I noticed on my last camping trip with my 5th wheel in tow that my 460 was rattling with pre-detonation. I haven't had that problem beofre, but the truck is fairly new to me. My smart-alec wife say's, "Well now you hav ethe deisel you've always wanted".
So, when pulling a heavy load in the hills on a hot day, should I use premium? Or should I be using it all the time?
I thought most FI computer controled engines had knock sensors and took care of the problem.
Thanks for any input.

 

I run cheapo gas. What else can you afford with these 460's.

You could try a bottle of octane boost if you want. I would also just check your timing. It might be out a little due to chain/sprocket wear. Just an idea. Advanced timing will cause spark knock or pinging.

 

I have found on a number of vehicles that when the timing is set to factory specs and running the lowest grade of pump gas I will get pinging. Either the manufacturers are aren't telling the truth about what the engine likes or (I suspect) the gas isn't the octane rating it says on the pump. My solution has been to retard the timing or run better gas when I go over the mountains or both). Not all EFI enignes have knock sensors. I don't know about the 460....I've never checked.

 

I've tried running 87 octane (per the owners manual) and always have had pinging - even when starting out in traffic. I've found out that 89 is the best all around gas for my pickup. Running 93 octane eliminates any pre-detonation, however I would not reccommend running it in the cold winters like we have up here because the first start in the morning requires extra cranking.

 

460 motor is only has 8:1 compression so 87 octane is just fine, Check your timing.

 

With no load and in cool to moderate temperatures my 94 F250 with 460 runs great on 87. If it is really hot it might ping just a tiny bit on hills.

When I tow a trailer, I can run regular in cool weather and few hills, but usually I need at least 89 and sometimes the 92 for hot weather and hills. What I usually do is have a tank of 87 and a tank of 92 and switch back and forth as needed, like when I get into hills. You could also go with 89 in both tanks if the weather is mild.

Usually I only need 92 when it gets near 100 degrees and I hit a lot of long hills that are something like 5% grades or worse.

I tow a trailer that is about 8,000#.

I also read(Car and Driver) a few years back that gentle pinging is an indication that your timing is set for optimum economy and will not hurt the engine. A rattle or harsh pinging requires higher octane or adjustments.

Jim Henderson

 

Brillliant idea. One tank of normal gas and another full of good gas for climbing hills. I'm all over that idea.

Thanks.

 

I tow a 10k 32 foot enclosed race car trailer all the time up and down hills, hot or cold weather using 87 octane gas. I have a 96 F-350. Once in a great while I hear a knock but usually only one or two before the knock sensor retards the timing. I don't know for sure if it has a knock sensor since I have never had the motor apart but it sure acts like it has one.

In any event if you are experiencing a lot of pinging this is not normal. I have tried 93 octane gas on occassion since I was wondering if the motor has a control system which jerks the timing around to maximum advance and listens for any pinging. Apparently it does not as I got neither more power or better fuel economy. The only thing that happened was my wallet was a little lighter.

 

Man, I envy you guys. It sounds like most of you have access to higher octane gas than I do. I don't know why, but Utahs gas normally runs 85 - 87 - 89 octane while anywhere else I venture to starts at 87 and goes to 91 or 92. Anyway, thanks for all the good advice. I really like the idea of keeping some high octane in one tank and the cheap stuff in the other.
It also wouldn't hurt to check out the timing assembly since it has nearly 138 K and I doubt it has ever been changed.
I just thought of something else too. Sometime back in the 80's I bought a water injection kit that never got installed. Maybe I'll start another thread on that idea.

 

Ypur truck has quite a few miles and may be in need of an engine cleaning inside. One thing to try might be to use some gas additive that cleans up cylinders. Chevron Techron (Not Proguard)is supposed to help a lot with carbon deposits. Costs about $10 a bottle.

In mountain states they usually can get away with lower octane fuels. I forget the reason why other than usually the antiknock requirements are lower.

Good Luck,

Jim Henderson

 

The reason higher altitude states can get by with lower octane gas is the lower absolute pressure of the air at higher altitudes creates less cylinder pressure on the compresion stroke and thus makes detonation less likely.

I wonder if the fuel companies adjust the price acordingly? I would bet they don't.

 

Right now the cheap stuff is $1.59. When we went throught Evenston, Wy last weekend it was as low as $1.43. I think I had heard about the air density before now that you mention it.

 

less oxygen in the air too

we are paying $1.39 to $1.72(literally across the street from each other and both are typical gas stations-not Sams or cash only ones) for 86 octane

 

EFI 460's do not have a knock sensor. At least my 97 doesn't. I get some pinging if I throttle down to the point just before a downshift and hold it there on hot days. If I run 89 or better (we have 93, and turbo blue 103 octane here in detroit) I never have any piging.

 

Hey Matt, I have to agree that upping the octane is going to be my easiest and cheapest way to go. I like Jim's idea of keeping one tank full of the good stuff and then the other with regular.
But I am very interested in your set-up. Did you get Doug Thorley headers? They are about the only ones I can readily find for my truck. What about your cat? Sorry for being so nosey, but I have wanted to set my truck up similar to what you have for some time.
Do you like your FIPK? I have wanted to buy one but decided to wait until someone with a 460 could give me a god/bad report.

Thanks,