Big Block Chevy "Restification"

While GM still sells 502 inch engines in trucks, and you can buy a GMPP crate engine up to 572 inches and 720 hp, for our purposes we'll focus on the MKIV produced from 1965-89. There's nothing wrong with the '90 or '91 and later MKV engines, but if your restoring an old musclecar chances are you'll be using a MKIV. These come in 4 sizes-396,402,427 and 454 cubic inches. The 396 / 402 was used in Chevelles,Camaros, Impalas, Monte Carlos a few Novas, and pickups from 1965-72. This engine was dropped from the lineup in 1973. The 427 was only used from 1966-69, mostly in Corvettes, although it was an option on the Impala and other full-size models. If your restoring a 427 'Vette or an Impala SS427 then you have to bite the bullet and pay the price for a 427 which tends to be steep. Otherwise you can usually find a 454 a lot cheaper. The 454 was used in various models and trucks from 1970-89, when the MKV was introduced. A 396 / 402 can make as much power as a 454, but it will be at higher rpm with less idle quality and drivability. Unless your restoring a numbers-matching SS396 Impala, Chevelle, Camaro or Nova, if you don't already have an engine and have to go buy one, I'd get a 454. They don't cost any more to buy or build than a 396, but they make substantially more power and torque with the same equipment. What's the old saying? "There's no substitute for cubic inches, except cubic dollars."  #1 Bottom end. The "Rat's" bottom end is practically bulletproof in stock trim. Unless you plan to run over 7,000 rpm for extended periods you don't need any special parts. If your planning to run Nitrous, then I would invest in forged pistons. Otherwise a standard rebuild will give you many years of trouble-free service. # 2. Cylinder heads. There are "Standard" heads and "Hi-Performance" heads. Standard heads have oval ports and 2.06 inch intake and 1.72 exhaust valves. High Performance heads have rectangular ports and 2.19 inch intake and 1.88 exhaust valves. Stick with standard heads. Here's why-Hot Rod magazine did a dyno test on identical 454 Chevy engines a few years back-i.e.-same cam, same carb and intake, etc. The rectangular port heads did not show a noticeable gain in horsepower or torque until 6,300 rpm. How often are you going to be above 6,200 rpm?  My point exactly. I don't mean to sound lassiez-faire, but you can make 350 hp on junk gas with 8.5:1 compression and iron intake and exhaust manifolds. With headers, a mild cam and an aftermarket intake you can make 450-500 hp so easy it's like stealing.  # 3. Camshaft. Again-I don't mean to sound lackadasical but the bottom line is it's pretty hard to over cam a 454. If your running an automatic tranmission and high ( low numeric ) gearing like 2.73-3.08 I'd recommend the factory L34 350 hp 396 Cam or the Edelbrock Performer cam. Both of these offer outstanding low and mid-range torque and will work with a stock converter and the high gearing. If you have a 4-speed or an automatic and an axle ratio between 3.23 and 4.10 I'd go with the cam manufacturer's recommendations on gearing, converter stall speed, carb size, etc. If your restoring a solid-lifter engine like an L78 396, an L88 427, or an LS6 454 Crane makes exact replicas of these factory cams under their "Blueprint" series and they are still available from GM as well. LIke I said in the small-block section-modern hydraulic cams operate trouble-free up to about 6,500 rpm, so other than nostalgia, or Concours Judging there's no need to mess with a solid cam that requires constant adjustment.  # 4. Induction. GMPP sells a factory iron Q-Jet manifold if your restoring an L34,L72,LS3 or LS5.  They also sell a factory aluminum one with a Holley bolt-pattern if your restoring an L78,L88,L89,or LS6. Or if you don't care about having an aftermarket intake the Edelbrock Performer and Performer RPM are both excellent depending on application. As for carbs-if you want it absolutely original then go with a Q-Jet or whatever Holley your engine may have had. Otherwise I'd go with an Edelbrock. They flat work and they don't leak or bleed over or blow power valves or any of the other fun stuff that Holleys do. # 5. Exhaust.  A set of headers can add as much as 50 hp to a big-block Chevy. I'd back that up with a good 21/2 or 3 inch exhaust system and turbo-style mufflers. If you don't want headers or are restricted by racing or concours class rules to iron manifolds you can still let it breathe with a good dual exhaust system behind the manifolds. I'd use at least 2 1/4 inch pipe and Turbo mufflers. Like I said-your really getting the "Readers Digest" version here-very basic guidelines of what to do and what to avoid to save money. I'd buy HP books excellent "How to hot rod Big Block Chevys" or "How to build Max performance Big -Block Chevys." Both give really in-depth info on how to build a powerful, reliable Rat motor that will give you years of trouble-free high-performance. Mastermind