What makes a 496

The head choice can make or break both the budget and performance of an engine like this. Rather than mess with a stock set of small-port truck heads, a new set of iron Summit rectangular-port heads were chosen. Not only do these have a much higher capacity than late-model stock big-block heads with their cc intake runners, but they also come complete and ready to rock with valves, springs, retainers, studs, and guideplates.

Like going with the stroker bottom end, replacing the heads instead of rebuilding stock stuff is quite a good value, especially if you consider the costs of reconditioning and upgrading a used set. The Summit heads which are made by Dart require longer pushrods than stock, and to determine the exact length required, it is best to mock-up the heads and measure what's required on your particular block with a checking pushrod.

Topping the heads is the induction, and here we again stuck to our lower rpm torque plan with a two-plane Edelbrock Performer RPM Air-Gap intake. Within a street rpm range, these intakes don't give much up to a single-plane in top-end power, but add big gobs of torque, making it an ideal choice for our street We had the carb fully restored, modified, and rebuilt with an baseplate by Performance Carburetors of Ontario, California, and came away with a great carb for about half the cost of a new piece.

These guys do great work. With that, most of our build was completed with no surprises, and the finishing touch was to re-install the MSD distributor that came with the engine core, and add a set of MSD's new Street Fire wires. Test Time Though our engine had grown to a , it was a pretty basic package not far removed from what the old-school street-build guys have been doing to s for decades.

With a flat-tappet cam, the break-in period is critical. Don't skimp on the cam break-in with any flat tappet, and make sure the engine is dialed in and ready to fire before attempting to start it for the first time. Before long, we were ready for the power pulls, and here the stroker showed its fat arm in action with torque rolling in hard right from the bottom of the pull.

In fact, with some tuning of the jetting and timing, the was belting out lb-ft right at the bottom of the test range at 3, rpm. That's torque that a pump-gas just can't deliver. Torque peaked at lb-ft over a range from 3,, rpm, while the engine kept making steam for a power peak of hp at 5, rpm. The engine showed a broad power curve at a moderate rpm level-just the thing for a reliable and fun street ride.

When it comes to making power on a budget, size counts, and the torque over the operating range of this engine will make it a much sweeter street mill than a smaller engine making similar power at a higher rpm, and without the low-end torque. With power this cheap and easy, what are you waiting for? Andy had our '72 vintage block cleaned, checked, and rough bored before finish honing the cylinders, with a torque plate, to.

He also line-honed the block and cleaned up the decks. Could we have gotten away with less machine work? Maybe, but Andy likes to build them right the first time. After getting organized, Andy started assembling the pistons and rods. Eagle is known for high-quality connecting rods and these forged 6.

They're bushed to work with full floating piston pins. The rods also utilize ARP fasteners and have alignment sleeves for easier assembly. The forged pistons are Mahle slugs and come coated right out of the box. Attention to detail is critical when building any engine, especially one that is expected to churn out big power. In terms of interchangeability, the biggest concern is chamber compatibility with the pistons and ensuring the compression ratio meets your needs.

One thing to keep in mind is that closed chamber heads cannot be used on an engine with domed, open chamber pistons because the dome will physically hit the head. Conversely, a domed closed-chamber piston engine can accept open chamber heads without interference.

For example, tossing a set of open-chamber heads on a could radically reduce the compression ratio because of the roughly 10cc larger chamber on a short-stroke engine. When GM converted to the Gen V, the big change was fitting the new big-block with hydraulic roller lifter camshaft. This was mainly aimed at reducing engine friction that promised better fuel mileage. This move not only changed the style of the lifter but also how the cam was retained.

When converting flat tappet big-blocks over to a roller requires the use of a button that contacts the inside timing cover to prevent the cam from moving forward. Gen V and VI engines use a steel retaining plate over the cam which requires a stepped nose on the camshaft and a different cam gear.

This move to hydraulic rollers also made a change to the rocker arm assembly. From the earliest days, big-blocks like their small-block cousins were fitted with individual stud-mounted rockers that required adjusting the installation preload. The factory hydraulic roller lifters also converted to what is called a net lash system where a rocker arm bolt tightens the stamped steel rocker in a set position. This design uses pushrod length to set the proper lifter preload.

There are kits available to convert these heads over to adjustable roller rockers. With both oval and rectangle port big-block cylinder heads, this dictates that the intake manifold port must also match the cylinder head port configuration. Production big-block intakes are, for the most part, uninspired but the aftermarket has you covered for either oval or rectangle port engines in both dual plane and single plane versions.

In the interest of brevity, this effort has just covered the crest of the monster wave of data available for production big-block Chevy street engines. Opportunities abound to build a big cubic inch street motor that even normally aspirated has the grunt to make an impressive street engine. Big blocks have plenty of flash based on the simple Machiavellian theory of Might Makes Right. With big cubic inches you can make big power and likely more torque than you can use!

This could be a with visions of grandeur with a Dominator carb — or it could be a inch that could really use all that Dominator airflow to make hp. This is a stock balancer for an externally-balanced big-block. The arrow points to the offset weight necessary to balance the crankshaft.

While the mass is balanced, that weight is still offset and creates a whipping effect that is multiplied by high engine speeds. This valvetrain shot gives you an idea of the splayed valve angles that improved airflow through the ports. This is an aftermarket aluminum head with roller rockers. This overlay of a rectangle port intake gasket over an oval port intake manifold offers an idea of the size difference between the oval and rectangle port heads.

A good aftermarket oval port head will make outstanding power even on a large ci or ci street engines. The early big-block heads were termed closed chamber left that limited valve size but did not require a huge dome to make compression. Later heads all come in a configured with a more open chamber right that laid back the far wall, increased the volume and allowing larger valves.