Fix that first, then a bigger cam will have what it needs to build power higher up in the RPM range.ĪFR 180s (64cc chamber to maintain compression) + GMPP LT4 Hotcam would probably be well over 400HP, and still have very docile street manners. But the basic restriction in the motor is the heads, no matter how you slice it. A real 400HP with just a head swap? Maybe not- the stock ZZ4 cam is probably just too small to hit that number. A small set of AFRs should blow them into the weeds. And the Fastburn heads are nothing special in the world of aftermarket heads. My selections in order of preference is the Hot LT4, the ZZ4, roller or the Ram Jet 350 cam. GM's 'Fastburn 385' crate motor is the ZZ4 with the factory Fastburn Vortec-style heads bolted on top, generating 30 more HP with NO other changes. Make sure you get a Camshaft with a fuel pump lobe if you have a mechanical fuel pump. After you upgrade the heads THEN do a cam swap and you get the big payoff.

A swap to a set of mild AFRs like the littlest 180s should be worth a much bigger bump in power than any cam swap. The core problem is that the heads just don't flow that well. GM tested that motor with the Hotcam and it picked up just a few HP at the cost of a few ft-lbs of torque. The heads and cam are dialed in to eachother to the point you can't really get much from a cam swap. That's enough power to put you into the high 12s with a 3,600-pound street car with decent traction.The ZZ4 is a well-matched combo from the factory. If you're looking for bang for the buck, put your money on the cam, springs, and rockers and you've still got a thumpin' 383 that makes 454 lb-ft of torque and virtually 400 hp.

Of course, this will add over $950 to the price of the crate HT 383. Overall, the combination of the GM Performance Parts Hot cam and valvesprings with the Edelbrock Performer RPM Air Gap, Holley 750-cfm carb, and Hedman 13/4-inch headers was worth an astonishing 100 hp and an eyeball-flattening 95 lb-ft of torque over last month's best.

The torque gains were mostly single-digit until the very top where the three amigos combined to produce 10 more horsepower at 5,600 rpm. The bigger headers and manifold lost barely a touch of torque at the very bottom of the power curve compared to the GM manifold and smaller headers, but it was well on its way to cranking out more torque by 2,800 rpm. With the headers, intake, and carb in place and a quick jet and timing test completed, Taylor again pulled the handle on the dyno and downloaded the power curve into Duttweiler's dyno memory banks.

Vortec 350 lt4 hot cam dyno