63 340/327 stripped manifold / Carb stud mounting hole

[Thomas S.]

https://www.forums.ncrs.org/showthre...+mounting+stud

[Jeff C.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

Heli-coil for sure
Jeff

[Joe L.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

One of the threaded holes used to mount the carb on my 63 327/340 is partially stripped. It is the driver side rear hole. The other 3 holes are blind but the damaged one is clear through which sounds to me like a previous owner had it “repaired” at some point. I found an old thread in the archive at. It is of course an aluminum manifold.

https://www.forums.ncrs.org/showthre...+mounting+stud

The repair mentioned in that post was for hole that was blind tapped and the reccomendation was to use a heli-coil. What would be the best way to repair the damaged threads and is there some type of insert that would re-established the “blind hole” in the manifold.

Thomas------

The hole could have originally been a through hole. Some manifolds had these but I do not recall if yours was one of them. No matter, though. Whether it's blind or through won't affect anything and there's no need to try to "convert" it to a blind hole. Just use a little sealer on the stud threads.

[Richard G.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

I have used 5/16 HeliCoils or ReCoil many times.
Inserts are not interchangeable between brands, so stay with one.
HeliCoils are the most popular and available everywhere. I would stay with them even though they are more money.
The inserts come in different lengths, be sure to order the length you want.
They can be inserted without a special tool. Just use a bolt with a nut on it for a insert stop.
That way you don't have to worry about having threads clear to the head of the bolt.
If the are used in a "through hole" you will have to catch the tang when you break if off.
Done correctly they are stronger and the bolt/stud can be removed and reinstalled with out damage to the threads.
In other words they are better than the new original threads.
Rick

[Thomas S.]

[Richard G.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

Tom;
You are correct, impact action is how it is designed to be removed.
On the shallow inserts it can be removed with a fine needle nose. Typically the tang is too far in for that.
Especially on inserts as small as 5/16".
There is a tang removal tool but typically not used for one time operation as they are expensive.
They are usually purchased for production applications.

I use a round punch. If anything goes wrong it is usually in the tang removal process.
It can pull the thread wire and deform it when hit. This makes it difficult to get the bolt to thread smoothly past the bottom of the HeliCoil.
If you set the insert deep enough the bottom of the tang will be below where the bolt ends. No need to even mess with it then.
This is likely how I would do it in your situation.
Because you are using a stud I am not sure this will be an issue.
If you remove the tang, even if it pulls the wire slightly the stud will likely go past it.
It will help hold the stud from turning out when the carburetor retaining nut is removed.

My bet is the job goes smooth and the most difficult part will be keeping the chips out of the motor.
Rick

[Thomas S.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

Thanks all.

Looks like the threads on the stud will limit the depth to roughly 1/2" so I will simply use a coil that is 5/8" long and not break off the tang. The hole is through into the number 5 manifold runner (no good access) so I'm concerned that the tang will likely end up in the wrong spot so I will take your advise. Stuffing a rag and running a shop vac in that runner is likely to take care of the small pieces.

[Larry C.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

The drivers side, rear carb mounting stud on my 1962 340 hp engine is intended to be hollow to allow for manifold vacuum hose to be connected. Corvette parts suppliers can provide this hollow stud.

Larry

[Thomas S.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

That is interesting for the 62 version. I have a 63 340 with a solid stud which is correct since there is a vacuum port on the carb. My issue was restoring the thread to that hole which was different than the other 3. Based on what you are telling me, the through hole was there from the factory. I had assumed that another owner drill it out at some point.

[John D.]

Re: 63 340/327 stripped manifold / Carb stud mounting hole

Richard, Excellent info on heli coils. The average fuel injection that comes in the door is taking around 5 heli-coils.
Thanks, John