OP stated OBD I. I’m sure these behave differently.
But - to figure this out , You would have to monitor real time w a scan tool. - Something will be out of whack. If not, something the old OBD I doesn’t monitor.
I flushed my dirty *** cooling system and put in a 180* thermostat. Mistake. These are looking for 195 or they are in open loop mode- like the choke is on.
Even had black smoke out the exhaust. -
No code. - had to monitor w tool while running to figure it out.
Stk magnum gasket will work good but are thick. Magnum gaskets are cut to hold push rods in place. You can use LA gaskets and pay attention during assembly. LAs come in all thickness and material flavors.