azfordman I am being nice. There are 10 threads on this if you search the forum. As undy asked which aluminium block are you looking for?
Boss 302, 351 windsors, 351 clevelands, FE blocks, 460+ blocks? The weight is the big reason most of you put aluminium motors in our cars. You can save from 50-175 of weight between Iron motors and all Aluminium. Some specs and what you want to do with the motor would also be a be help. What car manufactor you are looking at? I am guessing you are looking at Ford. The Boss block just came out. There is not alot of these motors on the street yet. Windsor aluminium motors have been around for years, The strokers with a 393 or bigger cube motor are the way to go. For racing on small tracks they are quicker than there big brother, FE. They are cheaper to build and have more speed parts than the FE. FE motors have 4 companies selling Aluminium Blocks. Dove, Shelby, Genesis, and Ponds. Kirkham is working on a special block, not sure on it's due date. Are you looking for strongest, most original, cheapest, or best engineered? When you come back with some more info of what you are looking for, then is will be alot easier to point you in the right direction for which motor to build and builder to build it. Are you going to street only? drag race? auto cross? roadracing? show and shine? combo of all. The other question is ,how deep are your pockets?
A good FE motor is about 15-20 grand. A stroker windsor is about 10-15grand. Which every motor you go with, stroke it and keep the rpms down. 6,500 is a save max rpm for any motor. Change the rear ratio is cheaper than replacing motors. Build torque motors. IMO 550 to 600 lbs of torque with an FE motor will keep you changing your shorts.
Also GO to a driving school for min of 3 days to learn how to drive.
This is the best info I can give you without more info. If you want to talk call me at 732-254-3536 est time. I am in NJ Rick L. Really needs specs first for the car. Cobras are alot of fun, But just like a gun that is loaded and not respected, it can go off and kill you. We have lost a couple of members over the years. Just letting you know what you are getting into. Even the SB cars are no joke and run with the fastest cars like vipers, vettes, porschs. These are also cars with no ABS, airbags, and min comfort and loud (unless you get under car exhaust)