Header Flanges, Gaskets

1 3/4" OD Finished Header Flanges - 3/8" thick

1956-67 365-390-429" Cadillac

(Part Number 20202E38.)  Also available with 1 5/8" OD
Starter Tubes and flange thicknesses of 1/4", 5/16", and 3/8".
Starter Tubes are approximately 2" long.
(FYI:  The above Finished Header Flanges were made for a customer in Brisbane, Australia.)

1 3/4" OD Finished Header Flanges - 3/8" thick

1968-76 368-425-472-500" Cadillac

(Part Number 20210E38.)  Also available with 1 5/8", 1 7/8", and 2" OD
Starter Tubes and flange thicknesses of 1/4", 5/16", and 3/8".
Starter Tubes are approximately 2" long.

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).

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:  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 before, 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 1949-1964 Oldsmobile engines too - except that they have FIVE basic exhaust port/bolt pattern configurations!) 

NOTE 2:  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" hex head bolts.  ANOTHER THING:  Because the 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 hex head 7/16" thread bolts (which is why round Allen bolts have some advantage here).  Using Allen Bolts and/or denting the header tube to add more "wrench" room is one way of dealing with this problem.  Another way we've been told is having the heads reworked to accept 3/8" bolts instead of the 7/16" bolts - which then allows the use of standard smaller head header bolts.  If that is done, we can supply these flanges with 1/16" smaller bolt holes to match the smaller 3/8" bolts.  We have lowered the prices of the Finished Header Flanges and the Header Flange Kits due to the deletion of the header bolts.

NOTE 3:  When we designed the "North Star" Cadillac header flanges we decided to offer two different widths (actually flange heights) 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 taller/wider version (which, by being taller, is also more rigid!) covers an exhaust slot found on the later (2000 and up) 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.  (The "wider" version - unavailable elsewhere - is particularly desirable in turbocharged applications due to its greater rigidity.)

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.

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