Hi all, I have a 1955 T-Bird with a 57 312. The exhaust manifolds however are set up as stock with the passenger side being from a Fairlane with a 6 3/4” outside diameter and the left side the typical 312 manifold with a 7 3/4” OD. The engine runs great but I’m wondering if It would be worth the effort to replace the right side passenger car manifold with a correct 57 312 manifold. The next time I take the car out I intend to take the temperature of both sides, I’m thinking the right side will be hotter but that’s yet to be determined. Any thoughts?

1955 312 T-Bird Warwick, NY

As I'm sure you know, the passenger side 55-56-57 Thunderbird exhaust manifold is the same as a passenger car.  The driver's side Thunderbird exhaust manifold is unique to the TBird.   It tuns down at a different angle.  My 55 Tbird is running 1957 TBird exhaust manifolds.  They are slightly bigger than the stock 55 manifolds.  I am sure there is a performance gain with the 57 manifolds, but I'm not sure if it would be noticeable.  The passenger side manifold is easy to find. I believe reproductions are available.

Here's the link to Ted's exhaust test.

http://forums.y-blocksforever.com/Topic55379.aspx

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Thanks for the link.  Ted's test shows a peak increase of 5 hp and 3 foot pounds of torque when switching from 55 to 57 manifolds.  That is an increase, but not as much as I would have thought. I have considered headers, but I'm trying to keep my car period for the sixties.  Headers were not something I could have afforded back then.  On the other hand, I couldn't have owned a TBird either. 

Miker / Phil thank you for your feedback and the great chart. It’s gratifying to know there are folks out there who share my passion for the YBlock V8. Back in the day the 312 was the engine my friends and I coveted and today it’s easy to understand why. I had an Isky 3/4 cam installed when the motor was rebuilt in 1985, I wish I knew the degrees of the grind. It comes alive in second at 11 to 1200 RPM, the low - mid range TQ puts a grin on my face every time. It’s crying for a 5 speed but I love my T86 OD too much. Do you know if the 55 left manifold was carried on from 55 to 57 in the 292/312 or if it was recast with different dimensions unique to 57.

1955 312 T-Bird Warwick, NY

If you have a few tools, you can improve your existing exhaust manifolds flow and save some money.  Here is what I did to two sets of manifolds for my '55 T-bird.  I use a die grinder and 6" diamond cut flame shaped carbide to open up the ports to match the Fel-Pro exhaust gasket, and then used 8" mandrel and cartridge rolls to polish the interior of the manifolds as much as possible.  I then used a large 1" ball stone rough grit to open up the flange to 2-1/4" or so on both manifolds.  A little elbow grease and time, but the results are worth it to me.  Just an idea if you have the resources.  Joe-JDC

JDC

Nice work Joe, thanks for the info.

1955 312 T-Bird Warwick, NY

It sounds like your car is set up much like mine.  My first hot rod was a 57 Ford Custom.  Every time I drive my TBird it transports me back in time.  My wife likes it because it a convertible.  I like my Y-block engine and O/D transmission.  The '57 exhaust manifolds are unique with their own casting number.  The '57 driver's side TBird exhaust manifold is harder to find. 

The two best things I did to mine was - after getting a '57 sized flat top passenger manifold:
(1) Did away with the right side "warm-up" butterfly completely (had it wired open before). Now a free, open cylindrical spacer. 
(2)  Sent the two manifolds away to be "ceramic coated" at JetHot in Tempe, AZ. They will blast them inside and out to get a fresh surface - then coat them completely. The process lowered the observed external temperature of the manifolds by a couple of hundred degrees - and under the hood of a Thunderbird it is a very obvious difference. I got them finished in "aluminum" - but they offered to use a cast iron grey color that wouldn't be too noticeable if the car was a restoration queen.

 
 Steve Metzger       Tucson, Arizona

Hi Steve, anything to reduce the engine compartment temp has my interest: any chance you could upload a photo of the finish on the exterior of the manifold?

Best Regards

1955 312 T-Bird Warwick, NY