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Cracked block. 4.9 Looking for reasons why. by Fieroseverywhere
Started on: 11-06-2014 10:45 PM
Replies: 32 (677 views)
Last post by: Fieroseverywhere on 11-13-2014 09:04 PM
Fieroseverywhere
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Report this Post11-06-2014 10:45 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
Any ideas?

Before.

Before (cropped)


After.


If you look close you will see 3 cracks. 2 go to the head bolt hole and 1 into the water jacket. The car had idled in the driveway for ~30 minutes but was shut down when it snapped. The head is straight and true, nothing wrong with the gasket or the dowel pin that I can see.

Try as I might I can't come up with a good reason why this would happen. Maybe someone else know something I don't.

[This message has been edited by Fieroseverywhere (edited 11-06-2014).]

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Report this Post11-06-2014 11:42 PM Click Here to See the Profile for imabaddudeSend a Private Message to imabaddudeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did you over tighten the bolt and torque them down in the right order? If that was over tight and then the block got warm and then started cooling, with the differences in metal and not being torqued properly, I think could cause something like that. Especially if over-torqued and torqued out of sequence.
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Report this Post11-06-2014 11:50 PM Click Here to See the Profile for hercimer01Send a Private Message to hercimer01Edit/Delete MessageReply w/QuoteDirect Link to This Post
I was gonna do that engine but after reading up on it stuff like that was not uncommon. The head bolts would usually strip out and need a helicoil. Overall I got the impression the block was just fussy if you tried to pull it apart. I had the donor car and everything but bailed out. Maybe you can have it welded?

Good luck.

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Report this Post11-06-2014 11:53 PM Click Here to See the Profile for hercimer01Send a Private Message to hercimer01Edit/Delete MessageReply w/QuoteDirect Link to This Post

hercimer01

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Has that been helicoiled there? Maybe weakend the block?
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Report this Post11-07-2014 09:04 AM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
Everything was torqued to spec in sequence. This was not the first time I've done a headgasket. I also did one when I rebuilt the engine.

This is also not a normal thing for a 4.9. Neither is head bolts stripping out of the block. I'm not going to say it doesn't happen but it is not a common problem. You can check around the cadillac forums if you don't believe me. And no. Nothing has ever been helicoiled. This crack is at the TOP of the block. Not the bottom where the threads are.

I will have my torque wrench calibrated and see if it was off. Thanks for the suggestion.
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Raydar
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Report this Post11-07-2014 06:27 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Not anything I've ever heard of with a 4.9. It might have been an uneven stress on the block, or it might just be a casting flaw that decided to make itself known.
Is it possible that the dowel was forced too far into the hole, and pushed against that ridge at the bottom of its hole? If the head gasket was thinner than the original, it's conceivable. When I looked at the pic again, it appears that part of that ridge is broken off. Look at 7 o'clock, and to the right of that. The ridge appears to be missing, unless it was just cast that way.
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Report this Post11-07-2014 07:30 PM Click Here to See the Profile for imabaddudeSend a Private Message to imabaddudeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Maybe it could have been a defect in the metal, like a contaminate getting in there during the casting, or just a bad mix. It could even be the head was slightly warped. I'm guessing heads were slightly warped and then from being torqued down the head being warped just caused the bolt to want to move, and from that force cracked the block. Honestly, that's weird, I've heard of similar stuff, but is definitely odd. Sucks that you put all that work into it just for that to happen. Anytime I tear apart an engine, I always get a valve job and have them check the heads for warping or cracks. Really, that's all I can think of it being.

edited because I started a sentence and didn't finish it, but still submitted anyways... Oooops.

[This message has been edited by imabaddude (edited 11-07-2014).]

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Report this Post11-07-2014 07:30 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:

Not anything I've ever heard of with a 4.9. It might have been an uneven stress on the block, or it might just be a casting flaw that decided to make itself known.
Is it possible that the dowel was forced too far into the hole, and pushed against that ridge at the bottom of its hole? If the head gasket was thinner than the original, it's conceivable. When I looked at the pic again, it appears that part of that ridge is broken off. Look at 7 o'clock, and to the right of that. The ridge appears to be missing, unless it was just cast that way.


Good eyes. However the ridge is not broken. The part that looks broken is part of the machining on the outside.

I took another look at the dowel pin though. It is slightly bent in the middle. Almost as if it was starting to shear in half. Its slight but its there. I suspect it was caused by the break. There is no reason for a dowel pin to shear off though. With 10 bolts holding on the head there is no way it could.

I believe the head gasket is slightly thicker then the original. I switched to Corteco White seal gaskets this time. They are a silicone covered gasket instead of graphite. Do you think they might have contributed?

Still can't narrow down the exact cause. Still going to run the TQ wrench in to be calibrated. Any other ideas?

[This message has been edited by Fieroseverywhere (edited 11-07-2014).]

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Report this Post11-07-2014 07:39 PM Click Here to See the Profile for imabaddudeSend a Private Message to imabaddudeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yeah, pics would be nice, of the dowel pin, bolt and of the head. if you have something straight to put next to the pin and bolt in the pic that would be a help.
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Fieroseverywhere
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Report this Post11-07-2014 07:42 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by imabaddude:

Maybe it could have been a defect in the metal, like a contaminate getting in there during the casting, or just a bad mix. It could even be the head was slightly warped. I'm guessing heads were slightly warped and then from being torqued down the head being warped just caused the bolt to want to move, and from that force cracked the block. Honestly, that's weird, I've heard of similar stuff, but is definitely odd. Sucks that you put all that work into it just for that to happen. Anytime I tear apart an engine, I always get a valve job and have them check the heads for warping or cracks. Really, that's all I can think of it being.

edited because I started a sentence and didn't finish it, but still submitted anyways... Oooops.



I was thinking of taking the heads in to get checked. My granite slab and feeler gauges say its flat but a second opinion would be a good thing I think.

We were typing at the same time.
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Report this Post11-07-2014 07:47 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fieroseverywhere:
...
I took another look at the dowel pin though. It is slightly bent in the middle. Almost as if it was starting to shear in half. Its slight but its there. I suspect it was caused by the break. There is no reason for a dowel pin to shear off though. With 10 bolts holding on the head there is no way it could.


I remember reading things regarding the different coefficient of expansion during the heating of dissimilar metals. Usually in terms of damaged gaskets on iron block / aluminum head engines. Or iron heads with aluminum intakes. This could be an extreme example of that.
Is it possible that it overheated? Or maybe there was an isolated hot spot, since it was sitting there idling for so long. Especially if the idle speed is stock. (Too slow, IMHO. Maybe not circulating as well as it needed.)
FWIW, the "hi temperature" dummy light sensor on the stock 4.9 is on that head, between the #6 and #8 exhaust port. Maybe GM knew about a potential "hot spot".
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Report this Post11-07-2014 07:52 PM Click Here to See the Profile for imabaddudeSend a Private Message to imabaddudeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yeah, with carpentry I like to take one measurement and do as many cuts as possible, but with cars, I measure and remeasure to an OCD level. Mainly because I hate breaking stuff, hate having to refix things, and hate spending more money than I already did. Sometimes though, fluky stuff happens. I'm pretty sure a lot of Fieros have this strange disease to where everytime you get everything working, some other part has to break right after.
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Report this Post11-07-2014 07:54 PM Click Here to See the Profile for imabaddudeSend a Private Message to imabaddudeEdit/Delete MessageReply w/QuoteDirect Link to This Post

imabaddude

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quote
Originally posted by Raydar:


I remember reading things regarding the different coefficient of expansion during the heating of dissimilar metals. Usually in terms of damaged gaskets on iron block / aluminum head engines. Or iron heads with aluminum intakes. This could be an extreme example of that.
Is it possible that it overheated? Or maybe there was an isolated hot spot, since it was sitting there idling for so long. Especially if the idle speed is stock. (Too slow, IMHO. Maybe not circulating as well as it needed.)
FWIW, the "hi temperature" dummy light sensor on the stock 4.9 is on that head, between the #6 and #8 exhaust port. Maybe GM knew about a potential "hot spot".


Very good point, that could be a potential culprit.
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Report this Post11-07-2014 08:08 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:


I remember reading things regarding the different coefficient of expansion during the heating of dissimilar metals. Usually in terms of damaged gaskets on iron block / aluminum head engines. Or iron heads with aluminum intakes. This could be an extreme example of that.
Is it possible that it overheated? Or maybe there was an isolated hot spot, since it was sitting there idling for so long. Especially if the idle speed is stock. (Too slow, IMHO. Maybe not circulating as well as it needed.)
FWIW, the "hi temperature" dummy light sensor on the stock 4.9 is on that head, between the #6 and #8 exhaust port. Maybe GM knew about a potential "hot spot".


Its a manual trans so idle speed is set ~800rpm. The thing that really gets me is that the engine was NOT running when the break happened. It had been shut off for about 10 minutes. There was no coolant circulating and the engine should have been cooling down at that point (past the point of heat soak). Probably right at the point of highest pressure in the cooling system. The ignition was still on but the temp light was not (bulb test pass also). Actually the coolant wasn't that hot. I got showered in it checking for where the sudden leak was coming from.

I tried to get a pic of the dowel pin but you just can't see the bend on camera.

Here is the head right where the crack formed...


And here is a pic with the dowel pin in...

The dowel pin is also out of round measuring .587"-577" OD head side and .584"-.577 OD block side ~.050" thick. The narrower part is directly inline with the bend. I'm still leaning towards this being a symptom of the break and not a cause. Just as a reference the head bolts measure .429" where it sits inside the dowel pin. So there is a bit of slop in there.

EDIT. And here is the headgasket where the crack was block side. You can see that the crack shows up.


And this is where the coolant was leaking out. Down the head bolt itself. The crack you see here is the one you barely see in the upper pics. That crack was not the leak. The leak comes from the one in the water jacket.

[This message has been edited by Fieroseverywhere (edited 11-07-2014).]

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Report this Post11-07-2014 08:34 PM Click Here to See the Profile for ericjon262Send a Private Message to ericjon262Edit/Delete MessageReply w/QuoteDirect Link to This Post
maybe moisture trapped in the bolt hole, freezes, cracks block.

Edit... I see why that is HIGHLY unlikely now....

[This message has been edited by ericjon262 (edited 11-07-2014).]

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Report this Post11-07-2014 08:41 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm thinking that this was a fluke. I'll bet it would never happen again.
Maybe due to a flaw in the block casting. The GM shop manual even mentions possible porosity in the block casting.

All speculation of course.
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Report this Post11-07-2014 08:46 PM Click Here to See the Profile for Neils88Click Here to Email Neils88Send a Private Message to Neils88Edit/Delete MessageReply w/QuoteDirect Link to This Post
Heat, force, vibration, material flaw....lots of things could cause this, but I think overheating is probably the most common cause (perhaps in conjunction with a material flaw). This isn't a common problem for a 4.9 block. Either way, I wouldn't waste your time getting this repaired. I think you are better off picking up a bare block and take the opportunity to do a proper rebuild (hone, new bearings, rings, etc, port the head while it's off etc.). The 4.9 is usually a really strong engine. You'll want to check that this wasn't caused by a cooling system issue...how old is your water pump? May want to change it now just in case.
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Report this Post11-07-2014 10:32 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
My guess is that a hot spot may have been created by an air pocket in the cooling system. I burp the systems that we work on thoroughly and always drill a 1/8" hole in the thermostat to minimize the possibility of an air pocket. This may not have been the problem but these engines have a reputation of being difficult to repair and/or rebuild. Successful 4.9L rebuilds have been done, but IMO, those engines were very carefully machined and assembled. A solid block to rebuild should be available as these engines are now very plentiful but as far as I know, not many engine rebuilders want to handle them. When you do find them the price tag for a remanufactured 4.9L Cadillac engine seems to be in the $3,000 range. I will soon have a 4.9L swap up and running and am starting to worry a bit.

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Fieroseverywhere
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Report this Post11-08-2014 06:33 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for all the suggestions. I'm leaning towards a fluke or casting flaw/porosity with this one. I can find no definitive reason why this break happened.

Neil's 88 - Water pump is only a couple years only. It was new when I put it in.

Dennis - I wouldn't worry about your swap. This is definitely not a normal thing for a 4.9. For the most part they are a rock solid engine. Rebuilds also are not very difficult. I've done it and am not afraid to do it again. The only part that's really different them most other rebuilds is the cylinder sleeves. A little extra time and care in the tear down process and its pretty simple. A full rebuild kit for this motor is about $400. $600 with pistons and pins. I just saw a 75k mile engine on ebay for $350 yesterday though so that seems like a better way to go. Bare block only runs about $150-$200. Cheap and plentiful.

I called a friend of mine and showed him the pics. He's confident he can weld it. He's been tig'ing aluminum for the last decade. And if this doesn't work I will have another block after we finish a swap on another car. I can transfer everything to that block as a last resort. Frustrating but not the end of the world. Thanks for all the suggestions guys. I'll just chock this up to a bad day! The real disappointment is all the other work I just did on the car that I now have to wait to enjoy. Such is life I guess!

[This message has been edited by Fieroseverywhere (edited 11-08-2014).]

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stickpony
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Report this Post11-09-2014 12:39 AM Click Here to See the Profile for stickponyClick Here to visit stickpony's HomePageSend a Private Message to stickponyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fieroseverywhere:

Thanks for all the suggestions. I'm leaning towards a fluke or casting flaw/porosity with this one. I can find no definitive reason why this break happened.



you using an oil cooler?
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Report this Post11-09-2014 11:27 AM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by stickpony:


you using an oil cooler?


Yep. Engine wasn't very hot. I was curing exhaust manifold paint per the directions on the can. Idled for 10 minutes, cool down for 10, idled for 20 minutes, cool down for 20. It cracked about 10 minutes into the second cool down. There was a loud snap then the coolant started hitting the ground.
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Report this Post11-09-2014 11:33 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fieroseverywhere:

Yep. Engine wasn't very hot. I was curing exhaust manifold paint per the directions on the can. Idled for 10 minutes, cool down for 10, idled for 20 minutes, cool down for 20. It cracked about 10 minutes into the second cool down. There was a loud snap then the coolant started hitting the ground.


Unless you have a circulation problem, this really shouldn't have happened, as you said.
Having said that, I always drill a hole in my thermostats. Mine is 1/8" which is really probably too large. Anything that allows trapped air to bleed off should be large enough.

Good luck, going forward.

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Report this Post11-09-2014 02:21 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:


Unless you have a circulation problem, this really shouldn't have happened, as you said.
Having said that, I always drill a hole in my thermostats. Mine is 1/8" which is really probably too large. Anything that allows trapped air to bleed off should be large enough.

Good luck, going forward.


This engine got a rebuild about 6 years ago so nothing is worn at all. Thats the main reason why I'm considering welding the cracks to correct this problem.

I use the caddy t-stat with an inline filler. I use a motorad high flow t-stat. They have a pre-drilled hole with a small brass valve in them (I clock it at 12-oclock). The valve falls away when air is present but but still functions as a completely closed t-stat where there is no air. When it does open it flows more coolant faster with the larger port. Been using it for about 4 years now. Shortens warm up time slightly then a straight drilled hole I think. Everything seemed to be flowing just like it should.

I'm think I'm going to take the heads in to be re-done first. Make sure they are perfect before re trying. As soon as Dick @ Allante source comes through with the steel rocker bridges I will put those on too. I'll just use this as an excuse to make a few more upgrades.
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Report this Post11-09-2014 04:06 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I might also suggest that you make sure that the sleeves and the top of the block casting are "to spec", in terms of "flatness". Whatever that spec is.
If the sleeves protrude, it might put odd stresses on the block when the bolts are torqued down.
(Seriously, I suspect that this is NOT an issue. I'm just clutching at straws, now. I'm sure you've got it covered.)

Having never been into one of these engines, but only hearing the horror stories from people who started on - and then abandoned them, I don't really have anything to go on.

[This message has been edited by Raydar (edited 11-09-2014).]

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Report this Post11-09-2014 11:50 PM Click Here to See the Profile for stickponyClick Here to visit stickpony's HomePageSend a Private Message to stickponyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fieroseverywhere:


Yep. Engine wasn't very hot. I was curing exhaust manifold paint per the directions on the can. Idled for 10 minutes, cool down for 10, idled for 20 minutes, cool down for 20. It cracked about 10 minutes into the second cool down. There was a loud snap then the coolant started hitting the ground.


yeah, thats just some random crack bro.. if you have someone who can weld it, i guess its worth a shot
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Report this Post11-10-2014 08:30 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:

I might also suggest that you make sure that the sleeves and the top of the block casting are "to spec", in terms of "flatness". Whatever that spec is.
If the sleeves protrude, it might put odd stresses on the block when the bolts are torqued down.
(Seriously, I suspect that this is NOT an issue. I'm just clutching at straws, now. I'm sure you've got it covered.)

Having never been into one of these engines, but only hearing the horror stories from people who started on - and then abandoned them, I don't really have anything to go on.



The sleeves have to protrude a little. If they don't the head gasket doesn't seal.

There is a lot of confusion about the sleeves and the 4.9 in general. Basically the pistons, rods, and sleeves are an assembly. You want to keep them matched if at all possible. The orientation of the sleeves is also important. You know.. I'll just post the pages from the service manual... give me a minute...

EDIT: Here they are...




There are other ways to check the sleeve height but this was the factory approved procedure. This is the most time consuming and odd part of a 4.9 rebuild. Most of the horror stories are highly overrated. In my opinion the tear down is the most crucial and nerve racking part. Those head bolts are a PITA to get out the first time. Lots of heat and WD40. Keep your fingers crossed on the 2 head bolts you can't lube. They're usually fine.

I managed to get a hold of a j-29776 cylinder sleeve height gauge. I'm working on building a j-29775 cylinder sleeve clamp tool. I'll do a lower end rebuild thread when I have everything together. If anyone wants better quality diagrams I can email you a set. Hopefully I won't be doing the lower end build twice.

[This message has been edited by Fieroseverywhere (edited 11-10-2014).]

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Report this Post11-10-2014 08:50 PM Click Here to See the Profile for Arns85GTClick Here to Email Arns85GTSend a Private Message to Arns85GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you can get a professional grade tig weld on that aluminum you should have no problem. I have not installed an oil cooler yet. However, I did find that I needed a 3 core radiator and I run a 160 degree thermostat. My oil is doing fine and not burning, and the overall temps are just fine. That crack still says to me it was torqued differently than its fellows. It may have been over torqued, seeing as we all make mistakes. If your cylinder compression is over 200 psi I would not do a rebuild. When it breaths better, it revs clean to 6000 with the OE cam. If you turbo it or sc it, you will want the steel valve trees though.

Arn
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Raydar
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Report this Post11-10-2014 09:34 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fieroseverywhere:

The sleeves have to protrude a little. If they don't the head gasket doesn't seal.

There is a lot of confusion about the sleeves and the 4.9 in general. Basically the pistons, rods, and sleeves are an assembly. You want to keep them matched if at all possible. The orientation of the sleeves is also important. You know.. I'll just post the pages from the service manual... give me a minute...



Like I said, I'm sure you've got it covered.
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Will
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Report this Post11-11-2014 02:02 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
It almost looks like the head expanded more than the block and cracked the block pushing on the dowel pin. The head would have to be WAY hotter than the block for that to happen, so I don't see how it could have done that while it was running without you noticing.

OTOH... if there were a hot spot in the head AND block cooled way faster than the head, that could account for a temperature inversion in the right direction... not sure if it could conceivably get to be a large enough temp difference. It would also have to be very low on coolant for either of those things to happen.

Maybe there was a machining error and the block and head dowel locations didn't match?

16mm is 0.6299"... If the hole was for a .625 dowel and a previous maintainer had hammered 16mm dowel into it, that could put enough strain on the block to fracture it.
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rogergarrison
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Report this Post11-11-2014 05:18 PM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Sorry, I wouldnt fix it...ive never had a welded up block or head stay together. I had some heads done on a Cutlass by a professional shop and they broke the next day. My only choice would be to replace it. Sounds like a good time for a winter project.

[This message has been edited by rogergarrison (edited 11-11-2014).]

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Raydar
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Report this Post11-12-2014 06:00 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I just went back and reread something...

 
quote
Originally posted by Fieroseverywhere:

I believe the head gasket is slightly thicker then the original. I switched to Corteco White seal gaskets this time. They are a silicone covered gasket instead of graphite.
....


Graphite is known for its low coefficient of friction (slipperiness?)
If there were different expansion rates, this may help to offset the stresses. Were the graphite covered gaskets soft? Or hard, like shims?

I wonder if they were designed to allow a bit of "slide", while still sealing; while the silicone ones appear to have locked everything in place.
Possibly a dumb suggestion, but this situation is new to me, and a special case.

Anyone?
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Fieroseverywhere
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Report this Post11-13-2014 08:26 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:

It almost looks like the head expanded more than the block and cracked the block pushing on the dowel pin. The head would have to be WAY hotter than the block for that to happen, so I don't see how it could have done that while it was running without you noticing.

OTOH... if there were a hot spot in the head AND block cooled way faster than the head, that could account for a temperature inversion in the right direction... not sure if it could conceivably get to be a large enough temp difference. It would also have to be very low on coolant for either of those things to happen.

Maybe there was a machining error and the block and head dowel locations didn't match?

16mm is 0.6299"... If the hole was for a .625 dowel and a previous maintainer had hammered 16mm dowel into it, that could put enough strain on the block to fracture it.


Thanks for the ideas. Unfortunately I don't this any of them fit the symptoms of this break.

While I can't entirely rule out a hot spot that particular corner of the head has a temp switch and is near the CTS. Neither of which showed any kind of excess heat. Neither did the scanner that was hooked up. Also after it broke the coolant was not very hot, I was covered in it trying to find where the coolant was coming from. I had to climb under the car to see it (FYI. the car was on jack-stands the entire time all of this was happening). There "could" have been an air pocket there which "could" have been hotter then the coolant. I don't find that very likely considering the situation though.

Machining error: This engine had 150k miles on it when I rebuilt it. I put another 25k on it since then. If there were an error I suspect it would have shown up sooner. I can double check some measurments to completely rule this out. I'll set aside some time to do just that.

The dowel pin was original. I am the only one who has ever been into this engine. Of that I am certain. Also the dowel pin is a light press fit into the block, but a sloppy fit into the head. I suspect this is for ease of install for the head bolts.

 
quote
Originally posted by Raydar:

I just went back and reread something...


Graphite is known for its low coefficient of friction (slipperiness?)
If there were different expansion rates, this may help to offset the stresses. Were the graphite covered gaskets soft? Or hard, like shims?

I wonder if they were designed to allow a bit of "slide", while still sealing; while the silicone ones appear to have locked everything in place.
Possibly a dumb suggestion, but this situation is new to me, and a special case.

Anyone?


I don 't have the old gasket anymore (victor reinz IIRC) but I believe they were both steel core. I know this one is. It was only the this outer coating that is different. I can't see the outer coating causing a failure like this. Makes me wonder though for sure.

I found another crack that I did not notice before. Or more accurately I believe it is the same crack that goes through the water jacket showing up outside the block. Its hard to see on camera but it is just above the drain plug on the ribbing. Clean through but small. I found it when I noticed a small amount of coolant below the drain plug. I thought for a second that I had found a place for air to enter the system. Turns out its just coming out of the crack above it.

full resolution cropped image. Here you can see all 3 cracks showing up on the outside of the block.

I just find it interesting that it goes all the way through the webbing. Its pretty thick there.

[This message has been edited by Fieroseverywhere (edited 11-13-2014).]

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Fieroseverywhere
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Report this Post11-13-2014 09:04 PM Click Here to See the Profile for FieroseverywhereClick Here to Email FieroseverywhereSend a Private Message to FieroseverywhereEdit/Delete MessageReply w/QuoteDirect Link to This Post
Oh. On a somewhat related topic. Here is the progress on the cylinder liner clamp tool (j-29775) I'm building. I post these measurments for anyone to use for their personal use. Not for sale.

I started with a piece of .25" plate 6061. It was cut to 18.125" x 5.125". I then used a 3.5" hole saw to rough cut the 4 cylinder holes. Bore spacing (and head bolt spacing) is 4.25" on center.


Heading over to the mill to do the final cut. The 4.9 uses a 92mm (3.623") bore and stroke. So I machined the holes out to 3.628"+/-.0005, This is .005" over the cylinder liner ID. If I were to do it again I wouldn't use such a tight tolerance. Its just not needed. 3.750" is fine as the liners are .250" thick




I then machined the 4 mounting holes. I used a 9/16" drill bit. This will allow some adjustment in mounting the clamps.


Then I cut the brackets down the middle to make the 2 clamps.



I will finish the rest of the set as soon as I can and post the finish here for now.

[This message has been edited by Fieroseverywhere (edited 11-13-2014).]

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