Originally Posted by red82c10
I will be using some 1987 swirl port center bolt heads on a 70s block with a Quadrajet carb and I'm wondering which heat range of spark plug to use.
The 70s carb 350 and a 1987 fuel injected 350 use different plugs.
Use the TBI plug. The Swirl Ports, if this is the 193 head with 64 cc chambers, will raise your compression thus the heat in the chamber. How the fuel gets dumped into the air is largely a moot point compared to the need of the plug to deal with chamber heat. This is a starting point once you get some use on them you may find it necessary to fine tune the heat range, but this will get you started safely.