Would you throw these valves out...??

[Mike Juzenas]

I thought I would do a quick post to show my results of measuring my valve stems and their wear...sorry about the wierd scan but I had it in Word so I wacked it into a Jpeg....

B1 of the intake is the stem size of the intake close to the base of the valve. B1 of the exhaust is the stem size close to the base of the valve and B2 is close to the top of the valve....the "Spec" is what Porsche defines as the wear limits of the valve.

The intake valve movement is speced by Porsche to be at the limit at 0.8...which is plenty loose in my books. My intakes are actually well within spec but some of the exhaust guides are toast..

I also cross posted this to Rennlist in case any of you are seeing double...



Notes and Observations:

1 - Intake valves 2 and 4 are toast. Intake valve 5 is on the limit and I will replace it.

2 - All the exhaust valves are in spec. If 7.970 is what the manufactured size then you can say they are half worn out. The problem I do not know the baseline numbers and wether, since I am in anyways, repalce them to make sure I get long mileage out of the heads.

3 - Looks like the valve guides on the intake side are well within tolerances but its interesting that 2 or 3 of the intake valves look worn.

4 - There are 3 exhaust guides well worn with 2 other just following. Why piston 2 is better is anyones guess?

5 - The measurement system used for the stems is a Fowler Micrometer with an accuracy of 0.00005". I checked the zero on the micrometer and each measurement was performed several times. The last digit of course is an indicator more than an exact measurement although I was able to repeat several of the measurements with little difficulty.

6 - The Guide measurements were taken using a Aerospace brand gauge with a scale to the nearest .01mm.

Some pictures:

The worse exhaust valve I have after cleanup...it looks much better...



The intake valves look brand new after cleanup..



Add the valves out of the heads and ready like soldiers to be measured...too bad some of them won't make the grade...



Using my fancy Fowler Micrometer to checkout the stem sizes...the digital readout helps us guys with bad eyesight...



Measuring the intake valve movement...

[cgarr]

You have to cut the seats to get a good seal (exhaust looks like it was not seating well) and I would never cut seats without new guides, as for valves, if there is no stem taper and no cracks (look very close) have them ground, but new ones are rather cheap too!

[afterburn 549]

As I have said b4, consider what a valve dose!! (opening and slamming the door shut) in a environment that hell would not have....most of the time I just throw them out and dont look back.....no questions. You will be happier knowing you renewed the TBO on them and not have a a top fall off, have a new margin and etc.

[davidppp]

Hello there.

I do reuse valves sometimes.

Cheap I know.

But it is essential to measure the stems at several poins not just assume we know the wear point.

In the 911 this varies consoderably for some reason I cannot fathom.

Some are badly worn down near the head...some near the top..

I have a feeling corrosion is a factor too in some cases..get a realyy good magnifier and look for pitting..

Bottom line, less then half of the valves I take out are usaeble..and even those tend to get put into store..

Kind regards
David

[Mike Juzenas]

My current thinking is to have all new exhaust and keep the three intakes that measure out perfect....then again for an extra three valves I can get all new.....hmmmm..

[afterburn 549]

its your engine