: HG's vs Pulled Threads



PaleAle
04-27-14, 12:54 AM
A block test is the definitive test for HG failure. If it fails the block test, the problem isn't the HGs, it's pulled head bolt hole threads in the block. The only repair is to remove the drivetrain (through the bottom of the car), drilling all 20 bolt holes, and tapping them to accept either inserts or studs, then replacing the head gaskets, and putting it all back together.

Hey MC, not sure why you'd say that. A failed gasket makes the block test fail whether the bolts are pulled or not, sometimes the gaskets just fail. How do I know? My friend is still driving a 2001 SLS that failed the test. We put it back together with new gaskets and reused the bolts in the same threads and torqued them to 100 ft/lbs, that was over two years ago. He still drives it without any issues and no hydrocarbons in the coolant. I don't recommend that approach but it proves that it isn't always pulled threads. Also pulling it out the bottom isn't the "only" way. I've done them out the bottom, out the top and in the car, without inserts, with and without studs and with bolts. There are several ways to do it. Each has their advantages and disadvantages. There really isn't an always or never that applies.

MoistCabbage
04-27-14, 01:54 AM
Thats one car. Rarely are the gaskets the sole purpose. And reusing the head bolts without thread repair is a very, very, VERY bad idea. Your friend is lucky.

PaleAle
04-27-14, 03:10 AM
Agreed. As I mentioned, I don't recommend doing it. However, my point was that the fluid test is for a breach, whether it's a cracked block or blown head gaskets, pulled bolts or not. It's not the only car I've seen that had gasket failure but not thread failure. I agree, most do and it seems most prevalent around cylinder 1, but not all. I also wanted to point out that out the bottom isn't the only way, nor are inserts or studs the only way. Your post seemed to imply both unless I misunderstood you.

MoistCabbage
04-27-14, 03:44 AM
Inserts or studs are the only correct way.

Through the button is the recomended (by GM)/usual way.

G_Ride
04-27-14, 05:53 AM
All that work just to reuse the bolts? :ill::ill:

PaleAle
04-27-14, 10:19 AM
Inserts or studs are the only correct way. Through the button is the recomended (by GM)/usual way. You seem to want to hang your hat on GMs recommendation here but if you recall, they used bolts when they assembled these. Was that incorrect on their part? There really isn't any difference between a bolt and a stud once it's assembled, unless you plan on pulling it back apart. Neither is permanent or immune from the metallurgic reaction between the dissimilar metals. Inserts, in my opinion, just give you twice as many threaded holes to worry about. As far as out the bottom, I think I've read on here that Northstar Performance pulls them out the top. It's whatever your preference is. It doesn't really matter how you get it out. ----------
All that work just to reuse the bolts? :ill::ill: Re using the bolts themselves isn't really an issue. If they were going to fail, it would have been during torquing. I know GM doesn't recommend it but many manufacturers do. Google it. I think the bigger concern is the threads are still fine compared to the improved design in 2004.

Submariner409
04-27-14, 12:05 PM
Ummm........... GM specifically says the head bolts are "torque to yield" units. Once used they may NOT be used again. Very specific procedures on this. The GM/Helm service manual says to replace all 20 bolts.

Studs are more expensive and labor-intensive than head bolts. Therefore, on a production line ...............

......... for starters: Overhaul procedures - "Remove and discard the 10 M11 internal drive cylinder head bolts ........"

Then we get into the service manual chapter on cylinder head bolt hole damaged thread repair options ....................

PaleAle
04-27-14, 12:53 PM
I'm not advocating reusing them. My intent was to use the example to prove that a bad gasket would make it fail the block test whether the bolts were pulled or not.
As MC said, He got lucky.

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Sub, for the sake of discussion.

......... for starters: Overhaul procedures - "Remove and discard the 10 M11 internal drive cylinder head bolts ........"

I believe their reasoning is that the torque to yield bolts have stretched and no longer have the same stretching capabilities. However the wildly popular studs don't either so from the torque to yield standpoint, a used head bolt is equal to a new stud. It's the larger diameter and the coarser threads that make the studs better.

Then we get into the service manual chapter on cylinder head bolt hole damaged thread repair options ....................

Which doesn't mention studs, does it?

Submariner409
04-27-14, 05:47 PM
A torque to yield head bolt stretches to a predetermined clamping pressure based on bolt shank diameter and degrees of turn after an initial preload. It will not recover its original length and strength and cannot be used again - GM does not supply total head bolt torque values - only successive degrees of twist.

Head studs do stretch to achieve clamping pressure - but they are (to a small degree) "elastic" - the total torque does not render them unusable after one use. Replacement studs normally use a coarse, meaty thread into the block and a fine thread for the nut/hardened washer. That fine top thread allows precise, repeatable torque values - that value determined by a number of factors including stud size, metallurgy and gasket compression (to a specific thickness)..... one reason that fiber/fabric head gaskets require different torque values than a MLS type.

Of course the service manuals do not discuss stud use: They were printed during each model year and are never updated. Dedicated studs - for repair of failed Northstar cylinder block threads - didn't appear on the scene until well after ? 2005 ?. Prior to that some mechanics used TimeSerts (the GM service manual repair option), later BigSerts and Norm's NS300L inserts, with either GM head bolts or ARP studs. (A particular VW stud, I believe.) Quite a few GM/Cadillac dealerships are now using studs rather than inserts for their in-house Northstar head bolt hole repair.

The GM service manual for my 2002 Seville even discusses the use of HeliCoils for some thread repair applications. The latest edition date for that set is 02/2002 (to cover the change to F55).

PaleAle
04-27-14, 08:18 PM
I agree with everything you just said. I also think MC is a very important contributor to this forum. However, my whole point was that I disagree with this quote.

QUOTE="MoistCabbage"]A block test is the definitive test for HG failure. If it fails the block test, the problem isn't the HGs, it's pulled head bolt hole threads in the block. The only repair is to remove the drivetrain (through the bottom of the car), drilling all 20 bolt holes, and tapping them to accept either inserts or studs, then replacing the head gaskets, and putting it all back together.[/QUOTE]

If it fails the block test, the problem IS the gaskets or a cracked block, pulled bolts or not.
And
The word ONLY regarding to the repair is just not true.

When you use the word only, much like always and never, you're often wrong.

Often is a word I seldom use,....John Prine
Sorry, it seemed like a good ending

Sorry to the OP for taking your thread so far off track.

PaleAle
04-28-14, 01:28 AM
"only" was in reference to inserts/studs being necessary, not to the engine being removed m through the bottom.

But you forgot bolts, like GM did it, which are every bit as good as studs and they're a lot cheaper. Inserts or studs aren't the only way. I've done many with neither inserts or studs so the word only is incorrect. Anyway, let's let it go. I really do enjoy reading your posts and I appreciate your input. I'll shut up now.

MoistCabbage
04-28-14, 02:03 AM
Yes, I agree, bolts are fine. But the shorter/fine thread bolts that were used before '04/'05 were less than ideal. Once the threads fail, you can't reuse the factory bolts. You also can't drill and tap for larger bolts, since larger bolts won't fit through the holes in the heads (hence the reason for dual diameter studs). The only way to use bolts on a block with failed head bolt hole threads, is to drill and tap it for inserts that will accept a stock size bolt.

PaleAle
04-28-14, 10:11 AM
Yes, I agree, bolts are fine. But the shorter/fine thread bolts that were used before '04/'05 were less than ideal. Once the threads fail, you can't reuse the factory bolts. You also can't drill and tap for larger bolts, since larger bolts won't fit through the holes in the heads (hence the reason for dual diameter studs). The only way to use bolts on a block with failed head bolt hole threads, is to drill and tap it for inserts that will accept a stock size bolt.

Back to only on the last sentence? Sorry, but It's not the only way. I had a few sets of my own studs made once, I really didn't see enough advantage for the bother. I'm back to my old way. I drill and tap for larger bolts. I simply bore the heads slightly on the drill press to accommodate the larger bolts. There's plenty of material in the heads. The bolts I use are bigger, longer and coarser than the 04/05 bolts.
As a guide to make sure I'm straight when I'm tapping, I stripped an extra pair of heads of their cams, valves, etc, bored the head bolt holes to the diameter of the shank of my tap and had the local machine shop mill off all the top material down to the top of the head bolt holes. They make a perfect jig for all 20 holes. It works, I've done several.
I did the last one, a 2000 Eldorado, in the car without pulling the engine. There are alternative methods. Studs or inserts aren't the only way.

MoistCabbage
04-28-14, 02:47 PM
And with that larger fastener, how do you determine the correct torque value or degree tightening sequence?

PaleAle
04-28-14, 03:20 PM
Snug, 60, 80, 100 ft/lbs has worked fine so far. How did Jake and Tim decide theirs I wonder?

Caddy-EaRL
04-28-14, 03:20 PM
Sorry but that's just plain silly to suggest that someone go to a machine shop and make them a guide plate out of an old head, and then grind out the holes in their heads to accept bigger bolts, then go on a hunt for a tap and bigger longer bolts. When the proper way of repairing gets you everything you need in one kit whether it be studs or inserts. People like the OP come here for help and advise on the best and easiest way for them to do their own repairs. Just sayin...

PaleAle
04-28-14, 03:46 PM
I don't care if you think I'm silly. I did the heads as a guide plate just to be more accurate when I tap. They work really well. I used to do it free style, this way is more accurate.

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I never suggested that the OP do what I do.. Apparently you only read part of the thread.

Caddy-EaRL
04-28-14, 03:57 PM
I never said you were silly. I read the whole thread. If your comments aren't meant as an alternative to the OP then you shouldn't be making them.

MoistCabbage
04-28-14, 04:01 PM
I really don't see a point in doing so much more work as an alternative to two well proven methods.

PaleAle
04-28-14, 04:19 PM
The original point was that you were incorrect on the block test statement and that there were only 2 ways to do the repair. We've gotten way off track and into this discussion.
The point of doing it my way, for me, is that it isn't really much more work. My drill press is 10 steps from my lift. Bolts are way cheaper than studs, they are readily available and I don't have to wait for them to do the repair.
I don't think it's a better way than studs. If I could buy studs and they were readily available for the same price as bolts, I probably would. Price and convenience are the deciding factors. Convenience is the biggest one but price is too. Have you looked up a base Deville or an SLS on KBB.com lately? Keeping the price of the repair in check makes sense to me.

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I never said you were silly. I read the whole thread. If your comments aren't meant as an alternative to the OP then you shouldn't be making them.

Umm, you started your reply with "Sorry but that's just plain silly"
Is there a problem with the OP knowing there is a different way?

MoistCabbage
04-28-14, 04:26 PM
Yes, a failed block test could mean either bolts or HG failure. Technically, on a pre '00, it could also mean a failed crossover gasket, since one deals off the EGR passage.

Instead of going into detail on the small chance that it may be just the gasket, but bolt repair would still be necessary (or at very least VERY highly recommended), or that some people take the engine out through the top, but sine who have done it that way wouldn't do it again, I simplified my answer.

Bottom line in N* HG repair - If you remove the heads, it is stupid not to perform some type of thread repair, and proven methods would be the safer choice.

Caddy-EaRL
04-28-14, 04:51 PM
Sorry but that's just plain silly to suggest that someone go to a machine shop and make them a guide plate out of an old head, and then grind out the holes in their heads to accept bigger bolts, then go on a hunt for a tap and bigger longer bolts. When the proper way of repairing gets you everything you need in one kit whether it be studs or inserts

Where in that exact quote did I say you were silly? But now you are

PaleAle
04-28-14, 05:03 PM
Bottom line in N* HG repair - If you remove the heads, it is stupid not to perform some type of thread repair, and proven methods would be the safer choice.

I agree. Its questionable to even install a used engine without doing it.

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Sorry but that's just plain silly to suggest that someone go to a machine shop and make them a guide plate out of an old head, and then grind out the holes in their heads to accept bigger bolts, then go on a hunt for a tap and bigger longer bolts. When the proper way of repairing gets you everything you need in one kit whether it be studs or inserts

Where in that exact quote did I say you were silly? But now you are

Really Earl? I thought the first six or seven words said it all. But maybe I misread it or don't understand english. So now I am Silly? What a silly response.

04GrandAmGT
04-29-14, 12:23 PM
Snug, 60, 80, 100 ft/lbs has worked fine so far. How did Jake and Tim decide theirs I wonder?

100 Ft/Lbs, that seems excessive, almost sounds like you made this thread to give MC a hard time, it doesnt matter weather your block is cracked, HG failure of any sort, Pulling headbolts, you will see it in a block test. VERY VERY rarely do they push Coolant into the crankcase, 99.99 % of the time they push the exhaust through the cooling system.

PaleAle
04-29-14, 01:25 PM
"100 Ft/Lbs, that seems excessive, "

I think you may be right. The guy who taught me did it this way. Any feedback on a lessor torque and why would be welcome.

"almost sounds like you made this thread to give MC a hard time, "

That's absurd. I have no issues with MC and wouldn't do that if I did. I simply challenged a statement he made that wasn't correct in my opinion.

"it doesnt matter weather your block is cracked, HG failure of any sort, Pulling headbolts, you will see it in a block test. "

Umm, that was part of the statement we're talking about.

"VERY VERY rarely do they push Coolant into the crankcase, 99.99 % of the time they push the exhaust through the cooling system."

I agree with the rarely. I've seen 3 in the few I've done. Not sure on the 99.9%, I think you may have made that up but I don't think it's quite that rare.

04GrandAmGT
04-29-14, 02:49 PM
in the year and a half ive worked for jake, ALOT of northstars have past my eyes, and ive only seen one, and that one was because car was sitting for a long time and coolant in the cyl ran past the rings. as for torque we torque our studs down to 75 ft/lbs for bolts i honestly would have no idea, personally if you are going to use bolts again, buy new ones and use the factory torque specs. about the block test, i didnt see there was a second page when i posted that haha.

galen717
04-29-14, 03:33 PM
I did my friend's mom's 2000 deville when it was at about 180k. She is still driving it going on five years later...just thought I would throw that in there ;-) this has been an interesting thread to read. I was relieved to hear someone has done it that way as well. I was almost intimidated to even admit that I did it after the way some people talk on these forums. I also agree that we shouldn't take all of our instruction from GM, after all it was their product that failed.....obviously they are still learning.

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Oh I forgot to mention what I meant was I did it with the original bolts and no thread repair. Just torqued to specs