RJUSMC

'87 951, Raceware head studs.
Currently into my first 944 engine rebuild. I had an emotional time getting the stock head studs out, noting that they were pretty scratched up so I think that they might have been out before. (I don't have the complete car history)

I'm trying to get the new head studs in. Book says "hand tighten" I can get about 5 of them to the 72-73mm deck hight, 2 more pretty close and the last three I can't even start. I chased the threads with a cheap Stanley M12 x 1.5 tap on those 7 without issue.

The problem is with the last three. I can't get the tap to even bite and I can barely get the new studs to bite. I am concerned about driving that tap down with a bunch of torque and possibly ending up with a heli-coil operation in my future. Should I get a $100 bottoming thread tap and drive it like a man or is there a better option?
MSC "Thread Forming Taps"

Thanks

wildcat077

I welded a 12 x1.5 tap onto a long t-handle and i clean out the threads until they’re all even depth wise.I use ARP heads studs
and screw them in hand tight.They should all protrude evenly within a few thousands of an inch if they’re installed correctly.
Yes , it seems some of the holes have some sort of residue in them , just run the tap, blow the hole out with air , and run the tap again
until all the holes are clean.
The fact that you were able to get all the original ones out is a good sign as some are pretty stubborn to say the least.

Cheers
Phil

RJUSMC

Thanks, Phil. I'll give it a shot.

V2Rocket

I may be imagining this but I believe at some point they switched the block threads to M12x1.75.

michaelmount123

A few comments on head studs that may be helpful:

The factory uses a strong thread locking compound when installing the studs, making them very difficult to remove. I use a Snap-On stud remover (M12x1.5) and a powerful impact wrench which is the best tool for the job. Occasionally heat is required on the block at the base of the stud area for those studs being difficult. I'll note here that LocTite should NOT be used to re-install the new studs. Consulting the LocTite instructions will tell you why. I install studs with Extreme Pressure Lube #3. It's thick, holds the studs from turning, and makes it easy to remove next time around. Amazon has it.

As Spencer posted, occasionally Porsche used M12x1.75 threads in the block. I don't think this was a change, but probably something done when normal stud supplies were low. I always compare the block side threads on the old stud with the threads on the new stud to make sure I've got the same threads. This only applies to the block side threads.

Chasing the block threads is necessary, but a tap is the wrong tool. Taps will remove additional metal and weaken the threaded joint. I use an old head stud with 3 axial grooves cut into the block side threads with a cut-off wheel. A nut welded on the opposite end mades it easy to run in and out of each hole and clean the threads without removing additional metal. Blowing out with compressed air completes the process and the new stud will go in easily.

MM

blade7

I removed all but one head stud from a 2.7 block quite easily by double nutting them. The last one was a real PITA, I had to use heat at it's base and around an hour of 1/4 turns backwards and forwards with the double nuts and grips. I want to know how shops get the dowel pin out when they deck the block though.

michaelmount123

There are specific tools for dowel pin removal (see Mr. Google), but those in the 944 deck are often too short to grip with the tool. Alternative is to drill the center of the dowel, tap to 8-32, and use a slide hammer with 8-32 bolt mounted. Not particularly difficult, but your machine shop can do it for you since most will lack the tools. The service is usually included in surfacing the block.

blade7

Thanks .

Mike Goebel

I was going to advise to use a thread chaser. I came across this video.

DYI Thread Chaser

Mike G.

BLUE952

The correct size tap used correctly will not remove extra material when chasing threads

wildcat077

I use this ... 12x1.50 ,never had issues with any engine and my race engines use ARP head studs which
are torqued down to 100 ft/lbs as per ARP

Cheers
Phil

huskeric

Just so I am correctly understanding... use the Extreme Pressure Lube on the studs into the block to 72mm - got it.
Do you also use any oil/lube on the top of the stud when installing the nuts/torquing?

michaelmount123

Yes! Aftermarket studs (ARP/Raceware) specify the lube for their top side threads, nuts and washers. RTFM. Porsche (again RTFM) says use engine oil on threads, nuts and top of washers.

huskeric

Thanks for the info. I did research the ARP website, but could only locate the section where it noted to use lube on the stud threads going into the block; hence, the question. As for the Porsche manual, as I am not using OEM studs, didn't find that helpful - also their torque specs are different.