lorito13 A little more info would help on your question. You can't compare apples to oranges. Most Cars and lite truck you buy now have either a complete aluminium motor or top half with an iron block. I am not a fan of the mix block because of different expansion rates and time of the rate. I have 2 Shelby motors, CSX#58 & CSX#428. I have been running 58 for 9 years. Racing 98% of the time. Started as a 452 and is now a 482. For the money and time you spend trying to find a good 427 or 428 block, have it sonic tested, pressure tested, bored, plate honed, cam bearings, enlarged or cleaned out
oil gallerys, you are at the price of a new iron block from Ponds or Genises. Sorry I forget which makes them. You have no worries about if your old block has a rot hole in a water jacket that was not picked up from pressure testing and after 20-30 heat cycles it cracks a hole. This has happened to guys on this forum. My motor weight is 495 lbs complete without fluids. This is the weight of a small block. Except for money issues or building the perfect orginial cobra why you would not go with a aluminium motor. 200lbs off the nose of the car, 150 if it's a small block. Aluminium grows more than Iron. When you match iron to aluminium over a lot of heat cycles, head gaskets and intake gaskets and seals will seep and leak a little when cooling down. The expansion rate works both ways, from hot to cold and back. Yes bolts do loosen up or time. This is part of smart maintainance of the car. If you drive normal, let your motor heatup on it's own, I have seen less problems. Most people get in the car and 10 seconds are out on the road just like their personal car going to work. This is not good over the long haul. For the amount of PLEASURE you will get from the car, a 1 day of maintainance is little to ask. I do this when putting the car away for the winter,
oil fog the motor, back off the rocker arm shaft assemblies, fill with a new filter and fresh
oil, build oil pressure in the motor, empty the fuel rails, drain the gas and add new with stablizer, make sure the coolant is 50/50 and topped off, moisture bags go into the exhaust pipes and are seal with tape. set tire pressure and jack car off the ground and level. In the spring drop the oil pan, check all studs and bolts on bottom end, new gaskets, and repeat the same for the top with checking torque on head bolts, intake bolts, rockershaft bolts, perlube and start motor, OUTSIDE the GARAGE.
. You are ready for the new driving season. I have found problems with my aluminium motor. Shelby has helicoils in all the fastener holes and some have pulled loose or backed out. I have replaced all the heilcoils with TIME-Serts. IMO they are alot better and are stronger than helicoils. At this time the car is still being run, so my major check before winter is not started yet. IMO the new stuff is better engineered than the 40+ old stuff except of the high nickel blocks ( if you can find one that is not .060" over or sleeved.) FE motor are thined walled but there is a test for checking them on this. IMO save the weight and go aluminium, it gives the car better balance for driving and racing. Rick L.