Thirty-four great articles by Warren Leveque
Please read these two "Preface Articles" before using the "Table of Contents" to select specific articles.
The 90% Solution
Being the Competition Chairperson presents me with the opportunity to be an insider. I get to know about all of the activities going on and the car development being done. Im sort of the middle man. A lot of this info passes through me and maybe some of it even stays. Of course this whirlwind tour that Ive been on lately helps also. The point is that the general membership doesnt know about the depth of the performance group within CORSA. The performance group doesnt even know because it is somewhat fragmented. Ill take this moment to shamelessly promote the performance online group: http://www.onelist.com/subscribe/fastvair, just so that you can know how many of you there are and not to be so timid with your views.
Many of this underground group are building what Ill call a 90% race car. Although stock cars are extremely welcome in autocrosses and time trials (of which there are many and growing) some want just a little more performance without complete dedication. The thing is, most dont know of the others doing the same thing. There is almost a formula for these cars, without any general consensus.
Very few enthusiasts are on the lunatic fringe like myself and some others, you know who you are. Extreme cars are often extremely broken. Ill list what Ive observed and know to be true about Formula 90%.
You need a good strong body or a rust bucket (like mine) with a roll cage. Most seem to prefer a good strong, but not restorable late model coupe. Nothing precludes an early model if you handle the rear wheel tuck-in with decamber and roll stiffness, and check the rear wheel bearings and axles often.
Unbolt everything! Removal of everything but the windshield will yield a car weight of about 2150 pounds. All windows can be lexan, but I prefer a glass windshield for its optical clarity. This is about 95% of the weight reduction of extreme race cars and the car can still be restored at some time if desired. Taking it to the road racing minimum 2045# requires butchering. Taking it to the new 1850# SCCA C/P autocrossing limit is unbelievable in scope. There will be very little Corvair left.
If running slick racing tires, some organizations require a roll bar, harness and fire extinguisher. Vintage racing organizations allow a six point cage. Use this cage with a diagonal across the door opening. If running any kind of performance tires you will need a racing harness.
If you want to retain the stock fender openings, use wheels of 7 inches width on the front and 8 on the rear, in any diameter you choose with 4.5 to 5 inches of backspacing. If you want to use the 10 wide cantilevered racing slicks, youll have to use 13 diameter wheels. This is what Jim Schardt uses to kick our butts. Id recommend the 13s because you can find the tires NOS or used for one heat cycle for far less than half price. Inexpensive steel wheels are fine for occasional racing.
If you are autocrossing, stock brakes are fine. If you are time trialing or vintage racing, venting and performance linings are recommended. Steering of 3 1/2 turns is quick enough. Any steering wheel will do. You need a good supportive seat to counter the increased G forces.
The suspension needs to be in excellent condition, but not greatly modified. Because the car is lighter, the springs will need to be cut 1 1/2 coils in front and one coil in the back. This alone may give the desired negative camber of one degree in front and 1 1/2 in back. All of the rubber bushing should be replaced, especially in the brake reaction rods and the rear lower strut link. Bolt -on lower rear links with rod ends are available. Solid motor mounts will improve the suspension reaction under engine torque. Use the stock front anti-roll bar with new bushings or any combination of bars or springs that will give the same front to rear roll bias.
You wont believe how well a stock Corvair suspension will work if in perfect condition. Use heavy duty shock absorbers. Early Camaro shocks will work with a pin change. Expensive dual adjustable shocks are for classes and cars where nothing else is adjustable. Check the lateral slack in the rear axles. If the change in camber is more than a half of a degree, something should be done. The slack can be removed inside the differential by new side nuts or by external lateral strut additions. Some race quite successfully with just added negative camber.
There is no advantage in amateur events of close ratio transmissions. The spacing of the first three gears is the same and the first gear ratio is useless. Just use a Saginaw gearbox or be careful. A 3.55 differential ratio is right for most situations. A Corvair needs a limited slip rear end the least of any car ever produced, but a four spider carrier should be considered if drag race starts are contemplated. A NOS clutch works fine if you can find one. I recommend a rebolted stock or scalloped flywheel with a low performance high pressure clutch cover. Use a high performance clutch disc, and of course a new pilot bushing and throw out bearing.
As in the suspension, you wont believe how well a stock Corvair engine will run if in perfect condition. You might as well go with a 140 horse power engines now. All of the engines are old enough to have valve seat failures, the 140s were the first to fail. Heres the largest expense unless you can find NOS heads; new valve seats, guides, and performance valve springs are a must. The heads can be milled .060 to remove the step. The step is most likely ruined anyway and needs a clean up. If you mill any more than this you must flycut the pistons for valve clearance. Premium gas will work at this compression ratio (true 9 / 1) Good forged pistons probably dont need to be balanced for reasonable rpm use. the crankshaft is excellently balanced from GM. The rods however are terrible, youll be lucky to balance six out of a dozen. They are plenty strong though.
The best camshafts for reasonable rpm use (6500 rpm) is advertised duration of 280 degrees or stock 140 for manual transmissions. If you go to wild camshafts, youll need close ratio gearboxes, huge carburetion, maximum compression ratio, and much more rpm. 6500 is the magic number for a long lasting engine. Stock rocker arms with widened and lengthened slots work well at this rpm.
Carburetion at this performance level ( true 180 hp ) can be bored out stock carbs with the turn cut out fixed, rotated, or add on 4 barrel units. Unless you are going to the six tube intakes, the bored out Rochesters are as good as any add on four barrel. Vendors sell some beautiful air cleaners for the single barrels. I believe the inclusion of six tube intakes, Webers or hogged manifold logs put us out of the 90% category just due to cost.
The oil starvation problem must be fixed with baffled pans, lowered pick-ups, and push rod tube baffles. The stock oil pump and cooler are fine for these uses if the side sheet metal or some substitute is retained. Synthetic oil is good protection for high temperatures. There is no advantage to cut down fans at these rpms. A good wrapped, silicone soaked fan belt restrained by a non-wobbly spring loaded idler will stay on under these conditions.
The stock distributor in perfect condition and a large coil will do the job up to 6500 rpm. There are several electronic conversions including the GM HEI if you are so inclined. Turbos need all of the juice that they can get.
Turbos follow all of the above rules, plus ignition improvement, water injection or race fuel, and a wastegate if you change the stock carburetor or exhaust scroll. 15 psi gauge is the reasonable limit of boost. 10 psi is better for longer events.
There is much discussion about header systems. The consensus seems to be that if you have to run a muffler, then you cant possibly have a properly tuned system anyway because of the space constraints. Just worry about the back pressure and the first bend after the exh. tubes. Dont trust a manufacturer just because he claims a turbo muffler, some of these are highly restrictive. Money is probably wasted on large tilted exh. tubes for the same reasons.
Also dont forget that we are promoting CORSA when we are racing, so dont forget the shiny paint job and the CORSA decal. The public cant tell a 90% car from a 100% one. Neither can you unless you are one of the ITs. You will have 90% of the performance at a fraction of the cost and 100% of the fun. A good driver nay even win in a 90% car.
I think that youll be surprised at the turn out of Formula 90 if you look for it. Its like a club within a club.
Every year when the season gets underway, Im always amazed anew how close some disparate cars run together.
Ive attended autocross events where the last run of the day decided whether a CS Toyota or a Modified or Prepared car won Fastest time of the day. I witnessed the same thing again at a recent Australian Pursuit. In both cases the theoretically fastest car won but not by much.
Ive quizzed many competitors about this phenomena and got no good definitive answers. Theres a lot of talk about IT drivers, courses for cars, preparation levels, etc. It just happens too often to be ignored. Since no one else seems to have a better handle on this than me, Ill just flail away.
Putting race rubber on stock cars ( which Im totally against) really skews this subject but serves to make it more noticeable. There are some really well balanced stock cars like Corvettes, MR2s, and Miatas available today. Putting the race rubber on them brings them up to the level of some of the Prepared cars.
Course design can unfairly skew the results. Too narrow courses unfairly penalize large cars. Narrow courses also dont allow choices of car placement and dont allow talent to be demonstrated. Courses which cause cars to nearly stop and then give lots of room to reaccelerate give the wins to powerful cars. Memory or confusing courses give the wins to more experienced people. Ive never understood tight challenging courses. If you have a small less powerful car; big momentum, type courses feel more like road racing , are more fun and equalize the cars.
Some of us even prepare the race cars out of competitiveness, which brings us down a level. Also prepared and modified drivers suffer from a lack of seat time since their cars cannot be street driven or tested. Seat time also cant be gained while broken. Add to this, the more powerful cars cant use the power if the surface isnt grippy, its bumpy, or raining. Also racing slicks dont perform well on cold surfaces. Still this doesnt explain it all.
Lacking a better theory; Ill present the hump theory.
In a typical 60 second event there are categories of performance or humps: Ill sort these as to how much improvement is possible in a typical 60 second run:.
Hump 1 10 seconds possible improvement 60 to 50
All real street tires. Real grocery getters. Most trucks Lost on course
All novice drivers. Rental cars SUVs No seat time
Poor running cars. Diesels Cone Hitters Rain
Difficult courses Ladies
Hump 2 5 seconds 50 to 45
Sports cars DOT race tires Street Prepareds
Sporty cars Experienced drivers Moderate seat time-6 events/year
Local competition Poor surfaces Aggressiveness
Cone free runs Good Front wheel drive cars More Cones
Hump 3 3 seconds 45 to 42
Drivers school grads All sticky tires Lots of seat time-12/yr.
Correct car preparation Factory stock race cars Regional competition
Hit cones on few runs Adequate horsepower Good form
Requires a good driver in a good car.
Hump 4 1 second 42 to 41
Right car choices Several schools Unbelievable seat time
The best stock cars. Prepared cars Race cars Runs one car exclusively Adequate power
Seeks variety of competition-National competition. Correct car placement
This level is still very driver talent dependent. An excellent driver can carry his car. Many combinations can win.
Hump 5 .5 second 41 to 40.5
The best stock cars ultimately sorted, Nationally competitive drivers.
The best prepared and modified cars, Lots of testing Moderate power
One clean run Hit all the correct spots. Appears fast
No Front wheel drive cars.
Hump 6 .1 second 40.5 to 40.4
IT drivers Ultra best stock cars-excess power Powerful Prepareds
Modified and Prepared with excess power Powerful Modifieds
One clean run Regional champs Correct car placement regardless of technique.
Hump 7 .01 second 40.4 to 40.39
IT drivers No stock cars Very few Prepareds-light-new tires
Excess power on grippy surface One clean run
Light Modifieds on new sticky tires National contenders
Appears slow No obvious technique.
Hump 8 .001 second 40.39 to 40.389
IT drivers Light Modifieds on new sticky tires National champs
Brain Stem driving One clean lucky run Did he just run?
Cant explain how they do it. Did he miss part of the course?
Notice how the humps get smaller and smaller and unbelievably harder to get over. Its the true law of diminishing returns. The person in the smallest , fastest bracket is trying harder to gain .001 second than the person in the largest slowest bracket is to gain 10 seconds. To the casual observer, the car that is finishing less than a second off the winner could easily close the seemingly tiny gap. That gap just might as well be the Grand Canyon.
Its easy to see how skill level and car preparation can raise a person several brackets (humps) until you get close to the top. The adept driver using a stock .
A well balanced, well prepared car on DOT race rubber can run over the hump in the less than .1 sec. bracket (humps 5&6) and be a genuine hero but can never make it over the hump into the final bracket.
The final hump requires: an IT driver in a small, light, powerful prepared or modied car and a little luck.
List of articles on these pages.
Click on "Page" or "Article" to JUMP to it!
The Basics of Solo
The "Death" of Prepared Classes
Competition Turbo Engines
A Tenth of a Second
The "Special Olympics"
Just Happy to be There
Competition Class (CC)--C/P --Chassis and Suspension
Turbo Weber Setup
Front Wheel Drive
Turbo QuadraJet Setup
Rent - A - Racer
The Road to Mid - Ohio
Requiem for the Lightweights.