the reason for using the smaller bolt pattern is that i will get about 4mm extra room as the diameter of the front part of the pulley is smaller, its not alot of difference but it means the idler pulley wont have to take the supercharger belt as far across, reason i dont want to go to far over is becuase its getting close to the other side of the belt, distance between the radiator and pulley is no problem as i already have the radiator slightly forward to clear the supercharger belt.To gain more space you don't necessarily need the very early pump. The HT to HQ one will do the job. The only difference between the two is the pulley bolt pattern, they have the same (short) offset.
Anyone know now were to buy cast impeller pumps now? im after the early eh, hd, hr pump, i am changing over from the commodore type to get room for a supercharger belt, my old pump with a cast impellor has been on the motor with water for about 12 months and done about 5000 ks but the pulley is in the way.
Dr Terry
i have a old one here but the bearing isnt very smooth, i also have a fairly new jumbo pump with a cast impellor that i was using before i started fitting the supercharger.