Car getting real hot....
This is from the 1973 FSM. From left to right it’s the 198, 225, 318 and 340. It’s interesting that ALL the water pumps are over driven with the exception of the 318. The 318 is only overdriven with AC. I have no clue why that’s the way it is, but that’s what the FSM for 1973 says.
The AC cars had the pump driven faster than the non AC cars, but they are still 20% overdriven without AC.
And virtually ALL the aftermarket junk pulleys out there are UNDERdriven. I cobbled my stuff together with some CFV pulleys and I’m at a paltry 6% overdriven. And I have 4 hours of phone calls to get that.
What happened between 1968 and 1973? I can’t say. What I do know is they are overdriving the pumps. They damn sure were no longer worried about the coolant not staying in the block long enough. I see 7, 10, 20 and 30 percent overdriven water pumps on OE stuff. 1973 was low compression.
The water pump should be overdriven as much as the belts will stay on. The issue is finding pulleys to do that is a real beeeeeeeeeooooooootch.
It is interesting that March Performance told me they would make up a set of pulleys for whatever I wanted as long as they would physically fit. I just don’t want to invest any money in that when the vast majority of guys out there STILL believe this slow the coolant down crap. And March wasn’t interested in doing the work and adding a part number.
One other interesting tidbit occurred when I told the guy on the phone that I know for a fact with steel pulleys you can get 30% overdrive. He said I was crazy. So I sent his the above picture. His rough math said if that was true (and it is as anyone who can read can see) they could do 24-25% overdrive with aluminum pulleys.
Maybe if enough of us call and ask for overdrive pulleys they might make them. But that would require a massive change in the thought process of many folks.
BTW, if you overdrive the pump and you still want 195 degree engine coolant temperatures, just run a 195 degree thermostat. It’s what sets the MOT.
This is from the 1973 FSM. From left to right it’s the 198, 225, 318 and 340. It’s interesting that ALL the water pumps are over driven with the exception of the 318. The 318 is only overdriven with AC. I have no clue why that’s the way it is, but that’s what the FSM for 1973 says.
The AC cars had the pump driven faster than the non AC cars, but they are still 20% overdriven without AC.
And virtually ALL the aftermarket junk pulleys out there are UNDERdriven. I cobbled my stuff together with some CFV pulleys and I’m at a paltry 6% overdriven. And I have 4 hours of phone calls to get that.
What happened between 1968 and 1973? I can’t say. What I do know is they are overdriving the pumps. They damn sure were no longer worried about the coolant not staying in the block long enough. I see 7, 10, 20 and 30 percent overdriven water pumps on OE stuff. 1973 was low compression.
The water pump should be overdriven as much as the belts will stay on. The issue is finding pulleys to do that is a real beeeeeeeeeooooooootch.
It is interesting that March Performance told me they would make up a set of pulleys for whatever I wanted as long as they would physically fit. I just don’t want to invest any money in that when the vast majority of guys out there STILL believe this slow the coolant down crap. And March wasn’t interested in doing the work and adding a part number.
One other interesting tidbit occurred when I told the guy on the phone that I know for a fact with steel pulleys you can get 30% overdrive. He said I was crazy. So I sent his the above picture. His rough math said if that was true (and it is as anyone who can read can see) they could do 24-25% overdrive with aluminum pulleys.
Maybe if enough of us call and ask for overdrive pulleys they might make them. But that would require a massive change in the thought process of many folks.
BTW, if you overdrive the pump and you still want 195 degree engine coolant temperatures, just run a 195 degree thermostat. It’s what sets the MOT.
