318 rebuild/upgrade

The LD4B is a 318 version of the LD340. Main difference is the intake port size. Otherwise the castings are the same. You could modify (open up the intake ports) an LD4B to match the larger 340/360 port size and end up with basically an LD340. Intake ports on 318/273 are the smaller variety, the 340/360 are the larger versions. The late magnum heads are similar to a 340/360 port. By the way, the easiest way to determine the intake port size is to check fel pro's gasket info, the dimensions are all there, only two sizes you'll find.

For those interested: What I'm building is a .060 over '68 318 (328ci). I have just finished porting a set of the 302 casting heads (bowls/gasket matched/intake ports opened up, valves unshrouded). The heads have 188/160 valves. I will be running the mopar 268/272 .450/.455 cam. Intake is an oem sinlge plane iron '66 4 bbl 273 intake - port matched and the secondary butterflies opened on an end mill to allow a 625 AFB. The CR is about 9:1 using stock 318 .060 over pistons, and a thin head gasket.

I have a set of the oem wrinkle valve covers. Motor will look exactly like a 273 4bbl except be 55 ci larger. Exhaust consists of the laysons shortie headers. Ignition will be a stock electronic unit recurved, and an orange box.

My only comment about the 302 casting: theres a heck of a lot of material to be removed from the intake ports. The pushrod bulge in the port has to be shaved down quite a bit. I am guessing the motor will make around 300-350 hp.