It's the nose (or ramp) that makes things tough for hydraulic lifters. The solid lifters have the ability to tolerate a more aggressive ramp rate thus giving you more average lift for a given duration.

I was surprised to find there are very few cam options for the miata. There is a potential for very good gains in this area. Local miata motor builder Dave Robello has had great results with his own custom grinds. I am leaning towards trying a set on my next motor.

That is not necessarily true. There is a good article from Engine Labs stating,

"Some racers discovered that a flat-tappet hydraulic can out-power a comparable solid-lifter cam, if the spring pressure is correct and the hydraulic lifter is adjusted one-quarter turn down from zero lash. This is partly because the hydraulic stick is effectively a bigger cam because it doesn’t require valve lash and clearance ramps. This can hold true up to about 6,500 rpm where the lighter solid lifter gains the advantage — provided that the inlet and exhaust components support the higher engine speeds."

"With hydraulic cams, the duration shrinks with more rpm due to both lifter compression of the air bubbles in the high-pressure side"

Engine Tech: Flat-tappet Lifters Still Viable in Performance Engines - EngineLabs

The only advantage with solid lifters in my opinion is the weight loss, and unless you plan on spinning the engine higher they are just a pain in the ass.

It was my understanding the ramp compressed the hydraulic lifter if the acceleration rates were too great just like the effects of high RPM. The solid lifter is better able to transmit the ramp into valve action than the hydraulic.

You mention optimum spring pressure. I am sure that is partially accounting for the differences. I don't discount what your saying to be true but all of my past experiences say otherwise. I gained 20+ WHP when I converted the lifters on my 993 from hydraulic to solid. No other changes were made. On air cooled Harley Evo motors we would limit the hydraulic lifters range and gain torque across the entire RPM band. This tells me the lifters are collapsing some. I am sure lifter design and oil pressure plays a big role.

I've personally weighed our stock hydraulic and stock shim over bucket lifters. The hydraulic lifters are around 4 grams LIGHTER than shim over buckets. There may be a 1 or 2 gram variance depending on shim thickness and how much oil is pumped into the hydraulic lifters.

But the hydraulic lifters are actually lighter. So people who think going shim over bucket is lighter, they're more than likely mistaken.

so my integrals are the equivalent of their full race cams, its good to know that there are more options out there now that integral is gone

^ For sure. I'm weary of changing out my CAMs until the rest of the car runs fine though, don't need to add more problems to the pile.

For boost applications we want more lift and very little change to duration, no? I'd love to see more low end torque, counter the loss up top with an IM and get an adjustable intake CAM gear and tweak for maximum power.

for boost, you also want less overlap, depending on your model year, oem has between 20 deg and 17 deg of overlap not including vvt, which is wanted for na applications, not so much for boost.

So for boost on a 99 head I'd want low overlap, high lift same duration CAM. Good information to know. I gotta find a few before/after dyno charts with a CAM like this..

whats the difference between CAM gears and cam gears?

not entirely sure....

CAM gear:

https://www.miataturbo.net/attachmen...ine=1364596814

Cam gear:

https://www.miataturbo.net/attachmen...ine=1364596814

Sounds ridiculous based on the 6500 rpm figure in your article, when the miata already goes to 6900/7200 rpms stock. Plus across the water, stock NBs readline at 7500 rpms with identical internals (well they had the MSM cam).

Just sayin, you are already spinning the engine higher and getting 8k out of the BP isn't "unheard" of.

Re-read the article I quoted. The information in it is not specific to Miata engines...

I realize that, but you are posting on a miata forum. So your original statement:
seems a little out of place.

Thats the same reason I stopped reading. If the stock redline is already higher than what you're quoting then... :jerkit:

Track,

My post was in response to the statement by k24madness that, “The solid lifters have the ability to tolerate a more aggressive ramp rate thus giving you more average lift for a given duration.” (Which is correct in most cases)

What I posted clearly says, "Some racers discovered that a flat-tappet hydraulic can out-power a comparable solid-lifter cam, partly because the hydraulic stick is effectively a bigger cam because it doesn’t require valve lash and clearance ramps.”

You keep insisting that I have made the statement that our engines can only redline at 6500rpm. Neither I, nor the article made any such statement.

What the article does state is that above 6500rpm a solid lifter has an advantage due to its lighter mass, and that, “With hydraulic cams, the duration shrinks with more rpm due to lifter compression of the air bubbles in the high-pressure side”. Track, How do you know that the Mazda HLA’s don’t lose a significant amount of duration and lift above 6500rpm? Do you have valvetrain simulation software or a Spintron?

Furturemore, solid lifters are generally lighter than hydraulic lifters which allows for higher rpms before valve float. So going back to my statement,” The only advantage with solid lifters in my opinion is the weight loss, and unless you plan on spinning the engine higher they are just a pain in the ass.” And yes, solids are a pain in the ass…

Once again, I never stated anywhere that our engines redline at 6500rpm. You have missed the point of the information I have posted.


This is the last time I am going to try and clarify my post. I could have better spent my time posting relevant information about cam specs I have used for turbo engines. I thought I could add something useful to this thread since have a Superflow dyno and a friend who grinds cams 10min away. But I have wasted too much time today, I need to get some real work done.



Chilicharger665,

LMP engines spin lower rpms and Formula 1 spin higher rpms than the BP engines. Therefore, by your logic their engine technology is irrelevant to us?

Reading comprehension failure? I only mentioned 6500 once and I never implied that your or the article stated "...our engines can only redline at 6500rpm".

I only said your comment doesn't follow logic because the BP has "eclipsed" the cross-over point which is the basis for your claim that solid lifters are more trouble than they are worth. (You will be hard pressed arguing that miata HLAs are less trouble than the miata solid lifters btw).

I am going to try to explain my thinking here, so you don't think I am just being an internet dick. It just doesn't make sense, when you say:
"...unless you plan on spinning the engine higher they are just a pain in the ass."

In a post about 6.5k as the point where Solid lifters have an advantage over HLAs, and in reference to an engine which readlines higher (and can be easily modified to higher RPMs than that).

I apologize about the now-turned-thread crapping, we can continue to have meaningful discussion about HLA/Solid lifters and the what nots (or camshafts since this is the original post).

"I could have better spent my time posting relevant information about cam specs I have used for turbo engines. I thought I could add something useful to this thread since have a Superflow dyno and a friend who grinds cams 10min away."

Hi Matt, I'm sure most of us would like to know more about lift and duration specs that have worked for your turbo builds. From what I've been trying to piece together a turbo motor would rather more lift and not a lot of duration (@258?) and no overlap. I've been trying to get through David Vizard's book but he doesen't talk too much about 4-valve heads.

Did you weigh the hydraulics when they were full of oil?