Octane question

[ejohnson03]

My search skills are not very good, so forgive me if this is a redundant post.

Since I am not a chemist and just want to know what fuel to put in my car to make is run at its best...

What octane should should I be using, and which fuel booster if any?

The new motor in my '76 Impala is 400cu.in. sb bored and stroked to 434 cu.in.
-- Eagle rotating asm. balanced crank with dished pistons
-- Comp Cam XR264HR > Duration 264/270, Lift .487/.495
-- Dart Pro1 215cc ported by Greg's Cylinder Heads and Custom Engines
-- Edelbrock performer Air Gap with 1" Holley Phenolic Spacer
-- 832cfm Holley HP double pump tuned by Nickerson Performance
-- Holley Hi Tek Dual Air Cleaner Assembly
-- Doug's Ceramic coated Headers - 2 1/2" tubes to Rhino Turbo mufflers
-- MSD dist with 42,000 volt super coil
-- Accel 8.8mm wireset with NGK Plugs

[maddad]

I'm no expert but that advertised duration may close the intake valve early for that motor and make a lot of cranking pressure.
Someone here is going to know the real answer.

[Awesome Bill]

My search skills are not very good, so forgive me if this is a redundant post.

Since I am not a chemist and just want to know what fuel to put in my car to make is run at its best...

What octane should should I be using, and which fuel booster if any?

The new motor in my '76 Impala is 400cu.in. sb bored and stroked to 434 cu.in.
-- Eagle rotating asm. balanced crank with dished pistons
-- Comp Cam XR264HR > Duration 264/270, Lift .487/.495
-- Dart Pro1 215cc ported by Greg's Cylinder Heads and Custom Engines
-- Edelbrock performer Air Gap with 1" Holley Phenolic Spacer
-- 832cfm Holley HP double pump tuned by Nickerson Performance
-- Holley Hi Tek Dual Air Cleaner Assembly
-- Doug's Ceramic coated Headers - 2 1/2" tubes to Rhino Turbo mufflers
-- MSD dist with 42,000 volt super coil
-- Accel 8.8mm wireset with NGK Plugs

You have to cc the engine after the head is on and the TDC was found. Then get back to us. We do not know how to answer this as you have posted. At least tell us what pistons you used, and what combustion chamber the heads are and what thickness head gasket with bore size.

[ejohnson03]

Okay, here are some corrections to my previous post.

Dart Pro1 Alum. Heads 215cc/64 chamber/ angle plug/ 2.05”/1.60” valves

Comp Cam - Custom Grind 3192S/3111S HR112
Gross Valve Lift .568in .565ex
dur@.006 273in 286ex
dur@.050 224in 230ex
lobe lift .3790in .3770ex
Lobe sep 112 deg.

Eagle Rotating Asm 12055
Mahle Pistons 4032 Forged - Inverted Dome (20cc)
Crank 4.0000" stroke standard 4340 Steel
Rods 6.000" standard H-Beam

The block was bored out to 4.155", but not sure of the gasket thickness.

[DartCamaro]

If my math is right you should be about 10.1:1 comp ratio. Depending on gasket thickness it could vary slightly. You would be able to use pump 92-93 octane regaurdless though.

[ejohnson03]

That is good to hear, cuz that is exactly what I have been running.

Would there be any benefit or detriment to using a higher octane, such as the 100 or 105 found at the local stations?

[DartCamaro]

That is good to hear, cuz that is exactly what I have been running.

Would there be any benefit or detriment to using a higher octane, such as the 100 or 105 found at the local stations?

You will not gain anything by using a higher octane fuel. Using octane that high will cause your plugs to foul out quickly and your chambers to carbon up. Using too low of a octane fuel and you will be running the motor lean and could potentially burn up pistons and or valves. In order to run 100-110 octane you would need to be about 11.1:1 - 11.5:1 and higher compression.

[ejohnson03]

Okay, great...

That is exactly what I thought.

I was running the Sunnoco 94 octane until they stopped making it.

So now I just run the Sunnoco 93.

Trying to stay away from BP, if you know what I mean.

Any thoughts on which gasoline brand is markably better?:eek:

Or are they all the same?

[DartCamaro]

I prefer to stay away from Sunoco. Around me at least, they have added ethenol to their fuel. Most BP stations around me do not add any ethenol. Ethonal/water can and or will help to cause detonation and poor performance. Just make sure to check the pumps around you and try to stay away from the ones with ethonal.

[Awesome Bill]

You will not gain anything by using a higher octane fuel. Using octane that high will cause your plugs to foul out quickly and your chambers to carbon up. Using too low of a octane fuel and you will be running the motor lean and could potentially burn up pistons and or valves. In order to run 100-110 octane you would need to be about 11.1:1 - 11.5:1 and higher compression.

we run pump gas on that compression all the time, just know where the timing needs to be and your fine. High test 91-93 gas is a ton better than you would think. I don't get worried about detonation until over 11:1, even with real street engines.

I don't like that much because you don't know what you get at the pump. So the possibilities are there to get messed up. Lower octane fuel does not cause running lean, af ratio does that. What lower octane will cause is detonation or pre-ignition. Hot spots are a problem with real street engines and heads that are left out of the box on the combustion chambers with sharp edges also left on the pistons to light the fuel mixture of when entering the cylinder and not having time to cool off the hot spots.

[DartCamaro]

Like i said....you dont NEED to start running higher octane fuel until you get ABOVE 11:1 - 11.5:1.

[BIG CHIEF]

Here is some added info on Octane in general and how its calculated and used.

http://en.wikipedia.org/wiki/Octane_rating

[Awesome Bill]

Here is some added info on Octane in general and how its calculated and used.

http://en.wikipedia.org/wiki/Octane_rating

very nice and informative. everyone should read this 10 times