hey guys i just bought a car with 9.5:1 compression and it has iron heads. I am guessing that i have to run 92-93 octane with this setup. am i right? Could i run 90 octane or is that too low?
thanks
Tom

 

I would argue that you can safely run lower octane if you are careful to set up your timing curve right. I have about 9.4:1 but with aluminum heads and I run 87 just fine.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

Just as Biochem said....You should be fine with a lower octane rating. Just make sure your timing is set correctly and everything else engine wise is tuned to where it's supposed to be.

What kind of car is it?...Does it have a knock sensor? Anything with a knock sensor will generally help keep you from screwing anything up due to knock.

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86 Trans Am WS6 Black with tinted windows, shaved door handles
ZZ4, Mini-ram, true duals, LT4 HotCam, AFR 195 heads.
***Too many other mods to mention***

"In the future, cities will become deserts,
roads will become battlefields, and the hope of mankind
will appear as a stranger" The Road Warrior

 

I have 9:3:1 with Cast Heads and run 87 with timing set at 6*

 

Just realize that by detuning your engine to Run On lower octane, your costing yourself Power )



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

but while the gas is expensive, it will save you a heap load of gas. What does the factory recomend in the LB9 and the L98?
I know my dirtbike engine with the alum cylinder and head runs a little over 10 at 89 octain with out pre ignition but the factory says 90, i guess it was close enough.

[This message has been edited by camaro6spd (edited May 09, 2001).]

 

hey guys i have an 89 RS, but it was converted to a carbed 350 if that makes any difference. will 87 be ok or should i run 90?
thanks
Tom

 

Only if I left the rest of the weights and springs stock. Weights can stay the same, but if you go with lighter springs, then you advance your timing quicker and it works out fine. This is for non-computer controlled vacuum HEIs only though Zio...



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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

As a general rule of thumb, 9.5:1 is about the safe limit of what you can run with 87 octane on, but like mentioned above, if you get too radical with your timing, you'll have to either up the octane or lay off. Either way, 90 should be more than enough.