown the most impact in improving my valve float issue, even though I started out at a higher pressure then recommended by the cam manufacturers.

 

The last thing you want to do is restrict the oil coming out of the pushrods. If you do, its a good way to kill your valve springs. They depend on a good flow of oil to cool them. Without that, you'll shorten their life considerably. One of the cam catalogs I have, says if you run topend restrictors, you can shorten the valve spring life by as much as half. Not good :noway:

 

I haven't heard too many positive things about any of the limited travel HR lifters for a street/ strip car, even though they may rev higher. Noisey like a solid, set up almost like a solid, so some people feel that if you go that far in terms of compromises, you might as well go solid. Right now its is like searching for the Holy grail of a high rpm, low maintenence, and quiet HR set up. I think the cam companies do too well selling us HR setups that even have trouble reving to their peak power in a lot of set ups.

 

Have run many sets of the limited travel in LS1 street engines. No more noise then a normal lifter. With anything though you are going to have some compromises. Have run them in BBC applications with no complaints.

 

Let me give you all something to "kick" around!!

1-You DO NOT want to be "limiting" the oil supply through the pushrods to the valve springs, you will "solve" one issue to have another. The oil is the only "medium" available to "cool" the springs. (Add) (As mentioned above)

2-Trying to get the retro-hydraulics into the "stratosphere" more likely than not, isn't going to happen anytime soon, possibly ever!

3-With the arrival of the "budget" 4.375" strokers AND where you can keep your +.250" rods in the program, we see this as "the ticket" to some serious HP AND torque (on the retro program) AND at the same time actually lowering the required RPM band. As it is now we are all in at about 6300 RPM anyhow with the 4.250" platform!

I have 6 builds already under way with the 4.375" cranks and I really expect to accomplish some excellent HP numbers, but moreso, I figure we will see some "super" torque numbers on the horizon from these units! Eagle was wise enough to "stay the course" with the +.250" rods and not requiring a longer rod change as well while "stepping up" the stroke! It will still allow all units to be "internal" as well on balancing, based on the present "target" of 2300 grams!

As you "extend-the-arm" you can lower not only the "static" C.R. but also the RPM band and not "give-up" any potential power gains! Read that as "lower rear gearing"! It tends to solve a multitude of problems, both gears and fuel requirements! This seems to be where it's heading from my point of view.

However, one "drawback", what you eventually encounter is the fact that you will reach a point of "extending-the-arm" to the point it will no longer fit in any block BUT an aftermarket. I would suspect the manufacturers of these cranks/rods would, for now anyway, like to make it fit with the "standard" 454" BB platform.

I personally would be (actually we're doing this now anyway) taking the RPM band now available, 6600+, and extract all the maximum HP possible from this program!

The 4.375" cranks will "fly" in the standard 454" BB's, with almost no "fitting" at the pan rails, but the lower bores are the issue, which is the same with the +.250" "arm" in some cases, not all. The 2 B.M. blocks seem to be somewhat slightly "tighter"! Remember, we're still talking BB's here.

I haven't tested any of these +.375" "arms" in any 9.75:1 builds to date. But I also suspect some "under 6000" "peaks" which will all but eliminate "chasing" RPM's with retro's!!!!! Also remember here, we are already at 750+ HP @ 6300 with the "short" stroke AND the 9.75:1.

Thanks Gary in N.Y.

P.S. The "anti-pump" retro-hydraulic lifters are NOT recommended for
"normal" street driving. As stated above, certain "class-cars" need these to "meet the rules"!

 

Man, I must really have this backwards then … I’m not trying to be a wise-guy, but I am missing something here.

I thought (don’t do that, it gets you in trouble) … the issues with hydraulics and high spring pressure, was the oil pressure holding the lifter up, would be compressing as spring pressures got higher. A solid roller has nothing to compress, so the spring pressure can be higher.

A pushrod restrictor would build more oil pressure in the lifter (than unrestricted), therefore creating a higher resistance to the springs trying to force it down.

Basically a hydraulic lifter has mechanical limits to it’s upper end. You set the valve lash to this. With more oil pressure in the lifter, you’re trying to give it more ability to not be pushed down by spring pressure (and oscillation pressures, ie valve float). A compromise between the ultra cushy (if we call it that) stock hydraulic dampening, to a medium cushy (pushrod restrictor) … before going to completely solid lifters.

The thing I don’t get … is why do you keep calling these things anti-pump up? I thought the point, was you were trying to keep the lifter pumped up … and not allow it to pump down (get shorter)?

Now, I really don’t understand the whole point to this conversation though? It’s been stated quite clearly, these pushrod restrictors were solely deviced to work around regulations in some “class” bodies. It’s like a restrictor plate in NASCAR … they ain’t using it because of the power gains! Unless you’re racing in these classes, and trying to engineer solutions to class restrictions … I would never, ever want to restrict the volume of oil going to the valve springs on a street engine!!

Neal

 

The problem with the lifters staying "pumped up" is if they do not bleed down fast enough, the valves will not fully close when they are supposed to. That bleeds off massive cylinder pressure causing instant loss of power. Or am I full of oil(crap)? So running the restricted pushrods would allow you to run higher pressure springs overcoming the extra pressure in the lifter. Am I full of it again?

 

I agree with 69CHVL..this is my first experience with a HR and my first experience with valve float. I always have run about the same size cams in my blown and NA small blocks and always reved well past 6000rpm with cheaper parts and never had an encounter with valve float. I know guys with blown SBC's and 12 lbs of boost taking their hydraulic FT's well past 6500rpm with average spring pressures and no hint of valve float. Therefore, I would think that while hydraulic valving is an issue, it is not the biggest issue for the rpm range I am refering to, and I am talking about HR's that can't even rev past 5800 on a BBC or past 6000 on a SBC. The key differences I see is greater lifter weight and more agressive lobe profiles and higher lift on the HR's. Again I am talking about ability to rev in the 5800-6800rpm range for a street/strip engine, not a 7000+ rpm engine.

 

Jake,

Thanks..nope, it is not the rev limiter.. the rev limiter doesnt cause violent explosions in my intake with gaskets flying past the windshield

I would never think of extending the rev limiter any higher...It would surely exacerbate the valve float problem I have been wrestling with for 3 years now. I am very traction limited and power does not fall off much past peak power, so it is easy to wind her out until you hit the valve float. 50% of the time I float the valves on my blower engine, there will be a nasty explosion and a need to call a flat bed if I am not within 2 minutes of home. She runs pretty lean with the gaskets missing . Thank goodness that it does't happen that often.

With this situation, I have to be very conservative about my rev limit. This is why HR lifters are not recommended for a high boost blower set up. For 12+ lbs many of the blower engine builders suggest solids, because an explosion under a roots blower is a much bigger thing than an NA motor.. in addition to blowing out intake gaskets, you can shear of the end off the crank and other good things.

mike

 

Hmm,
I know myself and others have experienced that the rev limiter comes on earlier than the setting and you can gain power and ET by giving it more window if you are trying to run it that close.
I don't know what ignition box you are running but figured I would throw it out there.
With the stiffer springs I would try it both with the setting close like you have it and move it 200 rpm just to see.

I can see a rev limiter doing weird stuff on a forced induction setup when the cylinder slips a spark or two.

 

Jake

I have an MSD 6AL igniton. 3 years ago when I first ran into the problem, I also thought it was a rev limiter and called MSD. They claimed that it does not start to come in a few hundred rpm early and should come within ~30 rpm of what was written on the chip. They explained to me how to use an ohm meter to see if the chip was labelled correctly and all that. Anyway, it was never the ignition and realized that after the second explosion that pushed an intake gasket out... the intake valve was hanging open and bringing causing an explosion right in the intake manifold.

mike