beerczar1976

'50 Special Exhaust Manifold Valve is unstuck!

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I ended up buying some of the AC - Delco Exhaust Manifold Valve lube spray.  After a few applications and some mallet caps with a socket extension used on the right end so I wouldn't bend the counter-weight arm, the dang thing loosened up!  This was only over the course of 15-20 mins.  I can now turn it under hand pressure.  Have no idea when last that flapper moved freely.  Figuring a few more soaks of this stuff over the weekend and it'll be rotating freely in the bearings.  Now, next question is...anyone have an idea of the measurements for the "L" bracket may have been that bolts to the bottom cowl side of the exhaust pipe union?  This bracket was what the spring end of the counter-weight arm would have hooked to.

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From my experience this measurement is not critical.  You could probably use any steel corner brace from a hardware store by just enlarging the hole for the manifold to exhaust pipe bolt.   Think of an "L" shaped bracket with 1 inch along each side.   You can stretch of compress the anti-rattle spring to where the valve is full open when hot.

Joe, BCA 33493

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Thanks. That's basically what I tried experimenting with this weekend. Not quite there. A 3/4"x3/4" L was too short to clear lip of flange. The 1"x1" L was about right for clearance, however, I think it's too tall. I tried to bend it outward (towards the cowl). It give a good spring tension to the Off position, but none when Closed (cold). Also caused it to kind of bind some halfway thru the swing. I believe manual lists same tension in both directions. Based on line drawings (which there are very few of in the Shop and Parts Manuals that show this part), I'm thinking original bracket may have been 1" left to right and 3/4" tall. I may try to bend the 1" back to vertical and put a downward bend into it to try to reduce the height some but retain the 90-degree L-shape. I'll let you know what I can get...Will also make sure that the spring end of the swing arm hasn't been straightened or bent out of shape at some point either.

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With the engine hot, the themostatic coil spring on the front side of the hot box will unwind a little allow the weight to drop by gravity opening the valve.   I say opening because the exhaust gases are then routed straight out to the exhaust pipe and not through the intake manifold plenum under the base of the carburetor.   Just be sure the valve can open all the way when hot; this is most important.   When cold the anti-rattle spring never really exerts any tension and it commonly just sits there to prevent the valve from rattling open and partially shut. 

Keep us posted.

Joe, BCA 33493

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Good note...as you mentioned "unwind" when hot...I'm wondering if the thermostat coil that's on there now may also be on backwards. I think when I swing the arm to the hot/open position, the coil tightens vice unwind.

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You need to follow up on this.   When hot, the weight on the arm on the firewall side should be down toward the block and the anti rattle spring should be  free and extended so that the valve is fully open.  If the anti rattle spring does not allow the valve to fully open, then you can stretch it a little. 

Joe

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See photos that show correct installation of coil spring.   When hot box is cold and you push weight on firewall side down to open valve the coil spring will resist your movement.   When hot the coil spring will relax and the weight will drop by gravity and open valve.  In first photo exhaust pipe would bolt to right side and left side on second photo.

Joe, BCA 33493

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a good product for loosing ext. heat riser  is named S,ok  find it on line. It is also a good penetrating oil for rusted nuts. there are other products out there try searching aviation shop supplies.

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