I have a ’72 Barracuda with a 318 engine. Wanting a little more punch, I came across a 1969 date-coded block for a good price. I am looking to make around 425-450 horsepower, and hopefully get into the 12’s in the quarter-mile. This will mainly be a street car, with occasional trips to the dragstrip.
The block will be .030-inch over with stock rods, a zero deck height, and pistons (not sure what ones) to give 10.5:1 compression ratio. I will want headers, but am not sure which ones. The heads are stock X castings with 2.02 and 1.60-inch valves; a freshening needs to be done. Will they need some porting to hit my goals?
The cam is an Edelbrock 7177 with 234/244 degrees of duration at .050-inch lift, with .488 /.510-inch lift. The intake is an Edelbrock Performer Air-Gap with a 750-cfm carburetor.
I am using a 727 with a 2,800-3,000 stall converter, shift kit, and either 3.91 or 4:10 gears in the 83⁄4. I’m not sure if I would run drag radials or slicks. The question is, can I get into the 12’s with this setup? And what recommendations would you have?
Keith, you are on track on meeting your goals with the combo you have planned. I would choose a forged piston from a company like Wiseco, using a thinner steel ring pack, like a 1.2 or 1.5mm compression ring. These thinner rings reduce drag, and seal very well. I would prefer a cam from a company that specializes in cams, like Comp Cams, and would look towards their Xtreme Energy Hi-Lift series to get more lift for a given level of duration. I’ve found these cams to work very well into the mid 6,000 rpm range. The X heads flow quite well, especially with a very good performance valve job and minor blending in the bowls. This blending will be definitely worth while, compared to a standard valve job, especially if a 70-degree throat machining step is included. You should be able to get right at your power goal with this setup and I’d expect a 12-second quarter-mile on drag radials with some tuning time on the strip.
I have a ’72 Charger with a 400 and an automatic transmission. This car has been a project for about four years, and is mostly used for “Sunday drives.” It always ran really well, but was lacking in the power department. After taking a ribbing from some of my buddies, I decided to do something about it. A local shop specializes in high performance work, and I decided to stop in and find out what they could do to give my Charger some power. They spent quite a bit of time going over a game plan, and ended up making several modifications to the car and engine. The rear gears were changed to I believe 4.10:1. A high stall 3,000 rpm torque converter was added to the 727. The engine received a Comp cam, an XE274H, a set of 1.6 roller rockers, and a new timing chain, pushrods, and lifters. The heads got a three angle valve job, along with new stainless steel valves and new springs. An Edelbrock Performer intake was used, along with an 800 Double Pumper carb. The car was fitted with Hooker headers to replace the exhaust manifolds, and a new dual exhaust system was built with UltraFlow mufflers.
The car certainly is much faster than it was before, especially from a dead stop. It will burn rubber at will with just a stomp of the gas pedal. The problem for me is the fuel consumption. I actually find it gets about 8 mpg in normal driving, and sometimes less than that! I am amazed that the fuel economy can be that poor. I do like the increase in power, and I sunk more than five grand in the modifications, but the fuel consumption seems to be excessive. Now I’m trying to figure out if making the changes was the right idea. I used to get well into the teens for mileage, and wouldn’t hesitate to take the car for trips of several hundred miles. The rpm seem to be excessive, and I can smell fuel when the car idles. I was thinking an overdrive might solve my problems, and have looked at some of the kits on the market. Is the increased fuel consumption mostly a matter of the change in gearing, or is it the engine modifications?
Harry, I would say that it isn’t one or the other, but rather a combination of the two. Certainly the gearing and converter are major factors, with the engine now spinning much higher at any given speed. However the camshaft is much, much longer in duration than the stock unit, and likewise the Double Pumper series’ of carbs are not known as miserly. Add to this the fact that you are still running the engine at the low factory compression ratio, and you have all the ingredients for abysmal fuel economy.
Here is what I would recommend if you are willing to re-address the combination in search of improved efficiency. I would add a modern overdrive transmission with a lockup torque converter of moderate stall, in the range of 2,500 rpm. I would swap the Double Pumper for a vacuum secondary carb or Thermoquad, but keep the aftermarket intake manifold. I would also cut back on the camshaft duration, and install something with no more than 224-degrees, like the Comp XE268H or even a XE262H, if you don’t mind trading some top-end power for more efficiency and a smoother idle. I’d then have the car tuned on a chassis dyno, preferably a facility that can control the load to set part throttle parameters to simulate a cruise situation.
This plan should substantially improve drivability and economy while retaining most of your newfound performance.