Valve Keepers
 

I'm going to use 993 valves in my 3.2 heads. The 993 valves are a nominal 8mm stem, so the old keepers, aka locks, won't work. So along with valves I ordered 24 new 993 keepers. The springs and retainers will come later as a set. The keepers and valves just arrived.

Normally one is told to be sure that the two keeper halves don't touch when installed. I assume this is so that the retainer will firmly wedge the keepers against the valve stem, so there can be no relative movement, no fretting, etc.

The last set of new keepers I bought, for 9mm valve stems, were "crushed" - they would not clip into the grooves. I solved that by grousing to the supplier, and just using the old keepers, which fit fine and had a little clearance so they didn't touch.

Here, the keepers touch. I haven't measured the slop, but it is considerable. As a pure guess, maybe 0.012 (3 times valve lash) minimum side to side movement with the two in place.

I am not looking forward to wearing my fingers to a nub trying to sand all of these down with wet/dry paper on a glass plate. I can think of no way of holding them so that a power tool could be used. We aren't talking a thousandth or so.

What gives? Any ideas? Is this one of those "they are all that way" things.

Walt (feeling Grinchy)

What's the upside to that?
JB

Walt,

Are you sure the taper in the early retainer is the same as the later cotters ( keeper ) ? This problem exists in the Jaguar XK engine, the early long cotters have a slightly different taper than the later retainers that were designed for guides with seals. You must use a matched set of cotters and retainers if you upgrade to valve seals.

JB - they are bigger.

Paul - this is not a seal issue. And I haven't gotten to questions of taper, which affect the OD of the keeper, where it mates with the valve spring retainer. This is a question of the fit of the keepers or valve stem locks fitting the valve stems properly.

These are the kind of issues which remind me that I am a somewhat experienced engine assembler. Being an engine builder is another level.

Walt

Don't know the original factory Porsche specs for either the 8mm or 9mm stems, but.....

Kolbenschmidt TRW list the cotters for the 9mm stems (MK-9H) as non clamping design (I'm assume using their valves as well) - there may be some useful dimensions on the cotter/valve stem drawings for you to compare with.

As for taper, you can measure the retainer using 2 different sized ball bearings, a vernier and some trig. calcs.

KS TRW Valve Cotters

KS TRW Porsche Valves

Walt,

I agree that these should fit tight. You could try to call someone like EBS and see if they have better ones. Only other option I can think of is grinding them down. Maybe mount them by the ends in vise-grips and rub on a grinding wheel? Kind of a crude approach but might work if you are careful.

-Andy

Its quite commonly designed this way.

the idea is to allow free rotation of the valve.

I cannot comment as to whether this is actually correct for the 993 sorry..never stripped one

Kind regards
david

keepers
 

They are both 7 degree keepers, the stock design is to allow the valves to rotate, you need to verify that the retainers that would fit a 993 cam housing will work in your pre 993 set up, I bet you will need a custom retainer.

Mike Bruns JBRacing.com

Thanks, Mike

I'll stop worrying about the loose fit of the keepers.

But I'm confused about custom retainers. Why might 993 retainers (in this case, aftermarket titanium ones made for the 8mm 993 valves) interfere with 3.2 and earlier cam housing?

I have worried some about the rockers, because the 993 valves are shorter (the intakes, anyway) than the 3.2 valves, and the keepers are much closer to the top of the valve stem.

What ultimately I want to do is use the 993 cam carriers (housing) on my 3.2 heads. They are a much more mechanic friendly design when it comes to working with the rockers - 2 bolts you can easily get to and they are off, no worry about leaks, etc. And use the RSR rockers, which I understand are significantly lighter. But I suspect the cost of these upgrades is beyond my reach at the moment.

Walt