R&D thread for shim-under-bucket conversion!
 

OK I know Mazda Comp sells this but I want other options. Because. :) Ok because i'm not a member. fine.

Anyone (Brian you have my head... got calipers?) know the OD and length of the buckets?

The valve stems are 5.96mm for intake or 5.94 for exhaust. Supertech sells a 6mm lash cap which I assume will work.

I remember hearing rumors that the 4AGE buckets were the right size, but rumors aren't guaranteed to open valves.

Here's the part info:
one of those is bound to be our size. or close. or close enough ;)

Also: at what point do the dual springs become necessary? The Supertech duals are about 50% more seat pressure (74lb) and about 30% higher rate overall.


notes:
Mazda Motorsports "solid lifter" p/n? B6N7-12-183
From a protege site the bucket p/n is: BP2Y-12-183
http://www.maruhamotors.co.jp/miata/...camfornb8.html


thanks guys.

I guess I should put mine up for sale.

errr, your what???

No idea if this is relevant or not, but I ran across this post over an mnutter regarding potential interchange between Miata, Zetec, Duratec (MZR), and Honduh springs (and lifters).

http://forum.miata.net/vb/showpost.p...9&postcount=24

Scroll about halfway down the post for the details, including "graded" solid lifters that don't require shims.

Any 6mm shims will work. I used a set of 16 off ebay made for a chevy. Cost $30 shipped.

You can get teh mazdaspeed lifters through MiataRoadster.com for only $200. For that price I wouldn't bother searching for other methods.

Glad to be of service.

200? well sheeit.

I've got an entire mazdacomp shim under bucket valve train from 99 cylinder head (springs and cams). They're stuff we ran in the motorola/grandam cup. I put them up on miatanet classifieds but got nothing but wieners.

Rob--we were discussing your cams, but never really got to terms. If you have a price in mind for the whole set up, shoot it my way. Honestly, all my spare change is going to the block right now, but maybe...

I'd assume that setup is too hard core for a street car?

Randy Stocker was telling me it would be pretty bad ass for a boosted street car actually. :dunno:

brian (neogensis "i've awaken the beast") has a good description of what it's like trying to get cams like this to idle - a lot can be tuned out, tho still lumpy compared to a stock cam. BUT with a turbo car and reduced overlap it shouldn't be as bad. I never ran these on the street, but on the track way up in the rpm they were just badass.

Without the cams, the valvetrain would be fine IMO. It's far lighter than the stock setup and will spin way easier.

Sorry about that Ben - totally forgot. I'll hang on to that stuff for your engine, just totally spaced.

i already sent the money to billwilner for the buckets. just need to find brian-neo's source for the cheap lash caps.

Brian, did you get all one size or custom sizes to fit your specific application?

I had to grind them manually to fit. I used a diamond coated knife sharpened. Takes forever but its worth it. Just search ebay for 6mm caps.

^Totally gonna show my ass here. I understand how shim under bucket works... but exactly what is the advantage over the current configuration of the valvetrain. What is this gonna buy you? What is the advantage?

I can deal with grinding my own caps I guess... I've got the sharpeners :)

Sam, the benefits are mostly reduced weight and the ability to run higher lift cams with less liklihood of destruction...

Normal shims are big quarter-sized things that are kinda heavy compared to the pea-sized lash caps used with shim-under-bucket. Plus at high rpm with big cams, if you float the valves, those standard shims are no longer captured by anything and can slip out from under the valves and do bad things.

but mostly the lower reciprocating mass means the valvetrain can handle higher speeds.

You dont risk spitting the tiddly-wing stock shims at high RPM, wich could damage the head. Its also lighter, which is a big deal at those RPM's.

What does this type of benefit does this modification produce, sorry to hi jack.

.

and less mass means you don't need stiff springs: less spring rate = less pressure on the cam lobes and less effort to rotate the cams

:rly:

so would stock springs handle a .400 lift cam at 8500 rpm or is that just silly...

oh herro: $30 lash caps. Are these the ones you got from the weight lifter company? haha

http://cgi.ebay.com/ebaymotors/NEW-B...2em118Q2el1247

So, longer duration/lift allows more air through the head? I thought the limitation of the head was the actual layout of the air passages (small) and not the size/volume of the valves.

In the end, how much more RPM are we talking about here? The number for the stock valvetrain seems to be 7200 as an upper limit. To be worth anything, I'd think you'd want to see a 500-800rpm improvement. So, would converting to shim/bucket let you get up to the 8000rpm range... 8500?

I hesitate to think what the next limitation is. Turbo flow? Pump gears? Bottom end?

This mod isn't for me, but I'm still trying to figure out what the end-result in performance will be. Will it make more power? Will it rev quicker? If so, then how much... and where will you see the gains... and will the wear-and-tear on other components be worth it?

That's my redline stock... I think people safely run 7500-7800 on the stock guts. Maybe that's later cars. minus the MSM.

the stress on the bottom end goes up exponentially with RPM so yes, that may very well be the limitation. I think with a full top to bottom motor build, running 8k isn't out of the question. Hell, I'll try it.

Lets see... all flow related items that need more flow with higher RPM become limiting factors: injectors, turbo, pumps can cavitate, harmonic damper, etc.

but the benefits are (if you keep your torque up) linear increase in hp as revs increase. Think S2000. Look at the power go up above 7000 rpm... yet torque is constant.

http://www.ultimate-racing.com/Produ...KitNewDyno.jpg

Over 300 HP at 7.5 psi wowza. Wish we were so fortunate.

couldn't be the .2 or .4 more litres... :)

I don't know the specs on the springs we used with our cams but they were noticeably less stiff just by squeezing. Ideally you want less spring rate for a lighter valve train since you're moving less mass. I'm paraphrasing the engine builder, but the spring rate needs to be stiff enough for a good return on the valve (quick action) with minimal force against the lobe at compression. That said, we weren't revving past 7500. Our cams were geared more for torque and not high rpm power. So rev limit would also play into spring rate to avoid float. My guess is that's the point behind upgrading the springs on the stock valve train - to keep those giant shims from shooting out.

FYI I have a built engine with basically stock '99 valvetrain, and I occasionally spin it to 8k, I have great power at 7k but power really starts to drop off around 7200 or so, and by 8k my hp and tq are just about non-existent... I think its due to valve float.

i think it's your cams

could be either or both. Have not seen too many N/A 8krpm dyno pulls, but yeah, Jerry seems to think the stock cams are really holding me back... I agree.

+1. the faster you spin the motor, the less time the valve is open and it needs to draw in the same amount of air. Cams are what's killing it most likely, I doubt it's floating valves.

valve float will feel more like a misfire

Got to be the cams then. I need to pimp my valvetrain.. someone buy my NX kit :)

cam grind group buy!! heh.

SO I found a couple things:

1. Manley makes 6mm lash caps that run for 30-45 for a whole set depending on where you get them (flatlander, summit, jegs).

2. the FM valve springs are the exact same rates listed on the supertech website. belfab has the set for roughly the same price.

3. Actually with a little looking around, Import Performance Parts/Flatlander has the valves and springs significantly cheaper than other places.

hmm.

Those are indeed the ones :)

kinda creepy, i'll probably go with flatlander and just get the whole valvetrain setup.

I'd like to find a place that can sell just the Ti retainers and locks.

The retainers are made specifically for the springs. The super tech springs require their springs seats and retainers for out cars. My super tech springs were actually shorter than the stock springs. The winding wasn't as tight though, so they could still support more lift.

I would definitely get the entire valve train in a kit Matt. Those are the shims I am using though. I probably have 40hrs invested in grinding them myself with the knife sharpener though. I couldn't find a place locally that would grind them for me. Most places thought I was crazy to even ask.

or i can just order the supertech pre-sized ones...$4ea is much less than I'd charge myself in labor.

You'll have to order them very last so that you can measure needed clearances.

Hello, the Miata is not an S2K!!!

Yes, you need better springs for 8500 RPM... Not a big deal really and a nice set of shim under buckets.

Mark

the miata is definitely no s2k. but i plan to spin it for all its worth.

I was over at Supertech in San Jose yesterday having a long talk with Willy, and I bought a set for my '97 M3, whose cam was done by Elgin. Elgin gave me a crapload more lift on the intake, and OE springs are damn close to bind. (despite the not very aggressive ramps)

Basically if you make a single spring a lot stiffer than stock, the wire will see too much stress, and a dual spring setup will be a better engineering solution; and then the dual setup is designed for the springs to have a different resonant frequency so that the result is a pair of small resonances instead of a single big one. This resonance can cause a "travelling wave" to move up and down the spring and cause the valve to bounce off the seat after closing. A bigger problem with boost behind the intake valves, which will need a higher valve-closed pressure (force, really). This is what manifests as "valve float" and loss of power at high RPM.

I first checked if I could use just the outer spring for my M3 and it turns out they're softer than the cone shaped stockers. I don't know if this applies to the miata because the miata has standard cylindrical springs. Cone shaped springs allow thicker wire (stiffer) with shorter coil-bind-length. So I had to buy the whole shebang. ($$$, esp. with 50% more cylinders than a miata) The little fuckers were more than half the price of my cam regrind.

In order to engineer dual springs you have to use their retainers. In order to sit both springs on the head properly you need their lower spring seat.

The springs primarily need to be stiff enough to decelerate the valves which peaks at the cam's nose. Deceleration is proportional to RPM squared, just like rod stress (not exponential ;) ). So spring open pressure (force, really), needs to stiffen proportionally to RPM squared, but inversely proportional to valvetrain mass (valve+follower+shim+retainer+keepers+1/3rd spring). If the springs are too soft, the lifter can "take off" like a ski jumper and cause rapid wear on the cam and lifter due to the "harsh landing".

Because the valve deceleration profile is a function of the cam profile and RPM, the spring stiffness should be specified by the cam designer. Ironically more lift can allow for a less aggressive deceleration profile despite a more aggressive opening ramp; but many factory springs run very close to coil bind, to prevent dropping a shim during a mis-shift. The bind prevents the valve opening too far and a gap under the lobe forming big enough to drop a shim. This may be why miatas don't seem to drop stock shims during a mis-shift, unlike say, a Sentra. More duration also allows for a less aggressive opening ramp. However, an aggressive opening ramp with a high peak velocity allows for more "area under the curve" and makes for more airflow for a given 0.050" duration - too much duration screws up low end torque.

Got a lil sum'n-sum'n in the mail.

http://farm3.static.flickr.com/2232/...459abf.jpg?v=0

http://farm3.static.flickr.com/2009/...844f64.jpg?v=0

and no I wont use a real camera. but I might clean the smudges off my lens.

I also just got the valves, springs, and retainers. biiiiiiiiiiiitchin.

Bumping the worlds oldest thread.

Did anyone ever use a micrometer to determine the OD and depth of the factory HLA?

I have a set of skyline GTR lifters in my room...(from the list) and I am interested in running them if they fit...

another big bump from me....you know I don ´t like to do new threads if there is no need to.

My question is simple. What is the right way to measure the thickness of the shim under bucket ?
I have custom grind cams with 33mm base circle. Is it ok to just install my valves, springs, retainers, then put on it mazdacomp bucket lifter (shim under bucket type) and measure cold lash between cam and the lifter surface, and from there determine the needed shim size ?
or do I need to use stock BP4W buckets with shims over lifter, measure each shim, put it in the head and measure the cold lash,, then to what I will measure add shim thickness, and somehow work out the thickness for shim under bucket shim ?
I think the first method should work if the lifter will not end up hitting something. But as this is my first shim under bucket lifter swap I don´t know how to.
Thanks for you help !

Measure lash without shims. Subtract the lash you want from that number. Now you have shim size.

that is what I wanted to hear ! thank you
Also is there a difference between mazdacomp and supermiata buckets ? I´ve read somewhere that 949 have them made by supertech, but they seem to be very cheap compared to supertech ones, which are sold by other vendors. on the other hand they seem to be the price range of the mazdacomp ones.