TraviZ

iTrader: (2)

what octane should i be running in me 9.3:1 engine?

jfreeman74

87

ede

whatever doesn't produce knock. start at the lowest and work up till knock, or knock counts disappear.

TraviZ

iTrader: (2)

knock.. is that the same essence as spark timing? or something like that if orget.. some dude (dwayne88iroc) hooked up is laptop and something like spark..and he said it was how many times the computer had to retard the timing..

IHI

iTrader: (1)

87 with no problems, but I always ran 92. I did'nt see any loss in et/mph at the track between the 2 so I ran the beter stuff.

87LS

I would run 89 pewrsonally. If your heads are stock, we don't exactly have the greatest flowing heads. That is a good amount of compression, with stock heads for 87. I would run 89 just to be safe

RB83L69

Run the lowest grade that doesn't knock, or produce knock counts.

No point in handing over any more cash to the oil companies than you really need to. If it doesn't make any difference, then ..... it doesn't make any difference.

"Premium" is no better in any way, except in the one respect, of reducing the tendency toward spark knock. In fact, it usually has a lower heat content than regular, meaning you have to burn more to get the same amount of energy, assuming that the regular doesn't cause knocking.

Bottom line: run the lowest grade that doesn't knock, or produce knock counts.

TraviZ

iTrader: (2)

how can i tell if its knocking?

GASGZLR

you won't be able to because the computer will pull out timting if it is knocjing and you should never hear it. If you have an ALDL link or one of those thing s to interface with the computer then you could see if it is knocking. I run 86 octane in my 89 RS V8 L03 no probs.

TraviZ

iTrader: (2)

well in my post above, i asked that question abuut this program..

but no one noticed that post i guess?

not sure what program it is, but it said something like spark control or something.

is that the knock u all speak of?

IHI

iTrader: (1)

Not being hip to the whole computer+engines=performance thing. Without the computer you will know it's knocking by the sound coming from the motor, it will sound like gravel in a can being shaken. Bout the only way I can think to describe it.

RB is right, there is actually more BTU's or output from lower grade fuel aka 87 octane over say 100 octane. the difference is is the temperature the fuel wants to pre-ignite. Higher ocatne fuel has the ability to slow down the burn process which allow it's with high compression and high timing.

ShiftyCapone

iTrader: (7)

Listen to RB and ede. You want to run the lowest amount before you hear knock. Some knock is not audible though and can only be detected by looking at a data log. That is what they mean when they speak of knock counts. For TBI cars If you are running 0* base in your car you can use 87. If you run 4* advance you will need 89. 6* advanced will require 92. You get the point. This is not always true but pretty accurate for 99% of all 305 TBI cars out there. There is no point in running anything higher than you need.

305LG4Cutlass

Well my 87 LG4 with 9.3:1 doesn't run worth a damn on 87. I always run 91. If I put 87 in it, it won't stop pinging until I back it off enough that the car is not making any power. Also if I run 94 octane at the track and advance it a bunch, I still get pinging even without causing any of that "crankiness" that over advanced timing can cause.

btw, this engine passed e test with almost all 0's, less than 10% of the limit on every part of the test, so I'm thinking that everything is in okay shape. Any ideas? EGR is working.

ShiftyCapone

iTrader: (7)

What is your base timing set at? How many miles does your motor have on. High mileage can cause carbon depsoists over time which can cuase serious ping no matter what fuel you use. The tips of the carbon will get hot enough to ignite the fuel.

RB83L69

My idea is, glad I'm not paying the gas bill.

If this is the stock computerized distributor, you need to back the timing off a bit. If it's a mechanical/vacuum one, you need to put in heavier springs or limit the vaccum or stiffen the vaccum spring (adjustment).

Fast305

My 9.5:1 305 likes 87 octane. I have the advance set at 32* total @ 2,500 rpm. It is pulling a 4,500 lbs brick. I do not have EGR. The only time I get ping is at tip in and when the transmissions shifts gears @ off idle. Rattles for a second or so after the transmission shifts. No big deal if you ask me.

sqzbox

Any ping is a big deal, it causes engine damage!

WaynesIroc

How would someone go about actually hearing a ping(what does it sound like). Is it audible when your inside the car or would you have to be under the hood or connect a computer through the aldl? Just wanted some clarification on this as I am not at all familiar with knocks and pings.

sqzbox

Put a BB in an empty coke bottle and shake it back and forth. That's about what it sounds like! Pinging damages the ring lands
between the rings.

ShiftyCapone

iTrader: (7)

Yup. The knocj that is not audible is picked up by the knock sensor and adjustments are made to prevent it. You can see unaudible knock with windal.

305LG4Cutlass

Its a vacuum advance distributor. I'll have to try adjusting the spring. I don't know how but I'll try and figure it out. LOL

It's got around 150k miles on it but runs like a top. Doesn't burn any oil and I use synthetic mobil 1. I imagine the long trips to work (40-50 minutes of driving one way), and synthetic oil and hard runs have probably helped keep it from getting too carboned up. When I had the carb off, the intake manifold looked like something I could eat off of inside.

btw, I really don't think anyone should put up with pinging. Even with a 305. It may make the difference between your engine lasting 200k or 450k.

Streetiron85

There's a product called an adjustable vaccum advance cannister, made by several companys, Crane for one.
They cost less than $20 and they're in the Summit or Jegs catalog.

ILikeFtLbs

Of course you can also hear knocking if your intake manifold is leaking. Go 89 and you'll be fine.

Dante93GTZ

iTrader: (5)

Back up here guys. Don't most of the V8's in 3rdgens have 9.3:1ish compression?

Our cars say 87 octane is recommended.

ShiftyCapone

iTrader: (7)

Yes you are right. However, if you run more than 0* base (manufacturer setting) you may have to go a higher ocatne fuel. Also, carbon depsosits can cause pre-ignitoon causes you to run higher octane as well.

305LG4Cutlass

Anyone thats tried advancing the timing will not want to run it at factory timing. Especially when you've got an LG4 every little bit helps. Putting it back to factory timing made it feel like a dog. I will put up with running 91 octane.

sqzbox

I even wonder if the 87 oct. is the same as it was back in the 80's.
With all the crap their putting in gas nowaday's for cleaner air, I wonder if it has the same performance property's as it did 15yrs. ago! Last week in So. Indiana, Marathon Oil Corp. screwed up and got their formula wrong and put too much sulpher in their 87 oct. and got 160 complaints because it efected peoples fuel level sending units. Now their having to pay those consumers to have their sending units replaced! SO much for consistency! I used to think if you stuck with the same brand that works good for you, you'd be safe. Now it's like Pepsi making Coke!

ShiftyCapone

iTrader: (7)

Fuels are better today than they ever were for both performance and the environment.

sqzbox

Yeah, for today's engines! A pre-unleaded engine doesn't last as long with out hardened valve seats, valve guides, and 93 oct. that was the rating for reg. gas back in the 70's. Used to be you could drive your 10-1 comp + up to a pump and fill up with 102! Now, you have to put it in a can first! and it's still unleaded!
Nowaday's if you want to buy a car w/300+ hp, you have to hand out $30,000 bucks plus for a $5,000 car with a computer.
The simplicity of hot roding has all but dissapeared! and taken the sport out of the average man's hands because of the price of today's parts to be compatible with today's gas. Now, you have to wait till cars are 15-20yrs. old for the average guy to afford to buy anything performance. In that case, it will probably need a re-build and resto. In the last 30yrs, average wage has gone from 5 to 8 bucks an hr. that's only 3 bucks an hr. while car prices have more than quadrupled! Used to be you could go and get a chevell, cobra, cuda, amx, and run 12's at the track w/$500 bucks of mod's. Try that today! Anyone that has been there knows what I'm talking about.