Lower head bolts, not studs

[Nditiz1]

Is this a poorly done rebuild or just a different method? I realize this is not ideal, but just wondering if any other builders have done this or seen this?

[safe]

Look like a stock barrel nut on a stud.

[Nditiz1]

Solid head, definitely do not look like the top ones. Stamped E K F

[Flat6pac]

The barrel nuts look small, what Allen size, doesn’t look like 12. Pull one and see…
Bruce

[917_Langheck]

Originally Posted by Nditiz1

Solid head, definitely do not look like the top ones. Stamped E K F

Did a little photo editing and I see a K in the upper middle of the "nut"/bolt

[mepstein]

Looks like a barrel nut to me. Stick an Allen wrench in it to confirm. Easy peasy.

[Dpmulvan]

Originally Posted by Nditiz1

Solid head, definitely do not look like the top ones. Stamped E K F

I think the rust is fooling you if I understand your question. I don’t see anything different than a barrel nut on a stud.

[Nditiz1]

Loosened it up. Allen bolt with at least 4 washers under. Not sure about this method....

[gled49]

Wow,I think you will be starting over. Never seen that. Does it look like the cylinder to head is sealing underneath.

[Dpmulvan]

I guess I was wrong, was hard to tell from pics. Never seen that before?? Wonder what thought process made someone do that?

[Nditiz1]

It does. The leak down numbers were pretty good on all except #1 and it was getting passed the rings. The builder used RTV though...smh

[boyt911sc]

Originally Posted by Dpmulvan

I guess I was wrong, was hard to tell from pics. Never seen that before?? Wonder what thought process made someone do that?

The the person who did the work was trying to save some money. Instead of using the OEM double threaded steel studs, the regular Allen bolts were used. The individual who did this job gets a high mark as a McGyver Mechanic but low marks as an experienced Porsche Technician. Replacement cylinder head studs are abundant and conveniently available.

Tony

[gled49]

What I wondered, is when you don’t have a good clamping pressure between the heads and cylinders, you get combustion and/or oil leaking at that sealing surface. Is it clean and dry or black and oily?

[Nditiz1]

Hard to say, I got this as a "was running" engine and it is dirty all over. I am weighing on doing a fix to correct this issue or throw it in the car as is. I don't see why the clamping pressure would not be as good if I am able to torque them or they are already torqued to 30 ft/lbs.

[JoeMag]

...not a pro builder, but I would not be a fan of the friction (steel against aluminum) on the case threads of torqueing those things into the case. Not sure what the threads look like, but those black oxide bolts rust when they get hot so might be like sandpaper on case threads screwing them in and out.

Does it look like the length of thread engagement is correct for what normal head stud is?

[safe]

Wow... I would strip down the entire engine to check what else is up...

[Henry Schmidt]

I've never seen this modification but necessity is the mother of Rube Goldberg or for you younger guys, MacGyver.
My questions would hover around bolt expansion rate, thread pitch and Case Savers.
Is it possible that the case was tapped to fit a core thread American bolt? yikes!

There should never be two different expansion rates between upper and lower studs.
"But the factory did it" ...sure, and that was just one of their many mistakes surrounding the 911 head stud issue.

[stownsen914]

Well, enterprising for sure. The bolt method will result in uneven clamping force, for starters. Think of how hard it is to remove factory studs - that’s how much force you have to overcome in tightening a bolt before any of the torque is applied to actual clamping force. Good luck figuring out what torque value is correct.

I guess the stacked washers were a convenience to avoid shortening the bolts to an appropriate length. I wonder if those washers are hardened. Regular washers may tend to squish under heavier torquing and loads (causing loss of clamping load I.e. “loss of torque”).

[Nditiz1]

I'm going to see if I can start the engine on the stand and then break it down replacing the bolts with factory steel studs.

[Prsh356]

Mickey Mouse award !