Will elaborate more later in the day.
64 cc on stock 302 heads chamber volume.
69 318 9.2:1 stock pistons.
.050 down in hole
1.772 CH
The other 93 D100 318 flat tops are
1.755CH
302 valves are fine as is for great port flow, you want to keep the speed up not slow it down when it hits the larger valve opening.
The 302 heads have hardened seats, improved ports and port flow over the stock 318 heads of the 70s.
Here is the magic: LD4B Dual Plane aluminum intake, the port runners match factory 318 heads. So no turbulance there as long as you port match the gaskets and if any casting edges are sticking out debur them. Same with heads to the stock exhaust manifolds.
Then you want to open up your full exhaust system to 2.25 or 2.5".
The reasoning is you have hot compressed exhaust gasses leaving the stock manifolds at the exit looking for a place to expand out all the way out to the back. Literally drawing the hot gases out of the engine as they are expanding all the way out to the back of the car.
318 Magic: Smooth Port Flow and Port Speed in and out of the engine. Ma Mopar designed the manifolds with this in mind.
You can put headers on but then you are changing the engineer's dynamics, that can create lesser performance.
We have hit on a layout that works very very well, and other can choose to differ.
I always like hanging close to Ma Mopar. Those engineers ate Steak and Eggs for breakfast and could not wait to get into work for the day.
Good luck on your build. We are all learing along the way.
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