Packard Forum Index » Post-War (1946-54)

I have seen brass nuts used on exhaust manifolds on several other cars I have owned. Lock washers are generally not used because the heat from the exhaust makes them lose their spring force. I think it is good practice to use a flat washer under any nut if a lock washer is not used. The flat washer helps spread out the load from the nut on the mating part.

After removing the manifold on my 120 I found the the front stud was barely holding on. There was hardly any thread left in the block so I drilled it out, installed a helicoil and installed the original stud size. It's held up well with no problems. I also installed the manifolds as posted by HH56. I tightened the 2 manifolds together at the hot spot using a straight edge on the faces, installed the manifold to block, torqued and then loosened the the 3 hot spot bolts, rechecked the manifold to block torque and then torqued the hot spot bolts.

So I got the Manifold off today.
I soaked them all in PB Blaster last night and then again this morning. I was surprised how easy the nuts came off. (Yes they DO have washer, by the way) However, I had to take most of them off with a the box-end of my combo wrenches; there just isn't room for a socket wrench -or- an universal joint (At least with my limited tools.)

Just when I thought I saw the weirdest of the weird, here's a new one.... I got the manifold off and sitting in one of the intake ports is a split washer! Just sitting there all nice and shiny from being washed with gas all those years I guess. I saw that and about had a heart attack. If that had made it's way in...... After setting the washer on the bench I noticed it's exactly the same as the ones under the nuts that hold the throttle to the manifold. And one of those was all new and shiny unlike the other three!

After a lot of research and Seeing what's there, I've opted to do a Heli-Coil. I picked up a kit at Autozone, but need to get a 25/64 bit to open the hole up.

Any Advice/tips on drilling straight?

BTW, I found this great article on manifold studs I thought I would Share. Link

There are several types of drill guides available but the better quality ones are a bit expensive for one time use. A small machinist square and good eye can be used or a tapping guide might be used also--if the hole size is close. A less robust item could be made if you have access to a drill press. A straight hole thru a block of hardwood could be made. A length of metal tubing or bushing stock with ID lightly larger than the drill bit could be inserted so the drill bit wouldn't mess it up and assy clamped against the block to guide the drill.

Attach file:

---

  (11.01 KB)


  (24.68 KB)

The drill guides are an excellent idea. Whatever u do don't break the drill bit off in the stud. Drill bits are extremely hard and that means nearly impossible ot remove if it breaks off.

Not drilling the stud, the stud fell out. I am drilling the block to accept the Heli-Coil.

Since you are only slightly enlarging the hole, IMHO I bet you will find the existing hole will help act as its own guide as the point of the bit should self-center in the existing bore to a degree as long as you are letting the bit do the work and keep it generally straight.

Helicoils are nice but have to be done right. My personal opinion, drill larger and tap it, and install a stud. put some sealant on it, and be done. Others may or may not disagree, but just about anyone can tap a drilled hole. It's a little easier to mess up a helicoil install than it is a simple tap job if you go slow and backup/clean the tap as you're working.

Need to look it up on google or something but there is usualy a special angle ground on the drill bit for cast iron to keep it from hanging up. I usualy don;t grind the angle any different but since it's going into a critical area mite be a good idea.

I've got to agree with cortcomp, put the next larger size stud in it. The reason why I say this is there's two different kinds of helicoils, the standard "spring" looking type and a solid type. Since it's going into coolant I'd be cautious about using the spring ones, seal the stud with blue Locktite at least. I like the oversize stud idea better.