Re: Woody am I ok with a H/E that has 3/8" flow? Also, MB yellow coolant?
Splinter: THese readings are with the Johnson pump in the car with the I/C and one of the measured H/E's as it would be when driven. THe h/e's measured alone would be largely inaccurate as the system has lots of friction that dilutes the differences the cores would have. Measured with a mechanical flow meter.
Ohnosea: Parallel cores would be set up with a pair of Tee's to divide the water so that each cooler gets 1/2 of the water and carries about 1/2 of the heat load. THe two outputs would also be reconnected so that they combined into one outlet pipe.
TO do this I would suggest that you get copper Tee's and some copper pipe to STUB out the Tee's about 1" or 2 " so that you can slip the hoses over the stub. A well stocked LOWES or Home depot also have a variety of plastic Tee's that may be what you want and with less labor.
At first I did connect the TWO cores in SERIES and saw that the total restriction was TOO high. At that time I tapped the mid point of the coolers to make an input. I connected the other two ends with a copper tee to make a common output.
Having two cores in parallel allows the water to go thru each core at 1/2 the linear speed it goes thru the I/C. You get better cooling this way and the fact that one core is above the other is little concern. It would be beneficial if the cores are in close proximity to the A/C coil surface to promote more draw- thru air due to the ram air effect and the operation of the fan.
Woody ENJOY