345 intake manifold cleanup

R

Richard

Member
I have a 345 4 bbl. Intake that has been sitting in the garage for about 15 years. Has a little bit of rust. What is the best way to clean it up, both outside, but more importantly inside. Will bead blasting / sandblasting do the trick, or is this too harsh. Hot tanking?. Would also like some input about really "cleaning" the insides I.e. Smoothing out the passages for better performance. Any thoughts will be appreciated. Thanks,
 
My weapon of choice is bead/abrasive blasting whenever corrosion exists. Clean and paint right away so light surface rust does not set in.
 
Flip it over and count the welch plugs...two...three...five??? No matter pull 'em all out and have it blasted by someone who knows what they are doing. Any decent automotive machine shop will have a "tumbler" type abrasive cleaning machine that works really well.

Then replace the plugs.

It's impossible to completely clean any complex casting like that without removing all plugs.

In this thread, you will see a 345 block that I recently had "bake and blasted". All signs of any grime, corrosion, rust, etc. Is removed in that process, the internal water jackets are completely clean and look "as cast":

http://www.forums.IHPartsAmerica.com/gas-engine-tech/1143-sonjamotor-lives.html

My machine shop charge $22 for an intake manifold bake and blast.

Any "port work" on those intakes is a total waste of time if the heads are not completely cut along with the intake as a package. These are truck motors and don't rev unless extensively modified.
 
Another question,

you mentioned the "plugs" on the underside of the intake. They look like what?? I have what looks like 5 half dollar size flat plugs. Do they drill out, or punch out?
 
richard said:
another question,

you mentioned the "plugs" on the underside of the intake. They look like what?? I have what looks like 5 half dollar size flat plugs. Do they drill out, or punch out?
Click to expand...

I posted this somewhere else but can't find it!

Here is a shot of the manifold under discussion showing a "five hole" design. Two of those locations are retaining exhaust gases, three are retaining engine coolant. Those casting ports are sealed with "welch" plugs. Not all IH sv manifolds are exactly the same, there were many variations over the years of the casting mold the "five hole" was the last one used before this stuff went out of production as that casting incorporates the egr system.
 

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Here is method I use for removal of any type soft plug.

I punch a hole in what's left of the sheetmetal and thread in a sheetmetal bolt.

Then I use a mini-slap hammer to remove, a real neat job that won't possibly result in damaging the counterbore surface by gouging.

Any automotive machine shop can do this for you, make sure they are instructed to do so. They can then install the correct service part plug before returning the manifold to ya. My machine shop charges a walk-in $4.50 per hole to do this if it's a "simple" plug/location
 

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As far as the "mating" surfaces (intake to head / carb to intake), what do you use for "straight" sufacing, or what should I look for when inspecting the actual surface?
 
Good post here, great info and photos. I went looking for more info on welch plugs and found the following:
brief history of the welch plug
By nevin hubbard of m.d. Hubbard spring company - since 1905 - fourslide/multislide stampings, wireforms, torsion springs, extension springs, expansion plugs, ground plugs washers, metal components
A brief bit of totally obscure history that I am one of the few living persons who knows.

My family business, established in pontiac, michigan in 1905, is the original manufacturer of the "welch" plug. The welch brothers had a motor car company at the turn of the century that was later bought by general motors - the welch motor car company. They would run the cars around pontiac to "break them in."

at that time core holes in the engine blocks were fitted with pipe plugs. During one of these run-ins a pipe plug backed out. In order to get back on the road one of the brothers drove a quarter or half dollar into the hole. From this they developed the welch plug, some with the help of my great grandfather martin hubbard. They then patented the plug and the m.d. Hubbard spring company become the sole manufacturer of the welch plug for the life of the patent. To this day we have the largest range of sizes available anywhere.

So the welch plug in origin is an American innovation and name.

Best regards,

nevin hubbard
m.d. Hubbard spring company
 
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