Different Valve Guide Part Numbers for Late 3.2 Heads

[mikedsilva]

I'm not a machinist..but am trying to understand why the later 3.2 heads have a different part number for the intake valve guides.

According to the PET pdf that I have.. for 3.0 and 3.2 up to 1986, the intake and exhaust guides are the SAME part number of 930 104 321 50.

The 87-89 3.2 uses the same part number for the exhaust but for the intake guide, they use 930 104 321 53.

My local supplier tells me that the 930 104 321 53 in an aftermarket item, is the same part number as the 96410432150, so I ordered a set of 6 to see.

Attached is a photo of the two guides. Both aftermarket .
The one on the left is the early guide, the one on the right is the 964 part number, for 87-89 intake guides only.
Yes, the ridges are different for where the seal grips onto, and the early style appears to have a step that limits how far it can be installed..

But what else is the difference if there is one?

[konrad911]

Well it's interesting, indeed, but does it matter?

I could imagine that the earlier years might have used different material for the guides, and with a year of change both the shape and material were changed. Just guessing.

When I talked to my machinist shop they said they always need to go some way of oversize anyway to have the proper fit, especially if smn massaged the heads prior to them. They make guides themselves, they make valve seats themselves, and copper beryllium seats made by them are just a fraction more than OE seats.

So either guide or seat it the material is correct and job is done as it should I don't care

[john walker's workshop]

The left one is probably a canyon brand guide, which I use all the time. The stop ring is convenient. The oranger color denotes phosphorus bronze and the brighter brassy one on the right is probably silicone bronze, which is a bit tougher to machine.

[mikedsilva]

Originally Posted by john walker's workshop

The left one is probably a canyon brand guide, which I use all the time. The stop ring is convenient. The oranger color denotes phosphorus bronze and the brighter brassy one on the right is probably silicone bronze, which is a bit tougher to machine.

thanks John.
I guess what I am trying to understand is why Porsche stipulated a different guide for the intakes on the 87-89 3.2.

[Magyar Kiwi]

Hi
Looks to me like an Engineer at Porsche made some change to the area where the guide seal fits, presumably to ensure better retention / sealing. Hence the new part number.
{This is assuming that both after market parts shown are accurate copies of the original Porsche parts.}
Cheers