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Unread 04-22-2018, 03:31 PM   #149
GlenL
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Default ARP head studs for 928

Working through the parts as I'm finishing up cleaning and prepping.

Here's a few pictures of ARP head studs that will be going in. These are ARP 204-4211 studs are are made for the 16V 2.5l 944 engine. They are precisely the right studs for the job except that the 944 engine doesn't have the one short stud on each side. (And you need two sets.) As the short stud is a supply challenge, I busted one of those taking it apart.

Something that experienced 928 engine builders say, and I've experienced as well, is that the replacement studs from Porsche are not as stiff as the original studs. They're also not as stiff as the ARP studs. Mixing them together makes it hard to get an even clamping force on the head and that leads to gasket failure. What I've seen/felt is that when tightening the new Porsche studs the wrench just keeps on turning to get to the right torque. I've been worried that the stud was actually pulling out of the block. No, it's the stretchy replacement stud.

So... I've got the 18 long studs. In the first pic there's one original stud lined up to show the lengths and thread lengths. The ARP are a bit longer, overall, with more threads on the top (nut) end. I'll have to see what I want to do about the short stud. Either use the new stud and one old stud or salvage a stud off a spare, older block.

ARP does make a near-correct short (142mm) stud that's actually 150mm but will work. They sell it in a special set for putting a 16V head onto a 3.0l block. Someone could (and someone does, apparently) get them and then resell a 20-stud kits for the 928. It was just a lot cheaper to get two kits and figure out the short studs.

The third picture is of a new Porsche short stud along with the original short stud and a long stud. Note the wear marks on one end of the original studs from the force needed to get them out of the block. If the new studs were compatible with the original studs I'd have picked out good-looking studs and just bought a handful to go in with the ones that look too beat up to re-use.
Attached Images
File Type: jpg ArpStuds.jpg (154.2 KB, 0 views)
File Type: jpg ArpStudBoxes.jpg (195.9 KB, 0 views)
File Type: jpg ShortStud.jpg (171.1 KB, 0 views)
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1980 928S Euro x2
1987 944 N/A
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