The Edelbrock Performer is...
The Edelbrock Performer is generally considered a stock-replacement unit, and we see here the effects it has on Shaker positioning when installed and a carburetor mounted atop it. A stock paper gasket was used between the manifold and carburetor on all the comparisons, so a carburetor spacer at least half an inch thick may be an option to restore height in this instance.
Though we planned to limit...
Though we planned to limit our comparison to only those manifolds that are compatible with Quadrajet carburetors, we had an Edelbrock Torker II handy and decided to compare its dimensions with the H.O. We found that it's roughly 11/42 inch taller than an original and biases the carburetor approximately 11/48 inch forward. It does, however, accept only the square-bore (Holley) type of carburetor, which in itself limits its use with an original Shaker assembly. This unit has had its coolant and exhaust crossovers removed by the owner.
Pontiac used two different...
Pontiac used two different rear A/C-compressor brackets during the '70s. The bracket used from 1973 forward (shown on top of the other) contains a revised front mounting-bolt location, which was likely required to provide sufficient clearance for the EGR valve added that year. All the aftermarket manifolds in our comparison accept this later bracket.
|Approximate Aftermarket Intake Manifold Carburetor Placement As Compared With An Original |
|Manifold ||Point A ||Point B ||Point C |
|Edelbrock Performer ||1/2 inch taller ||1/4 inch shorter ||1/4 inch rearward bia |
|Edelbrock Performer RPM ||1-3/16 inches taller ||1-inch taller ||Zero bias |
|Edelbrock Torker ||1/2 inch taller ||1/4 inch taller ||3/4 inch rearward bia |
|Holley Street Dominator ||1/4 inch taller ||1/4 inch taller ||1/4 inch rearward bias |
Here is a Performer RPM mocked...
Here is a Performer RPM mocked up for measuring.
During our physical comparison, we also explored the different types of installation hardware, such as the throttle- and air-conditioning-compressor brackets that each casting accepted. We learned that the Holley manifold uses only the throttle bracket found on Pontiacs from '75 forward. The Edelbrock castings, however, are designed to accept a '72-'74 throttle bracket, while the later bracket can be used if combined with the Edelbrock-supplied adapter. All the subject manifolds utilize the standard rear A/C bracket found on all Pontiacs from '73 forward. Since the various castings accept a few types of chokes, converting the Quadrajet to an electric choke coil may be a better option to minimize installation issues if a choke is desired.
|Manifold ||Throttle Bracket ||Rear A/C Bracket |
|Edelbrock Performer ||'72-'74 ||Late |
|Edelbrock Performer RPM ||'72-'74 ||Late |
|Edelbrock Torker ||'72-'74 ||Late |
|Holley Street Dominator ||'75 forward ||Late |