Muscle Mustangs & Fast Fords
Installing A 331-Stroker Kit In A Small-Block - Stock-Block Stroke Swap Part 4
From The Engine Dyno To The Chassis Dyno, Our 331ci Small-Block Ford Is Put To The Test.
When we began this build, we had planned to compare the engine dyno numbers to the chassis dyno numbers to show exactly what the drivetrain frictional loss would be in this application. Engine dyno numbers are also helpful in choosing the right torque converter, as we recently found out. Unfortunately our limited window of time on the engine dyno had closed, so we reinstalled the fuel injection setup and pulled the engine to ready it for installation into its new home between the fenders of a Fox-body Mustang coupe.
To get the coupe cruising down the dragstrip, Hurricane Performance's Jason Combs procured a C4 automatic transmission, fortified with various high-performance components from Performance Automatic. After a quick rebuild, we had our transmission, but we needed a converter. For that, we turned to Transmission Specialties in Aston, Pennsylvania. With over 30 years of experience building high-performance transmissions and torque converters, Transmission Specialties knows a trick or two when it comes to transferring engine power to the ground. Our application was pretty simple, and the company pulled a 10-inch torque converter off the shelf. It features an approximate stall speed of 3,000-3,400 rpm, which should work well in both naturally aspirated, and if we like, supercharged forms.
Transmission Specialties' Ken Kelley had a few recommendations when shopping for a performance torque converter. "As with anything else in life, you get what you pay for," says Kelley. "Specify furnace-brazed fins, which improves the strength of internal blades of the pump and turbine, and ask if the torque converter has been rollerized with needle bearings. Roller bearings provide less internal drag which reduce friction inside the torque converter. You'll also want to ask if the cover is made out of a stock OEM four cylinder converter or if it is a billet front cover, which adds strength to keep the converter from ballooning under load."
Kelley also notes that even with all of these points met, the best thing you can do is match the stall speed to the peak torque curve of the engine. "The torque converter should reach its stall speed at the same time the engine hits its peak torque output. That information is consistent with an accurate dyno sheet."
With the transmission situation resolved, the last part of the equation was the exhaust system. We were running 1.75-inch headers on the engine dyno, and while they may be a bit on the large side for this engine, we're expecting more power out of the mill down the road, so we called up Latemodel Restoration Supply for a set of its Mac 1.75-inch long-tube headers. They're offered in chrome and ceramic coatings; we opted for the latter.
Kooks, Bassani, and Mac are the only companies that manufacture a full-length header that will fit an automatic. To control costs, we went with the Mac's as its mild steel construction keeps the price down.
One issue we ran into, the headers use a 3-inch collector and ball/socket flange. Mac offers a 3-inch ProChamber midpipe, as well as a 3-inch after-cat exhaust, but we wanted to use a 2.5-inch setup for better clearance. To make the headers and the exhaust mate up, Latemodel supplied us with one of its 2.5-inch H-pipes, and Summit Racing sent us a Flowmaster ball and socket flange kit, which allowed us to neck down the H-pipe. Working with companies like Latemodel Restoration and Summit Racing, which carry a vast assortment of parts and brands, allows you to easily remedy a situation with just a phone call and a credit card.