Rear Mount Radiator

[Cobraaph]

I'm thinking about a rear mounted radiator on my '97 Cobra CP autocross car. The main reason would be weight distribution (F/R still sucks after taking out almost everything not essential to make the car run and drive). Has anyone tried this? If so, was it worth it? What are the obstacles? Is it better to put the water pump in the back or leave it on the engine?

 

[blacksheep-1]

Done it, in a corvette back in the 70s. You have to either use aluminum tubing, stainless, or some kind of ceramic coating. None of which is super cheap. We used a stock pump, but I think nowadays I would use a Mezeire (@Fabman could help you with that)
Install it in the trunk with fans. Back in the day we inlayed into the back of the car like the old " box" Chapparal. Unfortunately, I just deleted a photo of a WEC car that had a similar setup, it looked like they ran the venting under the rear wing to leverage it into some extra downforce.

 

[DaveW]

I did it in both my Fox CP car and again on the EM car.

In the CP car, I had a CSI electric water pump and it seemed to be very troublesome to get enough cooling. It worked for autocross runs but just barely. You could never just let the car run once heated up for more than a few minutes without the temp climbing.

When I did the EM car, I just used an engine driven pump and this worked much better. Once bled properly, I could basically treat it like a normal car and let it run and it would hold temp, or pull it back down if it got hot during a run.

The two things I learned for sure...

1. You need a ton of electric fan. I originally used a Mark VII OEM fan that was like 3400CFM and then switched to a dual fan setup that was 4500CFM. You need serious wiring and alternator for these setups

2. Make double sure absolutely NONE of your extended piping is any higher than it needs to be or you will never get it, or keep it bled. THe CP Car had some bits that were not on the floorboard, but at least 10" below the cap and fill point in the front and invariably it would air lock there when filling. On the EM car, I was much more anal about it and all of the tubing was as low as possible in the car and it only went up to get to the top neck on the radiator and thermostat housing on the front and this one was much more trouble free.

On the CP car, I found some thin aluminum 1.5" tubing and used that. I had a little beading tool and beaded all the ends. On the mod car, I couldn't find the tool and just used 1.5" conduit. It wasn't light, but the engine was pretty close to the back. When I did it, I didn't have easy access to a mandrel bender, so did everything with straight tubing and used rubber/silicone preformed bends for all the turns. My intention was to replace it later and get rid of the rubber, but I never got around to it and over 5 years, never had a single issue with any of the bends.

HTH,

DaveW

 

[Fabman]

I did a mid engine/front radiator/oil cooler rotary powered RX7 back in the day....every high spot get a bleeder, even if it was lower than the cap. If it went up and down it got a bleeder. I just ran nipples in all the highest points and ran a line back to a surge tank with the radiator cap. Never a heating issue and no air pockets. I originally had it rear mount rad/rear oil cooler and then front rad/rear oil cooler and I just could never get enough airflow through either of them with any amount of fans to come close. I tested (at the time) every electric fan I could get my hands on. I even went through the junk yard with a battery and a velometer (used for measuring airflow) and tested about a zillion factory fans plus scores of aftermarket ones. None were going to be enough. Then I just waved the velometer around in the air and that was 4 times more airflow than the best fan I could find at the time. A light went off in my head. So once I put the rad/oil cooler up front I never even used the fans, the natural airflow was more than enough on its own. Moral of the story, if you are going to do a rear mount setup, and are going to push it like in w2w racing, you are going to have to jump through some major hoops to make it work. Don't half azz anything or it will fail. Might fail anyway.