Freeing up heat riser--exhaust manifold off car

[Guest 36chev]

There have been previous threads about this, but I may have a

different take on the situation. I've taken the exhaust manifold

off of a parts car 36 Chevrolet and am leaving the original one on my car

until I get this fixed up. So I have complete access (the intake sits

right on top) to the heat riser flap that is supposed to close over as

the car warms. But it is rusted solid.

Are there recommendations on a chemical/acid/oil I could soak the manifold

in? I was thinking of dunking the whole thing in bucket or vat, sealing it,

and let soak. For several weeks now I've been spraying with PB Blaster and

tapping on the flap, but it is showing no signs of budging.

Would it be a possibility to put the whole manifold in a rust remover bath

(recommendations?) and kill two birds with one stone--free the valve and

clean the rust off of the rest of the manifold?

Thanks!

[Bhigdog]

If other methods fail use the gas wrench (oxy/acet torch). Heat red hot and work loose, keep working as it cools down. Almost never fails.

[Guest 36chev]

Thanks for the suggestion. I thought about heating the steel valve and shaft with

the oxygen/acet. torch, but how much risk is there of cracking the cast iron manifold?

Could milder heating maybe help draw oil or wax in? It seems like one solution

for rusted bolts is to heat and touch some wax, wicking it into the threads.

Still thinking about the soaking options.

Again, thanks for the input.

[Bhigdog]

I would try the soaking first along with tapping the ends of the shaft. It probably won't work. I've freed at least 6 by heating the casting, not the shaft, to dull red and tapping/twisting the shaft. I've Also removed quite a few studs from the manifold outlet that way without cracking one yet. I heat the casting a bit slowly but take it right to a dull red. Good luck.....Bob.

[The Old Guy]

Most old cars are only driven in warm weather, and the heat riser is not really necessary. If it does not free up easily, I would take the torch and remove the inside. From the exterior it won't look any different, and you will not have to worry about it ever sticking again.

[Coley]

PB Blaster is the best to spray it with. Using a medium hammer try moving it forward and back (not turning it). If you heat anything, heat the counter weight and not the spring end or the manifold. Just like removing studs, heat the stud to a low red twice, letting it cool down between heats. Then heat it again and let it cool down to room temp and it should turn out.

The reason you heat the bolt/stud or shaft is that it pushes the rust back and lets the bolt/stud or shaft move.

Acids can soak it free, but most will ruin the bi-metal spring, so be carefull with that...

[Guest imported_PackardV8]

Do not heat anywhere near the spring. Using a hammer JUDICOUSLY tap the end of the cross shaft backand forth alternating from side to side. If one side is a blind hole then u will have to drill a hole parallel and centre to the end of the shaft so u can get punch in it. DO NOT drive or twist on the weight or any other part of the heat riser. The weight is cast iron and breakes easily. Be patient, soak it with your favorite snake oil and tap the the shaft at each end.

[Ivan Saxton]

There are several different ways that you can approach this, and similar to the way you remove a piece of broken stud from a blind hole, you work carefully, starting with the least agressive method, always pausing for coffee and thought where necessary before progressing up the scale to more extreme measures.

You have alternatives which involve simple applications of chemistry, physics, and microbiology.

1) Water causes rust, and it softens rust. It is a polar solvent. Try soaking a rusty piece of scap in clean water, then rub the item with your finger, and observe the rusty water (solid particles in suspension.) If you are not encouraged by any change after 24 hours soaking the job, carefully use another approach.

2) Dissolve a chetating agent in the water. EDTA or citric acid have a strong affinity for ferric or ferrous ions, and the progressive sequestration of these causes further rust to be dissolved.You should be able to get EDTA powder from a pharmacy/drug store, while the most convenient source of citric acid is your lemon tree. Try making a dry rust stain on a piece of white cloth ( iron from the haemoglobin of a blood stain will do), and squeeze lemon juice on it.

3) There are two ways to use the coefficient of linear expansion. Heat the casting while keeping the valve shaft cool with wet rags or heavy fibreglass matting. It is best to heat fairly gently and evenly. Exhaust manifolds can stand a lot of heat, and if you run with retarded spark they will glow in the dark. You dont want to cause distortions.

4) Keep the manifold as cool as possible as above, while trying to heat the frozen shaft towards its plastic range. If the shaft cannot expand radially because it is confined, it will expand slightly, permanently, axially. So there will be slight shrinkage clearance radially when it has all cooled down.

5) Mix a decent solution of molasses in water. If you have not used this before, put a piece of rusty scrap iron in and leave it overnight. This will give you experience of the slow pace of the method, and also start the system working. I have never seen an authorative explanation of how this works, but my understanding is that the molasses is a desireable food source for bacteria which are not anaerobic, whereas the solution approaches that condition. The microbes therefore feel they have greater need and entitlement to the oxygen in the rust. When you wash the goo off the job, you find that the rust has been reduced to loose iron powder. You have to dry and protect the cleaned surface very quickly, or surface rust will form again as you look at it.

6) the best penetrating fluid type product that I have encountered is called Reducteur H72. This is presumably French. It may be no better than what you know but I cannot get. It was fairly expensive, but it is hard to get now because people have less appreciation for its cost than its efficacy. I was able to undo with a six-point spanner and hide hammer the fine thread sleeve nuts which hold the spring shackle pivot shafts on the rear of a model A Duesenberg chassis. I was unable to shift these with heat.

I hope this is some help.

Ivan Saxton

[mlander]

Manifold heat control

After you get that thing apart knock off the butterfly and throw it away! This thing caused more burnt valves than any other thing that I know of. When it is stuck in the closed position all the exhaust gases have to go through the passage in the carburetor area, a very small restricted area. I had this happen to an old 1953 Dodge V-8. If you want it to look stock this will not show up on the outside of the manifold. This will cause the engine not to heat up quite a quickly as when it is fully operative but if you take trips of over 10 miles you will not even notice it. Do not use a solid gasket as that will cause absolutely no hot gases to get to the carburetor which does need some heat!

M.L. Anderson

[Guest TexasClipper]

I know this is a thread from last year, but I was doing a websearch, found you folks, and thought this might help.

At a Packard club tech session last weekend, this same subject came up.

No one seems to know about Chrysler's manifold "Heat Control Valve Solvent" that I have had excellent results with and has been around for 30+ years.

It should be at the dealer parts counter.

It works. I've used it on Chrysler 318 and Caddy. About to use it on Packard straight-8.

You can use it on or off the engine. It also is a really good solvent in general for parts rusted under heat, like head bolts and the exhaust manifold studs.

It also lubricates that high temp shaft for some time. As PackardV8 suggested, a little judicious TAPPING with a good solvent is the way to go. I don't have a good history with torches and cast iron.

The Chrysler Slant Six group refers to it on their page on manifolds, and they also do a really good job in descibing other issues on reinstalling reworked manifolds or checking out new ones before wasting a lot of installation labor on a manifold BOB (bad out of the box:)

http://www.slantsix.org/articles/manifold-install/types-mounting.htm