New dirt racer - need help

[BARCRacing10]

By nature I'm a driver who is forced into being a mechanic so please bear with my ignorance, but I have two issues on my car that I could really use some advice with. Any help at all would be appreciated!

 

Overheating - At the first of the season we were ok (running about 170 - 190) but now with these 100deg. plus days we've been pushing 250 +. Already blown a head gasket and warped the heads and I'm pretty sure the heat warped my metering block on my carb. I am running a stock water pump, a racing radiator, and of course water with some water wetter. I've heard theories on a high flow water pump to push more water, but also heard about putting restrictors to keep the water in the radiator longer? The two seem to contradict each other to me?

 

Ride Height - I need to raise my front end about 2". I've been told that wether I make a spacer to go between the spring and the tower or I just go the easy route of buying a spring rubber I will get the same result, but both will change the spring rate? What's the best way to make the adjustment?

 

My biggest problem on both is that I run in two seperate classes - at I37 I run street stock and at SOS I run pure stock, so I am needing to figure something out that either requires minimum or no changes to be able to go from one to the other (so that cuts out spring jacks in the front for example).

 

Again... any help at all will be appreciated!

[Scott Lewis]

I had similar problems with my 351W. We had to run a gutted thermostate and changed to Purple Ice. I normally run between 175-190. In the summer I run about 195-220. I run a stock water pump. Purple Ice really seemed to make the most differance. I didn't follow the directions as far as the amounts go, I simply poured in the entire bottle. The oil we use also seemed to make a differance in engine temps.

[NickHolt]

Adding spring rubbers to a spring increases the wheel rate (that part of the spring rate that the tire "feels") of that spring.

 

Putting shims between the spring and the chassis does not add to the wheel rate of a spring. However, putting a shim in does increase the load on that spring unless the other springs are also shimmed.

 

Nick

[BARCRacing10]

So, If I shim left and right front the wheel rate of the spring should stay pretty close to the original spring rate? With the spring rubbers is there a formula that will tell you how much the spring rate will change?

[NickHolt]

If you shim both the LF and RF the same, the spring rates and wheel rates will remain basically the same.

 

There are all kinds and sizes of spring rubbers. Some manufacturers used different coefficients of elasticity (stiffer, softer), so, it's hard to come up with a hard and fast formula about how much a particular spring rubber will change a particular spring. The best bet would be to contact the manufacturer for his best estimate of the rate change expected.

 

NOTE: Raising the front end using shims and not the back end an equal amount might tend to add understeer (tightness, pushing, plowing) to the car. So, if your car was already tending to oversteer (loose, coming around), this might help the handling a bit. If the car was already understeering, it might add to the problem a bit.

 

Nick

[CuttingEdgeRacing]

Topic: Overheating

 

First, make sure you have a great air box going to your radiator, is priority one. Air takes the path of least resistance, so make sure everything is forced INTO that radiator.

 

Second, I believe in using water restrictors. You need the water to stay in the radiator longer. They are avalible all over the place, they are cheap and come in all sorts of flow rates. Buy a few different sizes and experiment.

 

Last, Consider changing the angles of the radiator IF POSSIBLE. Slanting the radiator can help air come across the surface of the radiatior better.

[BARCRacing10]

Topic: Overheating

 

First, make sure you have a great air box going to your radiator, is priority one. Air takes the path of least resistance, so make sure everything is forced INTO that radiator.

 

Second, I believe in using water restrictors. You need the water to stay in the radiator longer. They are avalible all over the place, they are cheap and come in all sorts of flow rates. Buy a few different sizes and experiment.

 

Last, Consider changing the angles of the radiator IF POSSIBLE. Slanting the radiator can help air come across the surface of the radiatior better.

 

I have looked at, and considered the restrictors. What do you know about a "splitter"? Some people have told me they come in a kit with the restrictors - it supposably keeps the water from crossing over and flows easier out of the motor?

[97car]

Put in a restrictor, as a general rule of thumb most use one with a 3/4 inch hole. Do you have a screen to prevent your radiator from getting clogged with mud and have you sprayed it out to wash out what may be already in the fins. Check your hoses and make sure you lower hose is not collapsingat rpm when warmed up. What are you running for a fan and do you have a shroud for it. If you are running a flex fan get rid of it and get a new plastic one as big as you can fit. A flex fan wears out over time and the blades flatten out at RPM and do not draw air and create a wall instead. Check you timing, also make sure the power valve is not blown and are you jetted rich enough, and look for vacuum leaks as well. I would suggest flushing out the engine and radiator and make sure you have all of the air out. Is the filler cap higher then the engine,if not you might need to raise the radiator or make sure that end is higher when filling the radiator.

[thumper]

The simplest answers are usually the best ones.You did not mention a fan shroud,they are a pain to make but the most necessary.The blade needs to be 3/4 out of the shroud in depth and must be complete 360 deg.I tried many fans,5 blade,plastic,flex fan etc but found the old 4 blade like a 6 cyl old Chevy works the best.Its really 2 blades that cross each other to make 4 blades.Its light and really pulls air without drawing a lot of HP.

I fried a few motors before I found my problem.My Ford heads and block although tank cleaned emmited particles that plugged the raidiator.It looked like chunks of rust.It came from the bottom of the water passage ways.Boiling and flushing did not remove them.I finally made a screen filter for the top outlet and captured this stuff.I had to clean the neck regulary for almost a full season.I found a company that made Gano Filters which was an inline possum trap for the top hose that would collect this gunk.I always used this device and every time I changed blocks or heads the gunk would come back at varrying degrees.

 

How I found this problem was sickning.After several damaged engines I cut open the brand new aluminum raidiator to see inside.Only the top 2 rows of tubes were open.To look inside the cap while running the flow looked great.But the raid was 90% plugged.To open it up ruined it but I was so happy to find the problem I was happy to buy another one.Problem solved..

 

When I went from asphalt to a bigger dirt track my VW started getting hot.The cure for it was adding a second electric fan.It did not get hot in the fall or spring but the dog days of summer were too much for a single fan on this track where I was on the gas for a longer time.So airflow is critical.

[LMR21]

First off why do you need to raise the front end, did you check the moment centers and roll center for the front and rear? Nick is correct in saying that the rubber will change spring rate and the shim will not.

Cooling is a process of temp differential and it hinges around flow. First you must get the hot water to the radiator to transfer heat, then you must transfer the heat to the air that passes through the otherside of the radiator. So in theory anything that helps water and the air transfer heat to one another better will help cool the engine. I will tell you that even though you dont see mud on your radiator does not mean the fins are not clogged inside. which is a major part of the heat transfer process. I have had engineers from texas am and ut look at the restrictor theory and they were both in agreement that it wont help unless there is a cavitation/NPSH issue.

[1-Crew]

A little theory on cooling..

 

The purpose of the restrictor has nothing to do with "keeping the water in the radiator longer". What it does is force the water pump to build pressure in the block. Water boils at different temperatures depending on pressure. At sea level, (14.7 PSIA) the boiling point is 212 degrees F. If you have a 15 PSI radiator cap, the system pressure can reach ~30 PSIA, raising the boiling point to 250 degrees F. If you have a restrictor in the outlet from the block, the pump works against the restriction, building additional pressure in the block. At 10 psi pressure added by the restrictor, the total pressure in the block from the cap and the restrictor is up to 40 PSIA where the boiling point is 270 degrees F.

 

Obviously you can experience boiling at lower average temperatures but that means that point temperatures inside the motor, most likely the head, are above these values. Aluminum heads conduct more heat from the combustion chamber to the water (for the same flow numbers, a iron head will make more power than an aluminum head for this very reason).

 

Water Wetter helps by minimizing these point sources of nucleate boiling (hot spots) since with just water, once a hot spot develops and is boiling the water, the steam pockets formed prevent cooler water from reaching the hot spots. Water wetter reduces the surface tension of the water so it can remain in contact with the hot surfaces.

 

Jack

[Double D racing]

A little theory on cooling...

WOW...Learn somethin new everyday...

[LMR21]

now dont go crazy and think that putting 50-60 psig worth of pressure is going to fix your problem, there are limits that the cooling system has, and high pressure hot water(steam once it reaches atmospheric pressure) will melt the skin right off of you, so be careful hovering over your motor after a race.

[Pacecar]

Jack is exactly right on the cooling topic.

A poor-mans water wetter is 2 drops (no more) of Ivory liquid soap.

[1-Crew]

Cooling - second half.. There are two components to overheating - running hot and boiling over. Pressure, controls the temperature at which water boils but by itself does nothing to regulate the temperature of the engine. Controlling the temperature is more complicated but is mostly a function of surface area and air flow. The easiest and most effective thing you can do to maximize airflow is shrouding. Thumper is absolutely correct about a well made fan shroud. Without a shroud, most of what the fan is doing is just stirring the air. The radiator is a restriction to air flow and air will flow around it as the path of least resistance unless forced to go through it by an effective shroud. When choosing a radiator, the more surface area (fin and tube) you have , the more effective the heat transfer to air will be. A larger overall size with two rows will present less resistance to air flow (and therefore better cooling) than a smaller overall size with three rows (for the same total surface area). On dirt, make sure you have some protection to keep dirt and mud from packing the front of the radiator and blocking air flow.

[LMR21]

I have contacted a few radiator companies in the past and was surprised to find out that they had no idea what the efficiency rating was on them, but most heat exchanger data sheets I have ever read was based on a 90% efficiency, perfect world setup, realistically more like 80% is what is seen. to figure it out you must know the differential temp of the air across the radiator(air in,and air out), this will tell you if you are clogged or restricted. use this

 

μt = t2 - t1) / (t3 - t1) (1)

 

where

 

μt = temperature transfer efficiency

 

t1 = temperature outside air before the heat exchanger (oC)

 

t2 = temperature outside air after the heat exchanger (oC)

 

t3 = temperature inside air before the heat exchanger (oC)

[Truck99]

Jack is exactly right on the cooling topic.

A poor-mans water wetter is 2 drops (no more) of Ivory liquid soap.

 

I hear a little fabric softener works well to "wet" the water also....and makes the radiator water smell a little better.

[STAGGER77]

One more thing that you might check that caused us problems in the past. Make sure that your radiator tubes have not expanded or blown out causing the cooling fins to crush and not allowing air to flow thru the fins to cool. What usually causes this is a radiator cap that had to high of pressure, don't use anything over 24lb. for an aluminum rad. and 29-31lb. are for stock rad.

[BARCRacing10]

I want to thank everyone for their help and advice, and will continue to read whatever other help is offered!

We made several changes before our race this last Saturday that had a very positive impact!

I bought a new aluminum racing radiator with a bigger surface area.

I bought a new fan.

Tried the purple ice as opposed to the water wetter.

Put a new 25psi cap on.

Somewhere in the mix we did something right. My temp stayed at 190 till a caution then climbed a little, but never got over 230, and it cooled down REALLY nicely after the race!

I'm thinking about possibly adding a high flow water pump and maybe adding a restrictor and hopefully my heating problems will not haunt me anymore.

[koab26]

I DRIVE AN IMCA STOCK CAR AND RUN A 362 CI. CHEVY SMALL BLOCK WITH A HOLLEY 350 2 BARREL CARB. I HAD OVERHEATING PROBLEMS DURING MY 20 LAP FEATURES IN WHICH THE TEMP. GAUGE WOULD READ 260 DEG. SO I ALREADY HAD AN ALUMINUM WATER PUMP SO I WENT TO A 1 TO 1 PULLEY SYSTEM AND THE LARGEST WATER RESTRICTOR AND I ALSO USE HALF ANTI FREEZE AND DISTILLED WATER. BINGO MY TEMP. DROPPED TO 195 TO 200 AFTER A 20 LAP FEATURE PLUS CAUTION LAPS. HOPE THIS GIVES YOU SOME IDEAS, GOOD LUCK.