Re: Different 302 engines which is better?
fuel mileage is determined how efficient an engine is and what type of induction system you use, NOT what year the engine was built.
Becarefull of mid 70's to early 80's 302 blocks, they had a casting flaw and the water jackets at the rear of the block, around cylinders #4 and #8 will crack and leak externally.
ALL 81 and newer 302's have a 50oz imbalace and one piece rear main seal.
earlier 302's and 351W use a 28oz imbalance and 2 piece rear main seal.
ALL 86 and newer passenger car engines got EFI and Roller hyd cam, which included a double roller timing chain.
Most 85 year model passenger car blocks are machined to accept a hyd roller cam.
302 truck motors are essentially the same, except they have provisions for a knock sensor at the rear of the block, truck 302's didnt get a hyd roller cam until 91.
Be aware there are 2 types of 302 EFI motors; HO and non-HO. HO motors were used primarily in the Mustang from 87 to 95, but were also used in Lincoln mark 7's LSC from 89 to 92 and in the 91-93 thunderbird. HO motors have better cylinder heads (E7TE casting), more aggresive cam (266 duration and .444" lift) and flat top pistions with valve reliefs. HO motor also uses the 351W firing order.
non-HO motors were used in all other passenger cars (crown vic, grandmarquis, town car, 86-90 thunderbird and lincoln mark 7's non LSC). these motors had low flowing cylinder heads (E6SE casting), small cam (.379" lift) and cast, dished pistons with no valve reliefs.