Water Pump underdrive?

[mike_starling]

Guys,

As explained before, the engine builder didn't quite listen when I told him the engine had to be a maximum of 6 1/2" from the front of the head to the nose of the water pump. So I am trying to fix that, but there is now little money left.

Looking at the engine, it is obvious that it needs to run two rows of belts rather than three. Two are non-negotiable (one for the water pump and other things and one for an oil pump as this is an SVO 4 bolt race block).

I was able to pick up an Explorer timing chain cover and a pump for very reasonable costs. It should get me very close to my max length.

Now I need to figure out how to do the rest without replacing too many pulleys as they too are not cheap. The crank has a two step Jones Racing Products pulley. The inside step is for a keyed belt and the outside is for a grooved belt. Bet that puppy is not cheap! The diameter of the grooved section is 3".

The current ratio for the waterpump is 3" drive pulley and a 4" pulley on the pump. I believe that a standard drive ratio is more like 1:1. Given an Explorer pump, can I go with the 4 1/2" Explorer pulley and be close to a rational underdrive ratio?

Also, looking at my Cobra which has a Coast stroker in it, the standard tensioner/adjuster and idlers are huge! Any slick way to do this at a reasonable price?

Several of you noticed the breather in the last posted picture ... don't worry, I have a remote replacement for it. Will wait to see if the valve cover and distributor clear. I'm not sure if the valve covers can get much lower with the T&D rockers and shafts in the engine.

thanks,

[Gary Gibbs]

My 1.25:1 drive ratio was spinning the pump too fast. I went down to a 0.9:1 and things seem better. I would guess a 1:1 would work if you are going to spin the engine up a lot. If it is primarily going to be a street motor with occasional runs through the gears I would go 1.25:1.

[mike_starling]

You mean that you'd overdrive the water pump? That is a ratio of (crank pulley diameter)water pump pulley diameter) being 1.25:1.

Are you running a standard pump or an Eplorer type pump?

Thanks,

[killroy]

While the explorer timing chain cover does have a better shape than the earlier models, the pump still has a crummy stamped impeller. I don't think it will flow much more than any other water pump.

On the Mustang (same pump) lots of people use "underdrive" pulleys which might just be less overdriven. They don't seem to have many problems except with the altrenator.

[Gary Gibbs]

Sorry for the confusion. 1.25:1 would mean overdrive the pump by 25% (faster then crank).