The 300 "big six" is a great motor. I had one in an 83 F250 4X4 that I rebuilt. Before the rebuild it was a bit of a dog, but after I had plenty of power. I put on the Offenhauser dual port intake with a Holley 390 and Hedman dual exhaust headers. Still not a high reving engine, but had lots of torque. One of the reasons the 300 is so popular is for its 7 main journals. The crank is bulletproof and the engine will last forever.
I had one in 88' F-250. Motor ran just fine, but the oil pan was so rusted you didn't dare run more than 3 quarts of oil at a time(or else it leaked to fast) Simply drive till the gauge started bouncing, and lifters rattled, then refill.. I probably put 5K miles on it that way, and finaly pulled the motor, to replace it with one that had a good oil pan.
The motor I dropped in had been sitting outside for 3 years, and was siezed when I dropped it in.(not seized as in bust it loose with a ratchet, but siezed as in dump the clutch in OD, and drag all 4 tires..)
That motor still ran just fine when I sold the truck 9 months later..
my brother has an 89 150 with the efi 6 - with 38.5 and 5.13 - he has abusded it for over 50k and it has over 175 k on it - other than a burned valve and some small oil leaks ( he drives over 4500 rpm all day :shaking: ) it has been strong - we put a 3" cat - 2.5 cat back - flowmaster - k&n - and MSD ignition on it - AND HE GETS OVER 12MPG - driving like he stole it -
he cant keep up with 95 5.8 f250 - but its close untill 35mph
I just finished building one but haven't run it yet. Word is these motors are tough. I did flat top pistons (from 352 FE), some head porting, clifford intake, EFI exhaust, RV cam on propane.. expecting about 220+ hp at 4000rpm.
Not the most powerful beast in the world but fine for my trail rig.. and should be very reliable. I have to laugh cause I have heard all kinds of crazy stories since I started building my 300.. tell someone you're building it and they'll tell you some crazy amazing story about how tough these motors are. Funny stuff, but they definitely have the reputation.
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