Chris White

Just use a 5lb sledgehammer and bend 'em over like nails.....

15mm is 'just' over 1/2", it will work with the possible exception of the head stud under the water coolant outlet.

But in reality it would be better to get the right ones!

Will Feather

Bumping this thread as I have this same question. 3.0 Block and a 2.7 head I ordered ARP 204-4301 studs which are listed for the 3.0 motor. Are these the correct studs?

Chris White

No.
The only studs that are the right length are the stock 2.7 studs.....and they will work just fine in holding the head down.

Will Feather

Bummer, thats what I thought. will have to see if ARP offers 2.7 studs.

Chris White

Any reason that you don't like the stock studs?

Tom M'Guinn

You need studs that are 150mm long, which isn't the same as a 2.5 or 3.0 stud. Raceware DOES make them in this length, though I had to call them to get them.

JacRyann

Here's something to consider. Has anyone broken/snapped the factory head-stud in use?

That's where yield & ultimate strength comes into play. And contrary to popular misinformation (like tuners claiming the 951 has a 0-1v TPS), these are not torque-to-yield studs. Although the nuts do strip with too many re-installs.

Now, the problems some people have is head-lifting due to combustion pressure. That's the realm of Young's modulus which is very similar between all steel alloys. Getting a stud that's twice as strong as the stock one won't make it stiffer. It will still stretch the exact same amount as the stock one at the same load. Just that it will stretch twice as far before breaking. The difference between 1mm or 2mm stretch before breaking is irrelevant in this case since you've already breeched the headgasket well before that.

What you really want is a stiffer stud. Stiffness goes up by the 4th power of diameter. Get some 9/16" grade-8 studs for $10/apiece and you'll be way ahead of any factory-sized stud, regardless of type of steel alloy or strength.

dizzyj

why not raceware? they make the right studs. can get at paragon.

Chris White

Some nice theoretical thinking....right up to the part about block thread failure. According to engineering 101 the stock threads in the block will fail at about 110 ft lbs. Go with a larger diameter stud and you can increase that a bit....but with only 4 studs per cylinder (and those are shared studs!) You will end up distorting the head or failing the block threads long before you see an increase in clamping with big studs.
so...back to the original question - what are you looking to gain with 'bigger' head studs?

JacRyann

I don't think I said anything about the block threads failing.

Just addressing people's impression that super-strong aftermarket studs are "better" than the stock ones. They won't prevent headgasket failures any better than the factory ones. And they won't prevent head-lifting any better either because any stud of the same diameter will have exactly the same flexibility and stretch. Stiffness/flexibility is not the same materials property as strength.

The issue isn't clamping pressure, it's how much the stud stretches for any given combustion pressure. A larger diameter stud with exactly the same clamping pressure will stretch and lift less with the same combustion pressure.

Will Feather

I guess that is my only option at this point. Unfortunately they are twice as much as rhe ARPs.

JacRyann

So what's wrong with the stock studs? What can the ARP or Raceware stud do that the stock ones can't?

michaelmount123

The 2.7 Porsche head stud is 944 101 197 01; they're stupid cheap and very high quality. A set is around $50.

Thom

I only had issues with Raceware studs. Stock 2.7 studs on the opposite have held as well as one can hope for.

Will Feather

Stock studs are a good option, and what I will probably go with. I just like the track record people have had with ARP studs. I am shooting for a fair amount of horsepower with this engine so was looking for a nice aftermarket stud.

But the stock 2.7's look like a good way to go.