perfromer rpm plumbing question
 

i just got in my new edelbrock performer rpm intake and noticed the tapped holes in either side of the thermostat housing hole (not the ones for the screws but the one inch holes). in the intake box it came with a threaded/barbed nipple and a plug. what are/can these holes be used for? i have noticed pics on the net of people putting temp gauge lines there and also it appears people are plumbing back to the rear of the head from there. what is the intended use of these holes?

Either hole can be used for a water temp sending unit. It is most common to use the one that is on the driver's side [left]. Just put a plug in the other hole.
Enterprising engineer types have also used the holes to run additional cooling lines to the cylinder heads.

i have edelbrock rpm heads and have the barbed nipples in them already and was planning on running both sides to the heater core as i have read on other posts in this forum.