1968 GT500 exhaust valve

[68blk500c]

I feel it was appropriate to begin this new topic instead of continuing:

SAAC Forum► The Cars► 1968 Shelby GT350/500/500KR► 428 PI Exhaust Manifold Question

Not only is it my long-time /observation/experience that original 1968 GT500s are equipped with the exhaust "flapper" control valve on the RH exhaust manifold of the 428 PI, the part is clearly supported by Shelby documentation.

 

[Lincoln tech]

You are talking about a "heat riser"?  Exhaust valve usually sits in cylinder head.

[68blk500c]

The Ford Master Parts Catalog calls it "Exhaust Control Valve".  aka informally as "flapper".  No, not what you are talking about.

While we are mentioning the MPC, the original/factory installed part is C7ZE-9A427-B.  Those were cast with C7ZZ stamping. 
The MPC lists a service replacement of C6OZ-9A427-D for F body (flapper style). 
The MPC does list a "spacer" solid version (non-flapper) as C7OZ-9A427-B, however this spacer is designated for Fairlane (B body) only, not Mustang (F body).

 

[Bob Gaines]

I am in agreement with my esteemed colleague.

[Royce Peterson]

The valve is listed in the Lincoln Mercury parts catalog as being applicable after January 4, 1968 P/N C6OZ-9A427-D. Curiously, the same chart lists the spacer for the 428PI application as C6AZ-9A427-B before 11/15/68. The spacer meanwhile is listed as P/N C8AZ-9A427-B (390, 428 exc P/C).

[Royce Peterson]

You are talking about a "heat riser"?  Exhaust valve usually sits in cylinder head.

The description calls it an "Exhaust Control Valve".

[68blk500c]

Royce, the PI or P/C application listed in the Mercury MPC would be for just that: a big body police car.  However, the Cougar 390GT and Comet 390GT should share the same exhaust valve as the Mustang/Shelby.

Correction:  Comet would share Fairlane application.  Cougar would share Mustang/Shelby.

This exhaust control valve had different applications using different designs other than for this topic.  Examples:
Galaxy, T-bird, even trucks, as well as Lincoln; same function, but different design for their application.

[Royce Peterson]

Royce, the PI or P/C application listed in the Mercury MPC would be for just that: a big body police car.  However, the Cougar 390GT and Comet 390GT should share the same exhaust valve as the Mustang/Shelby.

Correction:  Comet would share Fairlane application.  Cougar would share Mustang/Shelby.

This exhaust control valve had different applications using different designs other than for this topic.  Examples:
Galaxy, T-bird, even trucks, as well as Lincoln; same function, but different design for their application.

Pretty sure for 1967 model year all of them would share the same exhaust manifolds. The Comet / Fairlane / Mustang / Cougar all used the exact same manifolds in 1967 for the 390 and in the case of the Shelby, for the 428 as well. I do not believe the spacer was available in 1967 model year, being a C8 part number.

[68blk500c]

You are correct about the exhaust manifolds, however we are talking about the control valve/flapper, here, and it being original/factory/delivered on 1968 GT500 cars.

I wasn't fortunate enough to own a '68 GT500 when new, but I suspect this part, the exhaust flapper, was a nuisance part.  Springs probably got weak or broken, which caused noise.  The functional benefit was negligible.  It possibly was the source of exhaust leaks.  They got removed and discarded with most exhaust work.  Service departments probably chose the spacer alternative.

All of this boils down to--not many cars remained with their original valve/flapper.  I have noticed some highly original, unrestored '68 GT500s that have this part.  Those cars and the SA parts/assembly documentation cause me to strongly believe that it should be considered when concours judging.

   

[Bob Gaines]

You are correct about the exhaust manifolds, however we are talking about the control valve/flapper, here, and it being original/factory/delivered on 1968 GT500 cars.

I wasn't fortunate enough to own a '68 GT500 when new, but I suspect this part, the exhaust flapper, was a nuisance part.  Springs probably got weak or broken, which caused noise.  The functional benefit was negligible.  It possibly was the source of exhaust leaks.  They got removed and discarded with most exhaust work.  Service departments probably chose the spacer alternative.

All of this boils down to--not many cars remained with their original valve/flapper.  I have noticed some highly original, unrestored '68 GT500s that have this part.  Those cars and the SA parts/assembly documentation cause me to strongly believe that it should be considered when concours judging.

   

To reinforce what was said, back in the day when new exhaust was needed most shops fabricated the exhaust out of stock from pattern cards so as not to have to have inventory for a multitude of different make cars on hand. It was easy to make a H pipe that didn't require the spacer in place. I wasn't a owner from new but can remember having one done that way without the valve and locked up flapper in 1973.

[68blk500c]

Adding photo of original C7Z cast part to this topic.

[kendricks]

My money is that it's out of a FE engine....

When I rebuilt engines for a living back in the late 70's, every 391 truck engine that came in the shop had these suckers in them.....We did the engine work for the trucks and buses at Yosemite Nat'l Park...

If the stem diameter is 3/8", dollars to donuts it's FE....

As far as part numbers go, I'll bet there's a VMF'er who worked as a parts guy in a past life and has all the old parts books. Alas, all I have is 25 year old speed equipment catalogs...*G*

[Coralsnake]

Thanks for your input. The discussion is related to a very specific application of the part, not a general discussion.

I can also assure you there are people in this forum that are extremely aware of the resources used to identify parts and assembly procedures.



 

[TA Coupe]

Thanks for your input. The discussion is related to a very specific application of the part, not a general discussion.

I can also assure you there are people in this forum that are extremely aware of the resources used to identify parts and assembly procedures.



 

I think Kendrick's was just trying to be helpful,So no need to try and make him feel bad with your superior knowledge. I'm sure you didn't know everything as a newbie either.

    Roy

[Coralsnake]

You are mischaracterizing my post. I dont claim to know the answer.

I'm fine with everyones contributions.

I also dont think this forum needs to defer to VMF for any knowledge about Shelbys

I didnt see a similar post from you  regarding comments other members made on his other postings. Maybe I missed that?