Fuel octane requirements...
Thread Starter
Melting Slicks
Joined: Feb 2000
Posts: 3,052
Likes: 0
From: Vancouver BC, Canada
Fuel octane requirements...
I have always filled my car up with 92 octane fuel from Chevron. But I have considered that I may not need to. What was my engine originally designed to run on? It is a stock 454/270 hp, 8.5:1 compression, 113 cc open chamber iron heads, and is in good mechanical shape. Base timing is 11-12 deg at idle, with 36 deg at 2800 rpm.
Also, what exactly does 'knocking' sound like? I never heard it before, and I realize it is hard to describe in words. An example: a hammer hitting an anvil maybe?
Thanks. :)
Also, what exactly does 'knocking' sound like? I never heard it before, and I realize it is hard to describe in words. An example: a hammer hitting an anvil maybe?
Thanks. :)
Safety Car
Joined: May 2002
Posts: 4,938
Likes: 0
From: Western MA
Re: Fuel octane requirements... (Turbo-Jet)
IMHO, you could get away with mid-grade 89 octane, but I wouldn't go to the 87 regular. 8.5 really isn't high compression and was designed for lower octane and unleaded fuels. You will know knocking (pre-detonation) when you hear it. Most likely to hear it under load, accelerating lightly up a grade. Best way I can describe it is like a can with a small bunch of pebbles would sound like when you shake it. But you will know if and when you hear it. If you do, just switch back to higher octane. Also if your car diesels when you shut it off, could be indication it needs the juice :yesnod: Other posts have addressed this and one had a link to a chemists website which was very informative. :cheers:
Team Owner
Joined: Dec 1999
Posts: 26,555
Likes: 257
From: Florida
2021 C2 of the Year Finalist - Modified
C2 of the Year Finalist - Modified 2020
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St. Jude Donor '03 thru '26
Re: Fuel octane requirements... (JMV)
My 72 350CI, 200hp calls for 91 Octane.
Le Mans Master
Joined: Oct 2000
Posts: 6,209
Likes: 33
From: Texas-out west
Re: Fuel octane requirements... (OHSIXX)
I have always used lowest octane I could without knocking... Thus far with compression ratio of less than 9.0 I have always been able to use 87 with no problem. You waste money using octane higher than needed to prevent detonation. You WILL know when you get knock. :cheers:
Le Mans Master
Joined: Jan 2000
Posts: 8,721
Likes: 108
From: Canada
Re: Fuel octane requirements... (LT1driver)
I am using 92 most of the time and once in awhile 91 if that is all that is available, but I have somehere around 10.5:1 compression. Since it runs on this I see no point in putting 94 or higher in. My previous engine was 9.5:1 and it ran fine on 89 but knocked on 87.
[Modified by gdh, 7:03 PM 8/21/2002]
[Modified by gdh, 7:03 PM 8/21/2002]
Pro
Joined: May 1999
Posts: 749
Likes: 2
From: Gabriola BC
Re: Fuel octane requirements... (Turbo-Jet)
With your compression you should be ok with 87. Our CDN 87 is a little better than US 87. If you have never heard pre-ignition you are a lucky boy as it is very noticeable and good ears will hear it every time. My 350 has 9.6 CR and can get by with mid grade although I use 92.
bob
bob
