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Old 03-08-2012, 04:24 PM   #1
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Default ST Ti retainers don't fit the springs, chromoly options?

My builder called me with worrying news.
He had started disassembly of an a BMW endurace engine which had lost power after a minor mishap (broken trans input shaft, and 10.8krpm in the log).

A couple of valve springs were broken but the most worrying thing was that a number of other valve springs have galled the ST Ti retainers heavily and one spring had gone all the way though (the valve was hanging on the inner spring).

The outer springs that was left did stay o the retainers during the wash but did not the be very firmly.

This made hem look at the ST dual springs and Ti retainers for my motor and there is no fit at all between the retainers and the outer spring, all have a noticeable gap so the springs will not fit snug and have a high probability to move and wear the Ti.
To make matters worse there is nothing steering the inner spring on the lower seat.

So, I'm looking at options using preferable Chromoly retainers (to get away from the wear issue), but that would be custom I guess.
Are there any other retainers that could be used/modified (that would work with the BP valve stems/keepers)?

Or is this a non issue at 10.7mm lift at 7500rpm and the ST sloppy fit and soft Ti are fine?
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Old 03-12-2012, 08:26 AM   #2
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Hmm, the option might be local custom fabricated retainers of scrap material of offshore Alu-Ti alloy (non standard alloy to say the least).
But if anyone have knowledge about off the shelf retainers in CroMo that would work (after some minor machining) it would be much easier (and consume less favors).

But first my builder have to make sure that the ST dual springs are what they say they are (or even then, if they are suitable).
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Old 03-12-2012, 09:10 AM   #3
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Sounds like youre trying to fix a problem that doesn't exist. I have BP springs with OEM retainers on big cams revving to 8k.
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Old 03-12-2012, 09:48 AM   #4
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If they do not fit, then you sourced the wrong retainers, or the company that supplied them screwed up. When you first aquired the valvetrain components (springs and retainers), did you source them seperately?

I can assure you that a decent valve train manufacturer will be able to supply you with the retainer you need. If one can't do it, find someone else. Personally, I would stick with the Ti retainers for the added power.

To be sure they get it right, you may want to ship them a spring combo, valve, and keepers you plan to use. There are so many different configurations, it is easy for someone to make a mistake. Before you install them, be sure you do a test fit.
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Old 03-12-2012, 04:32 PM   #5
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Quote:
Originally Posted by miata2fast View Post
If they do not fit, then you sourced the wrong retainers, or the company that supplied them screwed up. When you first aquired the valvetrain components (springs and retainers), did you source them seperately?
ST Valves and the ST dual spring/retainer kit.
Based on the looks on the beemer ST Ti retainers we don't want to use that soft Ti regardless if ST would replace mine with a kit with matching springs/retainers. We'll use the springs and play poker with the retainers (as scrap value).

There are many ways to proceed but using the springs I have and getting retainers to them seems to have a higher probability to get done before May.

Stock springs and OEM cast retainers was used when I dropped a valve last year (OEM VVT cam and 7300rpm).
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Old 03-12-2012, 10:30 PM   #6
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Ti retainers have been used reliably in motorsport for a long time. Somebody either made a mistake, or there is a quality issue.
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Old 04-13-2012, 11:05 AM   #7
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Time flies when you have fun...

I made some photo documentation of our issues with the ST Spring/Ret/Seat kit and sent it to ST to get some comments.
The response was that they agreed that there could have been some improvements but it "should work".
So I place it here too and you can judge for yourself and if you have a different experience it just shows the variability.

First the Kit box

The labels on the bags in the box matched up except the seats which had no label on the bag.

Springs


The measurements of the springs are in order, a little variation as you can expect from springs.

To get a tight fit we here anticipate that both the seat and retainer would "snap" onto the spring requiring some (a lot of) force. But instead there is a significant gap to the spring dimension (the 20.0mm ID of the outer spring).


Notice the wonderful surface finish...

The retainer is also quite a bit smaller that the OD of the spring (27.5mm)

And the final picture does not look nice at all to me. The retainer could be centered by the inner spring but that's not the issue, a soft Ti retainer needs to be held in place by more than the seat pressure, i.e should be clamped by the spring radially and not have a gap).

Notice the offset due to the gap to the spring ID.
The surface quality on the seats are poor to say the least and the retainers does not look nice either.



Our suspicion against the ST Ti retainers is backed up by another head on the same workbench.
This is a BMW head that have seen 30 hours of endurance racing and was torn down after an over-revving event (normal 8-9k operation range).
It looks to be the same Ti material (same surface finish etc), and the same lack of coverage of the spring, but this edge is wafer thin.
In this case the Retainers actually fit the springs quite well, snug but not firmly.


The result when opening the head was not nice at all, many retainers showed huge wear and some were worn right through (the valved were hanging in the inner spring only). The seats also showed wear. Disregard the smooth retainer, that one was worked by a broken spring

Even though there was an over-revving event that explains the broken spring, the wear on the retainers are not sudden.

Are we too theoretical and scared to not use the ST Ti Retainers since "noone else have had issues"?
- Possibly, but why should Mazda engines be so much different than any other DOHC alu head engine?
Are my retainers identical to the ones received by buyers of the single spring kits previously (it should be according to the lists but suppliers can suddenly lower their quality without notice)?
Why am I using the too hard springs (ST harder duals)?
- It looked like a good option at one stage, now I'd prefer to have every available springs at hand so we can test them before choosing a setup. You should always take spec sheets with a bag of salt.

Wonder if ST can sell the softer outer spring (I guess it's a mix and match system since the dimensions are identical) to make it possible to get all three options?
Attached Thumbnails
ST Ti retainers don't fit the springs, chromoly options?-st_kit.jpg   ST Ti retainers don't fit the springs, chromoly options?-st_springs.jpg   ST Ti retainers don't fit the springs, chromoly options?-st_ret_id.jpg   ST Ti retainers don't fit the springs, chromoly options?-st_seat.jpg   ST Ti retainers don't fit the springs, chromoly options?-st_ret_od.jpg  

ST Ti retainers don't fit the springs, chromoly options?-st_ret_on_spring.jpg   ST Ti retainers don't fit the springs, chromoly options?-st_bmw_ret_misfit.jpg   ST Ti retainers don't fit the springs, chromoly options?-st_bmw_retainers_30hours.jpg  

Last edited by NiklasFalk; 04-13-2012 at 11:51 AM.
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Old 04-13-2012, 12:11 PM   #8
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That is just ugly...

Good catch before some real engine damage occurded.
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