Balancing your RX-7 after an engine swap...

An easy backyard way to check your balance...

...Before finishing a conversion, effort should be put into achieving a 50/50 front to rear balance of weight in the car. The easy way to measure this is by weighing the front and rear axles separately. The target is equal weight on both ends of the car with the driver seated and the fuel tank 1/2 to 3/4 full. An easy way to achieve this at home is to support the car at a point midway between the front and rear axles on each side, with the tires slightly off the ground. Be sure to protect the underbody of the car from damage. An inverted 12" section of channel iron placed over the "frame rails" is usually sufficient. Use a short piece of 1" square tubing between the channel and the floor jack / jack stand for a pivot point (the use of square tubing prevents the car from rolling forward or backward on the pivots). With the driver seated in the car, an assistant can easily lift the front or add weight to the rear to determine the amount of weight that has to be moved / removed.

1. The best way is to remove weight from the front until the car balances. This provides for the lightest possible car. Easy ways are installing an aluminum hood, aluminum intake manifold, lite exhaust components, aluminum heads, lighter starter / flywheel, etc.

2. The second most desireable way to achieve balance is to move weight from the front of the car to the rear. The easiest heavy component to move is the battery. The farther back the weight is moved, the more effect it will have. If the battery is located inside the passenger compartment, use a sealed battery such as the "optima" and be sure to anchor it down securely. Loose batterys in an accident are VERY dangerous.

3. As a last resort, add weight to the extreme rear of the car. Lead securly fastened to the inside bottom of the spare tire well is an excellent choice. Try to place the weight as low and as far back as possible to get the most effect for the least weight.

Even if you choose not to balance the car, your distribution will still be better than stock Mustangs and Camaros.

Some weight related numbers...

...An aluminum intake manifold is 28lbs lighter than cast iron.
...Aluminum heads save about 50lbs over iron.
...An aluminum block will lose ya another 55 to 95lbs.
...A 4.3 V-6 is only 11 percent lighter than a V-8.
...An aluminum hood(turbo II)will save you about 30lbs.
...Headers are 20 some lbs lighter than iron manifolds and headpipes.
...The typical RX-7 A/C system weighs 55 lbs.