327 needs more torque
I race at a local 11/43-mile asphalt track in the Street Stock division with a '78 Camaro. I currently run a 327ci that is my backup engine. I had trouble with the 350. I like the way the small engine responds in traffic and coming out of the corners, but the 350s are killing me during the last half of the straights. Many engine builders have told me the 327 is a very reliable engine, because the shorter stroke is easier on the pistons, rods, and bearings. With my budget, reliability is a priority. Can you offer some suggestions on how to overcome this problem? The engine rules allow only cast-iron heads, intake, exhaust, flat-tappet cams, Holley 4412 two-barrel carburetors, and 11-1 max. Also, the rules give the small engine a 100-pound weight break.
Marc Utheim - via e-mail
The question you ask is interesting, and I would suggest several things. Let's start with your first problem. Basically, you have a lack of torque in a 327 compared to a 350. This can be explained because of the difference in the stroke characteristics of each engine. A 327 has a stroke of 3.250 inches, while a 350 has a stroke of 3.480 inches. This means the 327 will have the ability to accelerate more quickly and obtain a higher rpm than the 350 engine-but with less torque. So this obviously means the 350 will win out when it comes to torque.
Torque is a very important component in making horsepower. Here is a formula you can use to prove this to yourself:
Torque x rpm = Horsepower
As you can see, the 327 engine with less torque will require much higher rpm to equal the horsepower output of the 350 Chevrolet engine.
For the 327 to achieve any similarity in horsepower to a 350 it would, by definition, have to develop higher rpm levels. Doing that, of course, would have some negative ramifications for a 327. For example, the reciprocating weights in the engine (which include the weight of the piston, pin, rings, and pin end of the connecting rod) are increased on the square of the rpm. This produces thousands of pounds of force on the lower end of the connecting rod, rod bolts, rod bearing, and beam of the connecting rod, which are holding everything together. So, by trying to match the performance of the 350 through increased rpm, the stress on a 327 engine will be greater than on the 350.
Now let's move to the next issue. Should you decide to continue to use the 327 and raise the rpm level, you will have a significant problem trying to supply sufficient air to the engine through a two-barrel 4412 carburetor (500 cfm). When you add that to the fact that you are only allowed a stock cast-iron intake and exhaust manifold, the possibility of matching the output of a 350 seems even more remote.
The only advantage you have going for you in this situation is the 100-pound weight reduction, but this is not likely to be enough to compensate for the superior power of the 350. The fact is that on an equal basis, it's usually very difficult to give up cubic inches and at the same time remain competitive.
So far I have given you reasons not to continue using the 327 in your race program, but there may be a scenario in which it would make sense to continue using this engine. For example, if you have a rule limiting the size and compound of the tires you can run, a smaller engine might run better. If a hard compound is required, the 350 engine with greater torque could spin the tire, making it difficult to hook the power to the track. As we have established, the 327 has less torque, and it's less likely that the tires would spin in this situation. Add in the fact that the car is 100 pounds lighter, and this could be a successful environment for a 327 engine. In a case like this, it isn't how much total horsepower you make, it is how much torque is produced over a given rpm band and how well this power band fits your racing requirements. Too much power can hurt a mishandling car a lot quicker than too little power.
I hope this gives you some insight into the potential solutions to your problem. While I believe there are some situations in which a 327 may work well for you against the output of a 350, as a general rule, I think it's safe to say that for best results there is no replacement for displacement.
Crane Cams, Daytona Beach, FL
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