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"Engine Must Be Run On 91 Octane Fuel".....Do I Have To?

Discussion in 'The Garage' started by dhdescender, Nov 8, 2003.

  1. dhdescender

    dhdescender 1/2 ton status

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    \"Engine Must Be Run On 91 Octane Fuel\".....Do I Have To?

    I noticed a tag when I pulled out my 500 (which I found out was actually a 472cid), that said the engine must be ran on 91 octane fuel.

    91 octane in canada sure as hell aint cheap here, can I get away with regular 87? The motor was built for propane, so it has hadened seats, so I imagine it currently not pining due to the advance.

    Any insight on these old motors?
     
  2. sled_dog

    sled_dog 1 ton status

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    Re: \"Engine Must Be Run On 91 Octane Fuel\".....Do I Have To?

    uhh your going to gasoline now? hardended exhaust seats don't have a lot to do with pinging, just means you can run unleaded gas without worry of valves going bad. Compression is likely the issue, compression is high enough that running on 87 won't be good. changing timing to help octane usage is fine but it will hurt performance.
     
  3. dhdescender

    dhdescender 1/2 ton status

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    Re: \"Engine Must Be Run On 91 Octane Fuel\".....Do I Have To?

    I was saying b/c the engine has hardened seats, it also has a compression and timiming advance for propane.

    I will run on propane, but I need to drive the blazer now, and the propane sytem needs some more parts to be completed.

    I suppose I can only wait and find out how it will run.
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Re: \"Engine Must Be Run On 91 Octane Fuel\".....Do I Have To?

    The compression ratio is probably too high for lower octane gasoline. Propane has an octane rating of around 110 /forums/images/graemlins/eek.gif so the engine should run great on that. /forums/images/graemlins/thumb.gif

    You may be able to get away with backing the timing off several degrees, but if the engine is still pinging on 87 octane then you'll need to give it better fuel or risk engine damage. /forums/images/graemlins/frown.gif
     

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