Weird ? about small block pulleys

[Dartvader440gt]

So my 360 swap is coming along. I don't know if this sounds dumb but I have a couple of different size crank pulleys. I believe the larger diameter came off the 360 and the smaller one from a 318. Is there an advantage from one over the other? My 360 is basically stock except for an aluminum intake, 4 barrel and headers. The cam is the basic towing spec cam for more torque. I'm just curious as to what pulley is better.

 

[4spdragtop]

360 balancer will most likely be externally balanced and cant be used with neutral balanced 318

 

[Dartvader440gt]

I'm just talking about the pulleys for the belts. I also have 2 different sizes for the fan pulley also.

 

[Dana67Dart]

If the water pump pulley is ( just a number) 6 inch dia and the crank pulley is also 6 inches in dia then you water pump will be one to one. If the crank pulley is larger dia than the water pump will be over driven by an amount. If the crank pulley is smaller than 6 inches the water pump will be under driven.


As for the alternator a 2.5" dia pulley to 3" with a 6 inch crank pulley it will charge ok.


So what size pulley combinations do you have?

And do they line up properly?

 

[4spdragtop]

I would get all the pulleys from the same engine.

 

[Dartvader440gt]

I would get all the pulleys from the same engine.

Easier said than done. Water pump pulley was MIA. I just have a few extras hanging around my parts piles.

 

[RustyRatRod]

If you have a pair where the water pump pulley is the smaller of the two, that's the pair I would run. You want the water pump turning a little faster for good pump circulation.

 

[CFD244]

If you have a pair where the water pump pulley is the smaller of the two, that's the pair I would run. You want the water pump turning a little faster for good pump circulation.

........And the appropriate impeller size and design in the WP for the overdriven application.

 

[rklein383]

These guys have a good selection of pulleys. Products: Pulleys - Bouchillon Performance Engineering

 

[Professor Fate]

Your pulley configuration will vary depending on the engine's original application- i.e. a/c, p/s, etc. An a/c engine, for example, will have a larger w.p. pulley (edit: meant to say smaller, for an overdrive ratio); but in turn, an a/c water pump has fewer impellers... What it amounts to is it's a "system", so the component selection should be the one that most closely matches your current configuration/intended usage.
And by the way- don't mix and match pre-'70 and '70 and later pulleys- the offsets are different due to the early iron water pumps being shorter than the later aluminum water pumps.
You should have no problem switching pulley sets between a 318 and a 360, as long as they are from the same vintage as I noted previously.

 

[RustyRatRod]

........And the appropriate impeller size and design in the WP for the overdriven application.

I've torn down a LOT of Mopar engines and I have yet to see one where the water pump was driven 1:1 or under driven. All I've ever seen the water pump was overdriven, if not only slightly. Of course, I've not seen it all by a long shot, either. But for any type of performance build, I would want my pump overdriven.

 

[72bluNblu]

I've torn down a LOT of Mopar engines and I have yet to see one where the water pump was driven 1:1 or under driven. All I've ever seen the water pump was overdriven, if not only slightly. Of course, I've not seen it all by a long shot, either. But for any type of performance build, I would want my pump overdriven.

That’s interesting, because the standard factory ratio was .95:1 for the water pump pulley. AC cars were overdriven at 1.3:1 or 1.4:1. But they also got a water pump with only 6 vanes, versus the non-AC cars that got an 8 vane water pump and the .95:1 ratio.

The factory pulley ratio’s by engine…

 

[Dana67Dart]

I've torn down a LOT of Mopar engines and I have yet to see one where the water pump was driven 1:1 or under driven. All I've ever seen the water pump was overdriven, if not only slightly. Of course

My stock 67 dart with 273 is slightly under driven

My reference to 1 to 1 was for reference only as was the size of 6 inches

 

[RustyRatRod]

That’s interesting, because the standard factory ratio was .95:1 for the water pump pulley. AC cars were overdriven at 1.3:1 or 1.4:1. But they also got a water pump with only 6 vanes, versus the non-AC cars that got an 8 vane water pump and the .95:1 ratio.

The factory pulley ratio’s by engine…

View attachment 1716001616

Thank you kindly! That's good info.

 

[4spdragtop]

Cool chart, is that from an FSM?

That’s interesting, because the standard factory ratio was .95:1 for the water pump pulley. AC cars were overdriven at 1.3:1 or 1.4:1. But they also got a water pump with only 6 vanes, versus the non-AC cars that got an 8 vane water pump and the .95:1 ratio.

The factory pulley ratio’s by engine…

View attachment 1716001616

 

[72bluNblu]

Cool chart, is that from an FSM?

Yep, it’s out of an FSM. I looked it up awhile back for yet another cooling thread to show the factory pulley ratios and what water pump went with them. I think it’s the ‘68 or ‘69 FSM. Some of the later ones have the chart too but they don’t list all the engines, the 273’s went away and then later they big block specs dropped off, that particular FSM has all the different engines. The ratios didn’t change through ‘74 anyway.

 

[4spdragtop]

I agree, mixing and matching is luck of the draw and can cause headaches. I've been lucky enough to use complete matched sets. As long as the wp pulley you choose is the proper depth, I would start with that and see?
Good luck

Easier said than done. Water pump pulley was MIA. I just have a few extras hanging around my parts piles.

Easier said than done. Water pump pulley was MIA. I just have a few extras hanging around my parts piles.

 

[Professor Fate]

That’s interesting, because the standard factory ratio was .95:1 for the water pump pulley. AC cars were overdriven at 1.3:1 or 1.4:1. But they also got a water pump with only 6 vanes, versus the non-AC cars that got an 8 vane water pump and the .95:1 ratio.

The factory pulley ratio’s by engine…

View attachment 1716001616

You got me thinking about my earlier post, I should have said A/C has a smaller pulley- I knew it was overdriven, but had a "senior moment" and erroneously wrote "larger pulley"... I edited my mistake to reflect my brain fart. Thanks!

 

[mopowers]

Does anyone know if an company makes/sells a set of single groove pulleys that overdive the water pump? I've never been able to find any.

 

[Professor Fate]

Does anyone know if an company makes/sells a set of single groove pulleys that overdive the water pump? I've never been able to find any.

Early or late engine offset?
Late:
Small Block Mopar 318 340 360 LA A/C Water Pump Pulley Chrysler Dodge Plymouth | eBay

WATER PUMP PULLEY 318 340 360 DODGE MOPAR PS AC 70S SMALL BLOCK | eBay

Or if you want a whole set (aftermarket, aluminum):
V-Belt Pulleys - Pulleys - Chrysler Small Block 318-340-360 - Chrysler

 

[mopowers]

Early or late engine offset?
Late:
Small Block Mopar 318 340 360 LA A/C Water Pump Pulley Chrysler Dodge Plymouth | eBay

WATER PUMP PULLEY 318 340 360 DODGE MOPAR PS AC 70S SMALL BLOCK | eBay

Or if you want a whole set (aftermarket, aluminum):
V-Belt Pulleys - Pulleys - Chrysler Small Block 318-340-360 - Chrysler

With those A/C pulleys, you then have to run a huge multigroove crank pulley. I'm looking for a single groove crank/water pump set that overdrives the w/p. The best March can do for single groove crank and w/p pulleys is 1:1.

CVR does sell a serpentine water pump/crank pulley set that overdrives the water pump, but nothing for a v-groove belt

 

[JDMopar]

This is an interesting and informative thread! I bought a new water pump and fuel pump for my 273 build at NAPA the other day. I'm using the 70 and up configuration on the motor. The water pump that came looks like a Flow Cooler brand pump, but it's an all new everything deal. It has a 6-blade impeller with a solid face towards the timing cover, if that makes sense. Hopefully, I have one more set of non-AC single groove later pulleys in my stash, but if not it's good to know that I can get some from Bouchillon.

 

[S'cuder]

Yep, it’s out of an FSM. I looked it up awhile back for yet another cooling thread to show the factory pulley ratios and what water pump went with them. I think it’s the ‘68 or ‘69 FSM. Some of the later ones have the chart too but they don’t list all the engines, the 273’s went away and then later they big block specs dropped off, that particular FSM has all the different engines. The ratios didn’t change through ‘74 anyway.

The table is from 1970, I think. It shows 383-2bbl, 440 HP & 6bbl, and Hemi. That choice was only 1970 for Barracudas.
Not that it matters a hill of beans in this discussion.
Thanks for sharing.

 

[Dana67Dart]

The factory pulley ratio’s by engine

Here is the same chart from the 67 FSM

This is what I'm gathering....

To increase the cooling capability of the system...


If you need more airflow through the radiator you do the following.

1. Speedup the shaft speed
2. Increase the number of fan blades
3. Increase the diameter of the fan
4. Increase the blade pitch

If you increase the shaft speed you do the following to the water pump.

1. Increase flow
2. Increase pressure
3. Increase the chance of cavitation

To reduce chance of issues from the above...

1. Decrease the OD of the impeller
2. Decrease the number of vanes

This video also does a good job of explaining (much better then me!)



And for a little light reading

https://www.sciencedirect.com/science/article/pii/S1110016819300109

 

[Dartvader440gt]

Looking at that chart for the aftermarket pulleys, it looks like higher water flow is 6 1/2 crank and 5 1/4 water pump pulleys. They say for better water flow in slow or stopped traffic use. The 1:1 ratio (6.5 to 6.5) pulleys is for a little more performance. So I'm thinking because my car is more for street cruising I should go with the smaller water pump pulley.