We are closing in on finishing our Honda Mini-Stock. We didn't make it to the track before the season's end. We have, however, been making laps around the house much to the chagrin of my dear spouse and the neighbor's dogs. Even on a track this short, we have been learning.
I want to take a moment to acknowledge the assistance I've been fortunate to have on this project. Tony Elliott and his younger brother Dalton spent three nights a week at my shop for several months. Tony is one sharp cat, young but mechanically experienced. He also did much of the welding. Dalton learned a lot during the project, too. Matt Bixler did his share of the dirty work. Dwight Bush lent a knowledgeable hand, parts and information throughout. So, no, I didn't build this project all by myself.
Remember this was to be a low-budget, entry-level car with a target of $2,500. Granted, there are classes at some tracks where the cars are in the category of $500 or less, but our competition will include cars costing in the $10,000 range. My intent was to introduce as many ideas and techniques as possible for building FWD unibody cars. It will be your job to sort out those thoughts and ideas that fit your situation. We spent a lot of time building and thinking. Much of our work was learn as you go. This meant that we sometimes redid things and in a different way. A one-off car, a unique car, is always a prototype. Prototypes can always be improved.
We didn't make our budget. The junkyard engine had gotten water in it and thus had to be taken apart and freshened. A bore job with new Perfect Circle rings and Clevite bearings, plus a 0.080-inch cylinder head mill, shot our budget limit down. Then we found that the engine management computer was bad so an HEI-type distributor from Performance Distributors was installed. These taken together have an upside: We now have no electronics except the ignition and a fresh engine.
Our rules at East Bay Raceway call for the suspension to remain mostly stock. The suspension pickup points have to stay in the stock location, and the suspension must remain stock appearing. The exceptions are that springs and shocks may be changed.
The Honda has a coilover suspension and is not a "strut" car, although it may appear so at first glance. However, many of the small FWD cars are of the McPherson strut design, in which the spring is mounted on or over the strut that becomes part of the spindle. That is a type of suspension different from a coilover.
Trying to cure severe pull-over...
Trying to cure severe pull-over on the squirters, I tried an air bleed in the pump circuit. The tube places the bleed near the carb vent. This had some leaning effect but not enough.
The Honda front suspension is actually an A-frame design similar to the Ford front suspension used in the Cup cars for years. The Honda coilover unit (similar to those used on Late Models) can be removed and the suspension will still control the placement of the wheel.
The rear suspension is also of a coilover design. There are multiple links with several pivot points. This is not a bad design, but you may need to stare at it a while to see how it works.
The stock coilover units are not adjustable but they are easy to disassemble. If you do not have a safe and secure means of compressing the spring, don't take the shock assembly apart. If you are not planning to use the stock springs, they can be carefully cut with a torch. I cut several using this method. This relieves the spring's tension and allows safe disassembly of the unit. Knowing I might use some of the springs again, I made the cuts one coil apart at one end. This saved a spring about 10 inches long.
AFCO coilover springs were used on three corners. They fit right over the Honda shocks. The left-rear has part of a stock rear spring. Knowing we had to draw the line somewhere on costs, the stock Honda shocks were retained. Well, they feel like they are good. We'll run them to start and see where we are.
My thinking for our little dirt car is to use strong springs on the right with weaker springs on the left. I know this is unconventional thinking, especially with a crossweight of only 29 percent, but you must understand that at this point the car has only made laps around the house. Initially this setup looks OK, but we haven't been to the track yet.
Jim McFarland suggested using...
Jim McFarland suggested using a larger plenum in the manifold. I got 2 two-barrel to four-barrel adapters and put them back to back to form a plenum. There was a small gain, but this told me I would need a huge plenum for a cure. Not practical in this case.
The Honda has a locked (welded) differential. With the track tires, only about 2 inches of stagger is available. I heated and bent the steering arm on the left-front spindle to increase the Ackerman effect. I think I want the left-front to do most of the work. That means as little weight as possible is transferred from side to side. All this is intended to make the front end stick down in the turns and not have the car push up. The crossweight (the wrong direction for a rear-wheel drive car) is intended to keep the left front of the car heavy.
We came up with an unusual way to adjust the weight of the car. The best way to do this is to use the AFCO adjusting sleeves that are made for coilover applications. If you have a few extra bucks, get them. Some sort of spacer is required because the AFCO racing springs are shorter than stock. That is good because it leaves room to raise and lower a given corner.
Already over budget, I went to the muffler shop. I ordered up several pieces of 211/42-inch tailpipe of lengths between 6 and 12 inches long. Then I had the muffler man form some flanges that would fit over the straight pieces. The flanges are welded to the straight parts at different measurements. Rather than use a screw-type adjustment, I now change out the tailpipe parts to achieve different heights at that corner-certainly not convenient, but cheap.
I made a dedicated wrench that fits all the nuts required to remove the coilover unit. At the bottom attachment point, I drilled the threads out of the mount. The bolt was cross-drilled for a hairpin clip. At least on the rear, a spring change or height adjustment can be made in about six minutes.
Replacing the needle under...
Replacing the needle under the squirter hold-down screw with a ball and a spring did the trick. A 0.155-inch steel ball and half of a ball-point pen spring was used. Once the spring was close, I adjusted the tension by washers under the squirter.
Currently, the spring setup is as follows:
* All springs are 10 inches tall* Right-front: 550 pounds
* Right-rear: 450 pounds* Left-rear: 120 pounds (cut stock spring)
* Left-front: 300 pounds
The car weighs 1,534 pounds. This is to make it legal for the 1 pound per cc rule at East Bay Raceway. During construction, I was concerned it might be heavy, so I built light. As it turned out, the car was light by a bunch. One benefit is that weight can be added where it will be most beneficial.
A&A Manufacturing makes clamp-on-tube lead weights. Each pair weighs 25 pounds. You should consider using these instead of home-brewing lead weights because there are no dangerous lead fumes from melting wheel weights and no time spent finding lead-just bolt these on and go. We used 250 pounds of these weights placed as close to the left and front as possible. Another nice feature about these is that there are no brackets required. Just clamp them to any tube and move them around as you want when making adjustments.
FWD cars on a dirt track have a propensity to push in the corners. The front wheels point into the corner while the car points out. I want the car to be going the same direction as the front wheels. My logic tells me that if the left-front has enough weight, stagger, and Ackerman, this will happen. Granted, there are those racers with this type of car going fast with far different setups, but nothing gets improved unless other things are tried.
With so much weight on the front, the rear could be sensitive to spinning out. However, the right-rear is also heavy (crossweight), which should help. Also at the right-rear, the upper link was shortened 11/48 inch. This gives a few degrees of camber to this wheel.
As you may have discovered, too much rear brake in a FWD car causes the rear to seek its own path. With rear weight at only 36 percent, I think almost any braking at the rear on a dirt track would have the above effect. Brake proportioning devices are not adjustable enough to get down to 5 percent rear and 95 percent front. Solution: The rear brakes are still on the car but the lines are plugged. You say you want four-wheel brakes so you can stop? With only 36 percent of the weight on the rear, a strong application of the brakes will likely shift at least 15 percent of the weight to the front. That doesn't leave much weight for forward traction on the rear wheels. Only a small amount of braking would lock up the rear. I think I would rather have directional control of the rear wheels at that point.
This is the Honda coilover...
This is the Honda coilover setup. On the left is a 10-inch AFCO racing spring. We used these on three corners of the car. Next to it is a Honda spring cut to 10 inches.Next is an assembled Honda coilover part. On the far right is a stock length Honda spring.
As you can see in the setup illustration (p. 60), the left-front is by far the heaviest corner. This is to make the left-front wheel with its 2-inch stagger (2-inch smaller circumference) pull down into the turn. With the left-rear being so light, use your "least best" tire on this corner.
Pete Paulsen at Wheels By Paulsen is heavily involved in Mini-Stocks and even races one himself. He recommended a selection of three-off and four-off 13x7-inch wheels. Ours are not the lightest available but are on the budget end. The 7-inch width is for the track-specified tire. We could have used an 8-inch tire, but Pete thought this might be a better setup on dirt.
Don't forget about using tire size to shift weight. If your track doesn't allow any suspension adjustments, do what you can with tire size. A taller tire increases weight on that corner, while a shorter tire decreases weight. Use this to help set crossweight.
The engine fired right up. The HEI/DUI from Performance Distributors found a home at 43 degrees of advance. I guess the semi-hemi combustion chamber with no squish band is the reason it takes so much. I found this setting by propping the throttle open to 3,500 rpm and twisting the distributor. I twisted it to make peak revs, then backed off just a bit. This came out 43 degrees. I never found anyone who knew what the total advance was supposed to be on these engines.
The left-front suspension...
The left-front suspension showing our muffler shop spring spacer. Also note the spot with the brake line tie-wrapped to the spindle. This spot is where the spindle was heated and bent to change the camber. To bend it, get it red but not cherry red, and then cool it slowly.
The Colt Cam sounded sharp. Geoff Bardal at Colt said this cam could be run to about 7,000 rpm with stock valvesprings. I can tell you, at this point it certainly sounds crisp in the shop. Geoff told me that when we need some more power and can invest in some valvesprings, he would be willing to oblige. The cam's specs are:
Intake: 292 degrees duration (adv.)
Exhaust: 300 degrees duration (adv.)Intake lift: 0.422 inch
Exhaust lift: 0.414 inch
Setting the valves is just like setting those on a V-8-there are 16 valves. The Honda has four valves per cylinder. The recommended lash on this cam is 0.006-inch intake and 0.007-inch on the exhaust.
Another surprise came when we picked up the carefully stored radiator/fan unit. While disassembling the fans, we discovered that the bracket attached to the radiator covered a big hole in the plastic tank. The front end of a Honda is less than tall, but width is not a problem. Most racing radiators are at least 19 inches tall. I spoke with Chas Howe at Howe Racing Products. His catalog lists several 16-inch-tall radiators. A 16x26-inch aluminum unit with two wide cores fit perfectly in the space available. Of course new brackets had to be made, but that was easy. So far, due to the size of the radiator, only one of the stock Honda electric fans has been needed. This will keep the alternator from working so hard.
Our final buttoning-up surprise came in the form of an intake manifold and carburetor problem. We couldn't get the fuel system to lean down at high speed. With the rules calling for a Holley two-barrel carburetor, we tried both a 500-cfm and a 350-cfm. This 350-cfm is a large carb for the small 1,500cc engine, but now it works with what we have. The problem was with the stock Honda manifold design. See the sidebar for the problem, the experimentation, and finally the fix.
This shot of the right-rear...
This shot of the right-rear suspension also shows a muffler shop spacer, but of a different length than the left-front. This is the way crossweight is adjusted. Look closely and you can see where the upper suspension link was cut, shortened 11/48 inch, and re-welded. This adjusted the camber at the rear.
Holding the driver in place is a complement of M&R belts, head nets, and a window net to boot. If the head nets seem superfluous with a window net, consider this. In a left-side impact, the seat holds your torso in place. How far does your head stretch your neck before the window net stops it? It might be too far. How about a right-side impact? In a frontal impact, my G-Force helmet with the G-Force neck restraint system keeps me from sticking my neck out too far.
Honda fever has caught up with us. The car is finished and waiting on racetrack availability. In my yard, I can only go about 100 feet on the gas. I got a little wide going down hill around the tree, and I got closer to the lake than I intended, but the front-wheel drive pulled me through.
I would do a few things differently if I were to build this car again. Knowing now how light the car is, I would have made it much stronger. Larger cage tubing (it is built to East Bay's rules) as well as more bracing would have been used throughout the car.
This has been a fun project. All of us have learned a lot. Now we are going to the next phase, which is putting our thoughts, activities, and theories to the test on the track. We will be back with progress reports of our learning curve.
As always, your thoughts, suggestions, and questions about our projects are welcome. Contact me at: firstname.lastname@example.org.
This shows the springs used...
This shows the springs used at each corner, the weights on each wheel, and percentages of left, front, and crossweights. This is the way the car is set up for its first testing.
Rich/Lean: The Manifold Story
You would think a large carburetor installed on a small engine would hardly be able to generate enough vacuum to pull fuel through the jets. Such was not the case here. The rules call for a Holley two-barrel carb, so I first tried a 500-cfm and then a 350-cfm. The problem was that the vacuum signal from the engine was so strong that at about 3,500 rpm, fuel would begin pouring out of the accelerator pump squirter. The signal was pulling fuel all the way from the pump. Additionally, the 65 jets in the carb may as well have been garden hoses. All this was with the 350-cfm carb I ran on my 383-cid IMCA Stock Car.
I spoke with Mark Campbell at Crane Cams, who said there might be reversion problems and that I might want to try the 500-cfm carb. Matt Held of Holley thought an anti-pullover squirter might do the trick. After trying these suggestions-with little change-I sent a new Stock Holley 350 two-barrel carb to Bob Oliver at Competition Carburetion. We spent quite some time discussing the situation. Bob went through the carb, modifying it for better response. He also had some suggestions on jetting and pump squirter type and size.
Still, there were only small improvements to the situation. The engine would foul a set of plugs to where the engine wouldn't crank in about four minutes of running in the shop. At this point, I tracked down induction guru Jim McFarland for his take. He said he had seen this before. When he and Smokey Yunick were developing a long runner, cross-ram manifold for a Chevy V-8, they encountered "standoff."
Jim explained that the carb does not know which way the air is going, only that it goes. His thought was the long runners on the stock manifold coupled with a small plenum might be the problem. He suggested I build a box under the carb to enlarge the plenum area.
The Honda came out impressively...
The Honda came out impressively light for our rules. No melting lead, lead fumes, or welding on brackets-these are from A&A Manufacturing. Clamp-on lead weights are attached to the left door bars and around the left-front of the car.
I purchased 2 two-barrel to four-barrel adapters, bolted them back to back, and installed them under the carb. Instant plenum. Well, maybe there was a little benefit-it raised the rpm by about 1,000 before the problem occurred again. It looked like this engine might require a plenum somewhat bigger than my old 10-gallon hat. So I began to look elsewhere. I even changed back to a stock cam. No change in the extreme rich condition.
At this point, I was not looking for a cure but a fix. Surmising that the intake manifold was at fault, I looked for another way. First I drilled a 11/48-inch hole in the accelerator pump circuit. This would act as an air bleed into the float bowl. My thinking was the pump would overcome the air bleed and still get some squirt to the venturis. When this semi worked, I felt I was on the right track. However, the vacuum was still pulling fuel through the squirters at about 5,500 rpm.
I do not consider myself a carburetor man. After taking the carb off and apart for the 741st time, I removed the squirter. I turned the carb over and tapped it gently. Guess what? A pointed-end pin fell out of the hole under the squirter. This pin is part of a needle valve assembly. I suppose its weight would keep fuel from being sucked through the squirters under normal conditions. Nothing about this condition would be considered normal.
The 16x26-inch Howe two-core...
The 16x26-inch Howe two-core racing radiator nestles down in the front of the car. With this size radiator, only one of the Honda electric fans was used, saving some electrical drag.
First I tried putting a spring on top of the needle to help it stay closed. But there is only about 0.090 inch of room between the squirter bolt and the pin. So there would be no spring on the pin to fix this. Rooting around in the nether world of Sleepy's Workshop, I found a 0.155-inch-diameter steel ball that came from some bearing I cut apart long ago. I dropped this ball in place of the pin. Then I installed half of a ball-point pen spring atop the ball. Instant improvement.
Then the pump didn't want to overcome the spring. To make adjustments, I stacked gaskets under the squirter. The spring adjustment needs to be where the pump can barely overcome it.
I'm down to 54 jets with a 25 squirter. The power valve is still the 2.5 that Bob Oliver sent with the carb, but this may be changed in the tuning process at the track. When I look in the throat of the carb at 6,500 rpm, fuel seems to be coming from the right places in the correct amounts. We'll know more after we check the plugs at the track. It has been an interesting problem to fix.
The Honda engine responded...
The Honda engine responded best when the DUI distributor was advanced 43 degrees total. The Airmass Headers can be seen sandwiched in between the engine and the radiator.
The switches are mounted to...
The switches are mounted to the interior sheetmetal. The ignition switch activates a junction block. With the ignition switch on, the starter button is hot. The electric fan is also turned on with the ignition. This keeps me from forgetting to turn it on during a race. For safety, the electric fuel pump is activated by an engine oil pressure switch. No oil pressure, no fuel. When the carb is dry-you just changed jets-a momentary switch is used for a bypass to supply fuel.
Tony and Dalton team up on...
Tony and Dalton team up on setting valve lash. Just like a V-8, the Honda has 16 valves: 0.006-inch intake and 0.007-inch exhaust on the Colt cam.