[Jack Shaft]

Its important to note making these changes on a stock model a engine raises the engines efficiency. Higher compression, adding fuel, using a mechanical advance distributor and making it breathe better results in better economy and a cooler running engine. That's something most model a guys don't get, they feel you are ruining the engine 'hotrodding' it. banging the bearings out of it, causing it to run hot and increasing wear..
Actually the opposite is true, raising efficiency extends engine life, upper cylinder issues decrease as well,rings seat better, less exhaust heat due to a better burn saves valves..Alot of the common issues with a stock engine disappear...exhaust manifold drooping, burned exhaust manifold gaskets,engine temperature issues...gone.