Rat Tricks
E.B. via CarCraft.com: I'm trying to get some information on a an '86 454 Chevy out of a Suburban. The numbers on the heads are 14081045 and on the block are 14015445 with a K-22 445 Hi-Perf. Pass. I need to know the horsepower, compression, cam duration and whether it's a hydraulic flat-tappet or a roller, valve sizes, and cc's of the head. I would like to do the motor in two parts, something like the article "Import Killer" (Aug. '02). I want a reliable 500 or so horsepower that's street driven on a regular basis and sometimes for distance. I wasn't planning on rebuilding the motor. I was going to port the stock heads, use heads from the 454 H.O. if they are sold separately, or maybe use aluminum heads. I also want to use an Edelbrock RPM Air Gap intake with a matching carb, a TH400 trans with a shift kit , a TCI 3,000-rpm stall converter, and 3.55 or 3.73 rear gears in a 10-bolt. The car is an '84 Olds Cutlass that weighs roughly 3,400 pounds.
My plans were to get a Comp nitrous cam NX 268 with 0.515/0.555-inch lift and maybe later add a 125hp shot of nitrous. The second part would be to bore and stroke the BBC to 496. Any help is greatly welcome.
Jeff Smith: We put our best Rat BratT-shirt on to do the research for your question, E.B. Your rodent is a 454 out of a '75-'87 truck, with oval-port, open-chambered heads. The power rating was dismal at between 230 and 245 hp using a flat-tappet, hydraulic lifter camshaft. We've not confirmed this, but it's a good bet these are the peanut-port cylinder heads, which makes them undesirable for a performance application unless you want to spend dozens of hours living with iron filings. There are better ways to spend your time and energy.
Having said that, older, iron, large oval-port heads could be made to work extremely well in a 454. In 1993, when I was at Hot Rod magazine, I did a story with John Lingenfelter about building a 496ci stroker with a set of ported, iron, large oval-port heads. This was back before there were aftermarket oval-ports. He knew port velocity combined with good airflow is the key to engine performance and that the rectangle-port heads, while flowing big numbers, were way too big-especially for a 396 and even for a 454. He chose a big mechanical roller cam of around 250 degrees at 0.050 and made 660 hp! The point here is that a set of ported, oval heads opened up for 2.18- or 2.25-inch intake valves would make excellent torque and horsepower. This could make a great 550hp combination with a conservative cam and a single-plane intake.
Getting back to your combination, the choice of the flat-tappet Comp Nitrous 268 cam is good because it offers decent valve lift with a relatively short duration, which will make great torque and horsepower, especially with a set of oval-port heads. If you choose to go with aftermarket heads rather than invest in iron heads, there are several excellent choices. Brodix has a new head called the Race Rite big-block oval head with 270cc intake ports (the '70s Chevy iron ovals were roughly 250 cc's) and 2.25/1.88-inch valves. Brodix claims these heads will flow over 300 cfm out of the box. The Brodix catalog price is $1,070.12 each, but you might find them for less on the Internet. One advantage is that exhaust ports are in the stock location, so headers for your car have a better chance of fitting properly.
World Products also makes 269cc oval-port iron heads. They sport larger 2.30/ 1.88-inch valves with 119cc chambers. A complete set of these heads (PN 3004KA) will run $2,799.95 from Competition Products, which is a bit steep for iron. There are fewer oval-port heads available for the Rat because everyone is building larger-cubic-inch big-blocks. The base now is at least 496 inches, but be forewarned that everyone else is starting at 540 and larger displacements. These engines like the larger-port heads and can generate some port velocity even with 360cc intake ports. But these motors are expensive.
If you decide on the 496ci stroker package, you can follow along with a buildup we will be doing in a couple of months with a 489 (0.030-over stroker 454) Rat using a pair of AFR 305cc cast heads. These heads flow well, and with their smaller port size, the velocity should do well. We're starting out with a used short-block we bought and will eventually work our way up to a much stronger package. Check it out in an upcoming issue.