What is behind this hole?

[rpowers]

Hello,

I'm finally doing the right thing and am replacing a manifold bolt with a new MMI stud.

See photo for wet hole on the right.

The old bold was missing many threads and was weeping water from behind.

The new stud is slightly larger (7/16 thread) so I am tapping over the old threads.

QUESTION:

What is located behind that hole?

As I am drilling out the old hole, how far back should I go?

How much space is the water passage?

Any penalty for drilling too far?

Thanks!

-Rick

[thatch]

Rick,
All 3 stud holes lead to water jackets. The front and rear holes only go about 5/8" deep before running into block material. The center hole however is clear for about 3" where it runs into the cylinder walls. One trick for getting the tap in straight is to install the manifold with the other 2 studs and use it as a tap guide for the third hole.
Tom

[ArtJ]

With the manifold in place as suggested, maybe you could use a socket
as a depth guide. The correct drill depth should be about the length of the
manifold bolt when going through the manifold hole

Regards

[rpowers]

What I found

OK, so I was able to figure out the short depth part...

I drilled carefully with small then larger bits until I just touched metal on the sides, with only barely hitting the back wall.

I also learned that I needed a short "end" tap, to get bite without a long fore-end.

Then I was able to clean out the threads and see what I have.

There were "spring" like bits of metal coming out. Is that a remnant of some "helicoil" device? I've never seen one.

Anyhow, I got all the bits out, had clean threads, and tried my new 7/16" (larger) stud. It certainly fit down the threads. It was actually loose a bit, and I was able to get some wiggle while fully threaded.

QUESTION: Will JB Weld be enough to shore up the space between threads, or do I need to do something more drastic.

It seems like if I can get the stud to thread fully then bond with plenty of JB Weld, it should be fully strong when the manifold bolts bear down on it. Am I correct here?

Thanks!

-Rick



MMI - "The kit includes one repair stud, regular 7/16" tap, and a blunt tap (called a "bottom" tap, which is sometimes difficult to find locally). The kit also includes a package of JB Weld to finish the job."

[thatch]

Rick,
JB weld should work good enough in this application. Again, if you bolt the manifold is place using the 2 good studs while the JB weld cures, you will insure proper alignment.
Tom

[rpowers]

Thanks Tom

Thanks Tom,

Can't wait to get it right- a solidly "stud-ed" manifold.

-Rick

[rpowers]

Job Done

It's done, and done well!

I was able to get clean threads in the block, new studs from Ken, and yesterday I JB-Welded them in place, of course with the manifold loosely in place to ensure alignment.

My trick was to use my automobile car jack to hold the manifold up to prevent it giving downward force on the studs, leaving them perpendicular to the block.

After 24 hours, I slid the manifold away, double checked the gasket and surfaces for any stray epoxy (none found!), then used the heavy-duty nuts to tighten the manifold in place.

It was quite a pleasure to re-attach the carb and fuel pump and start it up.

The previous water drip was gone, and there was a tight seal with the gasket, so no exhaust leaks.

Yea for me!

(If you would have told me a couple of years ago that I would be tapping threads in the engine block and installing studs I would have scoffed at the idea. You guys are great support!)

-Rick

[rigspelt]

Excellent Rick. Well earned satisfaction.