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post #1 of (permalink) Old 03-17-2001, 06:42 PM
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hi octane for 4.3?

I just bought a '88 S10 4x4 with a 4.3 V6 engine. It did not come with an owners manual, so I am relying on my Chiltons manual for information on my truck. The book says that the 4.3 engine has high compression, so it needs high octane fuel. Unfortunately, I believe the former owner was running 87 octane.
Does my truck need the high octane fuel that the Chiltons reccomentds? Did the previous owner destroy the engine by using cheap gas? The truck has high milage (over 200k), if that makes any difference.

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post #2 of (permalink) Old 03-17-2001, 06:50 PM
 
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Re: hi octane for 4.3?

<font face="Comic Sans MS">All that I've ever heard of a 4.3L (stock) needing was 87 octane. Do you hear it knocking? What's the timing set to (if at factory specs, it should be ok with the 87 octane)? Try running 87, if it runs good with 87, I'd keep running it with 87.

Do a compression check to make sure all the cylinders are within 10% of eachother in the readings, works best with it warmed up. Also disconnect the fuel pump when you do that and hold the throttle plates wide open. Attach the secondary coil wire to ground so you don't get shocked. Also do a dry/wet compression reading, not just dry. By that, I mean put a few squirts of oil in each cylinder when you get done with the try test to see if your score improves. That'll help tell you the condition of the rings (compression mainly)...

But anyhow, I wouldn't worry about it at all, if it's made it 200k miles then they did something right... [img]/wwwthreads_images/icons/cool.gif[/img]</font>

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post #3 of (permalink) Old 03-17-2001, 10:42 PM
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Re: hi octane for 4.3?

a friend of mine has a 4.3 in his blazer and he was thinking of mixing in some 101 octane with his regualr gas for some more power. is this a good or bad thing to do?? will it really make a difference in power? thanks in advance

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post #4 of (permalink) Old 03-17-2001, 11:59 PM
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Re: hi octane for 4.3?

well it will defiinatally will make a difference, but be careful, you might blow a head gasket, i would say 10% max.

Tim


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post #5 of (permalink) Old 03-18-2001, 01:07 AM
 
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Re: hi octane for 4.3?

<font face="Comic Sans MS">In theory it should make no difference or if anything decrease performance due to the flame actually travelling more slowly (octane measures resistance to igntion). What the higher octane allows you to do is run your timing more advanced, which is what actually produces any gains you feel with that.

With particularly exotic fuels you pretty much absolutely need a module like an MSD 6 or 7 (racing only for the 7) box to get a hot enough spark to run it.</font>

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post #6 of (permalink) Old 03-18-2001, 10:14 PM
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Re: hi octane for 4.3?

In theroy, but go fill up with race gas and come back and post your results. Youd be suprised what high octane does.

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post #7 of (permalink) Old 03-18-2001, 10:42 PM
 
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Re: hi octane for 4.3?

<font face="Comic Sans MS">Not sure about race gas but regular pump gas (highest octane there is) doesn't help mine out at all. I will have to try some race gas sometime. Does it have something to alter it? What does it have in there? Depending on what additives it has it might actually help performance now that I'm thinking about it. Maybe something to oxygenate it so it'll burn faster or something (almost like nitrous helps) or some such thing. But regular pump gas probably won't do much to help or it might hurt perf. a bit.</font>

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post #8 of (permalink) Old 03-19-2001, 08:11 AM
 
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Re: hi octane for 4.3?

With race gas you have to be careful not to get holes in your pistons. That stuff burns hotter, but if I'm not mistaken it also burns a little slower, giving high-compression engines something to work with.

My '98 runs just fine on 87 Octane fuel, no pinging or knocking. If you're running low grade gas as first, just try 89 octane then 92. If you can't run 92 octane without pinging and knocking, you've got other problems that need adjustments.

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