[h2pmr]

anybody got a list of 928 cylinder head casting numbers to cross reference with the actual Porsche part numbers?
i am just looking for the 87+ models, but if somebody has a reference for all models, it would be nice to share for future generations
cheers
Phil

[worf]

[h2pmr]

i guess part numbers of heads are not that important as they are NLA , so its just the numbers cast into the actual head that we need to know about.


i asked the question on here as a guy contacted me to see if i had a spare good head as his was badly corroded, and i just needed to know what the first head casting number was when Porsche raised the bosses of the head bolt mounts to stop possible cracking.
the guy who contacted me posted a head cancer thread on RL and Mr B gave the answer below, for 87-95 models ONLY:

1R and 2R heads are from 1987 and 1988 engines. They are prone to cracking at the base of the lower head washers. Avoid them, like the plague.
In 1989, Porsche raised the bosses. in the heads, to prevent this from occurring. These heads were 3R and required longer head bolts than the 1R and 2R heads.
Porsche made a few more changes, over the next few years (nothing extremely important, for your use), and 4R and 5R heads appeared on engines.
You can use any head from 3R and later.

so now we know.
i should have taken the time to check the 5R head i sold him to see if i could spot any of the changes between the 3R heads i still have, but i did not, the head was in lovely condition though
hope this helps someone
cheers
Phil

[MattiasH]

I just bought some 5R heads and to my surprise the casting numbers are from week 50 1998. Can they be from a replacement engine or maybe bought as spare parts?

[worf]

I just bought some 5R heads and to my surprise the casting numbers are from week 50 1998. Can they be from a replacement engine or maybe bought as spare parts?

Huh.

Interesting.

Seems odd.

[maddog2020]

anyone else ever seen 1r or 2 r heads crack? I've never seen or heard of any. I used to be part owner of a shop that did quite a bit of 928 work, years ago. I see misinformation from mr b quite a bit so I'm not surprised to see it yet again.

[Stepson]

Very Interesting!

[worf]

anyone else ever seen 1r or 2 r heads crack? I've never seen or heard of any.

I have not.

[h2pmr]

anyone else ever seen 1r or 2 r heads crack? I've never seen or heard of any. I used to be part owner of a shop that did quite a bit of 928 work, years ago. I see misinformation from mr b quite a bit so I'm not surprised to see it yet again.

i have not seen any crack either, my guess is:

if Porsche only used the 1R and 2R heads for 2 years then changed them, they must have found out pretty quickly that they could crack, so they could have been badly torqued down in assembly or badly cast or machined at the factory?

if an 1R or2R head has not cracked by now i don't think it will.

just my 2p
cheers
Phil

[maddog2020]

Not necessarily. Porsche made thicker blocks in 85-86 not because the previous blocks had problems. They went back to the thinner blocks in 87. Part specs can and do change over time to different suppliers.

[worf]

Not necessarily. Porsche made thicker blocks in 85-86 not because the previous blocks had problems. They went back to the thinner blocks in 87. Part specs can and do change over time to different suppliers.

And everybody loves the 3R (etc.) heads because of the "thickness." But the the aluminum matrix is far, far more porous than the 1 and 2R(*) heads and that is a contributing factor for extensive "coolant corrosion" and also makes them way more expensive to fix.

(*) I don't, off the top of my head, remember the casting numbers with respect to model year. But, 87-89 heads: nice and dense. 90+ heads: Swiss cheese aluminum.

I've put several sets of '87/'88 heads back on blocks and those 928s aren't spitting coolant out of 'em.