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I need to identify an engine part on a '57

Discussion in '1955 - 1966 Classic Ford Thunderbird' started by dickday0, Dec 13, 2017.

  1. I was wiping down the firewall and noticed a spring hanging from an exhaust part. The part bolted to the end of the passenger side exhaust manifold as it extends down and away from the block.
    It looks like the spring is supposed to be connected to the 2 rods shown in the picture. I removed it so it wouldn't get lost. Once I know what its purpose is, I'll connect the spring.

    Any ideas?

    Thanks 20171213_201837.jpg
  2. fordrodsteven

    fordrodsteven Well-Known Member Gold Donor

    I don't know that I can answer your question as to what it does exactly. I looked in my parts digest book and then went to my Hill's catalog. On page 67 it shows that the spring is there on that heat riser (P/N 9A427) and it does in fact go from pin to pin. I know that the coil spring and weight on the other side will open and close the baffle as the exhaust /car warms up. My guess is that this little spring helps to eliminate some vibration / fluctuation of the baffle and / or just puts a little tension on the baffle shaft to help it move open or closed more smoothly.
    dickday0 likes this.
  3. Wow, thanks for such a quick reply and researching it for me. I believe you've told me what I needed to know. There is a rod that goes through the end of the manifold. It rotates up and down. I believe the spring is part of this assembly.

    Thank you again for the help!
  4. fordrodsteven

    fordrodsteven Well-Known Member Gold Donor

    Your welcome. I'm just here hanging / surfing on the computer mainly because it's too cold to be messing with my car. It's going to go down to single digit temperatures tonight and there's no heat in that big garage! Lol
  5. fordrodsteven

    fordrodsteven Well-Known Member Gold Donor

    I remember that little spring on a few of my cars and when the spring was missing there was often a rattling sound coming from the exhaust. That's why I think the spring mainly holds the baffle from fluctuating.
    dickday0 likes this.
  6. From the little bit I've just now read, it doesn't sound like the disconnected spring would have anything to do with the engine running rough when it's cold. That's my only problem with the 312. Again, thank you.
  7. The part that is bolted to the passenger side exhaust is the heat riser and is used to direct hot exhaust gases under the carburetor by partially restricting the right exhaust pipe, thru a passage in the intake manifold. The coil spring on the side of the heat-riser is a thermostatic spring and it allows the heat riser to open up when the engine warms up.

    1955 Thunderbird Blue
    dickday0 and biddle like this.
  8. Thank you!
  9. Question... if the heat riser spring were missing, what impact would that have on how the engine starts/runs?
  10. The heat riser has a butterfly valve inside that the spring holds closed when the engine is cold and as the engine warms up the spring, being bi-metallic relaxes and lets the butterfly valve open up. Since there is a counter weight on the butterfly valve shaft opposite the spring, with the spring missing the butterfly valve should be open. With the bi-metallic spring missing and the butterfly valve open, the only impact I can think of would be the carburetor would be running colder longer and wasting gas. I cannot tell any difference in cold performance between having a heat riser or not. If they contribute to cold weather running, it is minimal.

    dickday0 likes this.
  11. After 3 tankfuls, I notice that the Tbird is sucking down the gas pretty good. Looking at mileage for a car that sat for over a year, with stale gas in the tank, is probably not a good indication of what's to come. So far it's averaged almost 12mpg.

    With the spring off, when I move the butterfly valve, neither of the two rods (that the spring would connect to) move at all. The valve moves freely, and, because of the weight, goes to the closed position when released.

    With the engine not running and cold, if I move the valve by hand, should I be able to see the spring open?

    Again, thanks for the help.
  12. Looking at your attached photograph, the counter weight is in the lower position and the valve is open, not closed. If you move the counter weight by hand, you should see the shaft that is directly across from the counter weight rotate.

    As far as your gas mileage, according to your VIN you have a 1957 Ford Thunderbird equipped with a 312 engine and a Fordomatic transmission. The weight of your car is approximately 3,440 lbs. and the estimated fuel mileage is 12.4 mpg.

    1955 Thunderbird Blue
    tbird and dickday0 like this.
  13. 12.4 Wow. Then the mileage I am seeing is pretty good, considering. Thanks for all of the info.
  14. tbird

    tbird Super Moderator Staff Member

    Yes, the 9-12 MPG cars are what opened the door for imports in the 70s when there were gas shortages and higher prices.
    dickday0 likes this.
  15. Now that I think about it, 12 is probably what I got on my '50 Studebaker. Back then, we really didn't worry about gas mileage too much. Gas was less then a quarter a gallon.
  16. My 1955 Thunderbird equipped with a 292 engine and a Fordomatic transmission weighs approximately 3,350 lbs. and the estimated fuel mileage is 13.1 mpg. Last year I drove it 1,200 miles (all city driving) and I got 12.7 mpg. Maybe its because the only fuel I use is 89 octane, 100% gasoline. Yes, the cost of the gasoline is expensive compared to what I use in my everyday cars, but you can't put a price on how driving down a winding road in a 1955 Thunderbird with the top down makes me feel!

    1955 Thunderbird Blue

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