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JACKNOB

993 cylinder head

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Greetings,

 

I am looking for someone who can help me with a dimension spec on 993 heads/valves.

 

Specifically, valve stem height measured from spring pad to stem tip. There is a finite (max/minimum) dimension for this distance that must be maintained to allow the hyd. lash adjusters to function properly.

 

I cannot find this simple spec anywhere. No one I know (and I know a large number of men in this game) has the answer or can direct me to a source.

 

Jack

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22 minutes ago, JACKNOB said:

Greetings,

 

I am looking for someone who can help me with a dimension spec on 993 heads/valves.

 

Specifically, valve stem height measured from spring pad to stem tip. There is a finite (max/minimum) dimension for this distance that must be maintained to allow the hyd. lash adjusters to function properly.

 

I cannot find this simple spec anywhere. No one I know (and I know a large number of men in this game) has the answer or can direct me to a source.

 

Jack

 

To my knowledge, Porsche did not use that measurement as spec on these engines.  Instead, they had specs for overall valve length from tip to tip as 110.1 +/- 0.1MM on the intakes and 109+/- 0.1MM on the exhausts, and installed valve spring heights on valves that passed the overall spec at 36.7 +/- 0.3MM intakes and 35.7 +/- 0.3MM exhausts as measured from the spring seat to the bottom of the spring retainer.

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Thanks for the reply.

 

The reason for my need to know the allowable installed distance from the spring pad on the head to the tip of the valve is to maintain proper function of the hydraulic lash mechanism in the rocker. We know what the Factory ships new replacement heads at. I am trying to discern what the allowable variance from the OE dimension can be. I know this info is not published by the maker. Very poor oversight or intentional pitfall I do not know. After re-cutting used valve seats the valve will sit lower in the combustion chamber and equally higher at the spring end. How high is is the limit? I realize there is a shorter adjuster for helping this situation. (Refer to 15 59 04 in shop manual). 

 

A few decades past I could have called an old friend at the factory and he would have given me about any info of this sort. We live in a new world now and P has joined the effort to quash the aftermarket.

 

Cheers,

 

Jack

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2 minutes ago, JACKNOB said:

Thanks for the reply.

 

The reason for my need to know the allowable installed distance from the spring pad on the head to the tip of the valve is to maintain proper function of the hydraulic lash mechanism in the rocker. We know what the Factory ships new replacement heads at. I am trying to discern what the allowable variance from the OE dimension can be. I know this info is not published by the maker. Very poor oversight or intentional pitfall I do not know. After re-cutting used valve seats the valve will sit lower in the combustion chamber and equally higher at the spring end. How high is is the limit? I realize there is a shorter adjuster for helping this situation. (Refer to 15 59 04 in shop manual). 

 

A few decades past I could have called an old friend at the factory and he would have given me about any info of this sort. We live in a new world now and P has joined the effort to quash the aftermarket.

 

Cheers,

 

Jack

 

Unfortunately, Porsche has become more parsimonious with time when it comes to engine spec minutia as they don't even want their dealer techs working inside these engines, and they are not the only OEM that behaves in this manner.

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Yes. I remember well a very costly law suit P lost concerning this very subject. I contributed technical data, so to say, to the plaintiff. 

 

We have gone to the trouble of making CAD models of the late heads (liquid cooled) for determining various geometry since P is not so helpful. We do heads for high end domestic race teams and for virtually any question, I have several direct phone numbers to engineers at GM special projects.

 

Thank you much,

 

Jacknob

 

 

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1 minute ago, JACKNOB said:

Yes. I remember well a very costly law suit P lost concerning this very subject. I contributed technical data, so to say, to the plaintiff. 

 

We have gone to the trouble of making CAD models of the late heads (liquid cooled) for determining various geometry since P is not so helpful. We do heads for high end domestic race teams and for virtually any question, I have several direct phone numbers to engineers at GM special projects.

 

Thank you much,

 

Jacknob

 

 

 

You might want to contact Jake Raby at Flat Six Innovations, he has actually published a lot of engine internal specs for Porsche's that cannot be found anywhere else.

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