Exhaust manifold intake bolts broke

K

KEN2939

Junior Member
The intake bolts broke off in the manifold causing a hole in the casting where the bolt goes in. Can I tap and install a new bolt or is it time for a new exhaust manifold. Thinking of possibly using a helicoil repair. The threaded bolt will fill the break in the inside casting. See photos. Thanks
 

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What will it hurt to try the helacoil?

This from another thread: I just got the new Snyder's Catalog. It sure is nice of them to print that and send it...

On the inside, a few pages in, they kinda send a warning saying some small parts guys have either passed on or retired....and suggest buying now if your anticipated part is an oddball. To that end I noticed both Snyder and Bratton don't list new Zenith carbs anymore.
 
A new or used (in good shape) exhaust manifold is what I would chose. If you want to repair that manifold, it will need to be welded up and re drilled and re tapped. I don't think a Helicoil is going to hold, but as J Franklin said, it would not hurt to try. If you weld it up and re drill it, you will have to use a milling machine to get the hole in the right location. While you are at it, you can machine the surface that mates to the block, as well as the intake manifold when the two are bolted together.

Another option is just the use the exhaust manifold without bolting the intake manifold to it. There will be enough heat transfer for modern gasoline. Just make sure you line everything up when assembling. Use the manifold gaskets with the copper or steel surfaces. Use a high temperature silicone material to seal up the hole so that you do not have an exhaust leak.
 
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Always worth repeating that most original exhaust manifolds, including every swap meet manifold I've ever seen and possibly your current manifold, exhibit the characteristic droop on the cylinder 4 port that leads to frequent gasket failures.
 
Alexiskai mentioned the first thing I always check. If a manifold has excessive droop then it's not worth trying to repair it. I had a drooped manifold and a cracked intake so I tried out a new set from Snyder's and they fit together well. I had to take off a little more casting flash to make them appear more original but they fit together and installed OK.
 
I have drilled and tapped and installed a bolt, 3/8" or 1/2", cut flush, and then drilled and tapped for the manifold bolt. A plug if you will.
The casting has a pocket for the manifold bolt, and can be drilled thru, or broken off, and is fragile. Just retapping, the manifold is likely to leak.
Or replace both intake and exhaust.
 
Bob, that is a good idea. In this case, after installing the plug, he could drill and tap the plug using the intake manifold as a drill guide. I would use Loctite or JB Weld to lock the plug in the manifold. It will burn out but not before he has a change to drill and tap a new hole for the bolt.
 
It's a crap shoot, castings do vary, I tried direct tapping, but ended up with this fix.
If the initial retapping breaks thru the pocket in the casting you have a probable leak.
 
Ken, do yourself a favor and take the manifold to a machine shop, and tell them you will be back to get it in 3 days.
 
Brentwood Bob said:
Looking at your pictures ken, I think it's scrap.
Click to expand...

I agree. This manifold has been thru the wars. It shows a lot of deep pitting and has been leaking at the gasket surfaces and probably needs to be surfaced with the intake to make everything flat again. By the time you fix the threads and surface it, you will still have a manifold that has lost a lot of its integrity.

Nothing lasts for ever.

I would just buy a new one. You will be money ahead in the long run.

My opinion,

Chris W.
 
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I would research the next largest size metric bolt that could be used. Then you can drill & tap a new hole.
 
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