Big Block Exhaust Manifold Comparison
by George Nenadovich
The top manifold is from a 67 Electra 225 with a Buick 430.
The bottom manifold is from a 1972 Electra with a 455. The 67 manifold appeared
only in 1967. The 1968-76 manifolds are the same. The arrows indicate the
major differences in the two manifolds. The 67 has about a 2" runner
for #7 cylinder while the 68-76 version are only about 1.5". The 67
manifold is about 10-15% more efficient. We will have a dyno test comparing
the two exhaust manifolds to determine a difference in torque and horsepower.
Also, notice the 67 doesn't have a circular donut for the
exhaust pipe to connect to since the 67 cars had a heat-riser which had
the donut on it. So, you will need to have an exhaust shop make an adapter
for you or use a composite donut to seal the pipe to the manifold.
Here is a back side comparison of the two manifolds. The
67, bottom, is shaped more like a header.
Dyno Results Comparing
1968-76 455 to 1967 430 Driver's Exh. Manifold
Results from a 455 w/open plenum intake, 800 cfm carb, MAXI
3 cam
Engine Stock 455 Ported 455 Ported 1967
RPM HP TQ HP TQ HP TQ
3000 275.3 482 275.8 482.8 274.4 480.3
3250 304 491.2 306.3 494.9 304.1 491.5
3500 340.5 511 339.7 509.7 339.5 509.4
3750 369.1 516.9 369.6 517.6 369.4 517.3
4000 394.1 517.4 395 518.6 397.3 521.7
4250 415.6 513.6 420.4 519.5 421.4 520.8
4500 430.6 502.6 434.1 506.6 437.5 510.6
4750 443.3 490.1 449.2 496.7 454.7 502.8
5000 450.7 473.3 457.3 480.3 460.4 483.6
5250 446.9 447.1 456.4 456.6 460.9 461.1
5500 457.3 436.7 461 440.2 466.2 445.2
5750 464.8 424.5 469.2 428.6
6000 457.7 400.6