Cadillac Big Block 425-500 Intake Flange


Includes one pair of intake flanges for the Big Block Cadillac 425, 472, 500 hot rod motor (see motor applications below).  These flanges are cut with a CNC HD (High Definition) Plasma cutter out of 3/8” Pickled and Oiled (P&O) steel.  P&O material is hot rolled steel that has been dipped in acid to remove the mill scale and then lightly coated with oil.  The end result is less work to clean off the mill scale as needed with hot rolled mild steel.


Motor Application:

Big Block Cadillac

            425 cu. in (1977-79)

            472 cu in (1968-74)

            500 cu in (1970-76)

            *more applications/years may work, verify before purchasing.


Ports designed to be used with 2” exhaust tubing.


In addition to the pair of flanges, you also receive 12 custom machined angled spacers from DOM tubing.  These spacers will allow the bolts to be threaded into the heads while allowing the bolt head to apply even pressure to the intake flange.  These spacers come loose, unwelded but can be tacked in place once you build the intake.  This listing does not include the metal to cover the lifter valley of the motor but can be easily fabricated using flat plate.


We are the only manufacturer of intake flanges for this motor.  Now you have the ability to build your own custom intake!


These flanges are designed in CAD and are test fit on an actual head to make sure proper fitment is achieved.

4 reviews for Cadillac Big Block 425-500 Intake Flange

  1. Steven (verified owner)

    There was an error in the tracking number given when the order was shipped, and so I couldn’t follow the order and I began to wonder if it had gotten lost, but once I brought it to Andy’s attention, he quickly corrected the error and I was able to track my order until it arrived. I did have to do a bit of filing on a couple of holes so that I could get the flange to bolt on easily. Not a big deal, though, as the flange was well made, 3/8″ thick, and perfectly flat. I would certainly order again if I needed something that HGHR sells.

  2. Al Molter (verified owner)

    I ordered online All good!

  3. jeff williams

    As per usual you came thru with great quality products and quick shipping.If there is a shortcoming it would be that I generally have to open up bolt slots a little bit with a die grinder, as the flame tapers so does the cut made. If you could open up the holes about .020 all the way around would be great and no grinding would be required. Would also like to see spacers available separately.

  4. jeff williams

    Have ordered 3 sets of intake flanges and 1 set of exhaust flanges for Cadillac 500. Excellent quality every time. Needed Holley carb flange,Mailed gasket for pattern,received flange in 2 days and my gasket was returned with it.Flange is now in catalog list.Thanks again for producing a quality part that I can depend on.

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