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

[Deezy]

That sucks. Just be sure that there is nothing more than just the water jacket behind that hole.

I have never had a motor down to the heads before. I'm not really familiar with the "anatomy" of where the water jacket runs. Maybe somebody can chime in with a diagram or something. At any rate, today is the end of my work weekend so my truck will likely be out of commission until next Monday, at the earliest.

 

[HotRodPC]

I have never had a motor down to the heads before. I'm not really familiar with the "anatomy" of where the water jacket runs. Maybe somebody can chime in with a diagram or something. At any rate, today is the end of my work weekend so my truck will likely be out of commission until next Monday, at the earliest.

You should be able to tell by looking inside that water port and back toward that side of the jacket to see how much iron is behind that bolt hole. I'd imagine it's going to go into the water jacket, but maybe not. Different head castings also have different amounts of iron and designs. I don't see of anything else that can possibly be behind that hole so worse case scenario your bolt will end up protruding into the water jacket and that should be OK.

 

[jetman]

Many years ago I drilled down into the water jacket of a running Cooper LM-9, never shut it down, just applied some extra silicone and its still going strong.
At this point you are definitely at a crossroads. I would suggest consider drilling down with the proper dia drill till you either: 1) have adequate hole for threads or 2) enter a water passage. Tap hole with a bottom tap if you have not pierced jacket, if you have pierced jacket use a standard tap and leave new threads a bit tight (do not run tap way in). In either case, use stud, as suggested above, for final assembly to avoid stressing new threads.

 

[R8rPhan]

Is there enough metal around the hole to go to the next larger diameter bolt? If so, couldn't it just be drilled and tapped for a larger bolt, then drill out the manifold hole to suit?

 

[kickdeez]

I have had good luck with helicoils in various different applications. I think a helicoil would work here, but as suggested previously, it may be best to exhaust all other options before going the helicoil route. I think you will be able to salvage this head and get something to work, just take your time. Be sure cover any open ports into the motor when you start to run a tap and/or drill so that you don't get any metal shavings into a cooling passage or somewhere it could end up in a combustion chamber. IF you end up having to drill down into the water jacket, put some serious consideration into how you are going to keep metal shavings, chunks, etc. from ending up in the cooling passage. It would be wise to flush the entire system when you get it all put back together anyway, but if you can keep the big stuff out, you are less likely to run into any significant blockage issues.

 

[theblindchicken]

I wonder if you could thread a section of copper rod, thread it into the head and take it to a welder to fill in the corner, mill the corner flat again and then rerun a tap through it to ensure its all good to go.

From my understanding, the filler for steel won't stick to the copper, thus you'd get it filled in with worrying about filling in the bolt hole. Just a thought, not sure if it would work though.

 

[HotRodPC]

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..

I guess I never knew there was a difference in a thread chaser and a tap. I thought they were one in the same and why I suggested a tap. I've always used taps on big jobs to clean out the threads because dirty threads can affect your torque readings if using a torque wrench. So you're saying I'm making the holes bigger by using a tap?

 

[74 Shortbed]

I guess I never knew there was a difference in a thread chaser and a tap. I thought they were one in the same and why I suggested a tap. I've always used taps on big jobs to clean out the threads because dirty threads can affect your torque readings if using a torque wrench. So you're saying I'm making the holes bigger by using a tap?

Yep, there is a difference, there are cheapo junk ones out there but if you look at ARP's they look just like taps but they don't have a sharp cutting edge they will not cut threads, using a tap will not make the hole bigger but you remove slight amounts of material off the threads, and if the threads are really cruded up you can take a fair amount off not knowing it, you'll still be able to torque the bolt down but any time you take material off the threads you're losing strength, and that can be critical with head bolts, especially on big blocks with their thin decks..

 

[Camar068]

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.

Yeh I got to thinking about it, the iron should have handled it better. I'm sure there was a crack or something there already.

 

[Deezy]

Well, tapped the head about a quarter inch down, not all the way through to the water jacket but a bit deeper. Got the intake manifold installed, plus a new Edelbrock 1406. Everything seems to be holding up in test drives yesterday and today, I'll be putting her to the real test driving 200 miles today.

 

[74 Shortbed]

Glad to hear you got it fixed..

 

[HotRodPC]

Well, tapped the head about a quarter inch down, not all the way through to the water jacket but a bit deeper. Got the intake manifold installed, plus a new Edelbrock 1406. Everything seems to be holding up in test drives yesterday and today, I'll be putting her to the real test driving 200 miles today.

Awesome !!!

 

[Rusty Nail]

Pics, wtf.

 

[75gmck25]

You are only supposed to torque an intake manifold down to about 30 ft lbs, so if you have a few threads to tighten into with the bolt with it should be enough to hold. It may last that way for a long time.

There is really no significant pressure in the port, since the piston is pulling air down into the cylinder. However, Intake manifold leaks pull air in, so running a little extra silicone sealer around the corner area where the manifold and head meet may not be a bad idea.

Bruce