6.5NA Water Pump Recomendations

[JBracey]

Hello All,

I recently picked up an 86 M1008 and am in the process of taking care of maintenance items that may or may not have been done. In the process of replacing the harmonic balancer I found that the long snout 6.2 did not fit. In my research I've found that I most likely have an NA6.5 that was swapped in at some point. I'm working on getting the numbers off the block to confirm this but I'm all but certain at this point. Unfortunately I had already installed a water pump for a 6.2 and I'm finding that the impeller is backwards to what the 6.5NA needs.

My question is: Which water pump is recommended for this motor? I know the newer 2000+ pumps have a better distribution but my understanding is they would have the same issue as the 6.2 pump.

See pictures link in my signature

 

[cucvrus]

Question: - 6.5 block identification | Diesel Place

 

[Barrman]

Serpentine belt or V belts? That is the difference in the water pump designs. Each has its own backing plate that will not work on the other pump. If you got a pump to bolt to your backing plate and block, then it is the same as what was there before. Unless you swapped backing plates as well and didn’t mention it.

 

[JBracey]

Question: - 6.5 block identification | Diesel Place

Thanks. I ordered an inspection camera so i can get back there. Just waiting for it to arrive.

Serpentine belt or V belts? That is the difference in the water pump designs. Each has its own backing plate that will not work on the other pump. If you got a pump to bolt to your backing plate and block, then it is the same as what was there before. Unless you swapped backing plates as well and didn’t mention it.

It's a v-belt. The pump fit on the backing plate but I'm getting enough pressure in the radiator to blow the cap. I also replaced the thermostat at the same time and I'm not getting coolant in the upper hose.

 

[87cr250r]

The reverse impeller is for serpentine belts. There are 3 pumps available. The 6.2 pump for v-belts. A 6.2/6.5 pump for serpentine. A 6.5 high flow pump for 96+ serpentine. The high flow pump will not bolt to the older backing plates. With that said, if you're using v-belts use the 6.2 pump. If you're using serpentine use the 6.5 low flow pump. If you want a high flow you'll have to buy a new backing plate. Centrifugal pumps make ~1/3 pressure when spun backwards so it will still work until you put some load on it. That means you'll have flow regardless of which pump is used. Just not enough if you use the wrong pump.