A "Pure Stock" Small-Block Chevy....

As promised in the previous post today we'll talk about building a small-block Chevy to run in the Pure Stock drags. There's only 3 displacements that you can run. ( Unless you have a '76 El Camino with a 400 ).  These will be 302, 327 and 350. These are all easily doable with a 350 block, as they all have the same 4.00 inch bore size. GMPP, Eagle, Lunati and other companies sell cranks with 3.00, 3.25 and 3.48 inch strokes to get your desired displacement. TRW sells the proper pistons. Every one has a list of "gotta haves" when talking about the SBC. 4-bolt mains, forged cranks, "Pink" rods, screw in studs, etc. Yes, if your building a NASCAR Nextel Cup racer that has to go 7,800 rpm for 500 miles at Daytona, you need all the beef you can get. For a street machine that only sees weekend trips to the drags, you don't need any of that stuff. Seriously. Two bolt main blocks are fine. Cast cranks are fine as long as rpms don't go over 7,000. I have seen guys run 2-bolt mains, cast cranks and cast pistons for 2 whole seasons in an IMCA race car without a rebuild or a single problem, and these roundy-round racers are far more abused than your car will be. As for rods-the stock rods are bulletproof, especially if rpms are kept under 6,500. Stock length is 5.7 inches. Many Nascar builders run 6.0 inch rods with custom pistons. You can do this if you want some extra torque in the mid-range, and your getting new pistons anyway. If your re-using the old pistons, then save the money for other parts that offer a bigger bang for the buck. # 2. Cylinder heads. There's three types of heads I recommend. The first is simply use the heads that came on the engine. Here's why. Some people diffentriate between "standard" and "Hi-performance" heads. Standard heads have 1.94 intake valves and 1.50 exhaust valves and pressed in rocker studs. Hi-perf heads have 2.02 / 1.60 valves and screw-in studs. But here's the kicker-both heads have the exact same size intake and exhaust ports. Any competent machine shop can install the larger valves in standard heads for a minimal fee, as well as screw-in studs if you want some extra beef.  Which you don't need. My friends and I have drag raced and circle-track raced Small-block Chevys for 40+ years and I have NEVER seen a stud pull out of a head.  The 2nd one is '81-86 305 "smog" heads. These have 1.84 intakes and 1.50 exhaust valves. However-their 58cc combustion chambers will bump compression on the average 350 from 8.2:1 to about 9.6:1 when replacing 76cc heads. The large boost in hp and torque from the extra compression will more than offset the slight loss of airflow from the smaller intake valve, or any machine shop can install 1.94 valves easily and cheaply. The third type is 1996-2003 "Vortec" heads. You can buy a set of brand-new Vortec heads from Scoggin-Dickey for $700. This is a screaming deal, because most machine shops would charge nearly that much to re-condition your old heads, and they probably couldn't duplicate the trick valve job that the GM factory puts on the new heads. Vortecs breathe better than other factory head and many aftermarket ones. Their 64cc combustion chambers will bump compression one full point over 76cc heads. All these features make this a 25-40 hp bolt-on. You will need a Vortec bolt pattern intake. GMPP offers a replica of the original Z/28 / LT-1 intake in cast iron in standard and Vortec bolt patterns. This manifold makes power from idle-7,200 rpm. It is almost impossible to out-power this manifold. It's also available in aluminum if your restoring a Z/28 or LT-1 'Vette or just building the motor to those specs. Stock class rules say the intake has to be the original "type"-which means either Iron or Aluminum depending on what model you have, or are claiming to clone. Carb choices are limited to two. If your doing a Z/28 / LT-1-you can use a #3310 780 cfm Holley.  Everything else will require a Quadrajet. Luckily-the GMPP manifold is a spread-bore bolt pattern and will accept either carb without need for an adapter. # 3. Cam. The cam I recommend for this application is the Comp Cams 270H Magnum. It has 224 / 224 duration ( @.050 ) and .470 lift. It will be a little lumpy in a 302, better in a 327, and really sweet in a 350. It pulls hard from idle-6.500 rpm. I'd only use it with a stick in a 302. With a 327 / 350 it will work with an automatic and a stock torque converter. However it will launch better if you have a 2,000-2,400 rpm converter. Crane, Comp Cams, and Lunati all offer exact replicas of the original Z/28 / LT-1 solid-lifter cam if you want to use it. However-the hydraulic Magnum cam works so well and is so maintenance-free that I don't think spending the time and money to switch to a solid-lifter design is worth the extra money or the time needed to constantly adjust valve lash settings. The other hydraulic design I recommend is sold by GMPP and Crane. It's an exact replica of the "350 hp" L46 / L82 cam. It has 222 duration (@.050 ) and .450 / .460 lift. It pulls hard from idle to 6,000 rpm and works great even with an automatic and a stock converter.     # 4. Exhaust. Since many circle-track classes require iron exhaust manifolds, there are several companies that offer ported and extrude-honed Iron manifolds for small-block Chevys. Most are ported reproductions of the classic "Ram's Horn" '60's 'Vette style-but they work almost as well as steel tube headers. Use at least 2 1 /4 inch pipes and low-restriction mufflers.  # 5. Gearing. Use 4.10:1 gears. This ratio will cover a 302's lack of low-end torque ( there's a reason '67-'69 Z/28's were only available with a 4-speed and 3.73:1 or 4.10:1 gears ) and get it moving with alarcity, and will give a 327 /350 some serious mid-range and top-end pull through 2nd,3rd and 4th. ( Or 2nd and 3rd if your running a TH350 ). Depending on car weight-obviously a Nova will be quicker than a Chevelle, or a 'Vette quicker than a Camaro-this combo should run very low 13s to mid-12s depending on traction and driver skill, and will cost very little to build, and will be bulletproof dependable.  Mastermind