34 coupe-cooling, aero and radiators question.

[sean]

Hello all, great site here. Newb searching for some info with little luck so far. Looking for help or advice.

A little background on the project. It's a fiberglass '34 Ford 3W coupe with a 3" chop. Stock wheelbase, tube chassis, a-arm front, 4-link rear. I'm not concerned with any particular class, records or running a certain speed. Just want to run safely and have fun.

The question is about a cooling system for it. I don't want a car that overheats. The current drivetrain is in, a twin turbo 500 Cadillac, the underhood area is cramped and doesn't have much room for a radiator (no suprise). I know a few guys that run the big Cadillacs and would like more cooling sytem capacity than their small radiators mounted in the front. Mounting a larger radiator in the trunk area is now under consideration, but getting air in and out is questionable. Is the 4"-5" flat area between the roof top and the trunk lid a low pressure area? Thinking the air could be drawn from under the car, through the radiator, and out the top in this area. What do you think?


Thanks  Sean

[jimmy six]

Just put in a 15 to 20 gallon water tank in the trunk and be done with it.

[Rex Schimmer]

Go with the water tank and make sure that you have a BIG water pump.

Rex

[sean]

Thanks, hadn't thought of a tank. I gather that it will work as a ballast also, and this style of body will need it. Should the tank be as far back as possible or mounted just behind the driver? Saw an article about center of pressure and CG, but don't fully understand it yet. The article seems to reccoment the ballst not be mounted at the rear most position. How is a water pump size determined? Can a stock mechanical water pump work?

Like some of the other rods on here, this isn't strictly a LSR car. It will see dragstrip use mostly with some street duty thrown in. Putting a water tank in for LSR is not a problem, it doing double duty as cooler and ballast plus its simplicity makes sense to me. In drag racing or street duty the water tank and its weight isn't so desirable. Do you think the radiator in the rear venting to the trunk/roof area idea will work? Or should it just dump back out the bottom?

Sorry if these are newb questions. Been a drag racer for some time and have cobbled together a few toys for that over the years. Went to Maxton and ran last summer in another toy of mine and now the desire to make this car work in LSR is guiding the build. Some of the designs and what will and won't work in LSR are new to me.

Thanks again

[Rex Schimmer]

Rule of thumb for water pump sizing: 10 gpm for every 100 hp. Big difference when you keep the throttle WFO
for 1-2 minutes vs 10 seconds at a drag strip!

Rex

[jimmy six]

Rex maybe right, but I had 22 gallons total for a 700 hp engine on 70% nitro long course and I use 10 gals for a 300+ hp on the short course on gas. I have no problem with either. Water should be outside of the driver area protected by a bullhead.............Good Luck

[Harold Bettes]

Hey 6,

What was the typical water temp (in the 22 gal reservoir) at the end of a run on 70%?

I am assuming that the H2O temp started off at about 80 to 100F. Is that close? Also assuming that the system was either open to atmosphere or pressurized to only a few psi.

For about 80-90 seconds?

This is so close to the thermal mass of water analysis for a dyno installation, just thought that I would compare the notes/results to some of that type of thing.

Thanks in advance.

Regards,
HB2

[jimmy six]

2 electric water heater probes were in the tanks and the generator on for 20 minutes before starting engine in impounds. By the time we left the starting line the engine indicated 120. Oil temp was at 160 when we left imounds also. Used only high gear 1 to 1, 2.56 rear, 32 in tires. Water temp was a little over 200 when entering the 4 the last time I looked. Car ran out of horsepower and moved 10 feet to the left real quick, then 10 to the right. From that time on the gauges didn't mean much as I was looking for the 5 mile sign 214 at the 4, 215 at the 5. As I shut it down the temp was at 210. CSI pump with a double feed to the block with -12's. 2 returns to the tanks with -10's with restrictors. Tanks tied together with 3/4" hose. Tanks were open with -10 hoses to the rear of the car incase a head gasket let go. 3400lb car

Running out of horsepower in a high-boy roadster is not much fun or a lot of fun as I look back at it. ... Good luck

[Rex Schimmer]

Jimmy, reading your post it appears that you do not run your water tank under pressure and the only pressure in the engine block is that provided by the restrictors in the water return lines. Do you think there would be any advantage to running your tank pressurized?  Obviously pressurizing the tank certainly makes it have to be a lot stronger but the increased pressure does raise the boiling point of the cooling water.

Does anyone run a water tank with a small radiator suspended in the tank, makes it like a water to water heat exchanger? This way you can run the engine cooling system with pressure cap and even a thermostat so that you can start your run with some water temp and the tank doesn't have to be pressurized. 

Just fishing around here for some ideas for my lakester.

Rex

[Harold Bettes]

J6,

Thanks for sharing the specifics. Did you ever test the unit on either an engine dyno or a chassis dyno for baseline data on either gas or methanol?

Regards,
HB2