by Warren Leveque
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Competition Class (CC)--C/P --Chassis and Suspension
Competition Class (CC)--C/P --Chassis and Suspension
This is not road racing. This is autocrossing, with speeds in the 20 to 60 mph range. The author has 10 years of road racing experience and about 30 years of autocrossing experience. The set -ups are not the same even though the goals are. Basically, autocrossing has no high speed braking, no sweeping turns and no high speed straights. the transients and peak G loads--lateral, braking, and accelerating are much greater in autocrossing. there is no relaxation and no settling in time. The reaction and anticipation times are much shorter. Everything comes to you at Warp Speed, requiring lightning reactions and a vertical learning curve since there is no practice.
Some goals are the same though. We must access the Corvairs strengths and weaknesses. The weight per horsepower ratio is inferior to the competition no matter how well prepared. The Corvair does have absolutely the best traction, making turn exits terrific. The Corvair is physically among the largest cars in the class, requiring more room to operate. It also has the poorest natural turn-in due to low front down (normal) force and a high polar moment. However it is now allowed to weight 1850 pounds. Soo... It must be down to weight to exploit it s best asset. Weight (mass) is inertia regardless of the lbs/power ratio. This sport rewards low inertia in nimbleness, transients, braking, and low speed (2 nd gear) acceleration.
If your car is unrusted, it can be reduced to 1850 # with out a cage and still be stiff enough. If you have all the road racing equipment for safety and longevity youll be hard pressed to make the allowed 2045 # . If rusted, it must be braced, so it might as well be with a roll cage. Removal or replacement of the rear and side window plus gutting of unnecessary interior sheet metal will be required. If you live near where I do, leave the glass windshield and wipers. Fiberglass panels except doors and tops are allowed. Be concerned mostly with reward weight loss and of course, unsprung and rotational weight.
Your suspension is fine if lowered one coil and decambered minus 1 to 1 1/2 degrees. Extreme lowering without moving subframes upward or relocating suspension points results in unwanted camber gain curves. The roll axis should incline downward toward the front.
All lag or compliance should be removed from the suspension and motor mounts. Engine torque movement affects the rear camber. Bushing replacement in the front is probably enough. the rear should have rod ends in the lower struts. The nylon bushings dont flex in the correct planes. The lateral movement of the axle should be eliminated either by spacers within the differential or by additional links parallel to the axles. If a Crown bracket is used (for its strength) move the strut mounting hole up 1 1/4 to restore the correct geometry. Crown brackets are for eliminating squat for Corveight acceleration--who are we kidding? the trailing arm bushing is fine if keeping the toe control link.
The roll distribution should be biased to the rear to make our looooong cars oversteer and take a shorter arc through the tight turns. You just have to live with the oversteer. It stops with you reaccelerate--neat huh? With understeer you just have to wait until it turns.
The desired roll bias can be achieved in various ways and the all work.
Very stiff springs can be used to achieve overall roll stiffness and rear bias. Since the suspension will have very little vertical movement, I can be lowered farther without worry of interference or camber curves. It will never lift a wheel, squat or dive. the disadvantages are that the springs must be so stiff that bump deflections can become a problem in cornering as well acceleration wheel hop.
The shock absorbers must be huge to control these springs. The car will have less motion feedback if needed by the driver.
The other method is softer springs and larger anti-roll bars. the advantages are better surface contact, more feedback, and tunability through bar and shock adjustments. The disadvantage is the possibility of wheel lifting if taken to extreme.
A good place to start is on coil off of HD springs. More may be needed if you succeed in getting your car really light. Remount the front anti-roll bar with harder bushings or rod ends and use a 3/4 or larger rear bar. If using an ADDCO bar it must be remounted.
Theres a lot of personal preference involved in set-up. It just cannot understeer. The greatest place to waste money is in expensive shock absorbers. If the wheel doesnt bounce, it is controlled. Early Camaro shocks will fit with a pin change.
The brakes are fine if perfect. Youre stopping a light car from low speeds. The bias is fine, they just cannot pull to one side or lock up. Dartiness under braking can be reduced by new brake reaction rod bushings with 1/2 of the spacer removed or rod ends, more caster--5 + degrees, and correction of bump steer under jounce. An adequate solution is to increase the length of the relay rod about 1 1/2 and reducing the tie rods a corresponding amount, or just hanging on tighter.
Three and 1/2 turn steering is quick enough. the two turn steering is for road racers. The factory quick box is preferred. The aftermarket arms yield the same ratio but because of inadequate ackerman cause scrubbing on very tight turns.
If mounting a rack and pinion this is a good opportunity to use rear steer (mounting behind the axle) to correct the ackerman.
For gearing, select an overall multiplied ratio of 6.5 to one in second gear with 13 tires and 7/1 with 15 tires for about 60 mph at redline. Plan on running in one gear because all of the gear boxes are WIDE ratio in the lower gears.
Remember the huge size of a Corvair when selecting wheels and tires. You dont want to increase the overall width or the rotational inertia. Adequately large tires for this light car can be used if the correct negative offsets are used. Four an 1/2 inches back spacing allows use of 9 or 10 by 13 inch diameter wheels or 5 inch backspacing allows use of 8 1/2 to 9in. by 15 or 16 in diameter wheels. the rotating mass is less if tire height is kept short and if heavy cantilever sidewalls are avoided. To do this the tread width should be less than the rim width. Generally, turn-in is improved and tire wear is equalized by running a harder compound tire on the rear. Super soft tires on the rear of a tail heavy, oversteering car can actually reduce cornering power due to the shearing forces.
If youre an older fellow like me, you dont want to walk a 1/2 to 1 mile course more than one or two times, so youve got to make the walks count.
The first rule of courses is not to get lost. The first time around dont worry about the individual pylons, just get the directions right. Think; left turn, right turn, straight, slalom, etc. so that youll be able to draw an elementary line diagram without pylons when you get back. If the course is lined, only pay attention to them on the first walk though. You wont see them at speed. If you are very experienced this may be the only walk through that youll need.
Try to walk the course at least once alone. Socialize some other time. Keep a lot of distance between you and the other walkers even if you have to wait an agonizingly long time. You need to see two or three turns at once. Look way, way ahead, the pylons directly in front of you dont count, if youre going fast, its too late to do anything about them. Theyre history. If you have to follow someone, make sure that hes a faster driver than you. It doesnt matter what class. Remember someone , maybe mistakenly, is following you. You young-at-heart fellows should definitely not follow good looking gals if youre trying to concentrate.
When you are able to draw the simple line diagram ( at least in your head) , then you can walk the course and look for key cones. Most designers use 150 pylons when 50 would do the job better. Your job is to find the 10 or 15 cones that really count and put only those on your line drawing. Mentally block out the rest. These important pylons should be, but may not be, pointers or tall or bright cones. Many cones are placed to be intentionally confusing, unnecessary, or redundant. Good designers will have placed pointers, taller cones at critical points, or placed orange cones on the left and yellow ones on the right for example. Pylon barricades may exist at points to absolutely turn you.
Think of the course as fast forward on a VCR. Warp Speed if youre in a really fast car.
Now you can draw or highlight, if you received a course map, your simplified course of 10 or 15 pylons. Then you can plot your run planning where your car should be placed to maximize the straights--these spots must be hit even at the cost of slowing to do it. You may have to plan two or three turns ahead to do this. Think: plan, plot, creep, stalk, until you see daylight, then hit it.
If it is possible , you should watch other cars before run before you do, from as may positions as possible. Hunt for elevated viewing spots. Only watch fast cars, it doesnt matter which class. If passengers are allowed, volunteer to be one , as often as possible.
If you have a choice of working positions, volunteer for some post which offers a viewpoint not otherwise available. Cushy jobs looking at a computer screen dont lend to course learning.
The first runs on the course should be as fast as possible. Spin on this run. Over brake, plow, etc. You need to learn the surface and the cars reactions. If you waste the first run to learn your way around, then you wasted your walk -throughs. Come really close to your selected pylons, so what if you hit them. You only get a trophy for one run.
When the event is over, there may be another great chance to learn. Some clubs allow fun runs during the scoring tabulations for a buck or two a run. this is timed, uncounted, practice for the next event. There is no cheaper track time.
The next event wont be all that much different . There are only about three maneuvers; pivots, slaloms, chicanes. This is the time for practicing new techniques.
Once more, this is not road racing. A 250 hp engine needing to be kept between 5500 and 7500 rpm without a close ratio gear box is not suited for autocrosses. Referring to the chassis preparation guide defines what engine preparation should be. The engine must be flexible since most of the course will be run in one gear. This means using either a stock 140 hp 4 speed camshaft or something one or two steps up in the range of 270 or 280 degrees advertised duration. The cam should make power from 3000 to 6000 rpm with the ability to buzz to 7000 to reach a corner even if the power is falling off. All compromises must be toward response. 110s do well in this instance.
Assuming a budget and desired reliability, a compression ratio of true 10.5/1 can be economically achieved. Use flat top pistons of .030 to .060 overbore. SCCA limit is .060, CORSA has no limit--The thin cylinder walls have their own limit. Mill the heads .100 to .120 and notch the piston a like amount. Mill the fin surface at least this much. A 38 to 40 cc chamber should result. Remember to add two spacers under the cylinders to maintain proper deck clearance of .035 to .040. Either shorten the pushrods the milled amount or use wear caps on the valve stems. the slots in the rocker arms must be lengthened to rev past 6500 rpm. 1.6 ratio rocker arms with roller tips for small block non-rail Fords will work and help reduce valve guide wear. Full roller rockers with the correct angles are available and pricey. You may need these and stud girdles if you insist on running 7500 rpm. You will need racing fuel.
Use racing valve springs shimmed to the correct height. Adjust the lifters cold to 1/4 to 3/8 turn down from no lash.
The oil pickup must be lowered into a baffled oil pan. Also baffle the pushrod tubes. Remote oil coolers dont work at autocross speeds, so save the weight and complication. You dont need a large oil pump either if you dont have a remote cooler.
The intake ports need to be enlarged by detaching the stock manifold, porting (hogging is more like it) and welding back on. In this case use bored out stock carburetors either turned 90 deg. or with relocated jets. This is good for at least 20hp and has excellent response. Large ports can also be obtained by milling off the log and replacing it with a triple barrel Weber adapter. This give s about the same horsepower and response as above but with much nicer and very expensive carburetors. The manifolds can also be removed and replaced with 6 individual runners to a center mounted progressive 4 barrel carb yielding large ports, flexibility, and ram tuning.
Large tilted exhaust ports show good results on the dyno and on the race track but may not be practical for autocrossing. Since correct tuning for solos require 48 primary pipes and muffling--nearly impossible to achieve under the car--much of the increased flow of the large tubes is lost. since the car will be running variable rpms. which range would you tune for? the first turn after the exhaust tube is important as is keeping the weight down.
A major advantage of a Corvair engine is its low rotational (flywheel ) inertia due to the non-counterweighted crankshaft of horizontally opposed engines. This doesnt mean much on a 100mph straight but when accelerating from 3000 to 6000 rpm in second gear, it is everything. This is why VW powered Midgets leave corners so quickly. This advantage must be accentuated by reducing reciprocating and rotating masses i.e.; light pistons, light flywheels, light crank pulleys, light fan, and small diameter wheels and tires. A 95 hp crank pulley works fine. the dreaded 4500 rpm harmonic is passed through very quickly.
Are you tired of adding up points in Improved Stock?
Do you want to keep your car street legal? Do you want a street sleeper? Do you want an engine swap?
Why isnt Street Modified absolutely filled up?
Ive come to the decision lately that I dont care what class Im in. Ill build the car I want and just let the chips fall where they may. But Ive gone way too far to ever go back to SM.
As I read the rules for SM, Im amazed at the rules flexibility. This is an engineers Heaven. DOT tires are required but they are now just as large and sticky as slicks. A Corvair engine may be in any location. No one has done this yet. How much lighter than a V8 would this be? It should take care of the turn- in problem by forward weight distribution and polar moment improvement. The engine can be ANY size with free induction and supercharging. I can easily envision my E/M / SC set-up of 3100 cc (192 cid) and supercharging; 250 to 300 hp in a 2500 pound street Corvair.
All of the high tech things that are not allowed in Competition Class are allowed. What a good place to experiment with exotic fuel injection systems.
I havent seen an all aluminum V6 or V8 in this class. How about a transverse Cadillac North Star or Supercharged 3800? What a killer these cars would be on the street!
I have witnessed a SM rear engine coupe with 6 tube, 4 barrel induction beat the CC cars. I looks like the limit hasnt even been scratched.
Now I suppose Ill have to eat these words when my CC car gets beaten by some of the above.
While on a Florida vacation/reunion, my brother -in -law caught me swivel-necking at a passing enclosed trailer. What was that about? he asked. What was what about? I denied. It was then that I realized that I was lusting after that trailer and/or its unknown forbidden contents.
People in cold climates recognize trailers and Robins as undeniable signs of Spring. Spring brings all of the long awaited fun activities. To put an entirely correct spin on it, America recreates or plays via trailers.. Perhaps even our heritage is immersed in trailers, i.e.: covered wagons, stage coaches, surreys, etc. Is circling the wagons so much different than what we do at trailer parks, race tracks, conventions and such.
OK you doubters, just take and impartial count as you travel down the expressway. You might see:
Camper trailers, tent trailers, fold out trailers, 5 th wheel trailers, tire hauling trailers, golf cart trailers, motorcycle trailers, motorcycles pulling trailers (quadracycles?), off road equipment, 4-runner trailers, bicycle trailers, go kart trailers, Hot air balloon trailers, airplane trailers, ultra light trailers, gliders, helicopters, horse trailers, sulky trailers, steam equipment, antiques, pulling tractors and trucks, monster trucks, show cars, hot rods, new cars and trucks, dragsters, fishing boats, house boats, ski boats, jet skis, pontoons,circuses, carnivals, country musicians, floats, Shriners, bands, jalopies, sprints, Midgets, Indy, Cart, Formula, Sportscars, Trans Am, Gt, and Autocrossers.
Along with all of these recreational trailers are their support vehicles, i.e, ,vendors, tire trucks, food, timing and registration, Race and Autocross supplies.
Car hauling trailers may vary from flat towing, dollies, unsprung, sprung, single axles, multi axles, open, enclosed, and for peoples who cant bear to be away from their toys--trailers with living quarters. Some trailers have complete climate controlled shops within. Other than money, the limit to trailer size is often how much you can park in front of your house, and how much tow vehicle you can manage.
When towing with an open trailer, there is a camaraderie and hand waving among similar types or interest. I honestly miss this when towing with an enclosed trailer. Im starting to see some enclosed transparent trailers--clean cars and camaraderie.
Most of us towers cannot look at new vehicles without rating their towing capability. the newest status symbol is that square 2 inch hole beneath the rear bumper. There is a special vocabulary for towers. Words like; gross vehicle weight, tongue weight, torque axles, surge and electric brakes, brake controllers, winches, ramps, stabilizers, sway control, and wind resistance.
Some of us are so addicted that we build our own trailers to personalize them.
Trailers themselves bring their own ambiance: the sound of load levelers, and sway controls chirping and squealing while parking, the sound of two or more axles being dragged sideways, power steering belts squealing, 500 cubic in V8 or V10 engines chugging, flashlights and yelling while receiving help hitching up. Come on back, you cant park here arguments, and my favorite complaint: the towing person parking right close behind your ramps so that you cant unload.
Who among us hasnt felt a little twinge of romance when coming over the last hill or around the last bend and looking for familiar competition vehicles and/or their trailers which brought them and wondering who brought which toys?
People are constantly asking me What is the significance of the Tweety Birds painted on my cars? At first I didnt think that there was any significance, it was just a lark. Maybe its my puppy dog. At car shows, young ladies with children in tow will be dragged past other cars by the child wanting to see the Tweety Bird. Honest, it was not my first intention, but I certainly dont mind it. Its also a good hook for business card (Tweety with glasses--did you notice?) but it also was not the primary intention.
Back in the seventies when I was road racing a D/P Yenko Stinger, it was an underdog. This was between the Reeves and Schardt successful years. People who took themselves way too seriously all had racing team logos even if the team consisted of only one member. Nearly all of the cars had some ferocious monster painted on the flanks--tigers, lions, bears, crocigators, etc. We even had team races identified by animal logos. MY team members were pushing for some kind of logo. Since I had very little money for racing, I had spruced up the cheap steel parts with yellow paint--like yellow widened steel wheels and yellow exhaust headers. Our very supportive local sports car club (SCCCI) had adopted yellow racing jackets with narrow red stripes. So as I was pondering the logo decision, I walked past a full length mirror in the mall and saw reflected back the image of a small guy dressed in yellow. The decision was made.
This decision was met with overwhelming positive acceptance. Our previous Team Cheap became Team Cheep. I actually had a few very successful years in this era, but since it was still such a low buck effort, the underdog character stuck.
As racing became too expensive to continue, I became more of an autocrosser. People came up and asked if they could be part of Team Tweety. I dont know to this day what they thought they were joining. We had a fairly large group of cars with Tweeties which would caravan to autocrosses. I was great camaraderie. We would race and socialize together and help each other out. When I would put on an event ( with my Tweety helpers) I gave out an extra award of a stuffed Tweety Bird. This was the Top Tweety award for an outstanding performance--not necessarily Top Time of The Day. People who won it acted as if they had struck gold--they loved it-- I loved it.
Tweety tee shirts and sweat shirts popped up everywhere. I still get them as gifts and still love them. I also noticed a lot of Sylvester decals and dolls on some of my rivals cars. At a recent Halloween autocross, I dressed up in my full size Tweety costume. NO one seemed surprised. I sometimes quietly give out Tweety decals (hand painted ) and lapel pins to persons whom I and my other Tweety pals agree have the Tweety attitude.
At the risk of over analyzing something which came about by accident and seemed to take on a life of its own, Im going to do it anyway. What is a Tweety?
Tweeties seem to have the afore mentioned underdog attitude--underbird?
Tweeties always seem to try very hard no matter what the circumstances or the odds. Although some Tweeties are National Champions without the accompanying attitude. Tweeties dont seem to know when they really dont have a chance. Tweeties are just happy to be there. They never get eaten by the mean old cat. Tweeties seem to have an unassuming, modest attitude no matter what their actual circumstance. There are no Big Shits here. There seem to be a disproportionate amount of lady Tweeties. Maybe we men still tend to take ourselves too seriously. And the most likely candidate for a Tweet is--the person who asks.
SCCAs Solo II E / Street Prepared class is for performance oriented mid-size sedans and PONY cars. The toughest cars are the V/8 Camaros and Mustangs. The Corvairs do have a good chance though if the rules are applied well.
Basically, the rules allow free bolt-on wheels, springs, anti-roll bars, seats, carburetion, and intake and exhaust manifolds. Nothing can be removed, and no internal engine modifications are allowed. The reason GM F bodies lead this class is because the 70 1/2 LT 1 Chevys and HO or SD Firebirds are virtually factory race engines internally. Ford also has some Boss factory race engines. this virtually killed the Corvairs chances until SCCA listed the Stage III Yenko Stinger ( GMs factory race Corvair) on the same line as all Corvairs which permits interchange of specifications.
SCCAs WRONG interpretation of free bolt-on intake systems prohibits equality of intake flow with the V/8s. They call our manifold part of the head. Bolting on a four-legged intake with a center plenum makes a poor manifold even worse. The large carburetor and plenum does make more top end power only because its larger. This is done at the expense of most of the lower range and throttle response due to the added corners and confusing piping. It is not ram tuned unless there is a separate uninterrupted path to each cylinder. However, I have seen good drivers make very good use of the increased power.
The most reasonable solution for legal low speed racing is to straighten and enlarge the corners in the existing log manifold as much as possible-per the Stinger D/P method. If you remove the manifold to do this and weld it back on, there can be no material added. There are many veteran road racers who can show you how to do this. Up to 20 hp can be gained with no loss of throttle response using staged, bored-out carburetors. Listing of the Stage III Stinger makes this possible.
The stock bored-out carburetors if rotated 90 degrees on the manifold cures most of the cornering problems. Vent tubes still need to be added for flooding. Cornering starving can also be fixed by jet relocation which permits use of the stock progressive linkage. If the venturies are bored to 1 1/4 you have as much flow as most 4 barrels and better throttle response. the carbs can be made as large as 1 3/8 to 1 7/16 but require extensive machining ,sleeving, and 1 1/2 throttle plates.
Stage III specs. allow 10.5 compression ratio and camshafts of about 300 degrees advertised duration and .050 lift. dont worry about the confusion regarding exact Stinger specifications; a cam of about 280 to 290 works better for autocrossing anyway. If you run a 310 to 320 cam all power below 5500 goes away and youll be slower without a super close ration transmission and 5/1 gearing. Select gearing between 6 and 7 to one overall in second and never shift down unless stopped.
The required use of muffling makes exactly correct exhaust tuning nearly impossible due to length constrictions. Any after market headers will be fine. Watch the weight in this area. Prepare the engine like any other race engine; baffled oil pan, notched rockers , notched pistons, heavy valve springs, balancing, .040 overbore, etc.
Utilizing the rear seat deletion (carpeted area) , Stinger rear deck lid, light seats, and light wheels will bring the car comfortably under 2400 #. Be creative, use the orphan clause for replacement of no longer produced items.
If you decide to use a Turbo, the best legal combination would be the exhaust section from an early model and the compressor section from a late model. After- market exhaust housings or compressors are not legal. Its important to go to the maximum cylinder overbore to increase flow to the exhaust turbine. Wrapped cross over pipes reduce the lag time. There can be NO exhaust leaks. If you use a large progressive Weber, a Rochester Q-Jet 4 barrel, Pro Injector, of any thing else around 600 cfm, 18 psi gauge pressure can be realized with this set -up. If you want to limit boost, a small Weber with small chokes will net you about 10 to 12 psi. No added waste gates are allowed. Since you need a muffler, you can use a Super Trap to control boost by varying the number of plates. You can limit the opening of your 4 barrel carb to do the same thing. Its not legal to change the compression ratio in either direction on Turbos, so youll likely have to use water injection of racing fuel.
The rules allow any non-metallic bushings. Take full advantage of this, especially in the rear of the car including the engine and trans mounts. Also the new rules permit the addition of lateral links to remove the slop generated in the differential. When using the free anti-roll bar rule, be sure that they operate freely without binding. Go for more rear roll resistance with your combination of bars and springs. HD springs cut 1 1/2 coils in front and 1 coil in back is a good starting place. 3 1/2 turns is fast enough for the steering. Stock brakes are fine if in perfect condition, they were designed for a 3700# car and youre only stopping from 60 mph. The battery should go into the trunk for better turn-in.
Wheels of any width and diameter are legal-no fender cutting. Sizes from 13 x 7 to 13 x 8.5 seem to work best considering the compromises of lowering, gearing, overall width, clearance, and flywheel effect. If you choose to run radials, use around 1.5 deg. negative camber. Bias tires only require about .5 deg. negative. The required DOT legal tires ( shadow tread-cheater slicks) are available in 225 -45 -13 sizes.
This car can be entered in CORSA events either in IS-3 or S M depending on your points total, its also a blast on the street.
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