Classic Inlines
603 W Pecos Ave
Mesa, AZ 85210

Hopping up the Inline Six

Why, yes, I always shift at 8000:
The 200/250 engine has a bulletproof 7-main bottom end that has ample strength to support fairly high levels of power and rpm. The stock oiling system is not bad at all. And the inline six is one of a few naturally balanced engine configurations (I-6, 60-degree V-12, horizontally opposed six) so they tend to be very smooth. Could that be one of the reasons you find these configurations on upscale cars like Porsche, Jaguar, Mercedes, Lexus, and BMW?This engine's biggest shortcoming is it's breathing ability (actually its lack of). In order to increase power you have to address intake, exhaust, combustion chambers, and carb selection as a combination to improve airflow. Unlike many small 4-cylinder engines, you don't need to buzz a 200/250 to 7500 rpm to make power. You can build substantial levels of power at more useable levels between 4000-5500 rpm, so when you're done, don't be disappointed with a 5000 rpm HP peak. You have at least 100 more cubes than a Honda and you'll way out-torque most of them. Ever see a Honda Civic that could make over 200lb/ft of torque from 2000 to 4000 rpm?There are Australian and Argentine derivatives of this engine, but for the most part, they are a rarity. So for now, we'll concentrate on the US integral intake engines.

I'm Kenny Bernstein and this is the six-cylinder funny car I drive to work:

Honestly assess what your intended use is before starting any performance upgrades. If you intend to use the car as a daily commuter, you probably do not want a 330 degree mechanical cam, a 12.5:1 Compression Ratio, and 5.30 rear gears! And you certainly don't want to build an engine that is a real screamer at 7000 rpm if it's going to be used in a rock-climbing Bronco or street driven in stop and go traffic!The rest of the drivetrain should be matched to the powerplant. Even a properly built high-performance 200/250 may be no fun to drive if torque converters and gearing are not matched to the engine's capabilities. 2.79 gears can be a bummer if you build an engine that makes 240hp at 6500 rpm but only 30 hp at 1500 rpm!A really powerful engine may need upgrades to the cooling system. And you may need to improve brakes, suspensions, wheels, and tires in order to use the increased power. Power without control is useless.

I added the SuperDyno Vortex Generator, how come I still can't do a burnout?
There is no "Wonder Carb" or "Super Header" which alone will add 30 hp to these engines. Merely bolting on a big carb may only make the head and exhaust shortfalls more evident. A big cam alone will only deliver a miserly increase in power while moving the power peak higher, making the car a dog to drive. Adding headers alone will certainly help, but the total gain may be disappointing because the carb and head cannot supply enough air for major power increases. Likewise, adding triple 1bbls to an otherwise stock engine will not give more power because of the short cam timing, port limitations, and exhaust restriction. Additions and alterations must be taken systematically in order for them to work together. An engine is just a big air pump. You have to make it all work together.

Working Smarter, not Harder:
Simply put, anyone who tries to build an engine without a technical guide is a fool. There are simply too many numbers, clearances, and procedures to remember it all. And trying to siphon this type of information from the Internet is just asking for problems. Even on the best of Forums a simple question may get you six different (wrong) answers. GET A MANUAL!! For 144-250 engine owners, I highly recommend the Falcon Six Performance Handbook. If your only experience is in building Small Block Chevy's, please see the comment above on manuals. If you have never built an engine before, get someone experienced to help. Not Bob next door who once watched his dad (uncle, brother, cousin, barber) build a Hemi, or the guy at the Autozone parts counter, or your buddy who has read every Hot Rod magazine ever published, but someone who has actually assembled (preferably several) engines.No matter how many times you read on the net how to use Plastigage or a torque wrench, it's always better to have someone show you. It might make the difference between a rear main seal that leaks or not. Local car clubs can be a wealth of information and assistance.

Major Tip:
Buy, borrow, or rent the proper tools! We've heard too many tales of guys who can't seem to get their car to run right only to find out they are completely clueless about what their ignition timing is set at because they don't have a timing light and they are doing it by ear. Or the guys who can't seem to conquer the chronic head gasket leak when all along all they needed was to use a torque wrench! Plug gaps set wrong cause they wouldn't spend a buck for a cheap gap gauge?! DUH!

It worked for me:
Below are some general guidelines on combinations that have worked well for myself and others. They may help guide your decision on which way to go with a buildup. These are not definitive buildups (the term "Stage" is arbitrary) and your results may vary according to the quality of the machine work, parts, and skill of the builder. Any two of you could build the same engine with the same parts and get vastly different results because of your skill level. While you could potentially mix parts from one level to the next (for example, headers), you have to keep the combination pretty much working together. Using a Stage IV cam when the rest of the engine is still at Stage I will not deliver big power increases and may actually cost power at engine speeds where you need it most. Remember, all of these mod's are useless and will not work if installed on a tired, worn out engine. An engine with bad rings, worn out valve guides, or loose bearings should never be the basis for a buildup. Lastly, if you really need a 350 hp street engine, you need to seriously consider stepping up to a bigger engine or a V8 (Blasphemy!). While it's theoretically possible to build a 400 hp turbo-charged, fuel injected, inter-cooled, log-intake, 200ci six cylinder, the cost might be prohibitive, which is one reason so few have attempted it. Accept the 200/250 for what it really is and work within its capabilities and you'll be rewarded by an economical, durable, and different alternative to performance.

Level I - Mild Street Use, Manual or Automatic Transmission
with a Stock Converter and 2.80 to 3.20 Rear Gear Ratio.
  • Bottom end - Stock with balanced rotating assembly, moly rings, and cast pistons.
  • Cylinder head - No modifications, stock compression ratio (8.0 to 9.0:1)
  • Cam - Stock cam or 254-264 hydraulic aftermarket cam.
  • Ignition - Petronix, Duraspark II, or DUI distributor.
  • Exhaust - Stock manifold or header with low-restriction muffler(s).
  • Carb - Stock, Carter YF or RBS 1bbl, or 32/36 Weber DGV 2bbl.

This is a good, near stock rebuild which retains good driveability and off-idle low end torque. HP will peak around 4000 rpm, with torque peak around 1600-2000 rpm.

Level II - Street Use, Manual or Automatic Transmission
with a Stock Converter and 2.80 to 3.20 Rear Gear Ratio.
  • Bottom end - Stock with balanced rotating assembly, moly rings, and cast pistons.
  • Cylinder head - Three angle valve job, increased compression ratio (9.0 to 9.5).
  • Cam - Stock 250ci cam or 260 to 264 degree hydraulic aftermarket cam
  • Ignition - Petronix, Duraspark II, or DUI distributor.
  • Exhaust - Headers with 2 1/4" single or 1-3/4" dual exhaust with Turbo, Flowmaster, or Impostor low-restriction muffler(s).
  • Carb - Carter YF or RBS 1bbl, or 32/36 Weber DGV or 38/38 Weber DGS 2bbl

Improved breathing due to carb and exhaust upgrade. Better ignition and timing curve with both centrifugal and vacuum advance. Increased low-end torque with peak torque at 2000 rpm, and peak HP at 4200rpm.

Level III - Street Use, Manual or Automatic Transmission
with a Stock Converter and 3.25 to 3.50 Rear Gear Ratio.
  • Bottom end - ARP rod bolts, balanced rotating assembly, moly rings, cast pistons.
  • Cylinder head - D5 (1975) or later cylinder head with 1.75/1.46 valves, three angle valve job, pocket ported, exhaust port divider (optional), aftermarket valve springs (302 or better), increased compression ratio (9.0 to 9.5), adjustable rockers.
  • Cam - 264 to 274 degree hydraulic aftermarket cam.
  • Ignition -
  • Exhaust - Headers with 2 1/4" single or 2" dual exhaust with Turbo, Flowmaster, or Impostor low-restriction muffler(s).
  • Carb - 350 Holley, 38/38 Weber DGS (modified log intake), or or Triple 1bbls.
  • Oiling system - Baffled oil pan. Optional windage tray.

HP peaks at 4500-5500 rpm, with the torque peaking around 3000 rpm. Good idle with 264 cam, slight lope with stronger cams. Combination may feel "soft" at off the line when used with auto transmission and stock gearing but comes on strong above 2500.

Level IV - Street/Strip, Manual or Automatic Transmission
with a High Stall Converter and 3.50 Plus Rear Gear Ratio.
  • Bottom end - ARP rod bolts, main studs, head studs, balanced rotating assembly, with optional gap-less rings and/or forged pistons.
  • Cylinder head - D7 (1977) or later, fully ported head, aftermarket 1.80 Intake and 1.5 exhaust valves, combustion chambers relieved, polished chambers, aftermarket springs, head milled to produce 9.5-10:1 compression ratio. Exhaust port divider. High test only (octane booster may be required).
  • Cam - 274 to 300 degree hydraulic or solid lifter cam.
  • Ignition - Duraspark II or DUI distributor
  • Exhaust - Dual outlet headers with 2 1/4" dual exhaust, or 2 1/2" single exhaust. Low restriction mufflers or the Arvinode Exhaust system.
  • Carb - 350 Holley, 38/38 Weber DGS (modified log intake), or or Triple 1bbls. Could also use Weber IDF or IDA carbs.
  • Oiling system - Windage tray, baffled pan (not commercially available - must be fabricated), optional oil cooler.

A 250 in this configuration could potentially make 170-200 HP at 5000 rpm, and propel a light car like a Mustang or Falcon down the 1/4 mile in the mid 14 second range.

Level V and Beyond

There's a great deal of room for exploring untested waters with this engine. Unlike the Small Block Chevy or Ford, very little development has been done. Custom machine work and intake manifolds, EFI, reshaped chambers are all untested possibilities. Very few custom cam grinds have ever been tested. Comp Cams XE series may hold possibilities, as do other profiles from other manufacturers. DIS ignition systems, custom forged connecting rods, and lightweight forged pistons may extend the rpm range higher than currently possible.

The 5.0/302 in a Mustang has been done to death......Now is the time to get Inline!

Written By:
- Fordsix forum Assistant Admin

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