Stupid 355 valve guide question, searched anyway...

How about Oil Consumption ?
Recent Compression/Leakdown ?
If the Seller does not allow a PPI------RUN !!!

 

Hello:

I have a 95 F355 Spider which was serviced at 4 different authorized dealers during a long term cross country round trip. The "valve guide" issue came up at the 2nd major (48K+/- miles - 10 years) when back on the west coast.

BTW: The car had no apparent symptoms - Just due for a major based on time.

 

A leakdown test tells you if the valve/s is/are seating (sealing) properly. It doesn't provide any insight to the "health" of the valve guides...correct? If so, short of removing the heads and valves, is there a reasonable in-car way to check the guides?

 

A leakdown test will provide you with insight as to the condition of the valve guides. If the guides are worn, the valve will not seal as effectively. You should really have a leakdown test done. Ideally the results should be less than 5% in each cylinder.

 

If no symptoms, how was it determined that the valve guides were an issue?

Doesn't a seated valve leak into the atmosphere (i.e., the valve guide doesn't provide any secondary sealing per se)?

(Not debating any of this; this is a learning opportunity for me...)

 

Yes there is always some leakage, but the issue is the amount of leakage. I purchased a 1995 F355 last year and the leakdown results were 2% for 7 cylinders and 3% for the other. This is considered ideal. Cars with problems will have cylinders with maybe 5% to 15% leakage.

As to how it happens, the mechanics at my dealership (Continental Autosports of Hinsdale, IL) have explained to me that, when the valve guides wear sufficiently, the valve stem will ride at a slightly different angle. This will result in the valve face contacting the seat at a slightly different angle, resulting in increased leakage.

 

Great data points to consider!

Ahh...that makes sense!!

Separate question: Do F355's utilize radiused valve seats or angled?

Thanks for the info/insight, Steve!