I just want to know which of these statements are true:

1. roller rockers decrease internal friction - YES

2. lighter rods and pistons save gas because they decrease the weight the engine has to accelerate in different directions all the time - NO

3. a shorter stroke slows down the piston speed and gives the same effect as #2. - I would adjust rod ratio, make stroke whatever you desire and build around it.

4. porting, headers, large manifold chambers increase the airflow, the engine has to do less "pumping" so less efficiency is lost this way - To big of port is lazy, a lazy port will drop the fuel from the air resulting sucky performance. Intake port needs to be mated to engine requirements. Exhaust port needs to be as smooth and large as reasonably achievable. Its less important to work on a good ex port, the intake port has 2 times the effect on an engine. But a hogged out intake is as bad as a choked intake port. Right is right.

5. balancing the crankshaft will stabilize the whole engine and cause less energy to be lost in vibrations - Not sure about energy loss, but it will be smoother and longer lasting. Its easier on parts and adds long life.

6. Aluminum heads will dissipate the heat better but will not help in getting mileage - Allum heads absorb heat, this takes heat energy out of combustion and costs you power. An allum head needs to have increased compression to compensate over the same engine with iron heads.

7. Aluminum block and heads will save weight, but not enough to make a difference in mileage - Any saved weight on the chassis may make a change, but the change may be .2 MPG change by saving 300 lbs in a 6500 LB van. Is that worth going to an allum block/heads if you dont own them? No.

8. decreasing vibrations, internal friction and the weight of accelerated parts (also in the valve train) will get me higher efficiency and slightly higher power, but lower torque. I doubt it will be measurable. This is a stock style engine not a top fuel dragster. Its not a concern, really.

9. going for low RPMs at mid compression (under 9.5:1) is going to be more efficient than running high RPMs in high compression (over 10:1). - This is common sense. You are biulding an engine for a 3/4 ton van, you need to maximize the engines cam for the cruise RPM of your van and that is based on gearing/tire size/and speed that you travel at cruise. What good is a NHRA capable 9000 RPM engine in a van that travels at 3200 RPM on the street?

9. so I go with Aluminum pistons, forged conrods, a stock 305 block and ported heads, an EFI, high octane fuel (I'm planning on 105 octane LPG) and a cam designed for efficiency. - All pistons are allum, but are you wanting good, better, or best? That would be Cast, hypers, or forged. Stock rods are more than fine, anything else is a waste. Stock block is fine, spend money on blueprinting it, get it all straight and true and it will spin easier and live longer. Porting heads is always a great idea, but the intake can be severly messed up by porting it with the hog and hope method. Learn, read, ask, learn more...and finally make a plan and stick to it.