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Is there a replacement stud that has oversize threads where it screws into the block, but the standard diameter and threads for the exposed portion? Might be worth a visit to a good bolt and nut shop to see what they have. I seem to recall these oversize service replacement studs were available in the past. Just a suggestion.

(o{I}o)

If not available easy enough to make one if you have a lathe or friend with one. But I'd suggest keeping just a hint of the shoulder of the larger OD at the end of the threads that go into the block.

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Yes there is. It is called a step stud. The end that screws into the block is the next size up and the rest of is made the same diameter and thread as the old stud so you can use the original size nut. If you can't find one any machinist can make you one. BTW Helicoils are OK, We used them in the NAVY, however they are a little hard to use properly and tend to back out easily when you don't want them to. The step stud is, by far, the best solution.

I would chase the threads on the remaining studs and use new hex nuts. Helps to obtain the proper and uniform torque.

I've been away for awhile and just got back to the site. I may have missed it but as you tap the block, one way to keep some of the metal shards from getting into the block is to coat the flutes of the tap with grease. The metal particles then stick to the crease. I remove the tap frequently to clean them of.
Hope this helps.

Well, the new stud is in.
Thanks to everyone for your help!
I ended up using a heli-coil and high-temp thread sealant.

Special thanks to Fred for the help, I'm sorry I didn't order this time from you, Max M. is about 40 minutes from my house and I like to keep business local to help the local economy whenever I can. I do have A list of stuff I will be getting from you next year though.

I've sent the manifolds in to have them blasted to a relatively new business in town, Hot Rods and Chrome. I was very ecstatic to see that they have their own spray booth.
They said middle of the week expected turn-around for about 20-25 bucks. Not a bad deal. That also lets the thread sealant cure for it's full 72 hours. I think I'm also going to have the manifold faces milled. I'm assuming the best way to do this is line them up as best as possible and have them milled together as one piece?

I did do the grease on the tap trick and it worked like a charm. I cleaned and re-greased about every 3/4 turn.

One interesting thing I noticed is that the manifold gaskets were put on inside-out. In the Packard manual it said the steel indented side faced the manifold and the asbestos went toward the block. Mine was reverse. The new gaskets I ordered don't have a steel side and I'm not sure which end goes in and which goes out.

I also ordered new valve cover gaskets. and found more butchery. Someone re-used the gaskets and used black RTV to fill the gaps. That was a fun clean-up. Another question, what's the purpose of the vent pipe on the rear valve cover?

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That's the down-draft tube. There's no PCV valves or vents on these to burn the oil infused vapors that build up pressure in the crank case. Back then they just pointed it down below the car and it gets drawn under the car. I could be wrong but that was my understanding.

Dave, connected to the outlet in the rear valve cover should be the road draft tube. It connects to the outlet and then extends down under the car and ends right below the firewall. The bottom is supported with a brace to bottom of the flywheel cover (as least on my car). My car was missing it's road draft tube when I got it, and I had to find a replacement.

Everybody got it wrong. The purpose of the road draft tube is to produce smog which blows against El Nino and winds up in Los Angeles

And people complain my posts are useless...

Dave,

Despite the trials and tribulations with your '51 300 Touring Sedan I see you've included it in the Packard Owner's Registry.