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.
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?