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460 EFI Compression ratio

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Old Jan 5, 2011 | 08:09 PM
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460 EFI Compression ratio

After a lot of reading about trying to get better with a 460 is kind of not worth it you spend to much money on mods an get low effects right?

If that was true i thought about lowering the compression ratio so i can run 87 octane gas. What compression ratio would work to achieve that goal? What can i do to the engine with out having to take apart my new engine. Ill list off my mods to help you guys.
headman headers
flow master muffler
MSD coil
no smog included the egr removal with a block off plate.
custom cam i wish i could tell you the lift an duration.
E4od trans
 
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Old Jan 5, 2011 | 08:35 PM
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Unless you have really cranked the CR up, theres nothing I see in those mods you listed to prevent you from running 87octane. And even knowing the static compression ratio, without knowing the cam specs its hard to say what kind of effects the cam will have on what kind of fuel you can run. Depending on the cam, you can have a 10:1 motor that needs race fuel, or a 12:1 motor that will run on mid-grade.

Whats your goal? More power? more mpg? towing? racing? etc
 
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Old Jan 5, 2011 | 11:26 PM
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My main goal is to be able to run 87 pump gas. I dont really need power the only time i play is when i have smart *** people on the road or in the snow. Mpg like i said in my first post would but hard to get with out putting a lot of money in an not getting very much improvement in the mpg. If i could get my cam spec would that help you out? By the way i did not say this in my first post but my cam works with the stock computer.
 
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Old Jan 6, 2011 | 11:06 AM
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What year is this engine? Any 460 since the early 70's should run fine on 87 octane gas. The compression has been in the 8 to 8.5 to 1 area since then on the truck motors. My 1984 F250 with 460 not only runs fine on 87 octane, even with the 13 foot camper and the dual axle trailer with 4 quads on it. I would suspect that you have to much timing cranked into the engine if you can't run the 87 octane or your base engine is an early car 460 with the 10.5 to 1 compression ratio. Then your only cure is a monster cam or change out the piston for low compression units.
 
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Old Jan 6, 2011 | 03:35 PM
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Ok it is a 93 truck stock engine. It runs on 87 but just seems sluggish on up hill.
 
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Old Jan 6, 2011 | 09:38 PM
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For starters, a good tune-up (plugs, cap, wires, etc), remove the air-horns if not already done, and double check the timing.
 
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Old Jan 6, 2011 | 09:44 PM
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Yep all done i seen many with base timing at 12 what dose that solve or help?
 
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Old Jan 6, 2011 | 09:56 PM
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The tune-up will make sure you are getting a good solid spark to light things off, the air horns (and opening up the exhaust with a better muffler, hi-flow or no cats) will get rid of the breathing thru the straw effect that the stock air tubes and exhaust cause, and bumping the timing a couple degrees will allow for an earlier burn, which in turn gives a hair more time for a complete burn. Giving some extra oomph on the lower end of things.
 
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Old Jan 7, 2011 | 12:28 AM
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Ok i will have to try 12* timing an see if that helps.
 
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Old Jan 7, 2011 | 11:46 AM
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Originally Posted by jeremy2008
After a lot of reading about trying to get better with a 460 is kind of not worth it you spend to much money on mods an get low effects right?

If that was true i thought about lowering the compression ratio so i can run 87 octane gas. What compression ratio would work to achieve that goal? What can i do to the engine with out having to take apart my new engine. Ill list off my mods to help you guys.
headman headers
flow master muffler
MSD coil
no smog included the egr removal with a block off plate.
custom cam i wish i could tell you the lift an duration.
E4od trans
Why in the world would you want to lower the compression ratio when it's already 8.5:1. That's low enough to be turbo'd and still run 87 octane. (not really but almost) There is absolutely NO need to run 93 unless you have at least a 9.5:1 if not 10:1 CR.

For better mileage:
Convert from bank-to-bank injection to SEFI
Get rid of all emissions.
Hedman Headers with 3" true duals for each side
Depending upon the cam it could help/make it worse
Do a tune-up...cap/rotor/plugs, etc.
And now that you've done all that you're going to have to tune it because the stock computer will not be happy.
You may get 2mpg better from all that^. If you want better mileage, buy a diesel.
 
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Old Jan 7, 2011 | 05:04 PM
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Yea i was not sure of my compression ratio i know some of the efi 460 have to run higher grade of gas for reason unknown.
 
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Old Jan 7, 2011 | 05:20 PM
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Originally Posted by jeremy2008
Yea i was not sure of my compression ratio i know some of the efi 460 have to run higher grade of gas for reason unknown.
I never heard this and can think of no reason why Ford would even consider it much less do so as it would require a complete (read very expensive) testing for approval to market the thing.
 
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Old Jan 7, 2011 | 05:32 PM
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i think i will try to just complete my truck the last thing i want is a cold air intake an i will leave it at that she just has her day or it is me thinking that she runs different who knows but i can deal with it thank you guys for the info. Yea my goal is to get a extend cab 7.3l 96 or 97 with a 5 speed or if i am lucky a 99 with 7.3l 6 speed cc or extend cab.
 
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Old Jan 7, 2011 | 08:40 PM
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The only time I have seen stock EFI 460s need 93 octane is when the timing was not set right, and was too far advanced
 
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Old Jan 7, 2011 | 09:04 PM
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Originally Posted by L. Ward
The only time I have seen stock EFI 460s need 93 octane is when the timing was not set right, and was too far advanced
I would agree with that. Usually caused setting the time without pulling the Spout.
 
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