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1965 to Present
4.84" Bore Spacing
5.0" Bore Spacing

DRCE (Oldsmobile)
4.84" Bore Spacing
DRCE II (Oldsmobile)
4.9" Bore Spacing
Edelbrock
Perf. RPM Olds
DRCE (Oldsmobile)
4.84" Bore Spacing
DRCE II (Oldsmobile)
4.9" Bore Spacing
4.6 Northstar
4.3 V.6

GM 18 degree V6
Stage II Buick V6
4.5L NASAR GN
Not For Use with OEM Stock Heads
GMC
1939 – 1962:
228-302 cid.
Atlas LL8
Vortec 4200
2002-up Trailblazer
GM Racing L6
Falconer L6
Edelbrock
Perf. RPM Pontiac
Gen I 55-02
Gen II LT-1 & LT-4
ZZ & Fast Burn
Gen III LS Series
Stahl
Adaptor Pattern
Stahl Spread-Port
Adaptor Pattern
Hooker
Adaptor Pattern
Alan Johnson
GM Performance Splayed Valve
Splayed Valve Adaptor
Little Chief
GM 18 Degree
Reher-Morrison
Adaptor Pattern
Not Available
SB2
R07

Not Available

Alan Johnson Splayed Valve
C821xx
CFE SBX
C840xx
Brodix BD Series
GM Performance R0X 4.5 Bore Center
C8152xx
Assassin
4.5 Bore Center
C845xx
Buick/Dart
Splayed Valve
For use on SBC
Not for use on Buick
SAP counterbored
Round
Round counterbored Oversized
SAP counterbored Oversized
Normally we recommend slipping the primary tube through the flange and weld it to the head side of the flange allowing the thickness of the flange to reduce the sheer load on the weld. On some applications counterboring is only the way to utillize an oversize tube with the available sealing surface on the head. The flanges are machined .150" deep to support the tube and allow the tube to be welded to the inside of the flange.
Many aftermarket heads are advertised as Raised Exhaust Ports. In most cases the ports and bolt pattern are shifted higher together. We refer to a design as "Raised Port " when it is revised with the exhaust ports shifted higher on the bolt pattern (as shown in the illustration above.
Ecotec 2.0-2.2-2.4
SPD Precision CNC Machined Flanges are available 3/8 or 1/2 inch thick in 1018 cold rolled steel or 304 stainless steel.
(Other thicknesses and materials can be special ordered).
Use the application buttons on the left to find the correct bolt pattern for your heads. Then use the associated link download the PDF with all of the flanges available with that specific bolt pattern.

In an effort to keep up with cyl. head manufacturers and CNC porting services, we are continually adding new appication to our line of flanges. If you don't find what your looking for give us a call or send us a rubbing.