New OEM steel studs loose?
 

I had some free time tonight after work and decided to install my new steel head studs. I had prepped the case stud bosses using an ARP "Clean Out" thread chaser and cleaning with Brake Kleen and cotton swabs. I applied thin thread of Loctite 271 to threads after cleaning the studs. They went in easy just using fingers. That made me concerned. I bottomed each one, then backed it out and measured from cylinder spigot/piston seal flange to top of stud at 135mm. The problem is, I pushed up and down on the stud and it gives slightly. I installed one of my old studs to see if it was the same, and it fit snug. Checked part # on bag. Correct part #. I have them all installed. I thought I'd wait till tomorrow after Loctie set-up to see how they feel. When the studs were bottomed out I couldn't move them as much. Have I done something wrong? Having the slight play on something so crytical is not inspiring confidence.

How much metal did the thread chaser remove, if any?

All threads have a tolerance to be able to fit. 1 is real loose and 3 is quite tight. 2 is where most fasteners are made and this allows easy assembly with good strength. What does happen is that the hole can be threaded and end up at the big side of the tolerance and your studs could be at the small side of the tolerance, giving you the loosest fit possible and still be withing the spec. Your probably fine unless you chaser removed material. Then your threaded hole could be out of tolerance. Some of the better engine minds will have to advise you on how loose it too loose.

Hardly any metal to none. Did it by hand with the ARP clean - out thread chaser. I wouldn't use this again. This morning after the loctite has cured, they're all tight. Feeling a little sick about this. Can't believe I thought I was using the right tool only to screw it up.

http://i197.photobucket.com/albums/a...ps08bdfea7.jpg

http://i197.photobucket.com/albums/a...ps4512691e.jpg

If you are worried you may need to check both the stud and the case and the above gauges would be useful as they are go/no-go type.

IMHO typical fit for a stud of this type would be 6g/6H and this would be OK for use with a thread locker.

This means an external thread with a tolerance of Class 6 and position 'g' with an internal thread with a tolerance of Class 6 and a position of H.

This is an ISO designation but is roughly equivalent to 2A/2B and is a reasonable average fit.

I would say that a good thread chaser shouldn't cause any real issues and we have used chasers for some time.

We do have a thread plug gauge and always check cases just for peace of mind and they are normally OK after this type of treatment.

I am not sure I would like to see the fit much worse than this although there is a small amount of leeway It all depends on where the lack of precision occurs.

If the fit is poor and it is the studs then they can be replaced with a more accurate part.

If the thread chasing has caused a problem with the case threads then you could fit timeserts.

Seems to me that if your OEM steel studs fit snug, the problem is with the ARP studs not the case.

I agree with Tom, if the stock studs are OK, the problem seems to be the ARP studs. Now I can see one or two being off but not the whole lot. Perhaps give ARP a call and discuss it. I too would be somewhat concerned with the fit you described.

Thanks guys, but I have OEM steel studs. The thread chaser is an ARP "clean out" tap. Wasn't supposed to undercut the threads. Should've known better. I spoke with a local guy here who said this is not uncommon. He advised the threads in the aluminum case are a shade under 10mm. When you use a 10mm chaser or tap it opens the threads.
I did a test today and double nutted the studs one at a time and tried to remove them with just force. 7 came out. Then tried a couple with a mapp torch for a few minutes. Still didn't budge. I'd say those are probably ok. Just gotta figure out the 7 that came out. Maybe the loctite didn't get fully around the boss. Local guy said he's never seen steel studs in an aluminum case back out even if they were tapped.

I wouldn't sweat it. If you did it by hand with no tools to gain you additional leverage on the threads, you didn't destroy the thread fit.

As long as the studs don't back-out when you loosen the head nuts in the future, you're fine. The threadlocker ensures that. The head nuts impart the force on the studs to establish the clamping force. How they're installed in the case, so long as they're not bottomed, is really not an issue. Of course i'm not saying the studs could be super sloppy floppy in their holes and that wouldn't matter. Just saying the studs are still snug in the case and that indicates to me they're fine.

For future reference, we can make a case stud chaser by using an old stud with slots cut in the threads lengthwise. This homemade chaser acts in a similar fashion by letting the stud threads push out any crud into the slots you made, similar to how a tap cuts threads and deposits the chips into the flutes/slots of the tap.

Also keep in mind that those who use Supertec's studs have a recommendation in the instructions to use a thread forming tap to prepare the case stud threads. A tap such as that is actually deforming the metal to shape the threads. Its not actually cutting any material since it doesn't have any flutes.

This isn't the exact tap specified but it gives you an idea what i'm talking about

McMaster-Carr Metric Thread Forming Taps

Thanks Kevin,
I lost sleep over the weekend worrying about it and being mad at myself. I'm sure I was no fun to be around. Anyway, loaded up the short block in the Tundra and drove over to Mullenix Motor sports and asked Ed to take a look. He thought they were fine. Slight wobble at end. He said not uncommon for timeserts to have same fit.

The best repair for this issue might have been to install Supertec head stud after the loose condition was detected. Of course that does require an extra expense.
The Supertec head stud has a longer threaded section at the base ensuring that the stud engages all the threads possible.
The forming tap we recommend for Supertec head studs is a PD-6-6 N.

Thanks Henry,
I thought about it and started to remove the studs on Saturday and get the Supertec studs, but after realizing I was going to need to torch them out and that I'm already over budget I decided not to.

My post was really aimed at the next guy who finds himself in a similar situation.
Of course budget is always a concern for most of us.

Henry
Purchased your studs and have a similar problem
When i bottom outthe studs all is ok , when i follow your instructions and turn out a 1/4 turn,
There is a little side to side movement to the stud.once locktide cured it was ok.
Is this normal?
Thanks
Ps: car is a 89 911 turo

It all depends on how the threads were cleaned. If the stud is tight after the Loctite cures you should be fine. It is of course the responsibility of the assembler to determine what is "too" loose.

Good timing
 

I just had exactly the same issue with a twist.

I was told (by the owner at a reputable vendor) to install my head studs to 140 mm -0/+1. I now have Blue loctite-d studs with 2-3 threads showing and a couple of them wobbling....

After research it now seems I got bad advice and they dimension should be 133mm - 134mm. So one more check - the motor is a 79 3.0SC (6391494) is the 133-134 mm dimension the correct one?

If so I guess I will try and pull these studs, clean out the threads with a pick to avoid a second run with a thread cleaner and reinsert with Loctite red.

135mm +,- 0.5mm is the spec for original Porsche style head studs if I recall it correctly from memory. Note that this is for engines up to '89. The 3.6 964-based engine that came along next has a stud height of 130mm and they use a modern 12-pt head stud nut. Stud height becomes less critical when you use "normal" nuts instead of the old inhex style barrel nuts.

Thanks
 

Well *#@$#(#*^%@&@##!!!!!!!
I will consider my sources of guidance more carefully in future... (and probably my vendors..)
I assume this is measured from the machined pad arrowed?

http://forums.pelicanparts.com/uploa...1392922830.jpg

C- correcto. Measured from machined surface that the cyls sit on, to the tip of the stud

Ahem...
 

Sorry for being a little dim (May be root cause of issues).
when you say 'machined surface cylinder sits on do you mean 'A' as in the (slightly unclear) arrow above or 'B'.
Thanks
Sam

http://forums.pelicanparts.com/uploa...1392929288.jpg

Sorry for not being completely clear. Yep its A that you measure from. You're correct there's two machined surfaces on the case- where the studs come out (A) and the cylinder spigots (B)