Mike J

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..



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.

The wost 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...

Toga

Wow! accuracy is the word here!
Crucial moment where you decide what to replace or not...
Thanks for sharing those moments Mike, keep up posting!

cabrio993

Mike, great writeup. Can't wait for part VII. Maybe that bad valve was your Phut-Phut valve!

deltawedge

Great stuff, keep it comming.

Were you able to determine any correlation between the carbon gunk on the exhaust guides (around the head of the exhaust valve inside the exhaust port) and the wear on the guides/valves? I have what look like stalactites on a few exhaust guides in the ports.

Mike J

I am not sure. I do know when the valves were pulled out that they had a heavy coat of oil on them...more than was expected. The oil was just short of being heavy enough to flow which implies the seal was not keeping all the oil out. With a bit of valve wiggle or play that seal has to work pretty hard. My machinist said that the amount of oil on the stems was more than it should be and, if it was leaking too much oil down the stem onto the head of the valve, woud lead to buildup of burnt oil around the exhaust valve seats etc. I did not have any stalactites but as you can see lots of black gooey gunk. Where else would that gunk come from other than the valve stem/guide anyways....