Engine Tech
ATTENTION: These pages were created & copyrighted by Steve Parker. They reside here on MonteCarloSS.com only until we can contact Steve to get his site back up in operation.

Engine Tech


Getting Started 

 

Background info to Performance enhancements

Probably the single most common problem modifying your car will be deciding on just what you want to do to it. The way you answer that question will help decide many things for you. Do you want to race your car full time, race it occasionally and drive it on the street, or do you only want to use your car on the street and racing isn't a concern for you? Other Concerns are Emissions Legality in your Home state. The laws vary across the country so you'll need to check into this first. This is VERY important, and if the car is going to be run on the street it is my opinion you should retain the Emissions equipment since we only have one world to live on, and all totaled the emissions system on your Monte SS only robs 5-10hp. Emissions legal hot rods help rodders by demonstrating to the public that we are responsible individuals and raising our image as a whole.


Street Only - If this is your only interest, then the next question you need to ask yourself is; Do I want to improve the performance of the vehicle, or keep it mainly stock? The Stock Rebuild listed on the page seeks to enhance performance by improving on Chevy's original build work. You'll be retaining nearly all your old parts, but this is also an expensive way to get max power from your original L-69 with mainly stock parts. You'll have to disassemble the engine to do this but you will not need much in the way of special tools for the tear-down. The Basics here are Balancing and Blue-Printing, gasket matching and basic head work, new Camshaft, rebuilding the Carb, rebuilding the Distributor, and rebuilding the heads. Some things can be left out, such as Balancing and Blue-printing and port work, but a combination of all these things will net you about 25+hp more than the stock L-69 engine, with other options you will even see more. Blue-printing will not alter the originality of the L-69. Of course you could do just a basic rebuild and not bother enhancing power at all. But what fun would that be?

Performance - A Performance Engine is Emissions legal and is designed around a daily driver that has enough guts to be a respectable car. This is probably what GM/Chevy should have done to the Monte Carlo SS from the factory. This approach can produce quite good results, and place you somewhere between Mustang GT and Camaro Z-28 SS territory. With this Engine, fuel economy is a strong consideration, the design seeks to improve power without hurting mileage by more than 2-3mpg from stock. The performance builds here are great choices for road machines, where you wish to have sports car like handling and power.

Street/Strip - Street/Strip engine is simply a engine you intend to race, either at the track, or against other people's cars Light to light. While it may have elements of a full race engine, it is a compromise between drive ability, mileage, and neck snapping acceleration. This is also one of the most difficult combinations to get right, since not everything that will help you go fast on the track will help on the street. Remember this is a compromise engine, and will not be quite as dependable as a true stocker, nor will it be quite as powerful as a full-on race engine. You can expect to possibly get your ET's down into the mid-13's, improve overall handling, and still have a daily driver with a careful selection of parts.

A good Example of this would be List-member George Dumpit's car the 'Grim Reaper' which is completely emissions legal, and smokes Mustang GTs and LT1 camaros all day long. (His car might give a Viper a good run.)

I have divided this Street/Strip section into two separate categories, one being Emissions Legal for those in states with the smog-laws, and the other being Street/Strip which isn't particular about its emissions as long as it goes fast, drives hard, and won't overheat getting to the grocery store.

Racing Only - These engines are intended solely for the track, and would likely be impossible to try to drive on the Street. They usually won't handle the stresses of street driving for very long without failure. Race cars, are cars that need to be trailered back and forth to the track, have no emissions concerns, no Noise level concerns, and have quite simply one goal in mind, winning the race. What you will find here is for Bracket Racing and amateur night grudge matches. It is intended for the beginner, aimed at getting a solid start on building the engine and getting involved in bracket racing.


Building for Power

There are many methods of increasing performance, all of which are intended to increase efficiency. The most common methods are by increasing flow of air (and fuel) through the engine. An engine is basically just a large Air pump, and by increasing exhaust flow and induction flow the power will increase. The selection of parts you choose to increase flow, and how they integrate with each other, determine just how much additional power you gain. Mis-matched parts may improve an engines ability to flow air/fuel and will likely increase your power, but your gains may be only fraction of what a matched set of performance enhancing parts could produce. This guide will give you combinations of tried and true methods used by other people thus saving a good portion of the decision making process and narrowing your choices to just a few.


Torque vs. Horsepower and the Power Index - There always seems to be some confusion about an engine's power output and what it all means to your cars acceleration. Torque refers to the power of the engine to overcome inertia, it is directly responsible for acceleration off the line and plays the largest part in quicker ET's. Horsepower is directly relational to torque and is a mathematical function of it. Horsepower is defined as torque times rotational velocity.
To make it quick and simple, torque gets you off the line and horsepower gives you top speed. There is more to it than that, but the definition will work for us when dealing with increasing power output.
The Power Index combines both the torque and horsepower figures for a total engine Power Index. This is useful for comparing two differently built/designed engines or engines of different displacements.

For Example: A 350cid with 345hp has 390 lbs-ft of torque for a Power Index of 735 while a 454cid engine has 305hp and 430 lbs-ft of torque for a power index of 735. The 454cid engine has less horsepower but will accelerate a given car to the same or slightly quicker ET. The big difference here will be your trap speed, the 350 will likely finish at a higher MPH than the 454, but with a similar elapsed time.

The Power Index can be very useful for bench-racing two different engines in a given car to help determine what would best meet your goals.


L-69 comments

One last thing before we get to the technical stuff. The L-69 (305 H.O.) that came in the Monte SS is a damn good engine and can see power levels reaching 300hp without the use of Nitrous Oxide, Turbos, or superchargers. It has the same stroke as a 350cid engine (3.48") but a smaller bore (3.736"). This makes for strong torque and better mileage but, will require a higher rev-range to achieve comparable power levels of larger displacement engines. Since the 305cid shares most of its parts with the 350, (and other SBC engines) it will cost you more money to build the engine to high horsepower levels than the larger displacement engines. Swapping in a 350 or larger engine is simply cheaper if you seek power levels above 270hp or so. The 350 and 400 engines are easily the most cost efficient method of gaining power period. The only exception is when your using a form of supercharging/turbos/nitrous.

As a rule of thumb, here is the order of cost difference between various normally aspirated engines to modify for the same power;

The 350 is the cheapest,
the 400 is just slightly more money,
the stroked 350 (383) is costly,
and finally the 305 is the most expensive.

Remember there is no replacement for displacement!


Rebuilding the L-69 

Rebuilding your 305 H.O. (L-69) engine back to stock, and then cleaning up the machining work is great for purists. The Engine will be exactly to spec as GM engineers designed it, this is Blue-Printing. Obviously to get everything to design specs requires machine work. Depending on your area, you'll spend up to $350 on block work. Rebuilding the heads and then being machined will run up to $450. Reconditioning the rest of your bottom-end could cost $250 and up depending on what options you go with. As you can see, Blue-printing isn't cheap, but if you want a completely original car and engine with more guts than the typical run of the mill SS this will give you a better-than-new engine with at least 25+hp over the average L-69.

Since you probably won't have access to the myriad tools involved in the short-block work, it is probably best to find a machine shop that will assemble the short-block for you. This is really cheaper than the buying just the 1 or 2 specialty tools you'll need to do it yourself. In fact, you can tell your machinist that you want the engine Balanced and Blue-printed and he'll know what you want done, if he doesn't look for a new machinist. The L-69 rarely requires boring if it has less than 150,000 miles, so tell your machinist that you only want it overbored if needed.

You also want a multi-angle valve-job and gasket matching/flash removal on the heads and intake. GM castings are rarely close to design specifications and heads with supposedly 178cc volume runners may actually be a lot less. You can get the chambers and exhaust ports polished, but leave your intake runner rough sanded, as this aids in flow characteristics. To keeps your cost down somewhat, you don't need to have your heads ported since this is expensive, but if you opt to get port work done its worth another 20+hp roughly.

Get your Crank magnafluxed and micro polished, cool-case nitrided (optional), and have the oil holes chamfered and the journals cross-drilled. (increases lubrication) Your machinist should check for roundness and if the crank needs turning have him radius the journals. Don't bother getting your crank chromed for a street motor it's a waste of money. You can also opt to get the counterweights knife-edged (extra $135 for 5-10hp). Recondition the rods, and here I would use the ARP rod bolts rather than the stock bolts. You can opt to have the beams polish for additional strength. If you need new pistons (as a result of an overbore, etc.) then go with a flat-top 2 valve-relief design, this will increase your compression a notch. I like the TRW and Silvolite styles.

Your exhaust manifolds are your number one inhibitor to power on the stock L-69, although extrude honing isn't cheap, it IS well worth the money if you plan to use stock exhaust manifolds. This can be worth 15+hp depending what other options you decide to get done.

This rebuild method will keep your monte "Factory stock" original for shows.  If this isn't a concern for your car, then I suggest saving your money, and building the L69 with aftermarket parts as described elsewhere for even more performance.

Some recommended rebuild parts:

Plus whatever your machinist recommends replacing/machining as needed.


Forced Induction 

 Intake Supercharging Without a Blower

The power and efficiency of an engine can be increased dramatically by utilizing certain effects that take place during the intake cycle.  Pulses existing in the intake can be tailored to fill the combustion chamber to beyond 100% V.E.! V.E of 130% is possible using these pressure pulses.   When the intake valve closes, a pressure pulse bounces back up the intake passage, and then back towards the valve. By making the intake path the proper length, the pulse can be timed to arrive at TDC of the next intake cycle, effectively supercharging the engine. Another benefit of this is that the additional pulse keeps exhaust gases out of the intake charge.   The pulse will work only through a very narrow RPM range. Above or below this RPM range, the pulse will actually work to decrease power. It is crucial that the pulse be properly timed.   There are several pulses existing in the intake tract. Determining which pulse to use will deter ming where the engine is going to make the best power.   The Second pulse is the strongest and longest lasting, although there is a 3rd & 4th pulse that can also be used.

The Following Formula can be used to determine the length of intake runner necessary to take advantage of the various pulses.

Pulse.......Formula...Lower RPM...Upper RPM...Strength*

2nd.........132,000/RPM......89%........108%..........+-10%
3rd..........97,000/RPM........91%........104%..........+- 07%
4th..........74,000/RPM........93%........104%..........+- 04%
* Strength of pulse varies with inlet flow and valve opening

To arrive at the inlet length, divide the numbers shown by the RPM for Peak HP.

Example: Peak HP=7500 RPM 132,000/7500 = 17.6"

This is the desired length from the intake valve to the air inlet entrance. For Engines with a Plenum (Tunnel Ram Type), Length is from the valve to the Plenum.

The Pulse in the above example will benefit from 89% up to 108% of 7500 RPM (6675 rpm to 8100 RPM). The greatest benefit will occur at about 3% BELOW 7500 RPM (7275 RPM). Below 6675 or above 8100, the pulse will actually work to decrease engine power.


Superchargers (Blowers)

Coming Soon....    


Turbo Chargers (Hairdryers)

Coming Soon....    


Nitrous Oxide 

 How Does Nitrous Oxide Work?

First, nitrous oxide is comprised of 2 parts nitrogen and one part oxygen. When the nitrous oxide is heated to approximately 572oF (on compression stroke), it breaks down and releases extra oxygen, which creates additional power by burning more fuel. By burning more fuel, higher cylinder pressures are created and this is where most of the additional power is realized.

Secondly, as pressurized nitrous oxide is injected into the intake manifold, it changes from a liquid to a gas (boils). This boiling affect reduces the temperature of the nitrous to a -127 Degrees F. This "cooling affect" in turn significantly reduces intake charge temperatures by approximately 60-75 Degrees F. This also helps create additional power. A general rule of thumb: For every 10 Degrees F. reduction in intake charge temperature, a 1% increase in power will be realized.

Example: A 350 HP engine with an intake temperature drop of 70 Degrees F, would gain approximately 25 HP on the cooling affect alone.

Third, the nitrogen that was also released during the compression stroke performs an important role. Nitrogen acts to "buffer or dampen" the increased cylinder pressures leading to a controlled combustion process.

Nitrous on a stock motor

A kit that uses the correct factory calibration does not usually cause increased wear. As the energy released in the cylinder increases so do the loads on the various components that must handle them. If the load increases exceed the ability of the component to handle them, added wear takes place. Nitrous kits are designed for use only at wide open throttle. Nitrous can be extremely advantageous in that it is only used when you want it, not all the time.

The key is to choose the correct kit for a given application, small block V8's (305/350/400cid) can typically accept up to 140 extra HP, and big block V8's (427/454) can accept  up to 200 extra HP. These suggested ranges provide maximum reliability from most stock engines using cast pistons and cast crank with few or no engine modifications.  

Most late model ignition systems are well suited for nitrous applications. In some higher HP cases, it may be advisable to look into a high quality high output ignition system.  Retard ignition timing by 4-8 degrees (usually 1 to 1-1/2 degrees timing retard per 50 H.P. gain).

Most stock fuel pumps will work adequately for smaller nitrous applications. It is important to check to see if your pump can flow enough fuel to your existing fuel system, as well as being able to supply the additional fuel required by the nitrous kit under full throttle conditions. It may be a good idea to dedicate a separate fuel pump to the nitrous kit.  In many cases a higher flowing fuel pump will be necessary.

For many applications an improvement from 1 to 3 full seconds and 10 to 15 MPH in the quarter mile can be expected. Factors such as engine size, tires, jetting, gearing, etc. will effect the final results.  A 125 HP Nitrous kit with a standard 10 lbs. capacity bottle will usually offer up to 7 to 10 full 1/4-mile passes. For power levels of 250 HP, 3 to 5 full quarter-mile passes may be expected. If nitrous is only used in 2nd and 3rd gears, the number of runs will be even more.  (It is possible to hold the button down until the bottle is empty, about 3-5 minutes.) However short (15 secs or less) blast are recommended.

Most Nitrous manufacturers make Emission legal systems, in fact NOS has an EO number for the 305/350 GM V8's, etc. In addition, there is no need to remove any smog equipment when installing a Nitrous system. You shouldn't have to rejet your carburetor when adding nitrous, the system is independent of your carburetor and injects its own mixture of fuel and nitrous.  The increase in oxygen present in the exhaust may actually increase the efficiency of the converter. Since the use of nitrous is normally limited to 10-20 seconds of continuous use, there usually are no appreciable effects. Temperatures are typically well within acceptable standards.

Using Nitrous should not cause detonation in and of itself.  Detonation is the result of too little fuel present during combustion (lean) or too low of an octane of fuel. Too much ignition advance also causes detonation. In general, most kits engineered for stock type engines will work well with premium type fuels and minimal decreases of ignition timing.

If you live or operate a nitrous system in colder climates, it may also be a good idea to purchase a bottle heater kit. Generally, ambient temperatures of 70-90 degrees F. will allow for best power potential of Nitrous kits.

More Power?

Generally, forged aluminum pistons are best if you wish even higher HP gains.  Another thing to consider if your seeking high HP gains is a cam swap  that has more exhaust overlap and duration. However, it is best to choose a cam suitable to normal use (when nitrous is not activated) since 99% of the time your not at full throttle. There are special cam grinds for nitrous competition which have more aggressive exhaust profile ramping, etc. Higher octane (100+) racing fuel may be required as well as spark plugs 1 to 2 heat ranges colder than normal with gaps closed to .025"-.030".  For gains over 250 H.P., other  special modifications could be necessary as well. These special modifications may include a forged crankshaft, a high quality race type connecting rod, a high output fuel pump dedicated to feeding the additional fuel demands of the nitrous system, and a racing fuel with high specific gravity and an octane rating of 110 or more.


Camshafts


Ignition/electrical System

 


Cooling System


Exhaust System

Exhaust Drone

Submitted by: Richard Kwarciany

Drone in the exhaust is due to the engine driving the exhaust system at its resonant frequency. You can't get rid of it, any length of pipe has a natural frequency, but you can change the frequency (RPM) it happens at. Stock exhaust systems are tuned to put the resonant frequencies outside the normal RPM range the engine is run in. Sometimes they add resonators for this purpose. To raise the resonant frequency of a system, shorten its length. To do this, you can try tail pipes that exit by the wheel (like GN's have), or you can try a muffler with a shorter internal flow path. If you have a true dual system, you can change the natural frequency of the system dramatically by adding a balance tube. If you can't shorten the system, then you can add slightly less than one wavelength of pipe. This will also raise the resonant frequency of the system. The wavelength in a single converter system (not true dual) is a little less than three feet at 3000 RPM. Shortening the system by a foot or so will move a resonance at 2000 RPM to about 3000 RPM.

To move a resonance, calculate the wavelength at the RPM that gives the resonance you want to move. Then calculate the wavelength at the RPM you would rather it be at. The difference is the length of pipe you need to add or delete. Add to lower the RPM, delete to raise it. If you want to raise it but you can't cut any pipe out, then add one wavelength of pipe minus the amount you calculated. This will have the same affect. If you add or subtract a multiple of a wavelength exactly, you will not change the resonant RPM.

      Wavelength = 1100 X 60 X 1/RPM X 1/4 X 1/2

                or

      Wavelength = 8250 / RPM

        Wavelength = standing wavelength
        1100 = speed of sound in air in feet per second
        60 = convert RPM to Revs per second
        RPM = RPM
        1/4 = four cylender firings per revolution (make this 1/2 for "true dual")
        1/2 = standing wavelength is half the wavelength of a "normal" wave


Monte Carlo (SS) Exhaust FAQ


Submitted by: Stu, Victor, George D, and Steve B.

There are two basic ways of modifying a crossmember to accept a dual exhaust. A hard way, but probably a stronger way, and a much simpler way. I'm of the opinion that either way will work since the crossmember is not a REAL stressed member, not like the frame, but don't go too nuts modifying the crossmember.

The Hard way: This method does involve removing the crossmember from your car, need to unbolt the 4 frame bolts and the tranny bolts. First off, you need to estimate where you will be making the cut. I suggest installing your headers and then eyeballing where the cut will be. Then you take out the crossmember. You need to reinforce the crossmember to make up for the loss of the metal. So I used channel steel which fit over the crossmember and welded it in place. Next, I broke out the torch and referencing off the marks, cut a big, wide notch into the crossmember. Make it wide enough to make up for any mistakes you might have made. Also cut pretty deep into the crossmember, at least 1/2 way through to create a reasonable amount of room. The extra height added by the channel steel on the crossmember required a little floor pan mods, mainly jacking up the crossmember and allowing it to self clear itself fit 3" under my crossmember, so you can stuff a whole bunch of exhaust under your car. Pictures of this method can be seen on the monte homepage.

There has been some email regarding the x-member the past few weeks if you want true duals on your Monte. IMHO, this should not be a problem. All you need is to find a good welder and for ~$20, he will use a combination of heating and impacting to create a C-shape in the crossmember under which the driver's side of the dual system will run. No cutting, no welding, no tranny removal, no loss in strength. A 30 min. job on the hoist. Basically heat the crossmember till its nice and red and then break out BFH and pound the crossmember to gain the additional clearance.

     When he's done, it should look like this:

                  ________________________________________________
          rocker  |                   ___________                | Tranny
           panel  |__________________/           \_______________| 

There are a slew of non emission headers for g bodies with sbc, so that shouldn't be a problem. I have used the headman and the dynomax headers. I really didn't like the headmans, but they were kinda old, so maybe they redesigned their headers. They dynomax headers I had were ceramic coated, I love the ceramic coating, makes checking the spark plugs easier.

As far as true duals for g body, I can only think of Torque Tech off hand. They make some nice mandrel bent 2.5" and 3" exhaust. But any competent exhaust shop can bend you up an exhaust for the car, and can probably do the crossmember mods (the easy version).

Emissions legal Cat back systems:
_________________________________

To my understanding, of emissions laws, anything after the Catalytic converter doesn't need any CARB/E.O. approvals, and you can do what you want. Here's a list of mandrel bent systems for the G-body.

DynoMax:

2.25" dual cat back, Aluminized mild steel, True SS exit, tailpipes
polished, DynoMax turbo mufflers, 
P/N: 17423
Price: $230 Hooker:

2.5" Dual cat back, Non-coated mild steel, Super comp mufflers, 
Exits like GN,
P/N: 16810
Price: $260 (Summit)


ATR (Applied Technology & Research) Stainless Steel: 

2.5" dual cat back, Stainless Steel with stainless core muffler wrapped with
aluminized mild steel (similar to walker ultra flow).  Exits like GN
Price: $495 

2.5" dual cat back, Stainless Steel with stainless core and external
muffler. (a little quieter than the one above)  Exits like GN
Price: $695 

3" single cat back, all Stainless Steel. Exits like GN, but only on
passenger side of car. (very loud)
Price: $395 

Hooker:
 
 2.5" Dual cat back, alumnized steel, Super comp mufflers, 
 Exits like GN,
 P/N: 16810
 Price: $260 (Summit)

Torque Technology:

3" dual cat back, Aluminized mild steel, Exits like GN, Flowmaster 3 chamber
mufflers
Price: 471.00

Turbo City:

2.5" dual cat back
Price: ??

Emissions legal Headers:
_______________________

In order for headers to truly be emissions legal, they must have CARB/E.O. approval. For header manufacturers to get CARB/E.O. approval, they must have a complete system from exhaust manifold to y-pipe. All of the factory emissions equipment must remain intact and be functional, i.e.: A.I.R., heat riser valve, O2 sensor. Also, the manufacturers must do testing for *each* specific application. Only a few manufacturers have done this, and to my knowledge, Edelbrock has the only emissions legal Tubular Exhaust System for the G-body. I have heard rumors that Headman and Dynomax has emissions legal systems, but I'm not sure if they have a legal system for the G-body.


Edelbrock TES (Tubular Exhaust System) CARB/E.O.#D-215-1:

LG4 engine, Non-coated,
P/N: 6878
Price: $305

LG4 engine, Ceramic coated
P/N: 7978
Price: $475

L69 engine, Non-coated,
P/N: 6879
Price: $335

L69 engine, Ceramic coated
P/N: 7979
Price: $505

Mufflers:

And now the forever asked questions about mufflers. Generally, Montes take an offset/offset configuration. There are a huge amount of mufflers which can fit the car. But the question that everyone has concerns the Flowmaster and the Dynomax Super Turbo mufflers.

First off, there are many things which effect the sound and volume of the exhaust. Most important are probably cubic inches, cam, headers, exhaust size, converter, and tailpipes besides the muffler itself. Any changes of these will make an effect on the sound and volume of the exhaust. But the muffler probably does play the biggest role in the tone of the car.

Flowmaster 2 chamber vs. 3 chamber:

Yes, Flowmasters are louder than the stock exhaust, but generally speaking the 3 chamber mufflers are streetable while the 2 chamber ones are pretty loud, so you might want to think about that before you go that route. As a side, in a test of mufflers done by a Ford magazine, they didn't find very much power difference between the 2 chambers and the 3 chambers, the difference mainly comes on the very top end. Contrary to popular belief, they are affordable, should be around $50 a piece if you order from a major mail order place.

To characterize the sound of Flowmaster, I would say they sound very much like open headers, just quieter. They have a certain crackle to them, like open exhaust. Flowmasters work on the baffled system, so there is no fiberglass to blow out. So, they should sound the same the day you put them on to years down the road.

Dynomax Super Turbo:

The dynomax has a different sound from the Flowmaster, they tend to have a deeper, more muffled tone. Hard to describe, but I would characterize them as being more refined, less crackly than the Flowmasters. Beware, when you first put them on, they will be pretty quiet. But since they are fiberglass filled, the will get louder the more you use the car. These mufflers tend to be cheaper, around $30 from the mail order shops.

Exhaust Size:

The stock monte SS exhaust is 2.25". But the stock design monte exhaust comes together into one cat and then splits into two pipes. This is not the most conductive to making lots of power, but must be retained to pass emissions. So generally speaking, for a stock SS, 2.25" may be more than enough. But if you're getting a new system, you might as well step up in size, since they allow you make more power later. But remember, the y pipe is still the choke point no matter how big you make the exhaust. But don't let that scare you, people have used the y pipe with dual 3" exhaust and still made tons of power. My rule of thumb is at minimum, get a 2.25" or 2.5" exhaust. I tend to lean towards the 2.5" since there usually isn't a big price difference. 2.5" on a stock 305 might be kinda large, but you might as well.

For true dual exhaust, I would suggest 2.5" when you get near the 300 hp level. 3" when you get around 400 hp. These are general rules, I had a dual 3" on a motor making around 350 hp. I didn't notice too much of a loss on low end, but then it was geared to eliminate low end problem. I still made a ton of low end.

Catalytic Converters:

For those who need to run, or at least pretend to run cats, there are a variety of options. The simplest thing to do if your cat goes bad (or even if it doesn't) is to hollow it out. Cats are made up or certain rare metals, platinum, palladium, etc. (which is why they're so expensive) on a ceramic honeycomb.

The most common cause for the cat to go bad is an over rich condition. So if you're tuning a carb on a car with a cat, be careful about running it too rich. Also, if your o2 sensor goes bad, the motor will often go rich, which may end up killing the cat. Going rich will cause the substrate material to melt and end up clogging up the ceramic honeycomb and generally causing a large amount of back pressure. Also, physically hitting the cat can cause it to break. So watch it when you ramble speed bumps and other might spot opportunities.

Federal law says you can't change your working cat unless its gone bad or you have at least 50k miles on it. If you cat does go bad, these are the symptoms: If you bang on the bottom of the cat or if you floor it, you may hear some rattling of chunks inside it. Unexplained loss of power is a good one. Especially if you floor it and it feels like there is a boat anchor tied to your rear, the engine will labor to make rpm's and it will just run like crap. Rotten egg (sulfur) odor. Not necessarily a bad cat, but if it is consistent, it is bad. The exhaust note will change, the engine temps will go up. Also, the cat gets very hot. The passenger side floor around the cat would get very hot.

Its pretty easy to breakup and take it out, broomstick should work. Remember to take out the broken chunks after you're done. Remember, running no cats on an originally cat equipped car is only legal for off road applications. For those who would like to keep a working cat, Summit Racing sells a hi flow cat which people on the list have used and liked. Its a PFP brand and should be able to be had for under $100. Call for specific part numbers. If you have a 3" system, Random Technologies makes a real high flow 3" cat; supposedly the least restrictive on the market. Not too much more restrictive than a straight pipe. It's $200 though.


Parts Reccomendations


Stock SS File GM Vehicle Codes Engine Tech Small Block Info Drivetrain Tech Suspension Tech Tires & Wheels
Emissions Legal SBC Street/Strip SBC Useful Formulas How To's Engine Swaps Bracket Racing Big Blocks