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Help!! My Intake Valves Keep Wearing Out!

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Help!! My Intake Valves Keep Wearing Out!

 
Old 01-10-2015, 04:00 PM
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Originally Posted by hornetball View Post
I'm confused about your statement re: factory shims. I was always under the impression that you shim as required to achieve a seat pressure (which is what I think BogusSVO was showing). Shims are shims. Is there something special about the OEM shims? Or are you saying to make darn sure it is checked and adjusted as needed? I can see how a machine shop would be tempted to skip this step on a vanilla rebuild.
I should have been clearer with my previous statement. Supertech advertized spring rates are achieved using the factory shims. Without them spring rates are lower.

By measuring and shimming to your own spec you can use whatever shim(s) you need to.
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Old 01-10-2015, 05:17 PM
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Gotcha'. Thanks.
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Old 01-10-2015, 05:44 PM
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I'm going to ask a stupid question. I thought the BP5A cam was a stock cam in most of the world and a drop in replacement here in the USA. Why do you need more spring than the factory springs?

robert
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Old 01-10-2015, 05:49 PM
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Originally Posted by robertcope View Post
I'm going to ask a stupid question. I thought the BP5A cam was a stock cam in most of the world and a drop in replacement here in the USA. Why do you need more spring than the factory springs?

robert
Pretty sure more spring = more revs
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Old 01-10-2015, 05:52 PM
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Originally Posted by aidandj View Post
Pretty sure more spring = more revs
"With the MS, Soft Cut (reduced timing to 10*BTDC) is 7000RPM and Hard Cut (Fuel) is 7200RPM." Yes, if he was turning more RPMs than stock, that would make sense, but he isn't.

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Old 01-10-2015, 09:15 PM
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Stupid question, sorry...

Factory shims.. Are we talking about these? (With an arrow next to it)





I mean, these are only 0.02" (0.5mm) thick.
How would such a tiny height reduction make a difference in spring rate?

Yes, I just found all 16 of these in a box of parts (I had received from the machine shop) left over from the time when I switched over to Supertechs. Guess they did not think they were necessary.
And, I had bigger fish to fry at the time, so I never checked...
Attached Thumbnails Help!!  My Intake Valves Keep Wearing Out!-2ek7qj.jpg   Help!!  My Intake Valves Keep Wearing Out!-17g5fi.jpg  
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Old 01-11-2015, 01:32 AM
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Yes godless commie those are suppose to stay. I forget the specs but kinda remember they are worth somewhere around 7lbs of seat pressure. I do remember they were a LOT more than I expected.
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Old 01-11-2015, 04:58 AM
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Originally Posted by robertcope View Post
I'm going to ask a stupid question. I thought the BP5A cam was a stock cam in most of the world and a drop in replacement here in the USA. Why do you need more spring than the factory springs?

robert
You're not missing anything. I'm having some real problems with this "fresh" engine -- and I shouldn't be. We're just trying to figure it out. It did exactly the same thing on ST valves and springs that it did on the OEM valves and springs (in other words, the OEM wasn't any better or worse). I'm obviously not a happy camper.
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Old 01-11-2015, 06:03 AM
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Originally Posted by Godless Commie View Post
I mean, these are only 0.02" (0.5mm) thick.
How would such a tiny height reduction make a difference in spring rate?
The spring rate is the same but the shims adjust the seat pressure (call it spring pre-load if you want).
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Old 01-11-2015, 02:23 PM
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Originally Posted by Godless Commie View Post
I mean, these are only 0.02" (0.5mm) thick.
How would such a tiny height reduction make a difference in spring rate?
Pretty simple - the spring rate on ST Singles is ~9.4lb/mm. 0.020" shim means seat pressure should rise by ~4.7lbs.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-11-2015, 07:23 PM
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Gents, I just pulled the head and posted some pics and videos on the other thread:

https://www.miataturbo.net/engine-pe...en-warm-82232/
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Old 01-12-2015, 08:05 AM
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No shim

[/URL]

Shim

[/URL]
Attached Thumbnails Help!!  My Intake Valves Keep Wearing Out!-2015-01-12%252007.55.56_zpsnk21qbaj.jpg  
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Old 01-12-2015, 09:16 AM
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Originally Posted by k24madness View Post
Yes godless commie those are suppose to stay. I forget the specs but kinda remember they are worth somewhere around 7lbs of seat pressure. I do remember they were a LOT more than I expected.
Originally Posted by NiklasFalk View Post
The spring rate is the same but the shims adjust the seat pressure (call it spring pre-load if you want).
Originally Posted by Savington View Post
Pretty simple - the spring rate on ST Singles is ~9.4lb/mm. 0.020" shim means seat pressure should rise by ~4.7lbs.
Originally Posted by TNTUBA View Post
No shim

[/URL]

Shim

[/URL]
Thank you guys.
I really did not know this.
You live and learn, I guess.
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Old 01-12-2015, 11:54 AM
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Something else to keep in mind, the stiffer the springs, the more force you add with the shims. It's a linear relationship. So, adding that shim to ST light doubles has more effect than on ST singles which, in turn, has more effect than on stock springs.

And I can tell you that the shims were left out on my September head rebuild.
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Old 01-12-2015, 12:15 PM
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Originally Posted by hornetball View Post
Something else to keep in mind, the stiffer the springs, the more force you add with the shims. It's a linear relationship. So, adding that shim to ST light doubles has more effect than on ST singles which, in turn, has more effect than on stock springs.

And I can tell you that the shims were left out on my September head rebuild.
Bingo. That's why on my "supertech heavy doubles" the effect was 7lbs+, IIRC it was closer to 9lbs.

Now onto the next question. What spring pressure should you run with a BP5A cam?
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Old 01-18-2015, 09:34 PM
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Machine shop pulled my head apart today. ST singles without OE valve shims.

Curious along with K24madness as to what is the recommended Valve seat pressure for BP5a cam, and does anyone have the part number or place to acquire a set of OE shims?

(If anyone has a set laying around PM me!)

Last edited by Chooofoojoo; 01-18-2015 at 10:07 PM.
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Old 05-23-2015, 02:20 PM
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Is there a current discussion on this issue on a different thread as I am interested in what people have found out now that it is 4 months later. I am fixing to install some 1+ overs and was thinking about just using the inconel exhaust with OEM intakes. I would like to also use the 1+ intakes if the suggestions above fixed the problem.
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Old 05-23-2015, 02:30 PM
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I ended up going +1mm intake and exhaust, but Manley not Supertech. Supertech light double springs, stock shim over bucket, bp5a intake, stock exhaust cam. Will be a zippy N/A motor for now, eventual TSE turbo. Motor is being swapped this week. Will report on findings over next few months.
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Old 05-23-2015, 03:52 PM
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Originally Posted by jmann View Post
Is there a current discussion on this issue on a different thread as I am interested in what people have found out now that it is 4 months later. I am fixing to install some 1+ overs and was thinking about just using the inconel exhaust with OEM intakes. I would like to also use the 1+ intakes if the suggestions above fixed the problem.
I run supertech undercut coated stock size intake valves, +1 inconel exhaust valves. I cut the seats myself, did a 5 angle on the intakes, 4 on the exhaust, kept the seat widths conservative. Stock shims/buckets, I just tipped the valves to adjust the clearances.

I run heavy double ST valve springs without the shims (opps). Reved the engine to 8,800 about 200 times, put about 2,000 miles on it. Broke a piston 3 weeks ago and checked the head, valves all seal perfect.

My guess is if you're vavles are tightening up, it's due to a machining error. Something is wearing in causing the clearances to tighten.
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Old 05-23-2015, 09:44 PM
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Any chance you guys are wearing out the valve guides and that is allowing the valve to move around a bit on the seat? This happened to me years ago on a honda engine.
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