: hg repairs

10-03-11, 03:51 AM
Hello, my question is: sure grip studs vs. inserts, what are main advantages of studs? Local mechanic is a huge fan of inserts and I had an argument with him about this. I understand that studs are better option for perfomance engines, but don't quite understand the details of it. Why "sure grip" studs? Those look pretty usual to me... And the nuts are like half an inch high, is it enough? I told the man that studs go deeper into the block... but he installs the inserts two inches deep also... What's the trick?

10-03-11, 09:29 AM
This is the opinion of an engine builder, not a machinist...........so, my $.02

The original head bolts for your engine use a relatively coarse cylinder block hole thread. All well and good. BUT, if the threads fail, then the hole must be machined to accept some sort of repair............

Studs are usually made with larger coarse threads on the block end: this supplies more holding "meat" because the stud lower end does not have to pass through the cylinder head bolt holes. Studs also use fine threads at the top - nut - end, so torque control is more precise and the nut/washer can be removed and used over and over. Studs are generally accepted as the stronger, more precise method of clamping cylinder heads and main bearing caps to cylinder blocks.

Cylinder head bolts must, of necessity, have thread diameters less than the bolt hole size in the cylinder head, and with an aluminum block bolts may strip or pull the block threads as they are removed. The thread pitch is a compromise because fine threads do not work well in aluminum, while extremely coarse threads are also a problem for both holding and torque control.

I would be completely comfortable with either Jake's studs or Norm Huhn's inserts.

Study the pictures and diagrams in both www.northstarperformance.com (http://www.northstarperformance.com) and in www.huhnsolutions.com (http://www.huhnsolutions.com) . You'll see the differences in the block and bolt/nut threads used on the studs/inserts.

For that matter, you could insert the block and use ARP Volkswagen studs - exactly the same end result with one more set of threads.

10-03-11, 11:24 AM

10-03-11, 11:34 AM
Thanks for your replies. I know about this site. It's just not very detailed. I've just found here one of Jakes monologues:

My .02 probably doesn't belong here.

I have installed studs in about 15 cars that have had timeserts in them before. I sold an engine to a guy in Michigan because he installed _orms in it. And it failed within two hours of driving. I have his block with those inserts in the back corner of my shop.

Factory head bolts. Designed to act like a spring. Long springy bolts. Good idea?! NO. Can you accurately torque a long springy bolt? Studs of any kind be it ARP, or mine, will not twist while you're torquing. You are at that point pulling straight up on the stud itself, stretching just enough vertically to provide an accurate clamp load.

As for two thread interfaces within roughly a 1/2" to 5/8" diameter. It works. yes. Big serts have been known to crack blocks. Why? the overall outside diameter is slightly less than that of _orms inserts. A sleeve of steel machined both internally and externally. Threads are slightly angled (60 degrees?) so what happens when you apply a high amount of torque inside a thin sleeve, when all threads are angled by nature? The insert expands. When an insert expands inside a precision machined hole, in an aluminum casting, what's going to happen? C - R - A -C - K.

A solid machined bolt or stud cannot expand in diameter under torque.

M11 is rougly the size of a 7/16" bolt. Imagine drilling and tapping a hole that's about .433" inside a 5/8" bolt. The solid part of a 5/8" bolt is about .5315 (17/32" because a 5/8" bolt is only 5/8 if you include the threads)

So you have an insert with a .433 inside diamter and an external wall (not including threads) of .5315. How thick is the wall? .0493". Not even a sixteenth of an inch. Go look at a tape measure and check out how thick one sixteenth of an inch is. Now imagine 21% less thickness. There's the thickness of the best insert on the market, that is supposed to hold the heads down on your high compression Northstar. I didn't even know about _orms inserts when I designed the studs. All that I knew was available was time serts. I didn't like that idea. I wouldn't be comfortable with an insert with a wall thickness of .0493 and any thinner than that is to laugh at.

To anyone who has inserts in their engine and it's holding up, I seriously hope and wish that you have continued success with them. I just don't want anyone going through this work, trouble, and expense more than once. Too many people bash Northstars already- they're well designed, awesome engines and don't deserve the bad rep they've been getting from some.

That was very useful. Much more detailed description.

10-03-11, 03:24 PM
I thought the link I gave you answered the questions you asked.

10-06-11, 09:59 PM
Blauweiss, joe Blau here and we have inserted 101 northstars and studded 5 or 6 with absolutely no failures due to thread issues. I hg failure on a car with customer supplied gaskets from rock auto. Wth my customers it comes down to money when they decide on which to use. The repair is expensive so every bit helps in this economy. If the studs cost what the inserts cost then it wouldent matter. I have redone several cars that were timeserted and failed. ..So in my opinion stud it or insert it but stay away from the timeserts just my 2 certs , i mean cents