www.zxrworld.co.uk

I have a L3 race engine which has the thin valve spring seats(part number 16007) as opposed to the thicker one (part number 16007/A) used on L1and 2 models. They are used in conjunction with the "blue" valve springs. My problem is that they keep shattering, leaving bits of metal to move around the engine and also the remaining part "floats" up, down and around the valve stem causing scoring and other problems. My questions are:
Has anyone else experienced this issue?
Are these thinner valve spring seats inherently weaker than the thicker versions and therefore should be changed often?
Is it wise( in terms of reliability/performance) to simply fit the thicker valve spring seats and compress the spring more?

Many Thanks

I'm not aware of any difference in valve spring seat.................and according to the Cradley parts microfiche the part number is the same from 1990 to 1999


Photos of each would be useful

I agree Cargo, the Cradley parts list only shows one part number and they only sell one type now, the thicker type. The microfiche on this web site shows that the l3 had a different part number. I'll try to get some photos done and uploaded to show the different thicknesses, however being the wrong side of 40 I've now become unable to operate electronic machinery so don't hold your breath for a photo!

Hopefully I have managed to upload a pic. The original Valve spring seat is shown on the right, it's these that keep breaking

Clearly there is a difference there................. but I've been inside lots of ZXR400 motors and never seen that thin one at the bottom of a valve spring

Could it be................that the thin one actually belongs at the top of the valve ? ? ? Long shot I know but maybe ? ? ?

Could be a superseeded part perhaps?? Realised quickly they are not up to the job and changed??

The thinner 'bottom valve spring retainer' accompanies the 'blue' stronger valve springs....usually fitted to the sp's........which were not an official import. Maybe thats the reason for lack of information on them ?
I suspect 'cyclic loadings' is the cause ?

Any idea what the repercussions are of using a thicker valve spring seat and therefore compressing the spring beyond the initial design. Since all 16 seats will have gone through similar cyclic loading I suspect they will all start to fail. I can't see a reason not to use the thicker seats but I have no real idea. Anyway, hope you are looking forward to Xmas as usual Roger!

Hey, just to add, I have stripped a couple of heads to lap in valves and have also noticed the thinner valve seat on one of these. This head had blue valve springs as opposed to the white ones. I have also noticed that one of the heads I have worked on had the blue valve springs and the thicker seats. A few people I know have fitted the blue springs without even looking at the seats also. I remember spending a bit of time googling the springs and seats at the time and could find no details on whether the blue springs were in fact better than the white ones for race engines.

Do you know if there were any issues that came about from running the thicker valves spring seats with blue springs? As far as I am aware the blue springs are preferred for race engines although I don't really know why. I assume they either have a greater spring constant or maybe are longer but don't really know.

The thicker spring seats will give increased preload..which will increase friction. 1.7mm of extra preload increases valve seat pressure by 5kg approximately ( thats linear). This could be advantageous to keep the valves under control on the 'over rev' and may stop the power tailing off between 14,000rpm...16,000rpm. It will also prevent premature valve float/bounce which can only be a good thing particularly for the exhaust valves which have a smaller 'window of oppertunity' to recover compared to the inlet valves. However increased valve seat pressure will cause cupping to the valves so will reduce longevity. You would also have to make sure 'on the nose' of the cam you were at least 1.25mm from coil bound.
Going back to your 'thin valve spring seat failure' i looked back on some of my uni work when i was an apprentice at Lotus and...' the tribological interactions of a solid surface's exposed face with interfacing materials and environment may result in a materials integrity being challenged'

Hope this helps...now back to wrapping presents

Yes, it helps a lot Roger, many thanks.
I'll be replacing the thin seats for the thicker ones and just put up with increased wear, I feel it's preferable to little bits of metals flying around the engine. The oddest thing was that the remains of the seat spiralled up and down the valve and effectively "welded" the valve and valve retainers together. Right, now to compose the ebay add for some virtually mint, extra rare SP race valve spring seat retainers!!