318 top end build

I'm currently working on an upper half rebuild, myself for efficiency and more torque.

This is what I have going to wake up the '73 318 in the Scamp-

Pre-magnum 302 cast heads

302 cast heads are a run above the stock, open chamber heads on an early '70's head. That is a good suggestion as mentioned above. The reason these heads work so well has to do with the porting, moving air around the valves and helping fuel atomization and having heart shaped chambers changes the propagation pattern and bumps the compression .5 to .75 above your existing actual compression.

-Edelbrock LD4B intake

This intake mic's at the same port sizes as the true 318 port size. This intake is widely regarded as the best flowing runner design for a mild performance 318, to keep velocity up. The higher velocity of the intake is exactly what the 302 head swirl porting banks on to work correctly, so this manifold would really help a 302 head.

The Performer suggested above is a great intake as well. The difference is in the actual port size measurements, along with the wat er neck being offset for A/C compressor clearance, you may need a different molded hose for it to work right with your current setup or a flex hose from the upper passage on the radiator. The port size on the Performer is directly between the 273/318 heads and the 340/360 head port size. It's a good mid-range intake for all of the LA engines, but if you could keep the runner size down, it would help velocity and keep from having a step between the head port and intake port for the air to catch turbulence through.

The problem with an Edelbrock LD4B is that they aren't always available, like the performer, but Holley makes a carbon copy of this intake that measures the same as the true 318 port size, which is closer than the Edelbrock Performer. The Holley intake that has the same runner design is the Weiand Stealth 8022 and the dual carb pattern version is called the Action Plus 8007 that works for both spread and square bore carbs.

The carburetor I would suggest is the latest creation by Demon Carburetion, which was recently acquired by Holley from Barry Grant, called the Street Demon.

This carburetor is a reverse engineered version of the Carter ThermoQuad, only the jetting and metering rods, as well as step-up springs aren't difficult to obtain 2nd hand.

The nice thing about this carburetor is that it has three primary boosters for atomization instead of one, per barrel, but it still retains the 1 3/8" primary throttle bores, so it has great throttle response from idle and excellent vacuum index. The secondary system, much like the ThermoQuad is an air door type, only it's on a tight square bore plane and is technically a 3 barrel carburetor with a new goggle valve design that bridges the secondary valves. This helps with fuel delivery in the intake and keeps CFM up when you want it, without killing your torque with an adjustable air door for primary to secondary blending.

For exhaust, I'm currently using rear exit dodge truck 360 manifolds, because they aren't as expensive or difficult to manage spark plugs in, compared to stock 318 manifolds or a 340 manifold. They don't clear power steering boxes without some grinding, but I managed to modify the driver's side manifold and the steering gearbox slightly to gain clearance.

These manifolds, especially if you are willing to use a manual steering box or make grinding modifications, have a 2 1/8" outlet and a more open design than the 318 manifolds and will help with driveability on a street car.

I've debated headers on my car and I know that fuel scavenging is better in equal length tubes, but the practicality and maintenance of headers can be more high maintenance than they are worth on a mild performance car and it's nearly impossible to get an equal length header on an A body without some other body/ chassis/ steering/ suspension modification.

The 302 head, Street Demon, Edelbrock LD4B/ Weiand 8022 Stealth combination is matched for high velocity/ vacuum index/ throttle response/ torque in the low end of the RPM range and more importantly, will help make power with good fuel usage, efficiently. This is the combination that I am using on a factory camshaft, but will work with other camshaft sets.

Hughes Engines cuts their camshafts on the wider Chrysler lobe measurements and has a different lift rate for their sets than most other companies cutting from CWC blanks. Check their selection out online or give them a call for some options, before selecting a cam. They make quality parts.

I'll be posting the results of this build on another thread, but I would suggest it to anyone building a mild performance street driven 318