Header Flanges, Gaskets

  Finished & Plain Header Flanges, Gaskets.



AMC, Studebaker, Jaguar DOHC 6, Packard, Allison V12 - Finished Header Flanges, Plain Header Flanges, Header Gaskets


Under Construction


We are still working on this page (it is based on the Oldsmobile page).  We have Finished and Plain header flanges (and gaskets for the later engines) for the early 56-65 250-287-327 AMC V8 with shared center ports as well as the later 66-74 290-304-343-360-390-401 AMC V8 with EITHER rectangular or Dog-leg shaped exhaust ports.  Please call if interested.  All flanges are available in a number of port sizes and three thicknesses - 1/4", 5/16", and 3/8".



Engine Series:

There are quite a few Mild Steel header flange designs to pick from on this page.  In fact, so many choices that the selection process might be confusing and may be even disturbing. Don't worry about this.  Once you figure out the basics of what you want to accomplish and are ready to place an order, we'll help you select the best header flange design for your headers.
(Stainless Steel header flanges
are not available at this time.)


215 Oldsmobile Header Flanges

1 1/2" OD Finished Header Flanges

1961-63 215" Oldsmobile

(Part Number 20405C38).  Also available with 1 1/4", 1 3/8" and 1 5/8" OD
Starter Tubes and flange thicknesses of 1/4", 5/16", and 3/8".
Start Tubes are approximately 2" long.




FINISHED Header Flanges (part numbers start with 20) are Plain Header Flanges that have 2" long tubes custom formed into the ports in the header flange and then TIG (not MIG) welded.  The header flange is then ground FLAT to remove any weld beads protruding above the gasket surface plus the ports are internally deburred to remove any weld beads that may remain inside the port.  (There are a few tube size and port size combinations that require longer than 2" tubes but these are quite rare.)  Header Bolts are included.
We call these flanges FINISHED because they come to you with all forming and grinding operations FINISHED.  All you have to do is bolt them to the cylinder heads and start to build the header from the end of the tubes.  Note that the formed area in the tubes is usually less than half of their length so they can be trimmed considerably to make the headers narrower near the head.

PLAIN Header Flanges
(part numbers start with 25) are simply that - NO starter tubes, NO other work performed. NO header bolts.

(part numbers start with 22) include Plain Header Flanges, Formed Starter Tubes, and Header Bolts.  These are only available for a limited number of tube and port size combinations. 
We see other companies intentionally leaving partially ground weld beads ABOVE the header flanges' gasket sealing area and saying that this IMPROVES gasket sealing by having these raised areas dig into the gasket.  BUT, we've seen these weld beads end up acting as pivot points that cause the header flange to bend.  (As you tighten the header bolts on one side of the remaining weld bead - exerting pressure to pull the header flange IN towards the gasket, the flange on the other side of the weld bead tries to pivot on those welds - tries to move OUT - reducing pressure on the gasket in the process - sometimes actually CREATING a gasket sealing/leakage problem!)  Their way of grinding a flange is much faster as they only grind off the TOPS of the weld beads.  Our way of grinding is MUCH SLOWER (BUT also MUCH BETTER) as we not only remove ALL of the weld bead above the gasket surface (eliminating any "pivot weld beads"), we also grind FLAT the ENTIRE GASKET SURFACE of the header flange to MAXIMIZE gasket sealing area!


NOTE:  Bypass going to the Home page (which is slow to load) by going directly back to the Header Kits page (or any of the other pages/areas listed above).

Header KitsFinished
Header Flanges
Header Flanges
Header Flanges w/Starter TubesHeader GasketsNotesNote

(Look at the bottom
area for more
Engine Description -
Cubic Inch Range
Flange Port Size1, Description
Photo?Photo?Flange Design Comments
  49-53 303"    123456789A123456789B123456789C1234567123456789A12345678
 49-51 Cadillac
 1 5/8", Square
20200D$314.50125200D$146.951------------------------ 1,2Head has one center port for two cylinders.
  When ordering, double check you have the correct heads!
 52-55 Cadillac
 1 3/4", Square
20201E$314.50125101E$146.951------------------------ 1,2Head has one center port for two cylinders.
  When ordering, double check you have the correct heads!
 68-81 Cadillac
 1 3/4", Rectangular
 "North Star" Cadillac
 Before 2000
 1 1/2", Round
20220C$290.50125220C$146.951------------------------3Uses 8mm header bolts which are very hard to find.  Order extras?
   Narrower design than the 20221 series (more universal).
 "North Star" Cadillac
 2000 & later
 1 7/8", Round
20221F$290.50125221F$146.951------------------------3Uses 8mm header bolts which are very hard to find.  Order extras?
  Wider design that covers exhaust slot above ports.
123456789A12345678Header Flange Design Comments and Explanations.123456789A12345678


CUSTOM HEADER FLANGES:  While the above Header Flange Listing is quite comprehensive, because we do so much CUSTOM designing in this area, one must understand that we offer much more.  Based on already existing header flange patterns, over the years we have made header flanges:  (1)  WITHOUT PORTS for customers using the header flanges to seal the exhaust side of the motor or customers machining the exhaust ports in the flanges to match a reshaped/relocated exhaust port;  (2)  WITHOUT BOLT HOLES because the customer wanted to drill the bolt holes themselves so as to locate the ports in the flange relative to the ports in the cylinder head a certain way;  (3)  WITH SMALLER than normal exhaust ports because the flanges were going to be used as SPACERS (between a header and a head) to add clearance to a starter, oil filter, etc.;  (4)  in Finished Header Flanges, WITH PORTS LARGER than normal relative to a tube size so that a smaller tube size header could be built but with a full size exhaust port in the header flange (one that does NOT block exhaust flow out of the head); etc.  In some cases these design revisions are done at no charge but where custom drilling is performed (some movement of the bolt pattern relative to the standard location), there is a $15-25 extra charge for the time involved.  Where only ONE flange is desired out of a set of two, we charge 75% of the pair price due to the setup time involved just to make the first flange.  We do NOT make PURE custom header flanges (i.e. one of a kind designs where only one or two pieces are needed) due to the development time involved.  Header Flanges are made from Mild Steel Plate - NOT available in Stainless Steel.



1 Port Size:  ROUND PORTS:  This is the Inside Diameter of the ports in the header flange measured in inches.  ON ALL OTHER PORT SHAPES:  This is the OD of the header tube measured in inches that, when reshaped, would fit into this port size.  In other words, this dimension does not truly relate to the size of the port  in the header flange but more relates to the tube size specified AFTER being reshaped to approximately match the port in the flange.  Keep in mind that we make many header flanges with several choices of port sizes.  We usually ship the flanges that match the cylinder head port AND the tube size being used as closely as possible.  There are reasons to NOT always ship the best match to the cylinder head port but that is usually due to customer requests or specific needs.  We always ask about this because we see no sense in blocking the exhaust port unless there is a good reason to do so.

To make header building MUCH easier, we supply the header flange with ports (those shaped other than round) sized about 1/16-1/8" oversize from a perfect match so that the tubes do NOT have to be shaped perfectly to be inserted into the port.  Port Shapes:

RD = Round,

OV = Oval,

RE = Rectangular,

SQ = Square,

DD = D-shaped port with flat on bottom in most cases,

SAP = Same Shape(s) As Port(s) in head.

NA = Not Available or Not Applicable

2 Header Flanges are priced as a set which means V8 and V6 sets have two flanges (one for each head). Most other engines have just one flange in a set. There are several exceptions to these rules but, where applicable, they are all noted.  Unless specifically mentioned otherwise, all header flanges are 1/4" thick. If you would like thicker header flanges, add $16.00 for 5/16" or $24.00 for 3/8".  All thicker header flanges are made to order and delay header parts shipments about 3-5 days.   

Made to order Header Flanges are NOT returnable.

3 Finished Header Flanges and Header Flanges w/Starter Tubes are shipped with a complete set of header bolts.

NOTE 1:  These engines used 7/16" bolts for the exhaust manifolds.  We cannot find 7/16" thread header bolts so you will have to either source these yourself or use 7/16" Allen bolts or regular 7/16" bolts.  Because the two bolts on each side of the center port are very close to the exhaust tube coming out of the flange, there is minimal room to get a wrench on these bolts (which is why Allen bolts have some advantage here).  Using Allen Bolts and/or denting the header tube to add more "wrench" room seems to be the only way of dealing with this problem.

NOTE 2:  When ordering these header flanges, be ABSOLUTELY sure you have the heads you think you have.  Every so often somebody buys an engine out of a salvage yard and doesn't realize that, at some earlier date - maybe 20-30 years ago, somebody swapped heads.  Since there are three basic exhaust side versions in these early Cadillac engines, the header flanges are not really interchangeable!  If you order the WRONG flanges, you can't send them back when you find out that they don't fit.  Either send us a tracing of the exhaust ports, bolt holes, and exhaust surfaces surrounding the exhaust port so we can check the tracing against our header flanges or buy exhaust gaskets or an engine gasket set for your engine to double check your heads.  (This happens with the earlier Oldsmobile engines too!) 

NOTE 3:  When we designed the "North Star" Cadillac header flanges we decided to offer two different widths to deal with the differences seen on the exhaust side of these two cylinder head versions.  The narrower version will fit all of the heads but the wider version covers an exhaust slot found on the later heads and, therefore, creates a much more attractive appearance.  Because of machining differences in the two different heads, the wider flange will NOT fit the earlier heads.

HEADER FLANGE DESIGN DISCLAIMER: On ANY header flange made to match ANY performance/racing factory/aftermarket cylinder head, due to the fact that the manufacturer - at any time and without notice, might reshape and/or relocate exhaust ports and/or relocate spark plugs and/or change the angle of the spark plugs - we can NO LONGER guarantee port alignment nor spark plug socket clearance. If you are using ANY of these "non-production" heads (or have ported heads) and are concerned with possible port misalignment, we will select the best possible header flange to match your exhaust ports IF you send us a tracing of all ports, bolt holes, and surrounding machined edges.  (Note that FAXing is not often accurate enough for our needs.)  There is a $10.00 labor charge (no discount) for comparing tracings to current flange designs.  There is also a custom flange drilling charge of $15.00 when it becomes necessary to relocate the bolt pattern to align ports to the port tracings as accurately as possible - and NOTE that custom drilled header flanges are NOT returnable!  Otherwise, should port misalignments occur, grind flange ports where needed. If spark plug or spark plug socket interference occurs, then modify flange as needed.