89 octane. this is a truck motor, not some high performance/highly tuned sports car motor.Gangsta_Bob119 said:Ive been filling up my bronco with 92 octane... Some people say that the bronco would run better on lower octane. What octane do you guys use in ur bronco?
Couldn't agree moreMikE2 said:You will actually get more power and milage by running the lowest octane fuel you can. If it runs on 87 without pinging, than use that. I have even seen 85 in some places, so if it will run on that without pinging, then thats even better yet. Running the 91/92 is only costing you more money and a few HP if its not needed.
Either your chambers have major carbon deposit, which is raising the compression ratio or your wheels and tires are too heavy (can't see that being a problem with a 351 though).SigEpBlue said:I can't run my baseline ignition timing any more than 12 degrees BTDC using 87 octane, otherwise she starts knocking up around 4500rpm. Must mean I have great compression, eh? :toothless Plus the low end torque is better with the timing not up so high.
I've thought about that, but I've peered into the cylinders. There's nothing besides the usual blackishness on the valves and piston crowns, and surprisingly little at that for an engine with 116k on it. I have yet to do a compression test, but I have no reason to doubt the engine's tune. You can almost balance a penny on the engine it runs so smooth! My other thought is that the fuel pump is crapping out at the top end, when it needs the most fuel. Running lean will cause spark knock as well. I was going to change it this summer anyway because I HATE being stuck in the middle of nowhere, and it's got over 100k miles on it. I know, I know...Sixlitre said:Either your chambers have major carbon deposit, which is raising the compression ratio or your wheels and tires are too heavy (can't see that being a problem with a 351 though).
This is true, and I've had this happen on a few Ford motors before. However, when setting the timing using those bad balancers, the timing marks would shake back and forth a bit. These DON'T at all. Even if it is lying, it's not by much; it gives me a good reference to go from, and it's consistent from time to time when checked. :toothless I'll be checking its accuracy this week after final exams when I'm home with a dial micrometer and a degree wheel, along with everything else I haven't been able to touch this semester (ball joints, shocks, U-joints, diff & X-fer lube, etc).There's yet another possibility that is the harmonic balancer has slipped on the rubber, making your 12 acuallu 16 or more.
Rick3373 said:I run 85, it is the regular fuel at higher altitude. Just jumped to $2.67/gal today, so there is definitely no reason to be spending more than that for the higher octane rated fuels.