Spark Plug Confusion

[Ernest]

When i first got the malibu, i decided to change the spark plugs, so when i pulled them, the previous owner(s) put in 41-993 units, figured that wasnt right, so i purchased a set of MR43LTS plugs that the ZZ4 engine actually called for.

Since then, i cant really recall before the change over, a pinging at mid throttle problem, i've been chasing my tail round and round trying to figure this one out, i finally got the ignition timing right, the carburator cleaned and tuned right, but the pinging issue persists unfortunately and i am running 93octane gas.

So if anyone here has any idea, why the wrong plug(41-993) running rich and the correct plug(mr43lts) running much leaner with the carburator(770SA) set as is, and i think i've finally narrowed the pinging down, the carburator needs to run richer, stock jets should be 72/pri and 75/sec out of the box, but i'll find out for sure after i do the rebuild on it and find out if any other changes were made prior. Most complaints from the line of street avenger carbs, they are setup lean from holley and im just finding about this now, but it came with the engine, so im working with what i've got because not looking to buy a different carburator, a waste of money it will be.

Thanks

 

[85442/86buick]

My 2 cents ,
what temperature thermostat are you running ? And what are you using for coolant...being in texas straight water ?

 

[Ernest]

Im not sure on the thermostat, i havent taken a peek yet, but the temp guage hovers between 160F and 170F at all times for now, and as for the coolant, its the GM orange 50/50 mix along with a 3row original copper/brass radiator and clutch fan.