How much timing can i run on 100octane?

igotyofire · Aug 13, 2007

Im sure with my Iron gt40s theirs a point up to which raising it is worth the gains...i know guys with aluminum heads always tend to run more timing then iron head combos. I just imagine that with the stock cobra configuration it may not be beneficial. But so far i decided im going to try running it at 14* degrees, not sure how much higher i can go and if i should even go higher.

WHITE94COBRA · Aug 13, 2007

I was able to run 14* when my car was basically stock, with 91 octane. If I went any higher it would ping, and lose power badly. There is a 76 station in aliso viejo that pumps 104 gas. I have never tried running it but I see quite a few people putting it in their vett's and a few mustangs, To me it's a waste of money unless your going to race the car, but even then I would just fill up a 5 gal. gas can, and use it when I got to said event. Also bumping your timing is simple! All you need is a timing light and a wrench to loosen the dizzy.

igotyofire · Aug 13, 2007

yea theirs suppose to be a 76 by my house that has 100octane from what people told me, if not then ill head to another location to get some. but i was just wondering does 14* sound way too conservative for 100octane. are the iron heads going to be a determing factor.....i know every car and situation going to be a lil different just wondering if i was in the ballpark or not

WHITE94COBRA · Aug 13, 2007

Even with 100 octane the car wont perform any better with more timing, all cars are different, but mine ran like shi* with more than 14*. You just need to take a few hours and adjust timing until you get it just right.

igotyofire · Aug 13, 2007

ic, in that case 100oct might be overkill and maybe some 91oct with possibly a lil toulune will be better

WHITE94COBRA · Aug 13, 2007

Our engines dont run high enough compression to need that high an octane, now if you were shootin some nitro, or boosting then I would tell you to go ahead and get some, then you could turn up the boost or a larger shot of nitro. Otherwise My suggestion would be to get 91, and if you wanted to be on the higher side of 91 put in a gallon or two of the 100, or just get some octane booster. I like the 1 or 2 gallons of 100 over the octane booster.

igotyofire · Aug 15, 2007

So i saw TDC on my balancer, what reference point are we looking for on the mustang? we assumed it was were it said "TIME" inside the engine bay and just lined it up with that and turned it to 14degrees

final5-0 · Aug 15, 2007

Let me share a few things I've seen with my Stang

I don't claim to understand it all
but
There is something about the chamber design on E7 heads

When you combine them with lean fuel/high spark GT pcm tables
It just makes the ping thing be prevalent

I did up some self ported E7's
I laid back the chamber slightly
and
Polished up the entire chamber

I ran 18 at the dizzy with 93 grade gas ... no ping

Later with a Tweecer ... I ran 36 total with 93 grade gas ... no ping

My point is ... the untouched E7 chamber can be ping prone

GT40's may not be as bad as E7's

Be thankful you are working with a Cobra pcm :Word:
as it gives you a bit more fuel & less spark

You will just have to play with it and see what it likes
but
Without pcm access ... you are gonna have no way to deal with very high
mid load spark table values and that is where you can sometimes get into
trouble with dizzy twisting.

Grady

igotyofire · Aug 15, 2007

ok well its already adjusted to 14degrees, i was just trying to verify the reference point ,do you line it up to that lil tab that says "TIME" when viewing from the passenger side?

WHITE94COBRA · Aug 15, 2007

Couple quick questions? Is your harmonic balancer stock? Can you read the numbers on the top of it? if not get a paint pencil or chalk and mark the 10* line, then mark all the way up to 20*. That way you can see all marks. Did you pull your spout? My stock balancer didnt have "TIME" on it anywhere??? Where are you located? If you not too far i'll drive over and give ya a hand.

Pokageek · Aug 15, 2007

I remember looking at those e7 exhaust ports and could not believe how SMALL they are! I mean, they looked like they were meant for a lawn tractor. Does porting help even though the runners are small? Ford really restricted these 5.0's factory ..dunno why! I mean, why didn't they do small improvements that would have given a nice gain in power? They didn't have to spend tons on that. then you could go higher on timing without issue.

juiced_94gt · Aug 15, 2007

There is 100 octane at the pump at the 76 in Norco on Hamner Ave.

reddy351 · Aug 15, 2007

Miscelleneous Ramblings about Octane...

One thing I had a hard time getting my head around with "octane"...it's not how much power higher octane can make over lower octane. It has to do with how stable the fuel charge is, under pressure and with heat. The same power is available with high octane as with low. (Maybe a small difference.) The difference is that at higher cylinder pressures (boost/lots o timing) the higher octane fuel will be more stable or less prone to ignite by some other force than the spark plug.

Where high octane has the upper hand (and the reputation for more power) is that more timing (or boost) can be added, before bad things happen to hardware. You can, however run out of "benefit" with timing as you can only have so much fuel (n/a) in the cylinder. Boost, however, can add a bunch more air/fuel therefore leaving something for the oxygen to burn. (When the oxy runs out of fuel to burn, it looks for something else. That would probably be the very "soft" aluminum in the tops of your pistons. That would make for a bad day.) Of course, you could make the (n/a) charge richer. Then you aren't going to like low speed driveability.

Food for thought/discussion...

igotyofire · Aug 15, 2007

WHITE94COBRA said:
Couple quick questions? Is your harmonic balancer stock? Can you read the numbers on the top of it? if not get a paint pencil or chalk and mark the 10* line, then mark all the way up to 20*. That way you can see all marks. Did you pull your spout? My stock balancer didnt have "TIME" on it anywhere??? Where are you located? If you not too far i'll drive over and give ya a hand.

oh, i live in chino hills, lil bit of a ways from HB, but we already set the timming yesterday, it just says "TIME" on it, its not on the balancer otherwise id assume it would be spinning.....posting pictures, and we put whiteout on what looks to be TDC on the balancer and advanced it 4degrees up. trying not to make this complicated but just asking incase next time i dont have my friends $400.00 snapon digital timing light their has to be a point of reference in which to move the timming about......and this is all im trying to confirm is where it says Time,lol apparently mine says time..i cant remember who makes my balancer i think its pioneer somthing but a non SFI one

View attachment 370119

WHITE94COBRA · Aug 15, 2007

Your balancer better have numbers on it!! Mine does, and so did the stock one. I'm in placentia right now, I sold my condo in H.B almost a year ago (I should probably update my sig.)
Anyone else not have numbers on thier balancer???

How much timing can i run on 100octane?

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