Higher octane question from the noob section
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3
Higher octane question from the noob section
its a 77 f150 with a 302 motor and a np435 transmission(4 spd with granny low). From the day i bought this beast i noticed gearing was spaced awkwardly, cruising 40 mph means reving the **** out of 3rd or ******* around in 4th. Through experimenting i noticed running 93 octane got rid of this. 3rd gear was no longer all low end grunt but actually moved the truck along nicely without “over reving”... my question is, since im no longer running 87. Do i need to look into retarding my timing? Or since im noticeing a difference just leave it as it?... ive heard “non mechanics” say im crazy and ive heard one mechanically inclined individual say just run it on 93. If im noticing improvement then dont make changes... Thoughts?
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
Octane level doesn't change gear ratios. I know what you're thinking though.
93 octane fuel won't hurt. It will help avoid detonation. As far as timing goes, running higher octane fuel means you can advance the timing. I wouldn't advance it to more than 35 degrees total timing though. I don't pay any attention to idle timing. Timing at idle is just a rough, get it in the ballpark setting. If you're going to advance your timing to peak performance, pay attention to the engine as you time it, and as you road test it. Any pinging, or a backfire is bad. Retard the timing a bit if that happens. Don't trust that the mark on the harmonic balancer is dead on. There's an easy way to determine TDC on the harmonic balancer, using a piston stop in place of #1 spark plug. And I wouldn't trust that the fuel coming out of the pump that's marked "93 Octane" is really 93 octane. I run non-ethanol 87 and add Lucas octane boost.
93 octane fuel won't hurt. It will help avoid detonation. As far as timing goes, running higher octane fuel means you can advance the timing. I wouldn't advance it to more than 35 degrees total timing though. I don't pay any attention to idle timing. Timing at idle is just a rough, get it in the ballpark setting. If you're going to advance your timing to peak performance, pay attention to the engine as you time it, and as you road test it. Any pinging, or a backfire is bad. Retard the timing a bit if that happens. Don't trust that the mark on the harmonic balancer is dead on. There's an easy way to determine TDC on the harmonic balancer, using a piston stop in place of #1 spark plug. And I wouldn't trust that the fuel coming out of the pump that's marked "93 Octane" is really 93 octane. I run non-ethanol 87 and add Lucas octane boost.
Lead Driver
Joined: Nov 2000
Posts: 6,628
Likes: 345
From: Albuquerque
The first thing to do is check your time at idle with and without vacuum and at about 3500rpm (short burst). Those three numbers are important to trouble shoot. If you engine is a tipical low compresson one it shouldn't need 93 octane. In some of these motors it's almost impossible to make them knock the compression is so low. Can you hear any?
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3
The first thing to do is check your time at idle with and without vacuum and at about 3500rpm (short burst). Those three numbers are important to trouble shoot. If you engine is a tipical low compresson one it shouldn't need 93 octane. In some of these motors it's almost impossible to make them knock the compression is so low. Can you hear any?
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3
Octane level doesn't change gear ratios. I know what you're thinking though.
93 octane fuel won't hurt. It will help avoid detonation. As far as timing goes, running higher octane fuel means you can advance the timing. I wouldn't advance it to more than 35 degrees total timing though. I don't pay any attention to idle timing. Timing at idle is just a rough, get it in the ballpark setting. If you're going to advance your timing to peak performance, pay attention to the engine as you time it, and as you road test it. Any pinging, or a backfire is bad. Retard the timing a bit if that happens. Don't trust that the mark on the harmonic balancer is dead on. There's an easy way to determine TDC on the harmonic balancer, using a piston stop in place of #1 spark plug. And I wouldn't trust that the fuel coming out of the pump that's marked "93 Octane" is really 93 octane. I run non-ethanol 87 and add Lucas octane boost.
93 octane fuel won't hurt. It will help avoid detonation. As far as timing goes, running higher octane fuel means you can advance the timing. I wouldn't advance it to more than 35 degrees total timing though. I don't pay any attention to idle timing. Timing at idle is just a rough, get it in the ballpark setting. If you're going to advance your timing to peak performance, pay attention to the engine as you time it, and as you road test it. Any pinging, or a backfire is bad. Retard the timing a bit if that happens. Don't trust that the mark on the harmonic balancer is dead on. There's an easy way to determine TDC on the harmonic balancer, using a piston stop in place of #1 spark plug. And I wouldn't trust that the fuel coming out of the pump that's marked "93 Octane" is really 93 octane. I run non-ethanol 87 and add Lucas octane boost.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Generally speaking don't ever want retarded ignition advance or timing. By that I mean anything less than the factory curve. It will only run hot and waste the bejeesus out of a tank of juice with no benefit. Most people in fact find a lot of performance and fuel economy has been "left on the table" by the overly conservative OEM distributor curve. Make sure both the mechanical and vacuum advance is working properly.
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3
Generally speaking don't ever want retarded ignition advance or timing. By that I mean anything less than the factory curve. It will only run hot and waste the bejeesus out of a tank of juice with no benefit. Most people in fact find a lot of performance and fuel economy has been "left on the table" by the overly conservative OEM distributor curve. Make sure both the mechanical and vacuum advance is working properly.
Trending Topics
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
Live, yeah I hear different opinions on octane also. Most are total horse poop. "Oh, you'll blow that new car up!", "You're throwing money away!", "It's eating your fuel line!", "Only a racecar engine can handle it!".
Most folks now (and probably back in the day too) have no idea how a carburetor works. Yeah, you can run dog water in vehicles that are produced now. Electronic fuel injection is constantly keeping the air/fuel ratio at 14.7:1. But the best carburetor can't keep your air fuel ratio just right during idle, cruise, acceleration, wide open throttle, etc. Sometimes it's gonna go lean, sometimes rich. Higher octane fuel can save you from detonation during those lean spikes. So running high octane fuel in your low compression ratio old bucket is not a bad idea. Same goes with high zinc motor oil to protect that outdated flat tappet camshaft. Our old trucks are so much fun, aren't they!?
Most folks now (and probably back in the day too) have no idea how a carburetor works. Yeah, you can run dog water in vehicles that are produced now. Electronic fuel injection is constantly keeping the air/fuel ratio at 14.7:1. But the best carburetor can't keep your air fuel ratio just right during idle, cruise, acceleration, wide open throttle, etc. Sometimes it's gonna go lean, sometimes rich. Higher octane fuel can save you from detonation during those lean spikes. So running high octane fuel in your low compression ratio old bucket is not a bad idea. Same goes with high zinc motor oil to protect that outdated flat tappet camshaft. Our old trucks are so much fun, aren't they!?
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Senior User
Joined: Aug 2009
Posts: 331
Likes: 0
From: Courtenay, BC, Canada
Unless you have a high compression engine (flat top pistons, or shaved heads, possibly a turbocharger) you normally would gain little or no benefit from burning premium gas in your rig. The higher octane helps prevent premature detonation in the cylinders.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
I run my old slick with a lot more ignition advance than stock. Y Blocks like it, and in stock configuration like mine they are low compression, they will tolerate low octane gasoline. But running close to the edge, you will notice it right away if you happen to get a bad tank of juice. The manufacturers ran conservatively for a few reasons, fuel quality (variabilty) was one, altitude another.
They didn't want warranty returns either, from enthusiasts grenading their engines. Crane Cams sez the OEM used weaker valve springs in domestic production for kind of the same reason, they act as a natural rev limiter so preventing uncommanded engine disassembly.
They didn't want warranty returns either, from enthusiasts grenading their engines. Crane Cams sez the OEM used weaker valve springs in domestic production for kind of the same reason, they act as a natural rev limiter so preventing uncommanded engine disassembly.
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3
Live, yeah I hear different opinions on octane also. Most are total horse poop. "Oh, you'll blow that new car up!", "You're throwing money away!", "It's eating your fuel line!", "Only a racecar engine can handle it!".
Most folks now (and probably back in the day too) have no idea how a carburetor works. Yeah, you can run dog water in vehicles that are produced now. Electronic fuel injection is constantly keeping the air/fuel ratio at 14.7:1. But the best carburetor can't keep your air fuel ratio just right during idle, cruise, acceleration, wide open throttle, etc. Sometimes it's gonna go lean, sometimes rich. Higher octane fuel can save you from detonation during those lean spikes. So running high octane fuel in your low compression ratio old bucket is not a bad idea. Same goes with high zinc motor oil to protect that outdated flat tappet camshaft. Our old trucks are so much fun, aren't they!?
Most folks now (and probably back in the day too) have no idea how a carburetor works. Yeah, you can run dog water in vehicles that are produced now. Electronic fuel injection is constantly keeping the air/fuel ratio at 14.7:1. But the best carburetor can't keep your air fuel ratio just right during idle, cruise, acceleration, wide open throttle, etc. Sometimes it's gonna go lean, sometimes rich. Higher octane fuel can save you from detonation during those lean spikes. So running high octane fuel in your low compression ratio old bucket is not a bad idea. Same goes with high zinc motor oil to protect that outdated flat tappet camshaft. Our old trucks are so much fun, aren't they!?
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3
This is what i hear most often. Often enough that im starting to think it has more to do with the quality of gasoline. newer computerized vehicles keep a constant A/F ratio regardles of the quality of fuel.
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3
I run my old slick with a lot more ignition advance than stock. Y Blocks like it, and in stock configuration like mine they are low compression, they will tolerate low octane gasoline. But running close to the edge, you will notice it right away if you happen to get a bad tank of juice. The manufacturers ran conservatively for a few reasons, fuel quality (variabilty) was one, altitude another.
They didn't want warranty returns either, from enthusiasts grenading their engines. Crane Cams sez the OEM used weaker valve springs in domestic production for kind of the same reason, they act as a natural rev limiter so preventing uncommanded engine disassembly.
They didn't want warranty returns either, from enthusiasts grenading their engines. Crane Cams sez the OEM used weaker valve springs in domestic production for kind of the same reason, they act as a natural rev limiter so preventing uncommanded engine disassembly.
Thread Starter
|
Mountain Pass
Joined: May 2018
Posts: 197
Likes: 3