Baffled Racers - Sleepy's Track Tech

Have a question for Sleepy's Track Tech?

Q: We are going to run a basically stock 400-cid small-block with 194 heads and a four-barrel carb in a UMP Modified that we are building. This will be our first year racing and we are wondering if we should run gas or alcohol? We are well aware of the benefits of alcohol in high-performance engines, but will running alcohol be practical in a basically stock engine?P.S. I read SCR because of your articles.JeremyVia e-mail

Sleepy: Gee, another satisfied customer. Jeremy, if it weren't for people like you, I wouldn't be writing this. The simple answer to your question is yes. Now, let's go on to why.

First, there will be only a small performance gain with a low-compression stock engine, so raise the compression if you can. A steel shim head gasket (0.015 inch thick) will help so long as the head and block surfaces are true. Spray the gasket with high heat aluminum paint for a sealant. Done it for years, works well. Alcohol responds well to high-compression ratios. I'm told it has an octane of about 140.

So if there is little performance gain in a nearly stocker, why use it? I try to stay away from pump gas because you never know from delivery to delivery what is in it. Therefore, I buy racing gasoline-expensive, but at least it is always the same. Though race gas is about twice the cost of methanol, I prefer methanol when rules allow. An engine will use about twice as much methanol as gasoline, but methanol has a cooling advantage.

An engine will run somewhat cooler on methanol than on gas. This might be a prime consideration with a 400-cid small-block because it can be more difficult to cool than the typical 350-cid small-block. Notice also that alky-fueled cars often have a smaller radiator. This can reduce front weight by a few pounds. It is not just the weight of the radiator, but also the weight of the extra water it carries.

The only downside might be the cost of obtaining an alcohol carb. This won't be much more than getting a reworked gasoline carb. Either way, throttle response and performance will be better with a reworked carb. Take a short cut somewhere else, put worn tires on the left, do what you can, but get a good carb. A good rule of thumb for selecting a carb supplier is to find out if they have a dyno. If they don't, then thank them and go somewhere else.

A quick recap on the benefits of alcohol fuel: There's a small performance gain with a close to stock engine; alcohol loves compression; overall costs are about the same as race gas; it cools better; and requires the proper carb.

Q: Sleepy, I have two questions. I race in a class that requires an automatic tranny. Should I run a tranny cooler, and if so where do I put it? I have seen them mounted on firewalls, in front of the radiator, and inside the car. How about using the stock cooler inside the radiator?

Second question: I have heard of trannys popping out of gear. How would you suggest solving this problem? We race in low gear on a 31/48-mile paved track in the Street Stock class.RandyVia e-mail

Sleepy: Automatic transmissions with a torque converter need a cooler. When using an automatic with a direct-drive setup without a torque converter, a cooler is not important in short races. Still, a tranny cooler is never a bad idea. The torque converter is where the heat is generated. A torque converter all but shears the transmission fluid as it moves through the converter's vanes.

In a race application, I would want the cooler separate from the radiator. Some- times the radiator does all it can do to cool the engine without the tranny (cooler) putting more heat into it. Although in the past I've mounted the cooler in the driver's compartment, I don't like to do this. I learned this lesson with a friend's car. The metal cooler lines came up through a hole in the floorboard. As the engine moved around while racing, one line rubbed the edge of the hole enough to wear a hole in the fluid line. At first, we thought it was funny when he rubbed the wall getting the car stopped on the front straight. Ever seen how slick the inside of a Stock car can get when eight hot quarts of transmission fluid are applied in a random manner?

Consider the firewall mount. When mounted flush against a surface, air cannot flow through the cooler, thus there is no cooling. In front of the radiator is not a bad place to put a cooler. If engine cooling is marginal, the cooler should be mounted to one side so it doesn't block airflow to the radiator. Just make sure it has its own access to air.

I have mounted coolers on the floor of the trunk over an opening. With some sheetmetal directing undercar air into the cooler, this works fine. When doing this, there must be an opening in the rear of the trunk lid area to let the air out. The rear vertical area of the trunk lid is best for this air exhaust opening because this is a low pressure area. Rear mounting also moves a slight amount of weight to the rear, but for the most part it is a safe place to put it.

Now, let's examine a tranny popping out of gear. When a manual transmission pops out of gear, it is usually because some bearings inside are worn, allowing the gear teeth to kick away from each other. When an automatic pops out of gear, there is nothing wrong with the tranny if it works when it is put back in gear. When the auto tranny pops out of gear, usually there is a linkage problem.

A Street Stock car seldom has a stiff chassis. The shifter is often firmly attached to the floor. The motor uses stock-type rubber mounts (sometimes with 20 years of abuse) that have considerable flex. Then a solid rod is attached between the shifter and the tranny. When the chassis and engine locations are flexed, the problem becomes apparent.

An OE cable system can work well. Otherwise, I like a rod attached to the tranny shifter, coming through the floor and located by a loop attached to a secure mount. The rear of the tranny would be best. A 90-degree bend on the end of the rod forms the handle. It can be a little awkward to feel the detents in the tranny with this mechanism, but the rod is free to move with chassis/engine flex without pulling the tranny out of gear.

Q: I would like to say how much I appreciate seeing an article about a Honda race project. I'm 20 years old, I pay for a race car out of my pocket, and I've found it affordable to race a Honda. I've raced for two years at Orange Show Speedway and this is the first article I've seen about building a unibody race car. Do you have any setup information for an asphalt-track Honda? I hope you are not catching too much flak about building a Honda.Thomas GibbonsVia e-mail

Sleepy: I haven't had to dodge any flak on the Honda so far. In fact, the response has been quite favorable. Building a unibody car takes a different mindset than building a car with a chassis to attach everything to. I think a properly designed unibody race car would be one in which all the sheetmetal could be removed and the car would still run around the track. I suppose this could never be achieved, but the closer you get, the better. Any- where anything is attached to sheetmetal, it must be done with a plate that spreads the load. Unibody cars are surprisingly flexible. If you haven't noticed, they are all spot-welded together with the spots an inch or two apart.

The above also applies to semi-unibody cars like Camaros. The front clip should be utilized as the front of the chassis and the rest built like an IMCA Modified. The sheetmetal could be trashed and the car still work. On Camaros, the worst-case scenario is when the cage is built and attached to the body and then braced to the front clip with the rubber body biscuits still in place. But I digress.

Making the stiffness of the Honda or a similar car greater by interior bracing greatly improves handling. I wish I could tell you some setup secrets, but I can't. After all, I'm learning, too. Most information I find on FWD unibody cars is directed toward road race cars, but an oval is different.

The following is only my thinking on the subject. I will let you know later how it all worked.

I'm writing this in mid-December and won't be able to race before late February. However, much to the chagrin of my dear spouse, I have managed 16 laps around the house. She didn't appreciate the berm forming across the front yard until I explained that I was doing some landscaping.

Lock the differential (weld the spider gears) and use strong springs on the right and weak springs on the left, no sway bar anywhere. Adjust crossweight to the opposite of the normal rear-wheel drive car. Just a guess, I'm thinking about 30 percent crossweight from the left-rear to the right-front (see illustration, p. 60 of this issue). Have some stagger, build in all the front weight you can, and drive off the left-front through the corners. Remember these are my thoughts, not absolute results.

Where to find it

In this issue of Sleepy's Track Tech, reference was made to various parts, tools, etc. Listed below are companies that manufacture parts meeting the previous descriptions. The manufacturer can direct you to the nearest dealer.