70 500cid on 87 octane?
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500, 472, 425, 368 Discussion, 70 500cid on 87 octane? in Cadillac Engine Technical Discussion; I may have found my 500. It's from a 70 ElDorado, thus it has 10:1 compression. Think I can run ...
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    davesdeville's Avatar
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    70 500cid on 87 octane?

    I may have found my 500. It's from a 70 ElDorado, thus it has 10:1 compression. Think I can run it on 87 octane gas? I'm confident I could run it on premium, but being a cheap bastard, I'd like to run it on 87.

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    lux hauler is offline Cadillac Owners Connoisseur
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    Nope. It'll probably take, at least, 92 octane to run right.

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    Allante North *'s Avatar
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    Spend a few pennies more and give that big ole 500 the juice she deserves.

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    Re: 70 500cid on 87 octane?

    Yeah....... Most places its 10c more, 20c at worst..... So your looking at an extra 2-4 on a 20 gallon fill up...... Pretty insignificant for 500cid of pure muscle.....

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    davesdeville's Avatar
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    Well it probably doesn't matter anyway, because it turns out that I can't get this engine.

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    MMNineInchNails is offline Cadillac Owners Enthusiast
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    You could run the 500 on 87, but it wouldn't love you as much. I could run mine on 87 too, but I love her so much that I put in 91 Don't neglect your pimp mobile. At least give her premium (or the one in the middle) not the lowest grade.

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    DaveSmed's Avatar
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    My 472 gets really cranky with the cheap stuff. It even dieseled once on me! So every time at the pump, 27 gallons of premium (@ $2-something....ouch!)

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    davesdeville's Avatar
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    And your 472 should be 10.5:1 compression. Hmm I'm pretty sure I could get away with running mid grade on 10:1, partly because I'm at 5200' asl. If that doesn't cut it, I'll pay the extra..

    Right now, my 425 is running like total crap. It will die if I floor it, and occasionally at idle. The damn high pressure power steering line is leaking from the pump connection again, too. So I'm pretty pissed at my car right now.. It had been sitting mostly for the past 3 years, so could old gas be the problem or at least part of the problem?

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    MMNineInchNails is offline Cadillac Owners Enthusiast
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    how's that carb doing of your fw?

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    davesdeville's Avatar
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    If it's not old gas, it's either the fuel pump or the carb. I have to figure out if I want to just try a swap now or try to keep the 425 alive for a while longer.

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    Why didn't you take the old gas out of the tank before running it again? To test the fuel pump, take disconnect the fuel line that's going into the carb (the line that's coming out of the fuel filter. Have a friend try to crank it over and see how much gas is coming out. If it's barily any, you need a new fuel pump. It should be shooting out at a good speed.

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    davesdeville's Avatar
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    I didn't take the old gas out because it drove fine when I test drove it, and when I drove it to my house. I'll take it out again later today and see how she does.

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    So far, I've put in no less than 12 hours of work on that motherf--cking power steering hose. It's just one hose. I took the old one off after an hour, then I put the new one on twice and it leaked still after another 8 hours, and then I tried with teflon plumbing tape which didn't help for another 3 hours. Then I took the new hose back and exchanged it for another one, put it on in 10 minutes, and spilled fluid all down the side of the pump. So now I'm waiting to see if it still leaks, if it does I'm through with it and I'll take it to a shop. I'll edit this in a while when I check to see if it really leaks..

    The 425 seemed to run much better tonight. It still lags seriously when I floor it, but it didn't die. I'm going to try to put in a new speedometer cable tomorrow, and I'll try to test the fuel pump and check the filter.

    Edit: It's still leaking, I think I'll try taking it off and putting it back on one more time, then I'll just take it to a shop.

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    lux hauler is offline Cadillac Owners Connoisseur
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    Buy a new fuel filter. I'm sure, if the car has been sitting, it's pulled stuff out of the tank and clogged the filter. Get some good gas in it too.

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    yeah dude those fuel filters are like $3 at autozone.

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