Track crew: What do you have in the top end?
 

My motor is coming close to a finish its got belfab rods, supertech 8.7:1 pistons, billett OPGs and a 99 head.

I figure, while its apart we might as well take every possible way to make this thing properly. Which brings me to the head. The 99 head i have needs some new valves. So i figure i might as well make the head bullet proof too, right?

What valves, springs retainers and why?

I am not entirely sure how much hp this motor will see, i dont *plan* on revving it too high probably no more than 7500, but to be safe i figure i should throw some springs in.


High HP track guys, what do you have on the top end of your motors?

I left everything stock with a valve-job. I only rev to 7k because peak torque is low enough that going over 7k isn't so spectacular.

Belfab springs, retainers, and oversized valves, all part of the full HP Kit, on a 99-00 head. I've been revving to 7500 and no problems. The (relatively) large turbo I have should let me get away with upping boost levels at higher RPMs to flatten out the torque curve. Dyno time will tell.

Besides, when I am setting up on the front straight to pass Hustler going into the Rattlesnake at MSR, the overrev will be nice :fawk:

shim under bucket conversion
standard sized valves with the reduced stem
supertech springs, Ti retainers, etc
viton valve seals

they're just all in a box.

I plan on using you and every-other street car on the track as my own personal urinal...again.

I need to do a valvejob. I'm going to add springs at some point. I don't expect to make power up there, but I want the extra 800rpm to play with so I can cut a shift out at a few tracks.

I don't plan to make power up there either but it would be nice to have that headroom.

What are the advantages or disadvantages of oversized valves?

My understanding is that the springs are the weak link for the rpms a race motor will see, does that mean stock valves matched with a set of springs is fine?

I used SI Valves' valves with undercut stems for better flow and reduced weight. Also got the intakes 1mm oversize. Don't have any numbers to compare, but it seemed like a good thing to do at the time. The set was only about $200.

I had a '95 and a '00 head to fool around with when my motor was being built so I had my machinist measure the spring rate for both sets. The '95 head had springs that were something like 7-8 lbs heavier so I used them.

WORD OF WARNING: If you plan on changing the valves in your BP4W head, plan on spending an extra $160 on shims as your lash will need adjusting.

Says the man with a 6spd and 4.1 diff. You could just up the boost and run a 3.6 you know...

Oversized valves will not flow better without headwork to take advantage of such.

Supertech et al valves flow better due to their shape.

Oversized valves, ported and cleaned up head; soft cut at 7250, hard cut at 7500...

- L

snowboardinghomo,
Headwork is great and all, but its a lot cheaper to slap on a 99 head and twist the boost controller. You'll have more than enough power and torque over a wide-enough RPM range that you will not miss the expensive head work especially if you go with that little ass pea-shooter turbo.

Just do a 3-angle valve job and "clean-up" the casting in the runners.

Hustler, i really dont know whats in the future for this motor, heck it might end up being a 400+ motor i just dont know.

I do know, that i never want to open it up again, EVER. I also know that i will be tracking the car on regular basis once it running well again. I also know that i am still learning alot with driving and driving on a track and it would be nice to have that headroom in the high RPMs not for power but for safety. Then again i feel like i am overdoing and overthinking this.


So stock valves, and a set of supertech springs will be fine pretty much for the life of the motor right?

without a doubt. You and I want the same thing...I'm content with 300whp. I don't think you understand how fast 300whp (dynodynamics) really is. You know what set-up I have and if its not the fastest street car on the track on any given track day, its not a mechanical issue...its the driver.

I've seen the TDR car bend a couple valves from an over-rev though; the springs are probably a good idea. Spend the money you saved on Penskes. From this point forward, I'm after real suspension and track time.

God dammit, a hundred and sixty dollars for fucking shims? :vash:

just ask your mom.

Yup. $10ea x 16 and BTW, you'll need to adjust lash if you get the seats cut even when reusing the stock valves. Actually, that's kind of worst-case-scenario. You will be able to reuse some of the shims but without a doubt you'll need to change a few. I bought about 10.

I did the lash myself because my shitty machinist didn't want to do it. If you are doing this yourself you'll need a micrometer or a set of calipers, a feeler gauge, a pad of paper and a lot of patience. What sucks is Mazda has discontinued many sizes you'll have a hard time getting the lash dead-on.

I have a a small cache of shims of various sizes that I'd be willing to trade & I have the tools. Let me know if you need a hand.

Is that retail price or Mazdacomp pricing?

retail

Oh thank god. Mazdacomp FTW.

Why?

In my experience this is generally done to accept larger lifters to deal with long duration and/or super high lift cams. Is there a Miata-specific reason for this or are you changing cams too?

HLA's FTW.

What do I have in the top end? Nada. Refreshed stock head with about 20,000 miles on it and a dozen or so track days.

I know this doesn't help you what so ever, but I thought I'd point out the lameness of my car one more time.

Do I dare ask? How much are they thru Mazdacomp?

I may do cams at some point (I phrase it this way because my build is as yet unscheduled and unbudgeted), but it's mostly because it's a little awesome and is one more thing that will let me spin a few grand higher more safely.

I just like to do things to do things.

[QUOTE=y8s;431826]I may do cams at some point... but it's mostly because it's a little awesome and is one more thing that will let me spin a few grand higher more safely. [QUOTE]


A fair number of the engines I deal with at work are shim under bucket (Cosworth BD, Cosworth DFV, BMW M12, Lotus Twincam) and they're without exception a PITA and time consuming to adjust shims on. I'd think twice about that mod unless you really need it.

good thing I only plan to do it once! :)

Do HLA's need to be replaced as well? I'm looking at upgrading springs but hardly ever hear of anyone getting new lifters.

The money you'll spend on springs, retainers and seats will get you most of the way to a '99 head swap. Do that instead - the benefit is far greater.

Do the headwork on the 99 head before putting it on an earlier engine...

- L

(The answer to the cry, "more power!" is simply, "more money!")

actually rumor has it that you can take off more material on the early head and it will flow better than the 99. A friend of mine just dropped his head off at Endyne, so we'll know something soon.

Total bullshit. Port height is like 50 degrees on the 94 head, 20-something on the 99 head. I remember seeing flowbench numbers of 175cfm for a stock 94 head, 205cfm for a fully ported 94 head, and 210cfm for a stock 99 head.

Good to know that the ported 95 head in my garage should flow relatively close to a 99 head.

Supposedly Endyn has an NA miata motor that made 240crank ponies. I'll let them tell me what to do, not some kid who lives in his mom's basement.

I'm already in to deep on the 94 head (it's been mildly ported) that I've got. So I think I'll just stick with it.

So as to HLA's anyone know if it's a good idea to replace them?

Alright so it looks like their are a few different strength supertech springs avaliable for the miata. I assume that we would want the stiffest ones, but am unsure.

Any specific springs we should be looking at?

Specifically:
49lbs@36.80mm
74lbs @ 34.20mm
70lbs @ 33.50mm
56lbs @ 34.20mm
58lbs @ 34.10mm

Link:
BELFAB RACING PRODUCTS

Is there any place other than belfab that we can get miata specific supertech springs? I had a pretty bad experience with their rods and all around dealing with them.

You want the lightest spring per rpm/lift range.

Thanks for the response, but why do we want lighter vs heavier?

From what I understand, heavier springs will excessively load the cam lobes and wear down the cams and lifters faster. You want enough spring load to keep the valves from floating at max RPM, with a little margin, and not more than that.

zx-tex speaks the gospel. Put money in the cup!

So lightest is best, but how light?

Anyone know what the length of the 99 springs are?

Thanks guys

sounds to me like you need to pick a better engine builder...like one that knows miatas.

At the least call supertech with your cam info and they'll tell you which spring to run.

supertechs are 56 for the single springs and 74 for the duals (seat pressure).

eibachs are 66 for single, 75 for dual.

who knows what stock is? It's not on solomiata.

I am trying to understand how this all works, vs just paying my builder to do it for me and not know why i choose what.

Thanks for the suggestion, ill shoot them a call.

Does the length of springs not matter when the strength of them is being changed?

I am confused because the springs are different lengths, different strengths and i am still not grasping why the length needs/doesnt need to be changed.

I guess this brings me to the question of:
Which supertech springs would be best for a high revving, high hp track motor and why?

length is somewhat irrelevant. you need to know rate and force required to get it to the installed height (which will be the seat pressure in lbs--technically not pressure at all).

so in that sense, length does matter, but it's not useful information by itself.

I can tell you that soft springs will have to be longer than stiff springs in order to reach the same seat pressure (force in lbs).

the math:

Hooke's Law: F = k * x
Where: F = force in lbs, k = spring constant in lbs/inch, and x = displacement of the spring.

if you compress a spring with a constant of k=10 lbs/inch by x=1 inch, you will exert F=10 lbs of force.

if a spring has a k = 5 lb/in you will have to displace it by x=2 inches to get 10 lbs of force or conversely, if you displace it by 1 inch, you only need 5 lbs of force. (you can see why softer springs are going to be longer -- you need more displacement to get the same force out of them).

Flyin Miata spring sets
1.6 58lbs @ 34.10mm
1.8 56lbs @ 34.20mm

Supertech spring sets
SPRK-MM16D1- 49lbs@36.80mm
SPRK-MM18D-K 74lbs @ 34.20mm
SPRK-MM16D2- 70lbs @ 33.50mm
SPRK-MM18S-K 56lbs @ 34.20mm
SPRK-MM16S-K 58lbs @ 34.10mm


By simple comparison you can see the single valve spring kits (the lower two of Supertech) are the same as FM do. FM spring kits are good for 9000rpm and a bugger load of lift (which you dont have to use). So you I would believe they are the ones to go for but I sure y8s calculations can be applied to find out how suitable they are.

My personal part of this is the worry of HLAs coping with higher RPM as in the UK HLAs tend to die above stock fairly easy. So what do you do to fix this?

Nick, why do you want to spend money on springs if you're not increasing cam lift or planning on revving to 8k+? You've got that '95 head in your garage. Have the spring rate on those measured.
IIRC, mine were around 55 lbs. vs around 48 lbs for the bp4w head. That's a 13% increase. Assuming the bp4w head is good to 7250rpm from the factory, a 13% increase in spring rate will get you easily past 7500.
IMO you should be changing the valves. Backcut valves will improve flow and as a bonus, they're lighter too. Lighter = more rpm