I bought this manifold about 5 years ago right after I started on the dual quads I ended up using. If I went to the single I would use it.
You can see the casting has a ECZ-9425-B and not the 8425. There are holes for a choke heat tube but no other casting numbers or casting company or logo. It came as a complete kit. Bolts, washers, gaskets. I don’t remember where I bought it but it was on-line and I had to sign for it on receiving it. I thought it may have been a knock off of a Blue Thunder or one they made with their logo not cast.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

That's a Blue Thunder. The have the Ford casting number. Later ones also had the firing order. That's as good as you can get.

James.  That Blue Thunder intake manifold you have looks like the version III as the versions I and II had plenum slots in the divider.  I’d have to see the back of the manifold to determine if it could be a version IV as that version had some material removed from around the right rear side mounting boss to give more clearance for the MSD distributors.  The version V manifolds have the firing order on them similar to what is found on the factory ECZ-B manifolds.
 
Here’s the link to the magazine article that prompted Blue Thunder to remove the slot from the intake manifold plenum divider.
https://www.eatonbalancing.com/2014/11/23/intake-manifold-plenum-slots/ 
 
And here’s a picture of a version II BT intake being machined for the aforementioned additional MSD distributor clearance.
 

Lorena, Texas (South of Waco)

John.  That’s a ’57 supercharger intake manifold.  Not mine.  It was simply in the shop for some repair work.  Looks like a misprint on the part number as I thought most of those were EDB, not EBD.


What you are seeing as ‘8425’ on those intake manifold pictures I posted earlier is actually ‘9425’.  The ‘9’ has the lower loop closing up to the point it looks like an ‘8’.

Lorena, Texas (South of Waco)

Ted, here are the rear photos. I’m guessing revision IV by the machining. 2 questions.
I see the vacuum threaded boss has 2 holes one to each plenum feeds. What’s the correct use for this?
The choke machined hole is in the aluminum casting only not in the crossover exhaust chamber under it. Is the stock tube to be used or a tube stuck in the passenger side and another in the driver side to the carb top like original inside the air filter for clean air suction.
I wish I could remember what I paid for the manifold kit but my brain doesn’t function on things like that. I should have put the recipe in the box.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Those pictures help to confirm that your particular manifold is cast for use with the MSD distributor making it a version IV.  The version IV is the same as the version V except for the addition of the firing order on the version V.  There is a version VI in the works and more details on that when it happens.
 
That vacuum port at the back is used for the vacuum wipers.  It can be used for power brakes but is not a suitable vacuum source for a PCV valve.  A PCV valve vacuum source does need to be either at the base of the carburetor or at the carburetor spacer where the vacuum source is shared by all the cylinders and not just those at the back.
 
Those small 1/4" holes on each on the side of the manifold adjacent to the exhaust crossover passage for the choke does not require any additional work other than hooking up the air inlet filter on the left side and the small line on the right side to the carb choke pot.  The factory hardware works with those two holes.  Instead of using a metal tube to go through the exhaust crossover passage, there is additional aluminum cast into the manifold which simply has the necessary hole drilled through the aluminum that allows the air going through that hole to be preheated before arriving at the choke coil. By doing it this way, no metal tube is required and thus no deterioration of the tube over time.  If not using that passageway, it’s neither an exhaust or vacuum leak.  With most new carburetors being supplied with an electric choke, that particular passageway in the manifold is not used.
 
Rest assured that whatever price you gave for that manifold several years ago is now less than what they are being sold for now.

Lorena, Texas (South of Waco)

Thanks Ted. This the first aluminum aftermarket manifold I have ever owned that did not have a casting logo hidden for casting plant or a “brand”. Always seemed weird that this was not done.
I originally thought all aftermarket manifolds had brands but noticed on the BlueThunder website theirs do not.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Here's the newest version V of the BT with the firing order.  If my intake is indicative of all of the latest versions of the BT, then it is degrading a bit in average flow from previous years.  I have noticed at least 10 cfm average drop in flow from the version IV and V.  The version IVs that I have flowed were averaging ~278-279 cfm, and with porting, was able to get the worst port up to 312 cfm, but this version V average flow is 268 cfm, and the worst port(#6) I have only been able to get to flow 296 cfm.  Joe-JDC

JDC

Joe- did you dimple the IV also.
I’ve also wondered how much it helps with atomization and efficiency of a stock engine at cruising speeds. .

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Yes, I did dimple the earlier version, a Mummert, several FEs, SBFs, etc., after Ted proved on the dyno that the dimples help with torque and horsepower averages.  I think he did an article in Y Block with the results a few months ago.  Joe-JDC

JDC