More on taking advantage of the "Original Type" rule...

The last couple posts weve talked about the Pure Stock drags,Musclepalooza, etc and how people maximize their performance and still stay within the rules. Once you've made your decision on a car-a '71 Chevelle might be a better choice than a '68-since you could get a 454 in a '71 model and the largest engine available in a '68 was a 396. On the other hand-a 3,400 lb '65 GTO with a 389 bored to 404 inches,a hot cam and ported intake and exhaust manifolds,and reworked 3-2bbls with mechanical linkage,a 4-speed and 3.90:1 or 4.33:1 gears will probably run a lot quicker than a 4,070 lb '71 GTO with a 455HO, a TH400 and 3.55:1s!!  Weve been over that-let's assume you've chosen a car-whatever it may be-and now you have to get it race-ready. There's several areas where a little tweaking can net you big gains. # 1. Induction. The rule saying the carburator has to be the original type allows you some room. For example the Carter AVS 4bbl that came on 383-440 Mopars from 1966-71 had very crisp low-end throttle response and good drivability. However-they only flowed about 585 cfm. A 440 V8 with a 585 cfm carb is like a 250 lb man trying to run while breathing through a straw. Fortunately Edelbrock's Thunder AVS series will fit nicely inside the rules and their's an 800 cfm version available. Simply switching to the 800 cfm carb will help you pick up as much as 25 hp and 30 lbs of torque. You can also play with spacers and jetting. Some cars run best with no spacer-some run better with a 1" or 2" spacer under the carb. Some cars run better with an open spacer, and some run better with a 4-hole spacer. You just have to invest the time to see what combination gives you the best e.t. The Carter AFB 4bbl that was on many 389 and 421 Catalinas and '64-66 GTOs, 409 Impalas, and many Ford and Chrysler applications in the '60s only flowed 500 or 625 cfm. Switching to a 750 cfm AFB or Edelbrock Performer ( which is an AFB under the Edelbrock name ) will give you a substantial gain. Ditto for dual-quad applications. Your 409 Chevy, 421 Pontiac or 426 Hemi will breathe better by switching the 500 or 625 cfm carbs for 750s. Especially for 4-speed applications-switching from vacuum to mechanical linkage on dual-quad and tri-power setups is usually good for a few tenths. The second part is the intakes. For example if you have a disco-era T/A or Formula Firebird with a 400 Pontiac-the 1975-79 intakes have a very restrictive throttle opening-the EGR valve intrudes so much that a spread-bore Holley carb won't bolt on. They severely restrict power above 3,500-4,000 rpm. The rules say the intake has to be the original type. That's easy-an Iron manifold that mounts a Quadrajet. Their are millions of Pontiac Q-jet intakes in junkyards and swap meets of '67-74 vintage that will bolt right on and allow the engine to pull hard to 5,700 rpm. This isn't an isolated example. Since the LS6 454 was slated to be available in the Camaro and the Nova as well as the Chevelle-the intake was lowered to clear the low hood of the new for 1970 Camaro. The intake is so flat that fuel has to flow UPHILL from the carb to the intake ports!! Since the early '70's stock class LS6 racers figured out that the taller '66-69 aluminum intake used on L78 and L72 396s and 427s is worth 20 hp and 25 lbs of torque over the flat LS6 intake. And their easy to find-GMPP sells this rectangular port high-rise intake to this day. If your building a "Tribute" or clone-remember cars don't have to be numbers-matching-you can run any engine / drivetrain combo that was optional on that model that year. Like I said in an earlier post you could put a Mopar Performance 426 crate Hemi into a '68 Dart if you wanted to. Let's say your building a Super Duty 421 Catalina clone. The chances of you finding a running or rebuildable 421 with 1962 or 63 date codes is almost nil. You have a better chance of being struck by lightning on the golf course. However their are millions of 400 Pontiacs out there and Kaufmann and Butler performance and others sell cranks and rotating assemblys to turn a 400 into a 428 or 455. Your allowed 15 inches from stock. You could easily build a 434 inch Pontiac with 6.8 inch rods ( stock is 6.675 ) and custom pistons. The heads have to be the original type-cast iron. You don't have to run '59-66 "Bathtub" heads with tiny ports and 1.96 / 1.66 valves. You could run 6X's ( which breathe better than any factory head except RAIV's ) with 2.11 / 1.77 valves. Your never going to find an original dual-quad Super Duty intake. However-Offenhauser made an excellent dual-quad Pontiac Intake up until a few years ago-I had one on my Judge back in the day, and I have one in a box in my garage right now. And Edelbrock still sells their excellent P65 dual-quad Pontiac intake. Either of these would fall under the "Original Type" rule. So would an Edelbrock Dual-quad intake for 348 / 409 Chevys or one for Chrysler Hemis. If you were building a Thunderbolt Fairlane clone-you could use a 390 instead of a 427 ( FE engines are externally identical ) and put a pair of Holleys on an Edelbrock intake. See what I'm saying?  # 2. Cylinder heads. Original type means exactly that. So if your car had iron heads from the factory-you can't use aluminum ones. But like I pointed out-you could put 6X heads off a '77 T/A on a 389 in a '64 GTO if you wanted to. Their both cast iron-but the 6X's breathe way better than the '64 heads!!  Like I mentioned the guy wanting to build a Nova-you can use Vortec heads on a small-block Chevy. You could use '92 and later "Magnum" heads on a 340 or 360 Mopar. ( They will bolt up to '91 and earlier blocks. You will need a "Magnum" style intake. ) Ford racers have known for years that "Explorer" heads-that came on late '90's and early 2000's 302 powered Explorers breathe better than any factory 289 / 302 head-even "GT40s" sold by Ford SVT. These would give your '60's 289 Mustang or late '80's "5.0" quite a boost. If you have a T/A or Formula Firebird with a 403 Olds V8-you can use the heads off a '68-72 350 Olds. Their 70cc combustion chambers will boost compression from 7.9:1 to 9.0:1 ( 403s have 83cc chambers ), and the earlier heads have larger 2.00 / 1.60 valves. You'll have to re-tap the bolt holes-'75 and later Olds 350 / 403s use larger bolts than '74 and earlier models but any machine shop can easily handle that. I think the difference is either 7/16 to 1/2 inch, or 1/2 inch to 9/16; I'll have to look it up. Also the Edelbrock catalog and Mondello Performance's catalog has this information as well. You'll have to use an Electric fuel pump if you do this-but you can also put 455 heads on a 350 / 403. ( You'll need custom pistons to get any kind of compression however, but it's do-able ) You can see regardless of manufacturer-you have a lot of leeway with cylinder head choices to make maximum power. # 3. Cams. This is easy-if the car had a hydraulic cam originally you have to run a hydraulic cam, no solid lifters. If the car had a solid-lifter cam from the factory you can't run a roller. That's it. Their's no limit on lift and duration. So you can run as radical a cam as your combination can handle. Because you have to run stock exhaust manifolds a lot of guys run dual-pattern cams-that have more duration and lift on the exhaust side to compensate for the restricted exhaust.  # 4. Exhaust. You have to run "stock type" exhaust manifolds which usually means cast iron. But their are several companies that sell "Ram Air III" exhaust manifolds for Pontiacs, and ported and extrude-honed manifolds for small-block Chevy, Ford and Chrysler stock class circle track racers. Any machine shop can port-match your manifolds to the heads. After that-you can run 2 1/2 or 3" inch pipes with a crossover and any mufflers you like. The exhaust won't be nearly as restricted as you think. # 5. Drivetrain. If you have an automatic-you can run a higher stall speed torque converter and still be legal. You can also run any axle ratio as long the rear end is the stock type. So let's say you had a '69 SS396 Chevelle with a TH400. Your saying it's an L78 spec car. You've already got the good aluminum intake and 780 Holley, and since you can run a solid lifter cam you've upgraded from the mild L78 cam to the super-hot L88 cam. To take full advantage of these changes you'll also need a 3,500 rpm converter and some 4.56:1 gears. Trust me-trying to run an L88 cam with 3.31:1 gears and a stock converter-the car would fall flat on it's face-it would actually be quicker stock!!  The entire combination has to be coordinated. See what I'm saying?  # 6. Driving technique. Here's where you have to do a lot of trial and error. If the car is a 4-speed does it launch better by dropping the clutch or by slipping it? At 2,000 rpm? or 3,000? or more? If it's an automatic-does it launch better by just floorboarding it, or by loading the converter against the brakes?  You have to play with shift points and see what gets you the best times. I know with one of my 403 Firebirds it ran fastest if I shifted the TH350 manually at 4,900 rpm ( 1-2 ) and 4,400 rpm ( 2-3 ). A buddy had a "5.0" Mustang. It would rev to 5,800 rpm or so-but he found he cut quicker 1/4 mile times by short-shifting it at 5,200. My brother's GTO would shift automatically at 5,400 rpm, but he went quicker if he held it in gear to 5,800-6,000 and shifted manually. So you can run just as fast as the guys in the magazines-but you'll have to put in a lot of work. Mastermind