How To Build A Pump-Gas 620hp Small-Block Mopar

Pump Gas Small Block Mopar Brian Haflinger

We first teamed up with Brian Hafliger of IMM Engines in Indio, California, in our June ’10 issue. We documented his build of a stout 408ci 360 stroker that made 485 hp with cast-iron RHS cylinder heads. In the months since, we kicked around the idea of investing a little more, going bigger with the cylinder heads and cam specs, and shooting for 600 hp with the same 360-based engine. After several months of gathering parts, we drove back out to the Coachella Valley to watch this version come together and run on IMM’s DTS dyno. We were thrilled to see the horsepower numbers soar past our goal of 600, with the needle finally indicating 621 hp at a thundering 6,800 rpm. Torque numbers weighed in at an equally impressive 541 lb-ft at 5,100 rpm. In a 3,500-pound Duster, this engine will do low 10s at the dragstrip all day long and sound awesome doing it. Interested in how IMM pulled this off? Let’s get to the build.

We arrived on a Friday to see our test subject in this condition: a bare 360 block bored 0.060-inch oversized. Ultimate displacement was 414 ci, with Scat’s 4.00-inch stroker package that comes fully balanced and complete with the crankshaft, pistons, connecting rods, piston rings, and bearings. That’s Hafliger’s dad, Fred, dropping the crank onto the Clevite main bearings. He used to own the business before turning it over to Hafliger in 2005.
We arrived on a Friday to see our test subject in this condition: a bare 360 block bored 0
In addition to the cast-iron Scat crank, the reciprocating assembly consists of forged Icon pistons and Scat’s 6.123-inch forged connecting rods (standard length for a Dodge 360). Hafliger opted for flat-top pistons to get a compression ratio of about 10.9:1. The rings included in the kit were a Hastings 1⁄16, 1⁄16, 3⁄16 package using a moly-faced top ring and standard tension oil rings. As we mentioned in last year’s article, the LA engine is cool because the crankcase does not require any clearance to fit the long-stroke crankshaft.
In addition to the cast-iron Scat crank, the reciprocating assembly consists of forged Ico
Hafliger selected a standard-volume Melling oil pump and a Moroso pickup tube to match the Moroso Street-Strip oil pan. He normally likes to use one-piece, 360 Magnum oil pan gaskets because they are better-sealing, steel-core gaskets, but the arches (the part of the gasket that fits over the front timing cover and rear main cap) don’t fit over the older non-Magnum LA engines. To fix this, Hafliger cuts the arches off the Magnum gaskets and uses the arches from the LA gasket kit, joining them to the Magnum gasket with RTV silicone. It works—the engine didn’t leak a drop of oil while on the dyno.
Hafliger selected a standard-volume Melling oil pump and a Moroso pickup tube to match the

The Edelbrock heads, which Hafliger treated to a massive porting job, are part of the 600-plus-horsepower formula. Out of the box, these heads have 64cc combustion chambers. With porting, Hafliger opened them up to 72cc. He also reground the valve seats to fit 2.08- and 1.60-inch valves (stock sizes are 2.02-/1.60-inch). Because he opened the chambers so much to improve flow around the valves, Hafliger chose flat-top pistons and milled the deck so they fit 0.005 inch out of the hole. He needed that combination to get the desired 10.9:1 compression.
The Edelbrock heads, which Hafliger treated to a massive porting job, are part of the 600-
Hafliger was merciless with the intake runners, opening them up so much that he broke through the casting in an area where a cylinder head bolt passes in between a pair of intake runners. Though it looks reckless, he did this on purpose to get the volume and shape he wanted to maximize airflow.
Hafliger was merciless with the intake runners, opening them up so much that he broke thro
He fixed it by opening up the bolthole slightly and driving in a 9⁄16-inch brass tube sealed with a Permatex high- temperature sleeve retainer. This process is called “tubing” the heads. It’s an old hot-rodder trick from the days when you only had stock cylinder heads to port.
He fixed it by opening up the bolthole slightly and driving in a 9⁄16-inch brass tube seal

Hafliger checked each combustion chamber to make sure he ported them all equally. Hand-porting these cylinder heads took nearly two days of work. He said if customers are interested in a combination similar to this build, he can sell a pair of CNC-ported heads that would match the flow numbers of his hand-ported heads.
Hafliger checked each combustion chamber to make sure he ported them all equally. Hand-por
He also checked piston-to-valve clearance before fully assembling the engine. With the cam installed straight up, intake valve clearance was 0.160 inch. With the cam installed 6 degrees advanced, the intake clearance was 0.110 inch. With the cam installed 6 degrees retarded, the exhaust clearance was 0.087 inch. Hafliger said he does not like clearances less than 0.070 inch.
He also checked piston-to-valve clearance before fully assembling the engine. With the cam
The cam Hafliger chose was a custom-ground Comp solid roller with DSZ family intake lobes and Xtreme Energy exhaust lobes. “Those DSZ lobes open fast,” Hafliger says. The specs were 260/266 degrees duration at 0.050 and 0.683/0.657 lift (with 1.65:1 rocker arms). The lobe-separation angle was 112 degrees.
The cam Hafliger chose was a custom-ground Comp solid roller with DSZ family intake lobes

Finishing the machining of the cylinder heads, Hafliger added a 30-degree back cut above the 45-degree seat. These are Manley Severe Duty valves, sized 0.100 inch short to fit under the T&D rocker arms.
Finishing the machining of the cylinder heads, Hafliger added a 30-degree back cut above t
The valvesprings are from Comp. With an outside diameter of 1.550 inches, Hafliger needed to open the spring pocket in the Edelbrock heads just slightly to make them fit. The installed height was 1.770 inches with 225 in-lb seat pressure. At 0.550 lift, the pressure jumps to 590 in-lb. Hafliger combined them with titanium Manley flat retainers and 10-degree locks.
The valvesprings are from Comp. With an outside diameter of 1.550 inches, Hafliger needed
Hafliger chose Cometic MLS cylinder head gaskets that offer a 0.040-inch compressed thickness. He sprayed them lightly with a coat of VersaChem Copper Spray gasket sealant before installation. He also milled the deck and cylinder heads to a 10 to 15 RA surface. MLS gaskets need an almost perfectly smooth surface to seal properly.
Hafliger chose Cometic MLS cylinder head gaskets that offer a 0.040-inch compressed thickn

The reason for a seemingly complicated list of valvetrain parts is that everything needed to fit under the T&D shaft-mount 1.65:1 rocker arms. At these spring pressures and lift rates, the stock-stamped rocker arms would surely have folded under the pressure. T&D’s rocker arms don’t deflect, and they pivot on a pair of needle bearings. The rocker bodies are quite large, however, and some spring and retainer combinations will not fit under them.
The reason for a seemingly complicated list of valvetrain parts is that everything needed
There was a snag when installing the rocker arm system: A few of the spacers between the rocker arms made contact with the pedestals on the cylinder heads. Hafliger had to cut some material off the face of the spacers to make room between the rocker system and the pedestals. Also, check out the 11⁄32-inch, 0.120- wall-thickness Manton Series 5 chromoly pushrods. They are hollow so they can accommodate the through-the-pushrod oiling required by the T&D rocker arms, and they measure 7.375 inches long. Hafliger needed to grind the pushrod tubes in the cylinder heads to ensure enough clearance for the larger-than-stock pushrod diameter.
There was a snag when installing the rocker arm system: A few of the spacers between the r
To optimize airflow throughout the induction system, Hafliger port-matched the intake manifold to the intake runners in the heads. He also smoothed the opening at the base of the carburetor so there would be nothing to impede airflow.
To optimize airflow throughout the induction system, Hafliger port-matched the intake mani

The last bit of grinding Hafliger had to do was on the intake manifold and the valve cover in a couple of places where the two were trying to occupy the same space.
The last bit of grinding Hafliger had to do was on the intake manifold and the valve cover
Hafliger and his dad hooked the engine up to their DTS dyno. You will notice they are using a modified Jesel beltdrive system. They’ve eliminated the water pump, using instead a pool pump to circulate water from the dyno’s cooling tower through the engine. The water inlets are modified Meziere water-pump spacers. This is a cool setup that allows cam changes without the need to drain the coolant. Incidentally, the Jesel system is designed for an R3 race block, and it required some modifications to make it fit the coolant passages in the front of the block and around the front main bearing cap. It is not designed to fit a production LA engine block.
Hafliger and his dad hooked the engine up to their DTS dyno. You will notice they are usin
With an out-of-the-box Holley 1000HP carburetor and 34 degrees of total timing, this combination made an impressive 597 hp and 530 lb-ft on a partial pull up to 6,000 rpm.
With an out-of-the-box Holley 1000HP carburetor and 34 degrees of total timing, this combi

Hafliger tried both a 1-inch open spacer and a 1-inch tapered spacer. The open spacer made better power and pushed us over the 600hp barrier. We saw 615 hp and 524 lb-ft. Bolting on a Performance Speed and Custom modified 1000HP carburetor netted a few more ponies.
Hafliger tried both a 1-inch open spacer and a 1-inch tapered spacer. The open spacer made
Advancing and retarding the cam affected the power numbers slightly but not enough to be noteworthy. The best performance came with the cam installed at zero degrees.
Advancing and retarding the cam affected the power numbers slightly but not enough to be n
Ultimately, the engine made a best of 621 hp at 6,800 rpm and 541 lb-ft at 5,100 rpm with a PC-modified Dominator carburetor. Obviously, this engine needs lots of air to make power, and the 1000HP had become a slight restriction at high rpms. Check the dyno charts for all the numbers. This would be a very effective combination in a 3,000-pound car with about a 5,000-stall converter. If you want more power than this, you need to invest in a forged crankshaft and a pair of Indy cylinder heads. End
Ultimately, the engine made a best of 621 hp at 6,800 rpm and 541 lb-ft at 5,100 rpm with