We get numerous e-mails each week, asking how to build up an inline six, so we decided to do a tech article with our recommendations. This information is only intended as a basic guideline, for building a daily driver, a weekend cruiser, or all out race engine. However there are certainly alternative methods and/or opinions for accomplishing such a task, therefore we recommend you do as much research as possible, before you start buying parts or tearing into your motor. While we have provided a wealth of information in our Tech Section and through the various Magazine Articles, we recommend purchasing a Ford Repair Manual, as well as the Ford Falcon Six-Cylinder Performance Handbook.

To increase power you need to address the induction and exhaust systems, combustion ratio and cam profile, and the ignition system. Unlike many small 4-cylinder engines, you don't need to buzz a small six to 7500 rpm to make power. In fact you can build substantial levels of power and torque, at very useable levels of rpm (2500-5000), for a daily driver or weekend cruiser. Installing headers and bolting on more carburetion to an otherwise stock engine, is a good place to start and will certainly help the performance. However the total gains may be disappointing and only make the shortcomings of the cylinder head, with its integral log intake manifold, and the stock cam more evident. Basically an engine is a big air pump, and as such, the modifications must be performed systematically in order for them to work together to produce the level of performance you desire.

While we have included guidelines for rebuilding the short block, you can skip over this step if it isn't required, or if it doesn't fit within your budget. The remaining steps (2-6) can be done all at once, or one at a time, and in any order. However we normally recommend up-grading the ignition and exhaust systems first. When up-grading the cylinder head, it may be beneficial to purchase a second head, thus reducing the downtime. This is also a good time to do the cam swap, as the cylinder head must be removed to swap the cam & lifters.

After the following modifications have been accomplished, the rear wheel horse power should be around 175HP (double that of a stock six), with gas mileage falling in the 20-26 mpg range. If the motor is properly tuned, it will have a smooth idle, excellent acceleration and throttle response, and plenty of power for climbing long hills or cruising down the freeway.

Below is a brief outline of the steps required to build a budget motor, as well as several options for increased performance and/or service life. If you wish to review each step in detail, click on the appropriate heading, or simply page down. Our intentions were to give you as much information as possible, thus demonstrating the various possibilities for building a mild performance motor. We've included several tech articles to help guide you along, or to explain a specific topic in greater detail, so be prepared to spend an hour or more to go through all of the information provided. If you're doing the work yourself, you might want to read the article on Engine Rebuilding & Safety Tips.

Related Articles: Hopping up the Falcon Six and Hopping up an Inline Six.

Short Block - 200ci
1) Start with a 7 main block if possible, and install ARP rod bolts.
2) Zero deck the block, and clean up the cylinders (maximum bore of .060 over).
3) Use the stock cast dished pistons (-7cc) with chrome moly piston rings.
4) Using a C/R calculator, adjust the combustion chamber size to achieve a 9.0-9.5 C/R.
5) Balance the rotating assembly, including the clutch assembly (if applicable).
6) Replace the harmonic damper with a quality rebuilt damper when necessary.
7) Inspect and replace the motor mounts and flex plate (if applicable) when necessary.

Short Block - 250ci (same as above with the following exceptions)
1) Unlike the 200ci, do not Zero Deck the block, as this will result in to much compression.
2) Use a C/R calculator and deck the block accordingly and...... (see #3)
3) Adjust the deck height and combustion chamber to achieve a 9.0-9.5 C/R.
4) To increase the C/R you can use pistons from a 255ci V8 (1.585” compression height),
..if you use these pistons, make sure you use a C/R calculator. DO NOT Zero Deck.

Short Block Options
1) Double roller timing chain set (200ci only).
2) Flat top and/or forged pistons.
3) High performance piston coatings.
4) Shot-peen'd connecting rods.
5) High performance balancer.

Cylinder Head & Carburetor - Basic
1) Upgrade to a late model cylinder head (see Tech Article).
2) Perform a 3-Angle valve job, and upgrade the valve springs (see Valve Train).
3) Clean up the chambers, port, and polish, as per your budget.
4) Install 2V adaptor and carburetor (see Tech Article).

Cylinder Head & Carburetor - Modified
1) Upgrade to a late model cylinder head (see Tech Article).
2) Install oversized valves (1.75/1.50 for a cast head)
3) Perform a 3-Angle valve job, and upgrade the valve springs (see Valve Train).
4) Clean up the chambers, port, and polish, as per your budget.
5) Modify log intake for direct mount 2V carb (see Tech Article)

Cylinder Head & Carburetor - Optional
1) Upgrade to multiple carbs (Tech Article coming soon).
2) Upgrade to an OZ250-2V cylinder head and removable intake.
3) Upgrade to an CI Aluminum cylinder head and removable intake.
4) Upgrade to a 4V carb if desired, but only if the engine build will support additional CFM's.
5) Upgrade to Fuel Injection (currently under development).

Cam Swap & Timing Chain
1) Install a performance cam and lifters, 264/264, 264/274, or 274/274 (see details).
2) In general, use 110 or 112 lobe center with automatic, and 108 or 110 with manual.
3) Install a dual roller timing chain (200ci only), and degree the cam whenever possible.
4) Option: If turbo charging, our 274/274-112 hyd or 278/278-112 solid cams work well.

Valve Train
1) Ditch the stock springs in favor of 302 springs, as explained below (see Tech Article)
2) Upgrade to an adjustable rocker assembly, if you don't already have them.
3) Upgrade to chrome moly pushrods if using a performance cam profile.
4) Option: Upgrade to a high ratio, roller tipped, or full roller rockers (see Tech Article).
5) Option: If turbo charging, use higher rate valve springs, such as our STY or Dual springs.

Ignition System
1) Install a Duraspark II distributor and a high performance coil.
2) Install an external ignition control module, such as our Dyna Module or an MSD-6A.
3) Option: Install a DUI ignition system, with a one wire hook-up and a relay.

Exhaust System
1) Install a single or dual outlet header, with or without a port divider.
2) Install a single or dual exhaust system which is sized accordingly. Do not oversize.

For the most part the same guidelines apply to both the 200ci and 250ci when rebuilding a short block, with the exception of piston selection, deck height, and the compression ratio, which we will detail later in this article. Remember to inspect your motor mounts, and replace them if necessary.

Crankshaft: While a four main short block is adequate for most street motors, we always recommend starting with a seven main block, in case you decided to hop up the motor or add a turbocharger at a later date. Not only is the seven main block virtually indestructible, the additional main caps help to minimize the harmonics of the long crankshaft, thus increasing the durability and service life of the motor. To further reduce harmonic vibrations, we highly recommend balancing the rotating assembly, including the crank, con-rods, pistons, flywheel, and clutch assembly (if applicable). If you have an automatic, you also need to inspect the flex plate. As a general rule, it's a good idea to replace it even if you don't see any physical evidence of wear and tear, as they are prone to cracking.

Note: 200ci engines produced mid '64 or later, as well as all 250ci engines, have 7 mains.

Damper: This is also a good time to replace the harmonic damper (also called a balancer). Using an old worn out damper, or an inadequate damper for the application, usually results in inertia ring slippage (spinning), which in turn results in the loss of timing accuracy and eventual component separation. A good quality rebuilt or new replacement balancer, or high performance balancer should be used if you plan to operate your motor frequently in the upper rpm ranges, as in a street/strip application.

Bore Size: When machining the block, never bore the cylinders more than is absolutely necessary. While .060 is the maximum you can safely over bore a small six, we recommend keeping it at .040 or less, as over boring adds very little power. On the other hand, it increases the likely-hood of over-heating, especially in warmer climates, and it weakens the cylinder walls. If you plan to add a turbo at a later date, we recommend a maximum bore of .020 over to maintain block integrity and reduce the likely-hood of cylinder wall failure. If you plan to add more than 12 lbs of boost, a virgin block (0.00 over) is preferable.

Pistons & C/R (200ci): While a stock 200ci has a compression ratio of 8.7-9.2, depending on the production year, we recommend increasing the C/R to 9.3-9.5 to enhance the throttle response and over-all performance. Increasing the C/R to anything above 9.5 requires premium pump gas at a minimum, and it may require water injection to prevent detonation when using a cast iron head, therefore it is considered undesirable. A common practice to increase the C/R is to use flat top pistons (see note below), however for a 200ci we prefer to use the stock dished (7cc) pistons, along with a zero decked block. Not only does this method improve the quench characteristics, it decreases the likely-hood of detonation and pre-ignition. "Zero Decking" is accomplished by machining the deck (the block surface where the cylinder head attaches) so that the top of the piston is flush with the top of the block, when the piston is at top dead center.

Note: If you wish to use flat tops pistons, you can use pistons from a 141ci four-cylinder Tempo HSC, as they have the same bore size and compression height as a stock 200/250ci piston. They will not work in a 144/170, as they have a small piston diameter.

Optional Pistons (250ci only): If your rebuilding a 250ci, you can use use pistons from a 255ci-V8 (80-81 Granada) to increase the C/R. These pistons have a compression height of 1.585” verses 1.500”. Using these pistons is basically the same as decking the block 0.85", as it raises the piston .085" higher in the cylinder. Make sure you deck the block accordingly (do not Zero Deck), and adjust the combustion chamber size, to achieve a 9.0-9.5 C/R. We highly recommend using an online C/R Calculator, or a Cam Utility Program, to assist you in determining the proper deck height and chamber size, for the desired C/R.

Compression Ratio: Here's a few tips to increase the Static Compression Ratio. However, these are "Rule of Thumb" guidelines, and as such, they should not be used to determine the actual Static C/R, or the Dynamic C/R. To determine the actual ratios we suggest using an online calculator to determine the Static C/R, and/or a Cam Utility Program to determine the Dynamic C/R, which will also assist you in selecting the proper cam profile by denoting the best time for the intake valve to close. For more information on Static and Dynamic Compression Ratios, and their differences, we highly recommend reading our tech article.

Forged Pistons & Coatings: Forged pistons are not needed for the average street or high performance motor. They are only required when power adders are introduced, such as a turbocharger, supercharger, or nitrous.

High Performance Coatings (HPC) offers two specialized coatings for upgrading stock or forged pistons. Thermal barrier coatings can be applied to the top of the piston, and/or the cylinder walls, to maintain combustion temperatures and reduce heat soak. Thus promoting a more efficient burn of the air/fuel mixture, which in turn increases the horsepower output. The S-Series solid dry film lubricant, when applied to the piston skirt, reduces friction and prevents scuffing and galling of the cylinder walls. By reducing friction and parasitic losses, the power output is enhanced, and the service life of the motor is greatly increased.

Piston Rings: When selecting piston rings, we recommend moly rings over cast iron. Cast iron rings are fine for typical light duty service where the vehicle is not subjected to long periods of high speed and is run primarily on paved streets, or when the motor is not subjected to unusual dirt or heat conditions. However moly (molybdenum) rings are preferred for occasional or continuous high speed and/or load conditions, where the engine is subject to periods of high temperature ranges. Moly rings have a high scuff resistance, superior strength, and improved oil control and retention, which makes them better suited to performance engines where they are expected to serve adequately, through-out the entire life of the engine.

Connecting Rods: The next item to cover in the short block, is the connecting rods. Most sixes came with forged steel connecting rods, with the exception of those produce from 1973 thru 1981. During those years Ford used a variety of materials, from cast steel, to cast iron, to nodular iron. In 1982, they switched back to forged steel rods once again. As such, the rod bolts are the weakest point in the bottom end, and they should always be replaced when rebuilding a motor. We recommend using ARP small block Ford (V8) rod bolts, for increased safety and strength, however they need to be installed by your machine shop as a small modification is required for fitment.

Shot Peening: While not required for the average street motor, shot peening is an option used to increase the fatigue life of a stock connecting rod. By compressing the surface layer of the connecting rod, the likely-hood of failure from fatigue, stress cracks, and/or corrosion is greatly reduced. Another common practice is to eliminate stress risers by de-burring the rods and grinding all edges to a smooth radius prior to shot peening.

Motor Mounts: This is a great time to inspect the motor and transmission mounts, which are commonly metal parts bonded together using a rubber compound. Over the years the rubber compounds dries out and becomes brittle, eventually resulting in failure and separation. Quite commonly this leads to un-necessary and costly repairs, and in some cases, can be life threatening  if a catastrophic failure results in an accident. Therefore it is essential to thoroughly clean and inspect these parts prior to reuse. If the rubber, or metal parts, show any signs of cracking or excessive wear, they need to be replaced. This is also a good time to inspect and replace the radiator and heater hoses, fan belts, vacuum lines, radiator cap, fuel pump and fuel filters, as well as all gaskets and seals.

Back to Outline

Log Adaptors: Many inline enthusiast use aftermarket carb adaptors to install a two barrel carb to the integral log intake, replacing the troublesome one barrel. There are many different types of adaptors, so you'll need to make sure you purchase the correct adaptor for your application and choice of carburetor. Depending on which carb you use, you can expect to gain a bit more bottom end and peak horsepower. The single biggest advantage to using an adaptor, is that the modification can be done without removing the cylinder head. For more information, please see the various tech articles we have written on this subject.

Log Modifications: Another method of upgrading to a 2V carburetor incorporates mounting a custom adaptor to a modified log intake manifold, and hogging out the carb opening. This method allows the use of Holley and Autolite carburetors, increased hood clearance, and substantial gains in horsepower and torque. Our dyno results showed gains up to 25HP, depending on the carb selection, over the stock 1V carb on a stock small six. The only drawback to this method is that the intake needs to be milled flat, which requires removing the cylinder head for machining. The intake is then built up with a metal putty or furnace brazing, machined flat again, then hogged out for a 2V carb. However, we feel this is a small price to pay for the gains achieved. Plus you have the opportunity to replace the camshaft while the cylinder head is off, for even greater gains in performance. It's also a great time to upgrade to a large log cylinder head. For more information, see our tech article.

Head Swaps: Another popular modification is swapping to a late model cylinder head, which offers larger valves, as well as increased intake and port volumes. The later model heads are easily spotted by the larger log intake and a 1.75" (verses 1.5") carb opening. The advantage is a substantial increase in performance due to the additional air flow available, how ever one must be careful to maintain the proper compression ratio due to the various combustion chamber sizes. Before you swap heads, spend a few more bucks to modify the intake for a direct mount 2V carb, and maybe even a little port work. For more information, see our tech article.

Cylinder Head Options: If you can find an OZ250-2V head, along with their removable 2V alloy intake manifold, you might want to seriously consider purchasing one. Even if it does stretch your budget to its very limits, or if you have to put off purchasing a set of headers or an upgraded ignition system, buy it if you stumble across one. They are getting rare and hard to come by, so you need to seize the moment if you find one that's available. You may not get a second chance.

The advantage of the OZ 250-2V head/manifold is that it relives the asthmatic conditions associated with the stock log head without any modifications, or multiple carbs being adapted to the log manifold. Dyno test have shown that a stock 200ci engine with only the OZ 250-2V head/manifold, a two barrel carb, and headers, yielded a forty percent increase in horse power. The disadvantage is that the heads were only produced for a few years, with production ending more than thirty years ago, hence only used heads are available. Due to their rarity, they are getting more expensive yearly, and normally require a full rebuild, including new guides and hardened valve seats. When purchasing one, you need to make sure the head was magnaflux'd, as they are prone to cracking. While they can be repaired to like new condition, it's expensive. Also make sure that the repair work was completed by a qualified shop, that knows how to weld cast iron properly. For more information, see our tech article.

Another great upgrade, though expensive, is our Aluminum Cylinder Head. We won't go into any details here, as this is far beyond the scope of a budget build, and because we have a great deal of information available elsewhere on our website. However we just wanted to take a moment and make you aware that an aluminum cylinder head does exist. From here, the options are endless.......

Back to Outline

Valve Springs: The valve springs are one of the most critical components of your engine. It is very important to match the camshaft and potential rpm range with the correct spring rate.  Stock valve springs will float around 4500rpm, and as such are not adequate for use with performance camshafts. Therefore we recommend up-grading to a valve spring such as those used for a small block V8 application (289/302). When selecting a valve spring, you don't want one with to much pressure as this wears out the valve train prematurely. On the other hand, a spring with too little pressure will float at higher rpm's, causing the valves to bounce, which also wears out the valve train prematurely. Therefore, when a stock or mild cam is used, we recommend 289 springs for motors which normally operate in the lower rpm range, and 302 springs for those that operate in the higher rpm range.

Option: If turbo charging, you need to use a higher rate spring, such as our STY or Dual valve springs. The reason for this is that it takes more pressure to close the valves when the motor is under full boost at higher rpm's.

Rocker Assembly: We recommend up-grading to an adjustable rocker assembly, if the motor doesn't already have one. This allows for proper adjustment of the rockers due to the changes in deck height and milling the cylinder head. While its not required, it may be beneficial to up-grade to chrome-moly pushrods as well. They are lighter and stronger than regular steel push rods, and offer increased strength so they don't flex at higher rpm's, or under the stress of higher lift cams and stiffer valve springs.

Option: According to our dyno test, up-grading to a high ratio (1.6 or 1.65) rocker assembly increases the average horse power by as much as 10-15hp, with the largest gains in the low and mid-range rpm's, where its needed most for a daily driver or weekend cruiser. For more information on High Ratio Rockers, see our tech article.

Back to Outline

Distributor: Up-grading the ignition system is probably the best modification you can make, and in our opinion, the first modification that should be done. Ditching the old points style distributor in favor of an electronic distributor, offers numerous benefits, including quicker starts, a smoother idle, improved cold weather starts, improved throttle response, lower emissions, better gas mileage, quicker revs, and improved performance. Tough to beat......

Petronics: One of the cheapest and quickest upgrades is to a Petronics Ignition. While it is light years ahead of the points style distributor, it is probably our least favorite, hence we will not go into this system in any detail. The one big advantage it has, is that it maintains the stock distributor, coil, and wires, for those who prefer to keep a stock OEM appearance. The disadvantage is that it doesn't cure the problems associated with the distributor itself. For example, if your planning a carb swap, you'll need a distributor that has centifugal counter weights. The other disadvantage is if and when the unit fails. If you don't have a spare in your glove box, odds are you're going to be left sitting on the side of the road and/or calling AAA for a tow. For more infomation, see our tech article.

Duraspark II: Upgrading to a DSII Distributor can be very reasonable, however much of the cost is dependant on the selection of the ignition module. The distributor, cap adaptor, cap, and rotor, will generally set you back about $75 bucks at any local parts store. When purchasing the distributor, ask for one from a 78 Fairmont, and be sure you pick up the cap adaptor, as well as the cap and rotor. Once you've picked up the distributor, you'll still need an ignition coil and module, for which there are many options. A high performance coil and plug wires are normally preferred, and can be purchase online, at specialty performance shops, and most local chain stores. As for the ignition module, you can purchase the stock Ford Blue-Strain module, Classic Inlines Dyna-Module, an MSD-6A (or similar), or you can build your own box using a cheap GM 4-pin module. Cost of the ignition module will set you back anywhere from $100 bucks, up to $300 depending on which system you use.

Wiring the DSII can be intimidating for some, however there's always plenty of help on the FordSix forum if you get stuck. However once the system is installed you'll notice a big improvement over the old points style distributor. Quicker starts, smoother idle, improved throttle response, increased mileage, and more power.

While most chain stores stock DSII parts, many are starting to offer the distributors as a "special order only" due to their age. On the other hand, Classic Inlines always has them in stock. We also offer a kit that includes everything you need, including the distributor, cap adaptor, cap, rotor, ignition module, coil, and wiring. Our kits also include easy to follow instructions, that show you exactly how to connect the wires. There's no guess work.

DUI Ignition: While the DUI is the most expensive, many of our customers agree with us, in that it is the most powerful ignition system available. Dyno results have shown the DUI to out perform both the Petronics and the Duraspark II systems, regardless of which module and/or coil is used. In two separate dyno sessions, we gained 13HP over a custom curved DSII, and 20HP over the stock distributor. While the DUI may cost more up front, long term maintenance is cheaper, and replacement parts are easily acquired from any parts store. For more information on the DUI Ignition System, please read our tech article.

Note: Still not sure which ignition system to use, then you need to read our tech article, which covers each system in detail.

Note: Most people know that a cam needs to be broken in when it's first installed, however very few know that a new distributor gear must be broken in, in a similar fashion. Breaking in the distributor gear helps reduce and/or prevent premature gear failure. For more information on this subject, please read our tech article. It's quite a long article too.....

Back to Outline

Headers: This one is pretty much, self explanatory, as everyone knows the benefits of a good set of headers. While we have never dyno tested the headers specifically, they are said to increase performance approximately 10-15 percent. While we personally think these numbers are a bit high, when adding just a header, it is probably fairly accurate when all of the above modifications are performed. During installation, put a liberal coat of RTV silicone on both sides of the gasket to prevent exhaust leaks. Locking header bolts may be beneficial as well, but regardless of what you use, make sure to torque the headers bolts properly. They should be torque'd down at least three times, during the install, after running up to a normal operating temperature and cool down, and again after four or five more cycles reaching normal operating temperatures. Always start in the middle and work outward in a circular pattern.

Exhaust Pipes: For mild street motors a 2.25" exhaust pipe is adequate for a single out system, while 1.75" pipes are sufficient for dual out. For performance motors, step up the diameters to 2.5" for a single out, and 2.0"-2.25" for dual outs. Mufflers are totally a personal preference, so we won't make any recommendations here. Personally we like open headers, to bad they're illegal on the street. However there's something to be said for a really quiet muffler too (sleeper).

Back to Outline

Building a Stage I Motor
Install single or dual out headers, and upgrade the ignition system.
Balance the rotating assembly and increase combustion ratio to 9.0-9.2 as follows:
200ci - use Tempo flat top pistons, or zero deck the block and use dish pistons.
250ci - use Tempo flat top pistons or 255ci-V8 flat top pistons - deck block as needed.
200/250ci - adjust the combustion chamber size (surface mill) as needed.
Rebuild the cylinder head using a 3-angle valve job and 289 or 302 valve springs.
Optional
Install a 32/36 Weber progressive 2V carb using a 2-1 adaptor.
Install a double roller timing chain set (200ci only) and ARP rod bolts.
Install a Class I performance cam with 250-270* duration (200-215* duration @ .050).
Install oversized valves, and upgrade to single valve spring with damper.
Upgrade to a late model large log cylinder head, if possible (200ci only).
(note: the 250ci already has a late model large log cylinder head)

Building a Stage II Motor:
Install single or dual out headers, and upgrade the ignition system.
Balance the rotating assembly and increase combustion ratio to 9.2-9.4 as follows:
200ci - use Tempo flat top pistons, or zero deck the block and use dish pistons.
250ci - use Tempo flat top pistons or 255ci-V8 flat top pistons - deck block as needed.
200/250ci - adjust the combustion chamber size (surface mill) as needed.
Install a late model large log cylinder head (200ci only - 250ci already has lrg log head).
Basic Port & Polish ( clean up the chambers, pocket port, and deshroud the valves).
Rebuild the cylinder head using a 3-angle valve job and oversized valves (175/146).
Upgrade valve springs to 302 springs or a single spring with damper, with viton seals.
Install a 32/36 Weber progressive 2V carb using a 2-1 adaptor.
Install a double roller timing chain set (200ci only) and ARP rod bolts.
Install a Class I performance cam with 250-270* duration (200-215* duration @ .050).
Optional
Install a high ratio rocker assembly and up-grade the valve springs accordingly.
Debur and shot-peen the connecting rods. Use ARP head bolts or studs.
Modified the log cylinder head for a direct mount 2V carb (2V conversion).
Up-grade to a 38/38 Weber, Autolite/Holley 240-350cfm, or triple 1V carbs.

Building a Stage III Motor:
Install dual out headers and exhaust system, and upgrade the ignition system.
Install a late model large log cylinder head (200ci only - 250ci already has a lrg log head).
Fully Port & Polish - giving lots of attention to the exhaust ports and chambers.
Rebuild the cylinder head using a 3-angle valve job and oversized valves (175/146).
Modify the log cylinder head for a direct mount 2V carb (2V conversion) or triple carbs.
Install a 38/38 Weber, Autolite/Holley 240-350cfm, or triple 1V carbs.
Upgrade valve springs to a single spring with damper or dual springs, use viton seals.
Balance the rotating assembly and increase combustion ratio to 9.5-9.6 as follows:
200ci - use Tempo flat top pistons, or zero deck the block and use dish pistons.
250ci - use Tempo flat top pistons or 255ci-V8 flat top pistons - deck block as needed.
200/250ci - adjust the combustion chamber size (surface mill) as needed.
Debur and shot-peen the connecting rods and install ARP rod bolts.
Install a double roller timing chain set (200ci only). Use ARP head bolts or studs.
Install a Class II performance cam with 260-280* duration (215-230* duration @ .050).
Optional
Install a high ratio, roller tipped, or full roller rocker assembly.
Up-grade to a Holley 500cfm or triple 1V carbs.
Install a solid lifter Class II performance cam (215-230* duration @ .050).
Install 180 intake and/or 150 exhaust valves, and use ARP Main & Head studs.
Install a baffled oil pan, with optional windage tray, and a larger radiator.

Building a Stage IV Motor:
Same as a Stage III motor with the following exceptions.
Increase the compression ratio to 9.5 or higher (see note).
Install a fully modified large log head, OZ250-2V head, or our aluminum cylinder head.
Install carburetion to suit (2V, 2x2V, 4V, 3x1V, 3x2V), or TBI/MPI fuel injection.
Options
Install gap-less rings, and or forged pistons, if needed (boost or nitrous)
Install a larger radiator, and perhaps an oil cooler.

Note: Once the compression ratio reaches a given point, high octane fuel, aviaition fuel, and/or water injection, may be required to prevent detonation. For the average street motor, we recommend no more than 9.5-1 for a cast iron head, or 10.5-1 for our aluminum head.

Back to Outline