Correct water pump

[pjm8047]

quick question. I’m going to replace my original 71 383 none ac water pump and I’ve seen a lot of water pumps online says fits big block Mopar’s but some have 8 blades and others have 6 blades. I haven’t removed it yet so I’m not sure what I needed.

 

[khryslerkid]

I've been useing the eight blade and no cooling problems at all. Pully size can make some difference, pump housings have minor differences, ect. Some pumps have slightly different blade designs also.

If I were you, and you haven't had any cooling problems, I would replace it with exactly what you have now.

 

[pjm8047]

Just checked service manual the difference is non ac has 8 blades and ac 6. Last line in pic.

 

[Ceedawg]

6 blade for ac since a smaller pulley is used, 8 for big pully. 8 on ac might give high speed cavitation

 

[Glenwood]

I had an 8 blade hv summit pump and it hardly flows at idle after the stat opens but flows well at higher rpms. I just changed it to a milodon hv pump with 6 blades which are longer. The flow at idle is much better.

 

[Montclaire]

6 blade for ac since a smaller pulley is used, 8 for big pully. 8 on ac might give high speed cavitation

Do you know the diameter for each pulley? They were matched per application. Since I already have the pulley I'm going to let that dictate how many blades I go with. Thanks

 

[Montclaire]

I'm reading the smaller should be 5 7/8?

 

[Canadian1968]

Went threw this over the summer. There is a post on DC.com . The 8 is supposed to be for non ac and 6 for AC.

Majority of the aftermarket are 6 blade but fin shape is different and they have a plate welded to the back of the fins that none of the OEM have. I do belive this supposed to help increase flow. One thing I noticed is that I would say 80% of after market are identical with different names on them . I went Proform aluminum hI flow from summit advertised as "mopar authentic."

Another member posted up one that he got off rockauto for 30 bucks or something like that . It is IDENTICAL to the one I have and paid almsost 100 dollars more . If I had to do it again I would get one from my local napa that has 8 blades for 60 bucks .

 

[JerseyJoe]

I took a $32 GMB (Japan) pump and welded the anti-cavitation plate on it. I also have a Flowkooler and it's the identical pump with their impeller on it. A little OT but I agree with KID if he has no other issues I would stick with what he's got.

 

[RJRENTON]

6 blade for ac since a smaller pulley is used, 8 for big pully. 8 on ac might give high speed cavitation

True, the 6 blade impeller used with the A/C application uses a smaller drive sheave, but the purpose was to increase circulated coolant, more GPMs at a higher velocity to improve heat transfer characteristics.
IMO....cavitation will not be a problem, as the entire system is under pressure, as the system pressure will negate the pump's suction pressure losses. Its the pump's suction pressure losses causes cavitation in the first place. In addition, the circulation (and pumping losses) is influenced by the composition of the coolant being pumped. Most, if not all, commercially available coolant compounds have a "anti-foam" additive to inhibit cavitation.
BOB RENTON

 

[Mopar Hunter]

I took this picture off another forum, the 6 blade looks like it runs the opposite way. Is that true?

 

[Montclaire]

I have a 440 in a 74 Barracuda with a 22" radiator (non-AC car). My concern is that with less surface area, faster transit through the core may not be a good thing. Mopar was using different pulleys and pumps for a reason. If the 8 blade and larger pulley was their answer on a non-AC car, that is what I'll stick with. The NAPA unit looks pretty good to me.

 

[BLK 68 R/T]

I took this picture off another forum, the 6 blade looks like it runs the opposite way. Is that true?

View attachment 1026874 View attachment 1026875

When installed in a standard application from 66-74, ac and non ac car water pumps all turn in the same direction (as far as I’m aware.) I think some marine applications were reverse rotation.

 

[RJRENTON]

I have a 440 in a 74 Barracuda with a 22" radiator (non-AC car). My concern is that with less surface area, faster transit through the core may not be a good thing. Mopar was using different pulleys and pumps for a reason. If the 8 blade and larger pulley was their answer on a non-AC car, that is what I'll stick with. The NAPA unit looks pretty good to me.

Incorrect assumption.... Thermodynamics states that the faster the heat transfer media moves (gpm and velocity) the more heat is transferred. Every one assumes the heat is transferred in the radiator but the other half of the equation is the heat source....the engine. There is more surface area in the engine to absorb heat than in the radiator to dissipate the heat generated, therefore the faster the exchange takes place, the more heat is transferred. Ideally, if the surface areas are equal, the heat absorbed and subsequently released could be equalized, but they are not, so the velocity and guantity of the heat exchange media must be increased to maximize the heat transfer rate...... Investigate the equation: Q (heat) = M (mass or mass flow) x Cp (specific heat [ability to absorb and release heat in a given amount of time ] of the heat transfer fluid) x delta T (temperature differences) for a better understanding. If your application is running "hot" consider up sizing the radiator to increase the surface area. Just my opinion of course.
BOB RENTON

 

[Montclaire]

I politely disagree.

 

[RJRENTON]

I politely disagree.

Thank you for your comment.....but....Please state your reasons/objections to the premise or better yet, your sample calculations, to demonstrate your point(s). ....."Inquiring minds want to know"....
BOB RENTON

 

[Montclaire]

I already graduated, thanks.

 

[RJRENTON]

I already graduated, thanks.

What school did you graduate from ..... PSU...or one of the branch campuses ....or perhaps Penn, or Drexel or Univ of Pgh or ???. What was your major??? Mechanical Engineering or ?? I did PSU + Pitt..... "Inquiring minds want to know".....
BOB RENTON

 

[Montclaire]

Anyone else have something productive to add? Thanks

 

[DAVID TEMPEST]

Incorrect assumption.... Thermodynamics states that the faster the heat transfer media moves (gpm and velocity) the more heat is transferred. Every one assumes the heat is transferred in the radiator but the other half of the equation is the heat source....the engine. There is more surface area in the engine to absorb heat than in the radiator to dissipate the heat generated, therefore the faster the exchange takes place, the more heat is transferred. Ideally, if the surface areas are equal, the heat absorbed and subsequently released could be equalized, but they are not, so the velocity and guantity of the heat exchange media must be increased to maximize the heat transfer rate...... Investigate the equation: Q (heat) = M (mass or mass flow) x Cp (specific heat [ability to absorb and release heat in a given amount of time ] of the heat transfer fluid) x delta T (temperature differences) for a better understanding. If your application is running "hot" consider up sizing the radiator to increase the surface area. Just my opinion of course.
BOB RENTON

Bob,
I bought a 68 Roadrunner with 440, three years ago. Previous owner set it up for the track. It has always ran hot in the summer. The fan blade is 18" without a shroud. I added a 16" electric fan on the inlet side with no improvement. I wanted to check the thermostat and was dumbfounded to find there wasn't one! I put in a high flow 180 deg thermostat. Still hits 220 deg when ambient temp is only 80. The radiator is 21" with significant amount of smashed fins. Should I replace with a larger 26" with premounted dual fans? Thank you in advance for any help.
David Tempest