How screwed am I? Broken intake manifold bolt hole in head.

[Deezy]

Title says it all... Front-most bolt hole on driver side crumbled while prying off the intake manifold.

 

[HotRodPC]

How much thread is left? Does the thread go through into the water jacket? Can you drill it out and install a helicoil?

 

[KnockingDiesel]

I have had this happen to me on SBF 302, I covered the ports and valley with gorilla tape, drilled the bolt (slow speed and grease on the bit to hold the shavings) then soaked it in high quality penetrating oil, stuck in the extractor and on the second try it turned loose.

Important, don't go cheap, I have seen cheap (i.e. HF) bits and extractors break in the bolt, that's when you're really screwed (hardened steel tough to drill through). Take your time and it should be fairly straightforward.

I have a no experience with auto parts store tool quality either. I have a friend who has all the high end stuff (I.e. Snap on). So i would see what is the best available to you locally, unless time isn't a factor then you could order the specific extractor and bit for a reasonable price.

Make sure you are drilling straight in to the bolt and use the appropriate sized extractor

 

[Deezy]

Knockingdiesel, the bolt came out, but prying the intake manifold off crumbled the outboard corner of the bolt hole. Apparently prying on cast iron is a no-no... I have about a quarter inch of thread left below the bottom of the failure and it doesn't seem to have gone near the water jacket. I may just thread it in and JB Weld it.

 

[jetman]

Is there a bolt broke off in the hole? Or did the head casting simply crumble? Kind of hard to tell with the photo..

^^ got it

 

[Camar068]

wow.....I see it now. Never put what your prying with in a hole like that. Good reminder to everyone to not do it. Sorry for saying but thanks for the reminder.

Hope it works for you. What did you use to pry, big screw driver or something bigger? if you didn't put a lot of pressure on it, I'd wonder about the shape of the rest of the head.

 

[HotRodPC]

It appears to me, the bolt is out. The problem being, the meat of the threads in the head has broken away.

If you have a 1/4 of thread left, then yes, I'd use a bit longer bolt, and some lock tight. I don't think you need to be afraid of getting into the water jacket a little bit just so long as it's tight and don't leak, but I'd try to avoid it if you can.
I'd suggest getting a stud glued in, but being the angle of the bolt, that would make it a real bitch getting the intake down and not moving your gaskets, especially the front and rear. Although, you could use silicone instead of the rubber gasket ends.

 

[KnockingDiesel]

Knockingdiesel, the bolt came out, but prying the intake manifold off crumbled the outboard corner of the bolt hole. Apparently prying on cast iron is a no-no... I have about a quarter inch of thread left below the bottom of the failure and it doesn't seem to have gone near the water jacket. I may just thread it in and JB Weld it.

Hey, sorry, I couldn't quite tell from the photo. That I have never run into.... The last SBC I had worked, had a heli coil in one of the intake bolt holes and exhaust bolt holes. As soon as I stuck a wrench on them I could tell there was something up with the hole. Maybe they were not installed properly or something. But if they were installed properly then I would not recommend them. Perhaps someone who's installed them will chime in

 

[Georgeb]

I would like to suggest you clean the hole out really well and see if there is any unthreaded area at the bottom. If there is get or make yourself a bottoming tap. This is a tap with a very short lead in on the end. I would tap the rest of the way down the hole backing out after each 1/2 turn to blow the chips out. Tapping in cast iron does not require oil but a little wont hurt. Be very carefull not to bust that tap off or you will be super screwed. I would use a stud in that hole but I would put it in after I installed the intake. You could double nut it to drive it to the bottom of the hole and then go to one nut and torque it like the rest of the bolts. Anyway thats what I would do if it was mine. In fact I was sure I was clear of the water jacket and head bolt I would even consider drilling it deeper.

 

[HotRodPC]

Hey, sorry, I couldn't quite tell from the photo. That I have never run into.... The last SBC I had worked, had a heli coil in one of the intake bolt holes and exhaust bolt holes. As soon as I stuck a wrench on them I could tell there was something up with the hole. Maybe they were not installed properly or something. But if they were installed properly then I would not recommend them. Perhaps someone who's installed them will chime in

I have used many helicoils to save automatic transmissions, both in the valve body bolt holes and in the front pump bolt holes when the aluminum threads give up. Used one in an intake once where the thermostat housing bolts to the intake and the old threads had just rusted away. All with good success. Patience and being 100% sure to use the correct drill bit size is the key to a helicoil being successful or not.

In this case, I would only use the helicoil as a last resort. Reason being, this isn't a situation where the threads are gone, it's a case where the material is gone. Helicoil will need that material to help support itself. If you have 1/4in of thread left at the bottom of the bolt hole, that's what I'd concentrate on making work. If it doesn't then I'd go with the helicoil and I'd still be leaning on that 1/4in of material to support the helicoil, but I just wouldn't drill it unless I had to cuz the helicoil is a last resort 1 shot over the bow to work. If it don't work at that point, then I'd say you're fuct and probably going to have to replace the head or have someone put in some weld material and tap it, then it becomes a huge project.

To have the best luck in getting that last 1/4in to work, I think I'd clean the threads that are left by running a tap. Not to cut any threads, but just to clean the threads because I know how those holes tend to get grungy and rusty. So clean the threads by running a tap, then blow the hole out with air to get all the debris possible out of the hole. Then you're going to want to use a little longer bolt than was previously used so you can take advantage of all the threads that are left. I'd go to the hardware store, Lowe's or Home Depot and I'd get a BRASS BOLT in the specialty hardware section. The brass is much softer and not as likely to do damage to what threads are left. The brass should give up before those threads give up. This way if something does go wrong, or the bolt gets seized, the bolt will give up and you'll still have your threads left and you'd have another shot at it with another bolt. I also would not get extremely aggresive on tightening that one either. Be sure to have plenty of silicone around that water jacket and be more dependent on the other bolt on the other side of the water jacket to hold.

 

[Georgeb]

I have used many helicoils to save automatic transmissions, both in the valve body bolt holes and in the front pump bolt holes when the aluminum threads give up. Used one in an intake once where the thermostat housing bolts to the intake and the old threads had just rusted away. All with good success. Patience and being 100% sure to use the correct drill bit size is the key to a helicoil being successful or not.

In this case, I would only use the helicoil as a last resort. Reason being, this isn't a situation where the threads are gone, it's a case where the material is gone. Helicoil will need that material to help support itself. If you have 1/4in of thread left at the bottom of the bolt hole, that's what I'd concentrate on making work. If it doesn't then I'd go with the helicoil and I'd still be leaning on that 1/4in of material to support the helicoil, but I just wouldn't drill it unless I had to cuz the helicoil is a last resort 1 shot over the bow to work. If it don't work at that point, then I'd say you're fuct and probably going to have to replace the head or have someone put in some weld material and tap it, then it becomes a huge project.

To have the best luck in getting that last 1/4in to work, I think I'd clean the threads that are left by running a tap. Not to cut any threads, but just to clean the threads because I know how those holes tend to get grungy and rusty. So clean the threads by running a tap, then blow the hole out with air to get all the debris possible out of the hole. Then you're going to want to use a little longer bolt than was previously used so you can take advantage of all the threads that are left. I'd go to the hardware store, Lowe's or Home Depot and I'd get a BRASS BOLT in the specialty hardware section. The brass is much softer and not as likely to do damage to what threads are left. The brass should give up before those threads give up. This way if something does go wrong, or the bolt gets seized, the bolt will give up and you'll still have your threads left and you'd have another shot at it with another bolt. I also would not get extremely aggresive on tightening that one either. Be sure to have plenty of silicone around that water jacket and be more dependent on the other bolt on the other side of the water jacket to hold.

This is good advice.

 

[Deezy]

So I tried to get a good shot but with a phone camera, it doesn't do to well. Below is the best I got. It appears that only one full thread remains in the hole. I may have to get a tap and a longer bolt as suggested. Unfortunately I don't have those on hand. I tried reinstalling the manifold but couldn't get the bolt to bite that thread that's left.

 

[HotRodPC]

That sucks. Just be sure that there is nothing more than just the water jacket behind that hole. In the event you go all the way through into the water jacket to gain more thread, it shouldn't be that big of a deal. It's not going to hurt for the bolt to hang out into the water jacket. You just might have to put some silicone on the bolt before you install it so that the threads are sealed and don't allow water to seep or leak out through the threads.

This also another good reason to use a brass bolt. If the bolt protrudes into the water jacket and going to have coolant around the tip of it, it's going to be subjected to rust. Brass should keep the rust away.

 

[74 Shortbed]

If the threads left are not the greatest now you definitely don't want to use a tap to clean them out, they cut metal as they are designed to do and will remove more material which you don't want with just that small amount left, you need a quality thread chaser like the ones from ARP to clean them up, something like that I use a locking insert or Time-Cert instead of Heli-Coil, that's common with bolts going into the water jacket and wasn't sealed right..

 

[Deezy]

wow.....I see it now. Never put what your prying with in a hole like that. Good reminder to everyone to not do it. Sorry for saying but thanks for the reminder.

Hope it works for you. What did you use to pry, big screw driver or something bigger? if you didn't put a lot of pressure on it, I'd wonder about the shape of the rest of the head.

I was using a big ol' flathead, and had worked it under all the way to the second or third bolt hole, lengthwise between the manifold and head surface. It was stuck on there real good, so I pushed down, and I guess the fulcrum point must have lined up on that corner just right. I can't imagine it was fully structurally sound to begin with because it gave pretty quickly and just turned into iron crumbs.

It sucks this happened, but hopefully somebody can learn from my mistake. I should've had a dead blow mallet handy and just smacked it off. Hopefully I can salvage these heads as I wasn't planning on doing a full motor build on my current budget... I wouldn't be as worried if it wasn't the corner bolt, which I feel is probably more important than the middle ones.