When it comes to small-block Mopar power on a budget, the 360 is the undisputed king. As the largest factory small-block, the 360 started life as an underappreciated smog powerplant in 1971, and the same basic configuration saw continuous production for a good three decades. While the 360 was offered in some performance oriented vehicle packages through the ’70s, the engine’s 340-cube little brother from the muscle car era got all the glory as the hot performance piece. However, the 360 had the cubes and the massive OEM production run to make it the logical choice for small-block performance today. Though out of production for about a decade now, by sheer weight of numbers the 360 remains readily available in boneyards across the country.
With today’s aftermarket parts, a 360 can easily be converted to a fire-breathing stroker with well over 400 cubic inches of displacement. While cubes are a sure way to more grunt, the factory 3.58-inch stroke combination remains hugely popular for lower budget builds or engine swaps. We wanted to explore the untapped potential of a basic 360 combination, taking the engine well beyond the typical 400 horsepower range of the basic street performance build. Our plan to get there would be to take the engine’s breathing to the next level, while maintaining a budget approach in keeping with the 360’s working class roots.
01. Our block was an older remanufactured 1977 360, which we found was already bored .040
02. A stock 360 cast iron crankshaft was ground .010/.010-inch under, and we were able to
03. The opportunity to internally balance our 360 was a result of the lightweight Scat 6.
Basic Bottom End
The foundation for our build is a common 1977 360 casting, pulled from a truck. We actually pulled the engine years ago from a junked truck, but the upshot was the block had been previously remanned. While a remanufactured engine is generally built to the lowest cost possible as far as the internal components, we were pleased to find the .040-inch overbored block showed bores that were in excellent condition. Normally an engine build will start with a trip to the machine shop for a bore and hone, decking, and usually line honing the mains. In this case, with our particular block, careful measurement showed that the existing machining was fresh enough to build upon. We just cleaned up the block, hand honed the bores, and called it good enough. The factory cast iron crankshaft was polished at its existing .010/.010-inch undersize, and the essentials were ready to go for next to nothing.
Filling the bores, we detoured from our rock-bottom budget approach, stepping up to a set of Probe forged flat-top pistons, and stock-length Scat I-beam rods. The previous rebuilder’s cast, dished pistons had no place in a performance build, so a piston upgrade was a must do for added durability and increased compression ratio. The Probe pistons offer reliability at an affordable price, representing a good upgrade over the existing pistons. To seal the pistons to the bores, a set of SpeedPro file fit moly rings were selected. Again, there are cheaper alternatives, but the moly rings are well worth the added cost for longevity of the bores and performance. We gapped the rings to .016-inch, top, and went much wider at .030-inch at the second ring.
The strong Scat 4340 forged I-beam rods offer peace of mind, and also provided the advantage of lighter weight than the stockers. These rods come with wristpin bushings, 7⁄16-inch ARP bolts, and all things considered are a sensible upgrade compared to rebuilding the stockers. The lighter rods and pistons enabled us to internally balance the crankshaft, eliminating the need for the stock 360’s weighted damper and flywheel. With this internal parts combination, the factory cast iron crankshaft did not require expensive Mallory metal to achieve the internal balance, getting there by just filling and welding the large factory balance holes in the counterweights. The crankshaft was installed with Clevite bearings at .0024-inch clearance using the factory main caps, secured by Milodon studs, and a zero balance Professional Products damper was hung on the nose.
The bottom end package was buttoned-up with a Milodon oil pump, windage tray, and pan. What we had on the engine stand at this point was a typical street performance 360, with sensible upgrades that were anything but extravagant. The piston to deck checked out at .013-inch deck clearance, with the previous block machining. Although this is off from our normal target of a zero-deck, but the deck checked square to the crankshaft, so we left it alone.
Looking to make the most from our utilitarian short-block, we would focus on two key areas—the camshaft and flow system, and we weren’t looking to go for the super-expensive stuff in either area. We opted for a hydraulic flat-tappet camshaft, since this configuration is the cheapest and most common setup in a budget build. The KV3H cam, however, was a very fast ramp .904-inch lifter lobe-profile, custom ground by Engle. Spec’ing out with 284-degrees of gross duration at .008-inch lift, and 241-degrees at .050-inch, 155-degrees at .200-inch, and with .368-inch lobe lift, the lift curve of this stick is extremely quick, but the overall duration is moderate by today’s performance standards. The camshaft was ground on a lobe separation angle of 110-degrees. We had tested this cam in a previous 360 engine combination, and found the stability and power production to be exceptionally good. A set of standard Johnson hydraulic lifters were modified with circlip snap rings and the cam and lifter combination went into the block with the installed centerline set at 104-degrees for 6-degrees of advance.
For cylinder heads, we turned to Dr. J’s Performance to try a set of their new Airwolf 220 CNC ported heads. Unlike high-end race units, these heads feature a stock intake and exhaust configuration, and accept straight rocker arms rather than specialty offset rockers. The sum of all of this is a cylinder head that is a direct bolt-on replacement for the stockers, taking advantage of readily available and moderately priced standard LA-series engine components. Where the Airwolf 220’s differ from other heads of this configuration, is in port capacity and flow. The heads feature intake ports with a minimum cross-sectional area of 2.48-inch – sizable enough for serious power. These heads are built for maximum flow from a “straight rocker” valvetrain arrangement, and with over 320-cfm peak intake flow on tap (see flow table), they set a new standard for a head of this type.
We had our Airwolf heads cut for a 66cc chamber volume, and when combined with Mr Gasket .028-inch head gaskets, we had a compression ratio of 10.38:1, and an ideal quench clearance of .041-inch. To provide valvetrain stability with our very fast Engle cam, the heads were fitted with Comp Cams’ 26918 Beehive springs, along with Comp’s locators, retainers, and 10-degree locks. The springs were installed at 1.71-inch, giving 151 pounds of seat load. With a set of Erson 1.6:1 rockers, our Engle camshaft delivers a whopping .589-inch theoretical peak lift, a point at which the Comp springs provide 395 pounds of open load pressure.
To feed the Airwolf heads, we brought a Weiand X-celerator intake manifold to Dr. J’s for the full porting treatment. The X-celerator is a small-runner single-plane intake that works well with production sized heads, but Bryce Mulvey of Dr. J’s noted that even fully ported this intake is a little on the small side for the large runner Airwolf heads. In retrospect, an Edelbrock Super Victor or Holley Strip Dominator would have been a better choice, but hey, it’s what we had. The induction system was completed with a Holley 950 Ultra HP carburetor, a giant member of Holley’s 4150 family of carbs. Ignition was accommodated by an MSD distributor working in tandem with the dyno’s MSD 6AL ignition system and MSD coil. To handle the exhaust, we just bolted on a set of tti 15⁄8 to 13⁄4-inch step headers that we came out of an A-Body Dart.
05. The valve notch orientation of the Probe pistons is symmetrical, meaning the intake a
06. Our camshaft is a special KV3 hydraulic flat-tapped grind from Engle, a very high vel
07. Back downstairs we installed a Melling oil pump with a Milodon pickup tube, and Milod
08. Our bottom end gets fed mass quantities of air via a set of Airwolf 220 CNC heads fro
09. With an intake port runner size of 220cc and steep flow curve, the Airwolf has the ca
10. The Airwolf heads feature a 2.05⁄1.60-inch valve combination, while the combustion ch
11. Making power with a flat-tappet hydraulic cam depends upon maintaining valvetrain con
12. With the pistons .013-inch in the hole at TDC, we went with a set of Mr Gasket .028-i
13. Although an older design intake, bridging the gap between the intake runners is a Wei
On The Dyno
We set out to bust through the typical 400 horsepower range of a usual street/strip stock stroke 360, and went into our dyno session with 500 horsepower as the bogie. With a basic bottom end and a moderate hydraulic flat tappet, we were definitely holding back as far as high-end race parts, but the ace up our sleeve was that deep-breathing set of Airwolf cylinder heads. We ran the valves to set the preload on the hydraulic lifters to a quarter turn past zero lash, and dialed 34-degrees of total timing on the damper for the initial fire-up. The 360 lit at the first crank of the starter, and we put the engine through the normal break-in cycle to bed the rings into the slightly used bores, and get the camshaft familiar with the lifters.
|Chrysler 360 (367cid actual displacement)
220 CNC AirWolf Heads
DTS Powermark Engine Dyno
Our first full throttle pulls had us handily over our 500 horsepower goal, with outstanding torque throughout the curve. Tuning with jet and timing loops showed the engine favored a lean reading on the lambda sensors, indicating very good fuel distribution. Our blow-by meter showed minimal leakage, confirming that all was well. We homed in on a best timing setting of 37-degrees total, and watched the power rise a few numbers with each pull as the rings mated with the cylinder walls. It wasn’t long before the 360 was ripping repeated pulls showing 522-523 horsepower at peak, and an outrageous torque peak of over 495 lb-ft. Even pulling down to a low 2,500 rpm, the 360 had plenty of shove, registering 375 lb-ft of low end torque. With power like that, our Airwolf-equipped 360 has the muscle to make the competition howl for mercy.
No credit cards were harmed in the making of this engine
|Polish factory crankshaft
||Sealed Power 87125CH10
||Sealed Power ZR977145
||Engle KV3H Engle
||Complete Airwolf 220
||Mr Gasket 1121G
||Holley 950 UHP 0-80805HB
||Dr J’s Performance
On The Bench
Dr. J’s 220 CNC AirWolf Mopar
Tested on SuperFlow 600 Flow Bench
Tested at Reher Morrison
Tested at 28-inches depression
|*With 17⁄8-inch by 3-inch straight wall pipe
Dr. J’s Performance
Federal Mogul, SpeedPro, Fel-Pro
(A Division of Holley)