What year manual states to replace them?
Every year I just looked up states to reuse them.
#04-06-01-032: Information on Northstar Engine Mechanical Repairs - (Oct 27, 2004)
It might be instructional to spend some time doing Google searches of the world's engines - powering every type of conveyance imaginable - that use studs for iron, iron-aluminum and all aluminum engines - for cylinder heads, cylinder jugs and block assembly.
Properly designed and machined, it makes not one whit whether the fastener is a bolt or stud - they are both dynamically elastic over a specific range of tension and stretch. Both Jake and Tim have done their metallurgical homework ..................By all that's holy, a stud is nothing more than a bolt without a permanent head. The ONLY reason to use a stud in a Northstar block repair is to eliminate another set of threads in an insert.
I'm not knocking studs (or bolts) or their proper application - Just how long do you figure the cylinder studs are on this 18-cylinder 2800 hp air cooled aircraft engine (Super Constellation) considering that the engine is almost 6 feet in diameter ? (or the incredible range of temperatures over which it operates ???)
just another anecdotal reference point
we've been using time fastener bigserts and stock head bolts ever since these repairs began
we've probably done over 1000 of these jobs ... from what i understand the only ones that have come back were some of the very first ones before the bigsert were used and regular timeserts were used
(that was before the thread pitch was found to be the main source of the failure ... and the bigserts fixed that)
I'm sure OP point was that the studs and headbolts are not spec'd the same. I don't agree, proper studs and installation using either is critical. Incorrect torquing of studs can cause issues for sure and in my opinion require more attention to installation, but so can bolts. If studs are a problem and will cause me issues 75k miles down the road big whoop. car's going to be junk by then anyways.
To reinforce Sub's aircraft engine point and to question the validity of AJ's "racecar" engine point. Here's what I say, look at every Piston driven internal combustion engine designed to travel over a million miles or log thousands of hours at max torque. Tractor, Semi, train, ships, submarines, construction equipment, industrial engines, ad-nausia. What do they use? They use studs. The type of metal is accouted for in design specs but otherwise irrelevant to choice of head fastener.
Bolts for heads are for costs or ease of service in applications where a fastener caused failure doesn't cost lives or significant relavent currency. The car is warrantied for 100K or less after that if your car breaks down, fix it or buy another one, otherwise nobody cares. So they get head bolts. I have to fork out bucks and spend a ton of time fixing this Caddillac if the head seal fails again. So it got studs.
That being said I don't think a Norm's or Big-Serted block with new bolts is a problem. Those solutions should work great.
I figured the second edition had the lastest information.......
Great chart for reference.... Possible sticky?
This is strange
OK This is an update
The Lower Crankcase Installation document that you posted Id #169055.
That one especially I was concerned with because if you reseal the bottom of the motor, the main bearing bolts are broken loose. At that point bearings were to be replaced along with the bolts. I'll have to find the page in my manual.
Yet, if there are revisions and certain procedures aren't deemed necessary anymore I guess that's a good thing.
It's a good motor with some unfortunate issues......
Thanks again AJ for the detailed information.....
Just for future reference, when I went through my Northstar I had issues with the main bolts. While loosening them by hand, with some quick tugs, I broke three of them. One was snapped in two with the lower half stuck in the block to the point I had to take the short block to a welder for extraction. After the first one broke I proceeded with extreme caution on the others and found two that had cracked to the point they were visibly twisting apart. Keep in mind this is not my first engine overhaul, I didn't go ape on it. These bolts are very hard, think brittle, and very thin, like a pencil. Because of my experience I will always replace them once removed. I believe it's not worth the risk trying to determine if the popping I hear coming out was threads or bolt shanks. I think I spent under $70 wholesale for all new main bolts. In any case never use power tools to remove or install them.
The distinct snapping noise of those bolts breaking loose is bone chilling.....
I said to myself....DAMN what in the world did they use to install these bolts?
I like Vernon, decided after that adventure not to reuse the old main bolts.
Again, no power tools for insertion or extraction.......
This is Tim, interesting conversation, hats off to AJ for his theories.
However, as good as he sounds, he is incorrect in theory. Having a few years as a Cadillac mechanic does not one make an automatic engineer.
Whether you ask me or Alan Johnson with CHRFab, you will find we have done our homework, we are engineers it is what we do.
GM's reason for torque to yield bbolts was for the weight and nothing more, they use minimum weighted material in a lot of different areas of the car, likewise this was the purpose of the aluminum engine.
One more thing, it is true that studs should never be at the deck surface, this is common knowledge
AJ is correct on this issue. Our studs have been engineered to go to the correct depth and we provide replacement dowels
for this purpose. Alignment studs are above the surface and will in facr distort the deck and should not be used.
Using correctly engineered studs will far out perform torque to yield bolts, hands down.
We have zero failures, but we have had to repair many after Cadillac dealers service departments sert jobs have failed.
The big Serts I just read about is also a set up for failure, and once they fail? The block can never be repaired again.
Big Serts should never be an option.