Another slick addition for your Rat would be these Dart adjustable 3/8-inch pushrod guidep
As we mentioned in the original oval-port head test, if you want to run a similar Comp hydraulic roller cam in your 454, the Edelbrock heads are shipped with valvesprings intended to be used with a flat-tappet camshaft. In our test, we wanted to make sure the valve-springs were all the same for each cylinder head, so we swapped them for a set of Comp 933-16 hydraulic roller valve-springs. The 933 Comp springs offer 220 pounds of load with the valve on the seat and 490 pounds at 0.600-inch lift. Frankly, since the Edelbrock heads continue to increase flow through 0.600-inch lift, you might consider a cam with more lift to take advantage of the heads' potential. Comp does have a single-pattern 280HR Magnum hydraulic roller that specs out at 224/224 degrees of duration at 0.050 with 0.566-inch valve lift for both intake and exhaust with a 110-degree lobe-separation angle. This will pump the lift closer to 0.600-inch lift, and then you might also consider a set of 1.8:1 roller rockers that would push the lift just below 0.600-inch lift. Anytime you increase the rocker ratio, you accelerate the valves more aggressively, which tends to make the springs work harder. The reality about valve float is that the first place the spring loses control of the valve is on the closing side as the valve approaches the seat. The intake valve is the heaviest of the two valves, so any loss of control will happen to the intake first. When the intake bounces off the seat during closing, it effectively increases cam duration, which isn't really what you want. Every time the valve bounces, it also allows cylinder pressure to escape back into the intake port instead of being captured to make cylinder pressure. If allowed to continue, this valve bounce will kill power and also tend to reduce the effectiveness of the springs. One way to help the springs is to use a lighter retainer. When we did that story in 2008, we used the Comp titanium retainers, as they were the only real alternative to steel. However, Comp has since come up with a series of tool-steel retainers that are not only nearly as light as the titanium pieces, but much less expensive. The stock steel retainers weigh 35 grams, while the titanium retainers only weigh 18 grams. The tool-steel retainers (PN 1732-16) weigh roughly 21 grams but only cost $153.95 from Summit Racing as opposed to $300.00 for the titanium pieces. You'll also need lash cap-style keepers (PN 611-16, $21.95, Summit Racing) in case you need to use lash caps (PN 621-16, $33.95, Summit Racing). This adds up to another $200.00, but now you'll have a bulletproof and lightweight valvetrain, which is a good thing when it comes to Rat motors since they tend to be somewhat abusive on valvetrain parts.
All these parts could easily be used on your existing 454 instead of going to a 496. What you'll give up with the smaller engine is both torque and horsepower. We can estimate the power by merely taking the existing power of our test engine at 582 and dividing by the displacement of 496 to get a 1.17hp/ci figure. We then multiply by 454 and come up with 533 hp. This might be a touch low since piston friction will be less with the 454's shorter 4.00-inch stroke, so 550 hp isn't out of the question even with your Edelbrock RPM dual-plane, since that's what we used on our test engine. Plus, with the bigger cam and more lift, you might actually get up into the 575hp range. Torque will also be reduced with the smaller 454 with the numbers crunching out to 565 lb-ft. This is still great power and more than enough to spin the tires or if you hook it up with a 3,700-pound car and a 3.55:1 rear gear to run low 11s at 120 mph without too much trouble. Sounds like a lot of fun, doesn't it?