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Old 01-03-2015, 07:18 PM   #1
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Default Help!! My Intake Valves Keep Wearing Out!

Red car.

Engine:
'95 BP Block
'01 Pistons
'99 Head, mildly ported
BP5A Intake Cam, '99 Exhaust Cam

History:

8/9: Rebuilt Engine put into service. Mazda OEM valves and springs.

9/13 ~1500 street miles + ~18 track hours. Head pulled due to loss of compression. Found extreme wear (concave surfaces) on the faces of all intake valves. Head rebuilt with all Supertech valvetrain including valves, dual valve springs and Ti retainers.

9/29 Engine with freshened head put into service.

12/28 ~500 street miles + ~22 track hours. Noticed slight miss at idle. Leakdown shows loss of compression through valves. Intake valve lash has closed up again.

Soooo . . . WTF?!? Is this normal? How long should I be able to go on a valvetrain before reshimming? If not normal, any ideas on what's causing the valve face wear? I wouldn't expect weak valve springs to be an issue with the dual Supertechs. In all cases, the head work was professionally done by a local machine shop.

Help!!
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Old 01-03-2015, 07:42 PM   #2
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Old 01-03-2015, 08:01 PM   #3
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If anything you made it worse with the super techs, which is evident in your shortened life span after rebuild. Were the seats replaced at any time?
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Old 01-03-2015, 08:13 PM   #4
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I think the seats are the culprit in both cases.
I mean, the way they were machined.
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Old 01-03-2015, 08:35 PM   #5
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Originally Posted by curly View Post
If anything you made it worse with the super techs, which is evident in your shortened life span after rebuild. Were the seats replaced at any time?
I got more track hours with the Supertechs than with the OEM valves. By the time I pulled the head with the OEM valves, the car would not idle. I'm catching the failure much earlier this time.

I don't know about the seats. Given that the machine shop has already rebuilt this head twice (the second time under warranty with me furnishing some parts), I'm "assuming" that they've checked/replaced/machined the seats as required.

Dang, I said that word again . . . "assume." A problem with the seats is really the only reasonable explanation I can come up with.
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Old 01-03-2015, 08:42 PM   #6
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2 heads, similar problems. Only commonality is the ST valves.

I suspect that there is a problem with them. Maybe not stress relieved, and the stems are bending? I dunno, it just sounds like too much of a co-inky-dink to me.
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Old 01-03-2015, 08:55 PM   #7
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Originally Posted by rleete View Post
2 heads, similar problems. Only commonality is the ST valves.
Uhhh . . . 1 head, 2 sets of valves (1 set OEM, 1 set ST). There is something in common here, but it's not the ST valves.
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Old 01-03-2015, 08:56 PM   #8
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Is it possible that you were sold a 94-97 intake cam instead of a BP5A? Using a hydraulic lifter cam with solid lifters can damage the valves and seats.
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Old 01-03-2015, 09:02 PM   #9
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Originally Posted by jpreston View Post
Is it possible that you were sold a 94-97 intake cam instead of a BP5A? Using a hydraulic lifter cam with solid lifters can damage the valves and seats.
The intake cam is prominently cast with "BP" and "5A." I have heard of at least 2 cases of a camshaft being mispackaged by Mazda. But I haven't heard of any with incorrect casting marks. Still, when I pull this head, I'll compare the lobe shapes to the original camshaft. Maybe??
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Old 01-03-2015, 09:37 PM   #10
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Originally Posted by Godless Commie View Post
Thanks for the link. I think these snippets from Andrew are likely to be my issue:

Quote:
Originally Posted by Savington View Post
Whoever cut your seats cut them too thin. I've run lots of ST valves and worked with a lot of motors with ST valves inside them, and there's no issue with the valves.
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Originally Posted by Savington View Post
I disagree with *****. When valve clearances tighten up slightly on a new engine, it's a normal thing, but normal is losing .002-.003", not the entire clearance (.011+). If you lose all the clearance, something is damaged, and resetting the clearance is not going to solve the problem. You'll be back inside the motor shortly (like in another thousand miles or less).

The engine runs fine when it's warm because the aluminum cylinder head expands faster than the valve does, which slightly increases lash clearance and allows the valve to make contact with the head again.

tl;dr: pull your cylinder head and replace your damaged valves, then find a machinist who is willing to cut a seat wide enough to prevent this from happening again.
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Old 01-03-2015, 09:54 PM   #11
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so find out what angle leaves the fattest footprint and request then re-cut specifically that way?
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Old 01-03-2015, 10:00 PM   #12
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Quote:
Originally Posted by hornetball View Post
The intake cam is prominently cast with "BP" and "5A." I have heard of at least 2 cases of a camshaft being mispackaged by Mazda. But I haven't heard of any with incorrect casting marks. Still, when I pull this head, I'll compare the lobe shapes to the original camshaft. Maybe??
Seems unlikely, but it's getting close to 20 years since BP05 cams were in production, and the BP5A is the most recent non-VVT cam casting. I could believe that racers have bought all the old BP05 stock and mazda is now having to grind BP05 profiles onto BP5A castings.

Either way, the quotes from Andrew sound like the more likely answer.
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Old 01-03-2015, 10:01 PM   #13
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What kinda revs are you seeing? Make sure the shop used the factory shims under the supertech valve spring seats. If still running heavy factory shim over buckets I would bump valve pressure a bit. All in all I suspect the problem is too little spring pressure for RPM's/Cam.
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Old 01-04-2015, 02:04 AM   #14
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Stock width valve seats and stock fuel cut with fresh seats should last 100+ hrs.

What rev limit?
Any money shifts?
Downshift too soon when entering corners? This is the most common BP killer that I see (and hear in videos).

NB1 valve springs are weakest. Run NA8 at minimum but ideally ST singles for stock RPM and ST light doubles if venturing to 8k
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Old 01-04-2015, 02:56 AM   #15
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Quote:
Originally Posted by rleete View Post
2 heads, similar problems. Only commonality is the ST valves.

I suspect that there is a problem with them. Maybe not stress relieved, and the stems are bending? I dunno, it just sounds like too much of a co-inky-dink to me.
No

Quote:
Originally Posted by Godless Commie View Post
I think the seats are the culprit in both cases.
I mean, the way they were machined.

Yes
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Old 01-04-2015, 08:32 AM   #16
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Have the springs pressure tested. Wouldn't be the first time I've heard of ST double springs losing strength in a short period of time.
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Old 01-04-2015, 09:49 AM   #17
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AWESOME. Props. Thanks guys.

Quote:
Originally Posted by k24madness View Post
What kinda revs are you seeing? Make sure the shop used the factory shims under the supertech valve spring seats. If still running heavy factory shim over buckets I would bump valve pressure a bit. All in all I suspect the problem is too little spring pressure for RPM's/Cam.
With the MS, Soft Cut (reduced timing to 10*BTDC) is 7000RPM and Hard Cut (Fuel) is 7200RPM. I noticed that my factory tach seems to read higher than the MS by about 200RPM, which I "think" is pretty normal. As I've been getting faster, I'm hitting hard cut regularly at the end of some short straights.

Quote:
Originally Posted by emilio700 View Post
Stock width valve seats and stock fuel cut with fresh seats should last 100+ hrs.

What rev limit?
Any money shifts?
Downshift too soon when entering corners? This is the most common BP killer that I see (and hear in videos).

NB1 valve springs are weakest. Run NA8 at minimum but ideally ST singles for stock RPM and ST light doubles if venturing to 8k
See above for rev limits.

No money shifts from me on this set of valves/springs, but I've had less experienced codrivers at some events, so . . . .

I have been guilty of early downshifts but am improving a lot there. This has been minimal from me on this set . . . but don't know about the codrivers.

Springs are ST light doubles (bought them from an outfit called 949).

Quote:
Originally Posted by guttedmiata View Post
Have the springs pressure tested. Wouldn't be the first time I've heard of ST double springs losing strength in a short period of time.
Good thought.

I'm getting pretty darn fast at pulling the head (sigh). Compiling my list.

For Machine Shop:
1. (Most likely) Check and triple check the darn valve seats. In my mind, the fact that in both instances we've had abnormal intake valve wear with normal exhaust valve wear points to a machining issue or other problem with the intake valve seats.
2. (Probable and SOP) Double check valve spring seat pressures, make sure they are properly shimmed and the springs are in spec.
3. (Unlikely, but just in case) Inspect the cam lobes. Make sure they have a mechanical lifter profile.

For Driver:
No money shifts and no early downshifts. Reconsider this codriver thing.

I'm still wondering about the discrepancy between the MS RPM and the factory tach. Anybody else have a factory tach that seems to read ~200RPM low at the top end?

Last edited by hornetball; 01-04-2015 at 10:21 AM.
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Old 01-04-2015, 09:55 AM   #18
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Quote:
Originally Posted by hornetball View Post
AWESOME. Props. Thanks guys.



With the MS, Soft Cut (reduced timing to 10*BTDC) is 7000RPM and Hard Cut (Fuel) is 7200RPM. I noticed that my factory tach seems to read higher than the MS by about 200RPM, which I "think" is pretty normal. As I've been getting faster, I'm hitting hard cut regularly at the end of some short straights.



See above for rev limits.

No money shifts from me on this set of valves/springs, but I've had less experienced codrivers at some events, so . . . .

I have been guilty of early downshifts but am improving a lot there. This has been minimal from me on this set . . . but don't know about the codrivers.

Springs are ST light doubles (bought them from an outfit called 949).



Good thought.

Compiling my list.

For Machine Shop:
1. (Most likely) Check and triple check the darn valve seats. In my mind, the fact that in both instances we've had abnormal intake valve wear with normal exhaust valve wear points to a machining issue or other problem with the intake valve seats.
2. (Probable and SOP) Double check valve spring seat pressures, make sure they are properly shimmed and the springs are in spec.
3. (Unlikely, but just in case) Inspect the cam lobes. Make sure they have a mechanical lifter profile.

For Driver:
No money shifts and no early downshifts. Reconsider this codriver thing.

I'm still wondering about the discrepancy between the MS RPM and the factory tach. Anybody else have a factory tach that seems to read ~200RPM low at the top end?
Normally the tach reads high by about 200 is what I've read. Is your tach driven by the MS or the coils?
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Old 01-04-2015, 10:00 AM   #19
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Coils (I think). Whatever the OEM setup for a '95 is. Car has an MSPNP Gen. 1, but the ignition system is otherwise stock (no COPs).
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Old 01-04-2015, 10:14 AM   #20
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Using a digital timing light would be an easy way to verify who's lying.

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