Your MS rpm is correct to within an extremely small error. It needs to be in order to correctly time ignition events

 

If running light doubles and not critically money shifted (8500+), then it's the seats. No installed or cut correctly. I've posted this before but BP heads don't flow much regardless of what you do so there is no sense in getting agro with teensy drag style valve seats that destroy valves in 10 hrs. The seats themselves need to be the correct hardened type as well. We lost a head a few years ago that had the wrong seats installed, also ate it's valves in short order.

Test the valve springs if you like but we have not encountered any losses in spring rate in any of our ST valve spring sets. Every set that goes into or comes out of one of our engines in is checked.

 

Great info. This particular head had been "ported" prior to my ownership, so there is a distinct possibility that there is something funky with the seats.

 

Not gonna get into a pissing match with a vendor, but my previous statement is from tested springs, not just theory. Might not be every set, but I will never put ST springs in my engine.

 

My tach reads 2-300 RPM high at the hgh end as compared to what the ECU reports to the scanguage. I think it's a deliberate Mazda "feature."

 

Its not metalurgically (did I make that up?) possible for a spring NOT to lose pressure once it's broken in. Valve springs are a wear item in a race motor and should be treated as such....valves shouldn't be wearing out before the springs do though.

 

I have personally seen popular name brand valve springs lose as much as 20% of their seat pressure after 200 autox runs.

 

Hmmmm . . . . 200 runs x 1.5 minutes ~ 300 track minutes ~ 5 track hours.

 

good info in this thread. thanks for posting everyone. I don't have anything to add other than my tach is the exception to the rule and it reads dead nuts accurate up to about 7500 rpm... I wish I didn't know that and I wish i didn't have the MS logs to prove it.

 

Yeah . . . but you have one of them fancy NB cars . . . .

(Oooops, I guess Mobius does too).

 

I think either of these guys could help you out with your valve issues


K Miata Home

NA/B 90-2005 - LFX products - V8 Roadsters

 

Inching closer . . . .

 

It would be curious to see the percentage of time spent at the upper RPM range in that time period.

 

I would say on National Level courses 75% of the time on course is spent above 5000. But that's just a WAG

 

I would guess the same based on my experience in a CSP car.

 

Head's pulled. I'm getting damn quick at it. Going to someone I trust tomorrow. My instructions will be simple . . . (valve face support) > ("flow")

 

Please take some close up pics of the valves and seats.
We can post and compare our cases when I get a chance to pull my head.
(Will at least be a couple days before this snow storm goes away)

 

Here's what my last set of valves looked like (the ones that were removed in September):

Intake Valve (trashed):


Exhaust Valve (normal):


Closeup of that Intake Valve:


I expect this set to look similar. They are very recessed into the head.

 

I'm expecting to see my intake valves look the same. I'm hoping otherwise. My intake valves all tightened up, builder (trackspeed) recommended reshimming and checking it more often. And I hope its just normal wear. If it opens up another .001 in the first 2 auto-x's the heads coming off and I know that this will the problem. I dont know why no one here is using the manley valves they cost $10 more per set of 8 and use a higher quality stainless. You arent even close to the first one to see intake valves exactly like that, it was the plague of a certain west coast csp car. I think he adjusted his machinist adjusted his valve job to compensate or something.

Add me to the list of people hearing about other people's ST springs loosing seat pressure. Those super cheap BC springs in bogous svo's thread seem better and better.

 

Do you ever read your own posts? You bitch about the valves, talk about a CSP car having the same issue, and then admit that the machinist adjusted the width of the ******* valve seat to fix the issue.

Cognitive dissonance at its finest. Jesus ******* christ.