273 Commando Rebuild Or Not?
I have not used a scope in the cylinders to verify that the pistons are in fact domed. However, the engine has the proper valve covers, double points distributor and a cast iron four-barrel manifold. The 67 Plymouth Factory Service Manual Spec depicts the compression pressure for the four-barrel (Commando) engine between 130 & 165 psi, See picture. Being that the compression of 5 of the cylinders are 150 psi or above, that leads me to believe that it is the high compression 10.5:1 compression engine. As the factory service manual indicates the compression for the 9:1 is in the 120-150 psi range. (The double asterisks next to the numbers in the service manual indicates four-barrel) The compression test was taken in Santa Monica which is about 105' above sea level.
I have not used a scope in the cylinders to verify that the pistons are in fact domed. However, the engine has the proper valve covers, double points distributor and a cast iron four-barrel manifold. The 67 Plymouth Factory Service Manual Spec depicts the compression pressure for the four-barrel (Commando) engine between 130 & 165 psi, See picture. Being that the compression of 5 of the cylinders are 150 psi or above, that leads me to believe that it is the high compression 10.5:1 compression engine. As the factory service manual indicates the compression for the 9:1 is in the 120-150 psi range. (The double asterisks next to the numbers in the service manual indicates four-barrel) The compression test was taken in Santa Monica which is about 105' above sea level.