Mark Houlahan
Brand Manager, Mustang Monthly
December 11, 2013

While the Mustang has always been revered for its V-8 performance, even today the base six-cylinder engine far outsells the V-8 model. The 200ci inline-six, first offered in the Fairlane as a four-main-bearing base engine, found its way under the hood of the new '65 Mustang as the base engine (replacing the smaller 170ci inline-six). By that time, the engine block had been recast as a seven-main-bearing unit to dampen crankshaft harmonics, making it one of the strongest inline-six Ford bottom ends ever built. These seven-main-bearing 200ci inline-six engines are smooth-running, easy-to-maintain torque builders that get the lightweight Mustang moving with little fuss. However, today we must deal with 80 mph highway speeds, $4.00 a gallon gas, and long commutes, all of which the small-six isn't well suited for. Giving the inline-six some oats means easier, safer merging with highway traffic, more power for maintaining those speeds, and simply making the vintage Mustang with inline-six power more fun to drive.

Adding performance upgrades to the inline-six is the same as the typical V-8 performance enhancements of increasing airflow through the engine. If you remember your basic auto mechanics 101, an engine is simply an air pump. If you get more air into the engine (along with the required fuel needs) and get that air out of the engine faster, you will make more power. Typical upgrades such as a performance camshaft, larger diameter exhaust/headers, and basic tuning of the ignition timing and fuel metering all help. Unfortunately, Ford's third generation small-six was designed with an integral cast “log type” intake manifold that suffers from thermal encroachment, poor distribution, and no easy way to improve the air flow (you can't easily port it). Major machine work to add multiple carburetion or a larger single carburetor is an option, but does not address the short comings of the stock cylinder head design.

Classic Inlines has been over every inch of Ford's third generation inline-six engines to learn what makes them tick and how to extract reliable street and strip performance. Ultimately, Classic Inlines' Mike Winterboer knew that in order to keep the inline-six flame burning, an aftermarket cylinder head with improved airflow (including a separate intake manifold) was needed. Mike turned to the Australian Ford market, where inline-six engines are the norm and big power is available right on the showroom floor. The Classic Inlines aluminum cylinder head takes many cues from the Australian 250ci 2V head with a few tweaks here and there.

Some might ask why Classic Inlines didn't design a cross-flow head. Mike's answer is simple—cost. Not just the cost of the head itself, but of all the ancillary items that would be required (valvetrain, valve cover, distributor, etc.). With his 250ci 2V-based design, all existing valvetrain and other hardware bolts right on, saving users money.

Classic Inlines offers its aluminum head in several stages—from bare casting to fully assembled with race-level port work. To complement its cylinder head offering, Classic Inlines has put together a catalog full of valvetrain parts, internal engine parts, and more, many of which are custom-made just for them. You'll find everything you need to build your inline-six from street performer to all-out race engines at Classic Inlines, and that's why Mustang owner Brian Stilwell has been buying parts from them for his '65 hardtop since he purchased the car a little over two years ago. Starting with Classic Inlines' dual exhaust and header kit and moving up to its Weber carburetor conversion, Brian has been saving his pennies as a firefighter to take his 200ci powered hardtop to the next level.

Brian reached out to us (he's in our local Mustang club) and asked if we'd like to tag along for the build to observe the transformation. We jumped at the chance to give our six-cylinder readers some love and even had Brian bring the car to our Tampa tech center for some before and after dyno sessions so we could see firsthand what the improvements meant to the inline-six community.

1. Brian’s ’65 hardtop already benefitted from Classic Inlines tubular headers with full dual exhaust, a Classic Inlines Weber two-barrel conversion, and a DUI ignition system. Brian’s goal is all bolt-on work to a stock bottom end. Future plans call for a built bottom end and possibly a turbo.
2. Brian and his father-in-law, Ricky Snellgrove, jumped right in and decided it was best to simply remove the engine so the work could be completed on a stand (removal tip, turn the engine sideways about half-way out and it will clear without removing the hood!). Plus Brian wanted to refinish the engine compartment. That being said, you can easily perform this work with the engine in the car.
3. With the engine out and with the C4 automatic supported by a transmission jack, the engine bay is ready for tear down, but Brian and Ricky opted to tear into the engine first.
4. With the plan being a full cleaning, painting, and fresh gaskets for the engine block, Brian and Ricky tore into the engine as a team. Within 15 minutes, they had accessories removed and the head separated from the block.
5. Next, the oil pan, timing cover, and well-worn timing chain were removed from the engine. Even with small-block Ford experience, the inline-six has some differences, so be sure to have a shop manual handy if you’re not sure how something comes apart. You’ll also need the manual for torque specs later.
6. Due to the height of the block casting and the location of the cam in the block, the lifters can be difficult to extract. A lifter tool is a handy little helper that exerts external pressure on the inner lip of the lifter body to help pull it out.
7. The inline-six camshaft can be a little tricky to extract as the reciprocating assembly can interfere. Be patient by rotating the crank as needed to remove the cam and go slow to prevent damaging the cam bearings.
8. Since we had the oil pan off, a cursory glance at the main and rod bearings were made, and though they were replacements (at .020-inch over), their surfaces looked good. One thing we did notice was the original rear main rope seal had been replaced by a later rubber lip seal, but the installer didn’t offset it in the block. We were surprised it hadn’t leaked.
9. Once the engine block had been cleaned and painted, Brian stripped the engine bay of all wiring and bolt-on hardware, then cleaned and scuffed the surface for an application of spray-on bedliner coating. The spray can application left a nice fine texture (similar to wrinkle finish powder coating) and must be seen in person to appreciate.
10. After the short-block had been given sufficient time for the paint to dry, Brian and Ricky began the freshening by adding a new stock replacement oil pump and pickup screen from Summit Racing.
11. Brian chose a Classic Inlines cam to complement the head swap. All lubed up and being installed here (while Ricky works the crankshaft for clearance), the cam measures out to .480-inches of lift with 214-degrees of duration at .050-inch lift. Unfortunately, there’s no easy way to convert the inline-six to a roller cam, so Brian will have to perform a traditional break-in on this one.
12. Brian also chose Classic Inlines’ billet steel multi-index dual roller timing chain kit for the 200ci engine. This setup is super strong to minimize flex and chain stretch over standard timing chain kits, plus you can advance or retard the cam in two degree increments. For the selected cam, Classic Inlines suggested installing it four degrees advanced to aid low-rpm torque.
13. Due to the design of the Classic Inlines aluminum cylinder head, a special ARP head stud kit is required. Classic Inlines offers a complete “A” kit and a partial “B” kit if you are already using ARP studs with your stock cast-iron cylinder head.
14. Another “while we’re at it” purchase was a replacement fuel pump from Summit Racing. Brian wanted to make sure the upgraded induction had plenty of fuel.
15. Since Brian opted to have the head shaved from the stock 50cc chamber down to a 46cc chamber, it was in our best interests to check the valvetrain geometry to order specific length pushrods. Besides the reduced chamber volume, Brian opted for the assembled head with additional machine work, which includes back-cut valves, multi-angle valve job, bowl blending, port matching, and full assembly in-house. The cylinder head was outfitted with checking springs and then bolted into place on the block.
16. The use of adjustable pushrods is required to determine proper valvetrain geometry and pushrod length. These tools are available through major parts/tool suppliers like Summit Racing, Powerhouse Products, and others.

Brian's plan included upgrading to the Classic Inlines aluminum head and intake, then compliment the addition with a performance camshaft, roller rockers, and a rebuilt/modified Autolite two-barrel carburetor with a cold-air induction setup while reusing his current header and dual exhaust setup. Future plans call for upgrading the C4 automatic to T-5 five-speed manual, and down the road a built short-block to handle some boost in the way of a single turbo setup. When Brian's ready for that step, we'll be glad to grab our camera once more for inline-six fans.

To keep performance gains realistic, we requested Brian keep the C4 automatic behind the upgraded engine for a true apples-to-apples comparison.

On The Dyno

Brian swung by the Mustang Monthly tech center so we could strap his hardtop down on our Dynojet for some real-world before and after numbers (note this setup has just 9:1 compression). We ordered an Auto Meter wideband oxygen sensor and gauge kit to help with our carb and dyno tuning as well. To keep performance gains realistic, we requested Brian keep the C4 automatic behind the upgraded engine for a true apples-to-apples comparison.

With such a drastic change in induction, camshaft, and so forth, it is imperative to ignore the "peak" numbers and look at the torque curve and where the usable power now is. You can see Brian's inline-six now has a good bit more torque down low and what's important to note is that the torque doesn't fall off as before, but is relatively flat through the upper rpm range for a nice broad torque gain you can feel behind the wheel.

All told, Brian spent a little north of $4,000 for the upgrades (head, cam, rockers, intake, port work, gaskets, ignition, pulleys, carb, etc.) and is happy with the results so far. Could he have dropped in a V-8 for that kind of scratch? Sure, but a V-8 swap adds a whole different list of other necessary changes (brakes, suspension, steering) that add even more to the cost. Besides, Brian knew going in his main goal was a bit more power and to keep the inline-six to be different. He knows there's a bit more in it with tuning and he's planning to test a larger carb (2V and 4V). Now that our dyno results are in, Brian's hardtop is going back into the garage for that T-5 five-speed manual transmission swap. We'll be dyno testing Brian's Mustang after the five-speed is in the tunnel to see what the C4 gives up in power (we're guessing between 20 and 30 HP). Look for those final five-speed dyno numbers to be posted with the online version of this story and/or on our Facebook page at www.facebook.com/mustangmonthlymag.

Baseline CI Upgrades Change
RPM HP TQ HP TQ HP TQ
2,40029.2964.1051.81113.38+22.52+49.28
2,50036.0775.7854.60114.71+18.53+38.93
2,60042.1485.1357.05115.23+14.91+30.10
2,70047.2891.9660.51117.70+13.23+25.74
2,80050.6595.0164.69121.35+14.04+26.34
2,90055.1999.9570.66127.98+15.47+28.03
3,00060.65106.1876.64134.18+15.99+28.0
3,10070.04118.6680.19135.87+10.15+17.21
3,20074.89122.9184.68138.98+9.79+16.07
3,30078.67125.2188.58140.98+9.91+15.77
3,40078.73121.6192.81143.37+14.08+21.76
3,50079.03118.6095.84143.82+16.81+25.22
3,60077.67113.3198.85144.21+21.18+30.90
3,70077.38109.8499.97141.91+22.59+32.07
3,80077.04106.48100.52138.93+23.48+32.45
3,90078.39105.56103.29139.10+24.90+33.54
4,00078.08102.52105.12138.02+27.04+35.50
4,10076.8398.42106.89136.93+30.06+38.51
4,20075.4894.39106.93133.71+31.45+39.32
4,30073.1289.31107.97131.87+34.85+42.56
4,40071.9485.87108.20129.16+36.26+43.29
4,50070.4682.23108.22126.31+37.76+44.08
4,60067.1976.72107.91123.20+40.72+46.48
4,70063.5571.01106.57119.08+43.02+48.07
4,80059.5365.14104.43114.26+44.90+49.12

17. With the adjustable pushrod installed on the cylinder that has had the soft checking springs temporarily installed (in our case cylinder number one), the rocker arm tip is checked for proper positioning on the valve tip and the pushrod adjusted accordingly. Once the adjustment is locked in, the pushrod is removed and measured so pushrods can be ordered for the particular engine combination.
18. Brian ordered a new nodular iron performance damper from Classic Inlines to replace the original and tired piece we pulled off. Using a damper installation tool, like the one shown here, makes the job easy and does not put any undue stress on the damper or the crankshaft. You can also catch a glimpse of the high-flow aluminum water pump we picked up from Summit Racing in this shot as well.
19. The stock pan was in perfect shape and simply required a good cleaning and a fresh coat of paint before being installed with new gaskets supplied in the full engine gasket kit from Classic Inlines.
20. New lifters are a must with a flat tappet camshaft so Brian ordered a matching set from Classic Inlines. A liberal soaking in break-in oil before installation is a good idea.
21. The Fel-Pro head gasket features their Permatorque sealing technology and a .050-inch crush thickness (Classic Inlines offers a few different thickness head gaskets). Like a small-block V-8, the head gasket’s end passages that are open should be to the rear of the block.
22. While not required for a straight aluminum head conversion, the shaft mount rocker oil feed is plugged in this particular build due to the fact that Brian is converting to Yella Terra 1.65:1 full roller rockers that oil through traditional-style lifters and hollow pushrods.
23. With the oil feed port plugged and the head gasket back in place, the Classic Inlines aluminum cylinder head is installed and the ARP fasteners torqued down from the center out.
24. The Yella Terra roller rocker arm kit uses steel spacers that bolt to the cylinder head in place of the shaft rocker arm assembly, then the roller rockers install onto these steel spacers in pairs.
25. All painted and detailed, including a new billet water pump pulley and billet water neck from Classic Inlines, the inline-six is ready to be reunited with the freshly painted and detailed engine bay.
26. Once back down on the mounts, the 200ci inline-six’s new Classic Inlines aluminum intake manifold and existing header kit were bolted on. The engine bay is taking final form at this point with new wiring, heater hoses, and so forth. Due to the location of the carburetor when using the Classic Inlines intake, a cable-style throttle linkage is required. A Lokar Mustang gas pedal kit gets the job done easily as a bolt-on solution.
27. Before adding the valve cover, a drill motor was used to rotate the oil pump drive shaft to pre-lube the engine with fresh oil and to verify that the valvetrain would be getting oiled properly through the new oil routing of the lifters and pushrods to the rocker arms. It took a few minutes, but eventually we had nice oil flow to all 12 rocker arms.
28. To make room for cold-air induction with parts from Spectre Performance, we opted to relocate the Mustang’s battery to the trunk using a Summit Racing relocation kit. The kit includes a battery box, retaining hardware, and plenty of cable and end terminals to make it all work. Brian’s Red Top Optima battery fit the box perfectly.
29. Brian sent his Autolite 2100 two-barrel carburetor off to Kurt Praxl at Carbontooters/KP Carbs. Kurt is a former Pony Carburetors employee who has carried on their tradition of custom and concours carb rebuilding. He tweaked the Autolite to Brian’s cam specs and got it right back to him.
30. With the final installation of a re-curved DUI distributor now wearing a black cap and wires, a stock valve cover powder coated wrinkle-finish black with a Spectre Performance air breather, and a Spectre Performance cold-air induction system, this ‘65’s inline-six is ready for action.