Saturday, March 8, 2014

Building a Car for LCP or Express: Historic C

La Carrera Panamericana


V8 AND V12 – 1955-1965+

These notes are based on the official rules, as well as the folklore, of La Carrera Panamericana.  However, nothing herein should be considered official.   

Please print out and study the most recent edition of the rules that are posted on before buying, building, or modifying a car.  The rules are there in both English and Spanish, but the Spanish version is the official version.  How’s your Spanish? 

It is difficult to develop a comprehensive and consistent set of rules for such a wide range of cars – from former beaters and grocery-getters to exotic, single-purpose racecars capable of speeds over 200 MPH. 

When these notes say “by Rule” below, it means what follows is stated explicitly in the rules for 2013, or at least I think so.   (The final rules for 2015 may not be posted in final form until much later next year. so you must go by the 2014 rules.  I do not expect much change from 2014 to 2015. 

If it does not say “by Rule,” then it is folklore, opinion, or advice, based on my personal observations over the past decade.  Of course, all of this may change when a new inspector shows up at the start of the race, or the owner of the race wants to allow something different at the last minute.   

The Pan Am is unlike a typical vintage race in the USA or Europe.  Carrera inspectors are primarily interested in safety and somewhat in having a fair race.  They are not much concerned, if at all, about originality.   They are also not experts in old American cars,  but seem to know more about European cars. 

Because the rules are based to a degree on custom and tradition, the inspectors’ interpretations may be highly subjective.   Regardless, if you are a rookie, read through this document, especially the final observations at the end, and then re-read the Official Rules.  As noted above, be aware that the rules or the interpretation of the rules may change at any time, even in the middle of the event.  Viva Mexico! Via la Carrera!

Selecting a car:  About half the cars in LCP are Mustangs, Falcons, and Porsche 911s.  The Organizing Committee wants to see more diversity, like more Chevys and Chrysler products.  They are especially fond of four-cylinder cars, likle Alfas.  Of course, many of these cars are now getting expensive, so remember, most of the cars outfitted for LCP cannot be used in vintage racing in the U.S. or especialy Europe, unless they are built so they can be retrofitted to comply with vintage or FIA rules.

Also be mindful that the cages in most vintage cars and even SCCA track cars may not pass inspection in LCP or the Chihuaha Express, which require a FIA-style full roll cage.

How much will it cost to build a safe, dependable car with enough speed to have fun?  Probably around $50,000 for a non-exotic U.S. V8 or more for a Alfa, unless you have a lot of donated labor.  And then, it is purpose-built.  In most cases, it is far more economical to buy a car that has already competed in a recent Carrera or Chihuahua Express.  Of course, speed costs mega dollars.


When the modern Pan Am was launched in 1988, only cars made from 1940 to 1954 were allowed to participate, as in the original race (1950-1954).  This was later changed to allow cars made through 1960 and later, cars up to 1965.  Now some cars up to 1968 and even to 1972 (four cylinders only) are accepted.  

The rules for all classes have changed since the 1988-1999 period.  If a car competed in the event in 1993, it may not be eligible to run in 2008-2009, or may require significant modifications to qualify it for a specific class.  The safety requirements are far more stringent.  Even a car that ran the race in 2008 may require significant modifications, especially to the roll cage and safety equipment. 

Historic Classes.  Production autos made from 1955 through 1965 are eligible for the four (4) Historic classes: A, A+, B, and C.  Some cars made after 1965 are also eligible, if they are essentially the same as a 1965 model, that is, have the same engine, look the same, and afford no performance advantage (engine and suspension).  This is called (unofficially) the “continuation rule.”  Historic B goes up to 1972, but cars in that class made between 1965 and 1972 require special permission, as do the cars in Historic A Plus. 

Examples of the continuation rule in the Historic classes include a ‘66 Mustang in Historic C; a ‘68 Porsche 911 in Historic B, and ’76 BMW 2002 or ’71 Mini Cooper S in Historic A.  Normally, the sports version of a model is accepted, but sometimes, the organizers frown on racing engines or a 356 Porsche with special racing heads.   

Additionally, by Rule, only small block V8s with ieon heads are allowed in Historic C.  Some cars, like a Camaro are limited to a max 302 c.i. engine, and Cleveland heads are not allowed on Ford engines.  Historic C cars must weight 2800 lbs to carry a four-barrel carb. 

Summary of classes:

Historic A+.  Sports cars and sports sedans made from 1966-1972 with four cylinders engines under 2000 c.c. may run in a new class, Historic A+, created a couple of years ago.   These cars may also use a modern engine of 1600 c.c. or smaller.  Thesew cars are subject to prior approval by the Organizing Committee.  

Historic A.   Four-cylinder cars with original engines manufactured from 1955-1965 may run in Historic A.  Some made after 1965 may be considered. 

Historic B.  Six cylinder cars from 1995-1972 may run in Historic B.  Those made from 1966 to 1972 must receive prior approval. 

Except for wheel rim width and a couple of other items, like carbs, the rules for Historic C cars are about the same in concept as the rules for Historic A, A+, and B cars.   

“Specials” and Replicas.  Cars of “special interest” and true replicas may petition to be included in the competition, but some may only run in Exhibition.  Replicas with modern suspensions and engines should run in Exhibition.  Those with V8s would run in Historic C.


Engines in Historic class cars should be from the same family (GM, Ford, Chrysler, Jaguar, etc.), as the chassis and by Rule, be from “the period.”   However, late-model Studebakers have been allowed by the inspectors to use Chevy engines.  Crate engines are clearly not from “the period,” but they seem to get through tech.

Boss 302.  By Rule, effective in 2009, a Ford “Boss 302” four-main engine (block and and Cleveland heads) is not allowed.   However, a 302 Ford engine is legal in Historic C.  

Dry sump.  By Rule, these engines are not allowed in any class. 

Internal engine parts.  By Rule, all moving parts of an engine are "free."  Any piston, ring, cam, rod, crankshaft, valve train, etc. may be used--made of any material.   

Period speed parts.  Parts “from the period” are allowed by Rule.  Examples are aluminum manifolds and different carburetors.  Documentation may be required for other items. 

Ignition.  Any ignition system will pass tech. 

Exhausts.  Tube headers are OK by Rule, and the rest of the system is “free.”.  “H” and “X” pipes OK.  Mufflers are highly recommended (by me), but not required.  “Cut-out” pipes are OK. (!) Think about driving a car with an open exhaust for seven will be deaf and not popular.

Displacement.  You may use the largest small block engine generally available to the public in that model car in 1965.   Big blocks may  be used in full-sized cars only.

Examples: Mustang, Comet, Caliente, Falcon = 289/302
Nova, Chevelle, Corvette = 327
Impala = 409, 427 (maybe not a 400 small block)
Galaxie = 427 

There is no explicit rule, but it would be improper to install a big block in a small or intermediate-size car.   Also, some limited production engines, like a 396 in a ’65 Chevelle or ’65 Corvette probably would not be allowed, or be subject to protest. 

Bore.  By Rule, up to a .040 service bore is allowed.  Displacement is subject to P and G test, or tear-down inspection at the end of the race for the top four finishers in each class.   

Stroker engines.   Not allowed, but the rules do not expressly forbid such.  It is OK to use a 327 crankshaft in a Chevy 350 block to “de-stroke” (decrease the stroke and cubic inches) it and make it eligible, or use a 302 crank in a Ford 289 block.


            Historic A – factory or period piece(s)
            Historic B – factory or period piece(s)
            Historic C – By rule if the car weighs less than 2800 lbs., it must use one two-barrel of 500 CFM.  If it weighs 2800 lbs. or more, it may use a four-barrel of 600 CFM. 

A 600 CFM  Holley is probably the most popular carb for this event for V8s.  Because of the high altitude and thin air, big carbs are not a significant advantage.  The inspectors have checked the serial numbers of carbs. 

Radiators and fans.  Just about anything goes.  Aluminum and bigger radiator OK.  Fans-- electric or pulley OK.  

Oil and transmission coolers.  All OK.  Dry sump—not OK.  Accusump (oil accumulator)—OK. 

Cylinder heads.   Aluminum heads (and engine blocks) are NOT allowed in Historic C.  This is stated in the rules, but the inspectors have bumped these cars into Exhibition.   

Fuel injection.  By Rule, fuel injection (FI), superchargers, and turbos are not allowed on any Carrera car.  If your production car, however, has a mechanical FI system installed at the factory, like a Mercedes or Porsche, ask for prior approval.   Most Mercedes with factory mechanical FI and some Porsches with factory FI have been allowed to compete.  Because of the changes in altitudes along the route, FI is considered a significant advantage, especially among the cars in contention for a podium finish. 

Fuel pump and fuel lines.  Any kind is OK (see Safety). 


Ignitions.   As noted above, the ignition is “free” (MSD, etc.); alternators may been replaced.  Historic C cars should have a MSD with a rev limiter.  Top speed (RPM) is limited based on a formula to 144 MPH.

Generators.  Alternators may replace generators by Rule.  Belt drive—free. You may rewire the whole car.  Serpentine belts are OK. 

Master switch.  An external master switch for the entire electrical system is required on the outside of the car.  Mounting another master switch inside the car may be a better option, since there are not many corner workers along the route.  The switch should cut off all power in the car.  Most racecars have a switch inside and outside of the car. 

Battery. There is no rule about the battery.  Thus it may be relocated to trunk or passenger compartment.  If in the passenger compartment, it should be boxed and vented, if a wet cell.  The positive terminal should be shielded (insulated).  You may use a light-weight starter.   

Lights and horn.  By Rule, all running lights, horn, blinkers, and flashers should work.  Sometimes they check.  Rig something up to get through tech.  Headlights, wipers, and turn signals are important, although we generally do not run at night.  However, cars should run the speed stages with their headlights on.  Heaters/defrosters are optional. It usually rains at least one day, so wipers may come in handy. 


Transmissions and rear axles.  By Rule, transmissions and  solid rear axles should be original or from the period.  There is a limit of four forward gears.  But modern four-speed (forward) gearboxes, such as updates of a Muncie, are been allowed.   Sequential or “straight-cut” gear boxes, like a Jerico, are also not allowed by Rule.  Some people have been criticized because of the transmissions in their Mustangs, but I do not know the details.  Could it be a “top loader” problem? 

Drive shaft.  The material (steel, aluminum, or carbon fiber) is not an issue, and drive shaft loops are not required. 

Rear axle.  By Rule, the axle should be original, that is, solid or “live,” unless factory IRS.  (No Jag IRS on your Chevy!)  Any axle ratio OK, posi-traction OK; replacements live axle (like a Ford 9”) are OK.  The specific allowance for 9” does not appear in the rules, however.  Some people use aluminum center sections, too. Most people like a 3.50 rear gear or maybe a 3.25, given the long transit stages.

Oil coolers. Engine, p/s, trans, and diff.  Allowed and encouraged by Rule. 


By Rule, modern ventilated disc brakes, front and rear, are allowed and encouraged.  Pad material is "free.”  Any caliper or rotor is OK.  A modern, dual master cylinder OK and recommended; brake bias valve OK.   An emergency brake is optional.  A car is only as good as its brakes. (Drilled rotors are not considered a good choice by many racers. Slotted rotors are OK.)


Suspension.  By Rule, the shocks must be located in the same position as stock.  This is about the only specific rule regarding suspension.  Some negative camber is recommended. 

Control arms.  You may strengthen stock control arms by “boxing” them and using bigger, stronger parts (ball joints, bearings, spindles, etc.).   Tubular control “A” arms are OK if mounted in the stock location. 

Shocks and springs.  You may use any shock or spring, as long as the shock is mounted in the stock location.  Coil-over springs are not allowed, but who knows, if the shock is still located in the same position as stock.  

Steering.  By Rule, the steering may be “improved.”  But the application of this rule is not clear. Regardless, rack and pinion has been considered improper for Historic C cars.   Power steering is OK.

Frame.  May be strengthened, and sub-frame connectors added to unibody/monocoque cars.  There is no rule to prevent the roll cage from going through the front and rear firewalls and to the suspension points, as there is in some vintage organizations. 

Anti-roll devices.  Any front or rear sway bar or Panhard rod, etc. is allowed by Rule. 

Shock-tower or Monte Carlo braces.  OK 


Roll cage.  The rules about roll cages are not clear.  The written rules, for example, do not match the diagrams presented.  Each car is evaluated differently, it seems.  The Carrera inspectors are heavily influenced by FIA and WRC cages, which are somewhat different from the track cages approved in the USA by NASA, SCCA, and even NASCAR. 

Before you buy and install a roll cage in a car, you should send a drawing or diagram, with information about the tubing, to the North American Coordinator or chief inspector for an opinion or ruling. 

By Rule, every car must have at a minimum a six-point roll cage with a bar across top of windshield, and at least two bars or “x” across the doors.  This means that there will be a steel rectangle or “halo” over the heads of the driver and navigator, with a ¨”x” brace across the ceiling.  An “x” brace in the door is expected now.  There must be one diagonal brace under or behind the main roll hoop.  Two main roll hoops, connected by lateral bars is acceptable, too.  In larger coupes, a windshield brace or Toyota bar may be required.  This car has a brace near the passengers heads that might suffice.

Diagrams of roll cages will be provided upon request.

Tubing.   1.75” OD x 0.089” wall thickness (minimum) or thicker mild steel tubing is required for Historic C cars weighing around 2800-3400 pounds.  If the tubing is much thicker, like 0.134” then the OD may be ¼” smaller OD.   (By Rule, an inspection hole should be drilled in the cage, but so far, I have not seen the wall of any tubing measured.) 

There is no clear requirement about the type of tubing, other than OD and wall thickness.  DOM is better than ERW tubing, but seamless DOM is the best.  Chromoly is OK if properly welded.  They sometimes check the welds up by the A pillars. 

Smaller cars may use 1.50” OD tubing.  Heavy cars (4000+ pounds) should use 2.00” at least for the main components of the cage.  Some cars may require more support tubing than other cars.  Eight or ten point cages are better, especially in convertibles. The faster and heavier the car, the stronger the cage should be. 
If you are building a new car for the Carrera, please consult about the cage's design before it is welded up. 

Roof.  Carrera inspectors want to see an “X” brace over the passenger compartment (as in the photo above), like WRC cars.  This rule was enforced in 2012.  Their are options using two diagonal bars, too.  

Bends and Gussets.  All bends in the tubing should be mandrel, without any “wrinkles.”  The inspectors also want to see the four corners of the “halo” over the crew’s heads strengthened with gussets (tubing is safer than plates), and they want to see at least two diagonal, rear braces for the main hoop.  

Lateral reach.  In addition, the inspectors do NOT like to see the lateral support bars that run across the top of the front doors—the forward supports of the main hoop—to extend more than 23-24” from the juncture with the bar across the top of the windshield without some vertical or diagonal support.  

In the photo above, for example, there is a vertical brace near the crew’s shoulders, a “helmet bar” in drag racing terms.  “Toyota bars,” which are diagonal bars that run from the floorboard near the front of the door and up to the top of the A pillar area of the cage, are increasingly popular, too.  They will help to brace the front edge of the car’s roof and cage. 

Most serious cars accidents in rallying are frontal collisions with a boulder or tree, or a roll over, not side impacts like in track racing.   Thus there is more emphasis on supporting the front of the cage at the top and the ability of the cage to sustain a series of flips and rollovers without caving in on the crew’s heads.  See example below. This car rolled and flipped violently 8.5 times at over 120 MPH and this roll bar deflected less than ½ inch.  It was a ten-point cage. ERW  1 and 5/8” stock. 

Seat Belts.  By Rule, five point 3” belts (not more than four years old).  2” shoulder belts should be OK with HANS but it is not clear. 

Head and neck restraints.  HANS, Leatt Brace, or other SFI or FIA approved neck braces have been required since 2009. 

Seats.   they want to see FIA seats but by Rule will accept Kirkey aluminum seats, properly installed.  Any seat that folds or slides forward or reclines is not acceptable.  Strong or reinforced attachment points to the floor and roll cage are important.   Modern FIA approved seats (carbon fiber) do not need to be attached to the roll cage, but the backs of aluminum seats should be braced to the roll cage.  Seats with a frame made of lightweight tubing are not allowed (like Corbeau).  No sliding seats will be accepted.

Fuel cell.   Fuel cells are not required in Historic class cars and Original Pan Am.  However, in my opinion, every car should  have a fuel cell.  Even the plastic cells may be OK but not recommended.  The capacity may be increased, but you cannot carry extra gas in cans.  A 16 to 32 gallon cell is recommended. 22 gallons is a good size for V8s.

Gasoline.  By Rule, you must use gasoline sold only at the government monopoly PEMEX stations. No racing fuel or aviation gas.   Fill up at gas stations only.  Premium gas is available every 100 miles or less.  Service trucks should not carry gas by Rule.  Occasionally, you will see a car or two being fueled by a service truck.  It’s probably not PEMEX. Welcome to Mexico! Competitors are not supposed to give other competitors gasoline, by Rule.  Additives and octane boosters are allowed, but not needed at higher altitude in most cars. 

Fuel delivery system.  Any system from stock to modern is OK.  A re-circulating fuel system is recommended to reduce vapor lock.  If the fuel cell is located in the trunk, there should be a sealed firewall between the trunk and passenger compartments.  Electric fuel pumps and fuel cells should not be in the same enclosed space (not a rule).  If the fuel lines run through the passenger compartment, they should be braided steel or enclosed in a steel tube.  Junctures at the firewalls are not recommended.  Some people prefer a stock mechanical fuel pump, others like two electric pumps, or a combination of the two. 

Fire suppression system.  It is required and should be non-Halon.  Nozzles should not point at the heads of the crew. The system should extend to the engine, if not the fuel cell.   A “Firecharger,” an AFFF system, is OK.  A 4 Kg or 10 lbs system is required now (2013).  They also require one hand-held 2 lb. ABC fire extinguisher in the cockpit.  Check 2014 rules. I recommend carrying two hand-held units even if you have a fire system.  You might need to fight a fire in another car or in the weeds under your car, if you miss a corner and go off. 

In 2012 they wanted to see two triggers/pulls for the fire system.  One inside the car and one outside.  Some people attached a trigger to the roll cage behind the driver’s head that could be reached from outside the car.   

Emergency kit.  By Rule, a kit is required--two red flags or red triangle, two soft neck braces, flashlight, and (basic) first aid kit.  A spare tire and jack are required.  You also need two seat-belt cutters in the cockpit, in reach of the crew. 

Hood and trunk lids.  By Rule, they must have pins or cables. 


Interior.  May be stripped (door panels, headliner, carpets, etc.). 

Window.  By Rule, Lexan side and rear windows are OK, but front windshield must be laminated safety glass. 

Lights and horn.  Car must be "street legal" (lights, horn, brake lights, whipers, flasher, turn signals, etc.). 

Locks.   Optional.  Should work on ignition and doors at night (my recommendation). 

Steering wheel.  Any wheel is OK, but wooden wheels are considered dangerous.  A detachable wheel is a nice safety and convenience feature.  Take it with you at night or lock it in the trunk. 

Under car.  Protect the oil pan and other low points, like the flywheel housing, with an aluminum or steel bash plate.  The Rules recommend 20 cm of clearance.  Five inches seems a reasonable minimum.  Speed bumps are the biggest menace.  Reinforce the load-bearing ball joints, if possible.  (Use stock spindles, but not the type that lower the car.) 

Fiberglass.  No fiberglass body parts, unless manufactured like that or approved by tech.  No big air dams or wings.  Originals bumpers are required, unless fiberglass like on Shelby.  (Fiberglass body parts are common in Turismo Mayor but are showing up in other classes.)  Shelby Mustang front ends are popular. 

Paint.  Any color/design.  But please, no offensive slogans in Spanish or English.   Your sponsors’ decals cannot be in competition with the official sponsors.  Place your sponsors’ decals on the hood and truck lid, leaving the sides clear for official decals and official sponsor’s decals.   

Weight.   By Rule, the car may 5% less than manufactured (delivered) weight.  Bring proof.  To use a four-barrel carb in Historic C the car must weigh 2800 lbs. or more at tech (wet), without driver and navigator, tools, etc.  Properly installed ballast is OK, but it is subject to the approval of inspectors.  Cars may be weighed during the race and at the end of the race. 


Wheel and rims.  Maximum of 7” wide rims for Historic C by Rule.  See rules for Historic A and B.  They will measure rim width.  Any wheel material OK by Rule.  Wheel lugs, valve stems, valve caps are “free” and should be upgraded if possible. 13-14-15” rims OK.  No 16” rims.  Steel is stronger, but alloy rims are OK.  It has been difficult to have an alloy rim repaired in Mexico. 

Tires.  By Rule, any DOT approved tire, readily available, but no racing (non-DOT) tires, no shaved tires. Check latest rules.  Currently, at least 50 aspect ratio and at least 60 tread wear or higher is allowed by Rule.  Yokohama A048 or Toyo RA-1 or A-888 “track day” DOT tires are popular with the more competitive teams.  The tire must have “DOT” and tread wear marked on them or European equivalent.  Finding speed-rated tires (“H” or higher) in 15" is always problem.  Most tires will last the entire race, but the Yokohamas seem to have a shorter life span. 


During my fifteen years of observing the technical inspectors go over my car and ohers in all classes, I have seen only two or three cars not allowed to run the race because they had inadequate or incomplete roll cages or other major safety issues.   If your car passes the safety inspection, you will run in a class or in Exhibition.  It is highly unlikely that you will be sent home. 

However, several cars in recent years have been bumped into Exibition for violations of the technical rules for their class.  The most common problems has been the use of  aluminum heads in Historic C. 

As noted above, if any Historic C car weighs less than 2800 lbs. on the scales, it must use a two-barrel, 500 CFM carburetor.   Many cars are weighed each year. 

Installing fuel injection on a car that did not have from the factory it is not allowed.  However, the inspectors have allowed cars with factory installed mechanical FI to compete in Historic B, like Mercedes 220S and some Porsche 911s.  Check with the organizers if you plan to win the race in your FI equipped Porsche 911.  Please note that the final decision will be made by the inspectors at the start of the race, and they may reserve a preliminary decision by the organizers. 

Unlike SCCA or other sanctioning bodies, La Carrera does not have the basic rule – “if the rules don’t expressly allow a modification, then you can’t do it.” So some people try to push the limit with things like major suspension modifications, engine set-backs, five speed transmissions, and stroker engines. 


If you are a new competitor, or show up with a new car and mount the daily podium early on, you can be assured that other competitors and their crews will look your car over closely.  If they find something wrong, they may protest it during the race, and you may be moved to another class or consigned to Exhibition.   

Protests about a car, by Rule, should be filed in writing before the race begins.  However, the Stewart of the race will entertain written protests during the event.   Engines are regularly checked at the end of the race, and cars are sometimes weighed during and after the event. 

All competitors want the race to be as fair as possible, but some competitors want to win badly, so there’s a natural tendency to push the limits.  Someone recently said about NASCAR, “it is only cheating when you get caught, until then it’s innovation.”   

This sentiment should not be your approach to the Pan Am.   There are no cash prizes to win—only bragging rights.  Build your car to be strong, safe, dependable, and, yes, fast.  With 289-427 cubic inches in Historic C, plus the advantage of modern technology, we can go fast (safely) while preserving the historic nature of our cars and the race.

This document is unofficial and certainly not comprehensive.   Please remember, it was compiled by a competitor in Historic C, who does not make, interpret, or enforce the rules.  I can only try, on the basis of my experience and observations, to explain them for all competitors.   

All competitors should read and follow the official rules.

© 2009-2014 Gerie Bledsoe