Greg

I would like to get a little bit more lift and duration with my hydrolic roller cam. Can I switch out the hydrolic rollers for solid rollers? How much duration and lift should I get with this??

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'89 Formula 383 TPI

AlkyIROC

no. Hydraulic cams and solid cams if they are flat tappet or roller have different ramp profiles. You can't use the different lifters on the different cams. Hydraulic cams Will destroy and engine with solid lifters because of how the ramps are designed to open the valves.

It just won't work. OK it will work but not for very long.

After re-reading your post I need to add...

You won't get more lift with solid lifters. Hydraulic lifters are already at zero valve lash. Solid lifters need a few thousands valve lash so you would actually lose lift. Duration can't be changed. Even adding 1.6 rockers to get more lift won't change duration. The only way you can play with duration is with a solid cam and lifters. By adjusting the valve lash loose or tight, you can slightly change duration. This is only a tuning aid to see if the engine will benifit from more or less duration that the cam has ground into it.

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[This message has been edited by Stephen 87 IROC (edited June 28, 2001).]

AFRO IROC Z

Stephen,
I was wondering about what you said about not being able to changed duration. this is not to argue, i just want to be informed. Now with the 1.6 ratio rockers wouldn't you reach .50 lift sooner on the lobe and then reach .50 lift later on the closing ramp, wouldn't that be an increase in duration but only because of the rocker not because of a change in the actual duration ground into the cam. I was hoping you could clarify, as i said this is so i don't go around thinking the wrong thing. Thanks.

AlkyIROC

With hydraulic lifters at zero lash duration can't change even with 1.6 rockers.

The lifter starts and stops moving at the same location on the cam.

Total duration (advertised) and .050 are 2 different things. I wish I could find the article on cams. It's better than the ones from Crane and CompCams.


[This message has been edited by Stephen 87 IROC (edited June 29, 2001).]

jcb999

Steven pretty well hit it. But, one thing I have recently found, is that in most of the more mild solid rollers, the rate of opening is very close to what the current design hydrollers are obtaining.

But, yea you will end of giving up more than your getting. Because of the exact statement above. I am getting over .6 lift with 1.6s and around 238 degrees duration. To get much more than that even with a solid, your going to go to something in the 258 to 260 degree range at .050. That will get you close .67 net lift. But what do you need the extra .070 lift for? Without airflow in all other other areas (and gearing to match), you going to loose more torque than you will pickup in hp (and makeup in the quarter).

You can get about 2 degrees of duration (at .050) by going to 1.6s, but not much more than that.

[This message has been edited by jcb999 (edited June 29, 2001).]

AFRO IROC Z

Stephen,
Isn't duration measured by when the valve is at .50 lift and greater. with 1.6rockers insead of 1.5 you would reach that .50 lift when the lifter is lower on the cam lobe. the lifter wouldn't have to be as far on the opening ramp of the lobe to achieve this .50 lift, if this is wrong please explain to me. One of you guys says you can't increase duration the other says you can. BTW, i am talking about changing duration with different rockers.

[This message has been edited by AFRO IROC Z (edited June 29, 2001).]

jcb999

well since duration at .050" is measured at the tappet, no in the purest sense of the of term, there will not additional duration (at the lifter), but at the valve, you will realize a slight increase in duration.

I probably should not have said .050 in the previous post. It was just a point of reference. I really should have said at .075 valve opening to be more accurate.

[This message has been edited by jcb999 (edited June 29, 2001).]

Tas

he was asking about using solid rollers with a hydraulic roller cam, not with a flat tappet cam.

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AlkyIROC

It doesn't matter if it's flat tappet or roller. Hydraulic cams and solid cams have different ramp profiles for each type of lifter and although using solid lifters on a hydraulic cam will work for a short while, you will eventually break parts because of how much differently the valves are opening.

As for the duration part, OK, you will gain a very slight increase in duration at .050 with 1.6 rockers when compared to 1.5 rockers but the amount gained will be too small to be of any use. The only way to see just much is gained is to use a degree wheel.

The .050 number is given by cam grinders as a base number. 2 different cams can have the same duration at .050 but have completely different ramps because of different total duration.

jcb999

And or lift. A change in either one by the slightest amount with change everything. You can look at durations at .050 and at .2 between cams that have the same lift. Even if the advertized is close, depending on how current the design is and how far the company pushes the valvetrain, duration will move around by 3 to 5 degrees.

AFRO IROC Z

I wasn't trying to be difficult I just wanted to know if duration would change even if by the smallest amount, I wasn't wondering because I was looking for a performance gain, I was just wondering. I am trying to learn as much as I can, I ask a lot of questions so that there is no doubt in mind. I just wanted to know I wasn't thinking the wrong thing, thanks for clearing that up for me. BTW, Greg If you switch to a higher ratio rocker you will get more lift, but as stephen said the small amount of duration derived will be too small for an increase in performance due to duration. If you want more duration get a different cam. Then you can have more durationa and more lift at the same time.


[This message has been edited by AFRO IROC Z (edited June 29, 2001).]

Grand Prix

Hold on a second, Stephen 87 IROC I think I'll have to ask for a little more elaboration. In the past it was my understanding that in the flat tappet world it worked like this. The mechanical cams used a more aggressive profile that would cause a hydraulic lifter to pump up if it were used on a mechanical cam. This would limit RPM potential badly and would quickly cause problems. On the other hand, a hydraulic cam has softer ramps that are buffered by the lifter itself. If a mechanical lifter were used it would work just fine, the engine would just run like crap. This is because the valve is starting to open before it is supposed to. The differences in mechanical cam's rated duration would support this. On a mechanical roller cam the lift rate is very steep, so it would be reasonable to assume once again the hydraulic lifter itself (not the contact wheel) would have difficulties keeping up. Not to mention the heavier tappet would be harder to control as it accelerates up the ramp. Now, a hydraulic roller cam should have far less of a baby ramp opening the valve. So unlike the old days the valve lash itself should take care of any unwanted premature lift. You have no lifter guts to worry about in the mechanical lifter, and the cam is flat since the lifter doesn't rotate on it. So exactly why would things break now? The hydraulic cam is so much more aggressive than the mechnical that the valve train can't keep up? I can't say that swapping lifter types is a good idea, but right now I can't see why it would fail.

AlkyIROC

Hydraulic lifters are designed for zero lash. All solid cams need some valve lash. Usually around .018". If you try to zero lash a solid lifter, chances are things will break or performance will decrease. Also that .018 valve lash is deducted from the valve lift so a .500 lift cam is now .482.

Theoretically you could lash a solid lifter on a hydraulic cam to .006" (done years ago with old designed cams) but with new hydraulic ramp designs it's not a recommended thing to do with new style cams. You don't gain anything from using solid lifter on a hydraulic cam except for a bit of an increase in top end rpm without valve float but all you need to do is put anti-pumpup hydraulic lifters on and you get the same results.

There's nothing from stopping you from trying it but cams are ground for hydraulic or solid lifters for a reason.

JoelOl75

All cams designed for running 'lash' have take-up ramps that smoothly meet the rocker tip to the valve stem before they accellerate the valve open. Hydraulic cams have no provisions for this since they have 0 lash and if run with lash will seriously 'smack' the valves to death after time.

Also on the closing ramps a cam for lash has a softer closing ramp to avoid bouncing the valve on the seat from too harsh a closure.

At least this is what i was led to believe...