[rel3rd]

Went to this huge car cruise/event at Ocean City, Maryland this past weekend and for reasons unknown, decided to dump a few gallons of 110 octane leaded CAM2 race gas in the tank....admittedly, solely for the race gas SMELL out of the tailpipes...:sad:

Since my car runs fine, with no audible or visual signs of detonation, with 87 octane (10% ethanol) gasoline, what effect on driveability would the much higher octane gasoline have?

Yes, I already KNEW that the car would run worse, but with 273's it wasn't going to win any burnout contests anyway.

The car seemed to be surging at light throttle cruise (2K rpm/55 or so mph). From how it felt, I compared it to a lean surge I got on my old Harley when I didn't jet the carb up after doing head and cam upgrades.

FWIW, car ran GREAT pre-Cam2 with it's brand new QFT 750VS carb, out of the box.

 

[Rich-L79]

High octane gas burns slower so to compensate you need to run more initial timing. Since you haven't likely reset the timing, it is running like the timing is set too low. It will be sluggish at pretty much all RPMs.

 

[Philip]

Compression ratio also factors in to using higher octane. The 400sb in the Nova responded well to the 110 octane used last month. The static compression is 10.6:1 and the timing is 20° initial, 38° total with another 12° added by the vacuum can on full manifold vacuum, not ported.
Idled smoother and pulled much harder, dropped 1.6 seconds off of ET and gained 19 mph over the 91 octane pump gas normally used.
It did smell cool too, maybe it was from the purple color

 

[rel3rd]

Thanks for the replies guys but you may be reading into my question a little deeper than I was meant to be asking.

The car idled and ran fine if accelerating... just had a mild surge at steady low rpm cruise. Just was wondering if the race gas would cause that ?
Fwiw, mine is advertised as 8.8:1 compression and runs great (normally) with 36* total timing, with 16 of it being initial on 87 o tane. Any higher and it has hot start issues and doesn't seem to run any better anyway....

 

[nastynate]

Compression ratio also factors in to using higher octane. The 400sb in the Nova responded well to the 110 octane used last month. The static compression is 10.6:1 and the timing is 20° initial, 38° total with another 12° added by the vacuum can on full manifold vacuum, not ported.
Idled smoother and pulled much harder, dropped 1.6 seconds off of ET and gained 19 mph over the 91 octane pump gas normally used.
It did smell cool too, maybe it was from the purple color

Wowzers, that's a lot of pickup from a 10.6 motor.. Do you have a really small cam in it?

 

[Willie496]

So 12.5 c/r 427 BBC?
Race Tech 118 or VP113

 

[69 Malibu]

Wowzers, that's a lot of pickup from a 10.6 motor.. Do you have a really small cam in it?

I can see .16 and 1.9 mph but something must have been way off to pick up that much if its not a typo

 

[Neal Wright]

Long term use isn't recommended for rubber fuel lines. Other than that, not much.

 

[jeff swisher]

My 1985 honda V65 magna had 10.5 compression i would race against my friend's yamaha V Max.
I tried all kinds of things to beat him ,, as the races we had were usually even steven.
I could beat him out of the hole every time so i would just cruise through the first 60 feet
and then it was a race of power and shifting after that...
side by side racing...
I ran 91 octane and decided to do a 110 leaded ,,well he beat me by 4 car lengths..
the bike ran perfect..but slower...tailpipes became grey instead of slightly black...

I found out he was runnin 87 octane the entire time....so i tested 91 octane vs 87 at the track..2 tenths quicker in the 1/4 on 87 octane...
A year of tweaking and i got it to run 11.51 to the V Maxe's 12.0...but i would spank him out of the hole with my 1.8 60 foot...

 

[rel3rd]

Since my car runs fine, with no audible or visual signs of detonation, with 87 octane (10% ethanol) gasoline, what effect on driveability would the much higher octane gasoline have?

The car seemed to be surging at light throttle cruise (2K rpm/55 or so mph).

Anyone?

 

[Philip]

Bob at what rpm are you getting full advance? If it is somewhere less than the full 36° and your vacuum advance is not pulling the full amount at cruise it could have a lean surge at cruise.

On mine it is all in by 2200, when cruising at this rpm that is 50° of advance.

Nate I have a Lunati 60103 with 1.6 rockers, Lift .522 I/.538 E. duration 268 I/276 E on 110 lobe separation.

Todd nothing was changed but the fuel. All the improvement was on the second half of the track.
Time slips before and after, I already know my reaction time sucks My memory of the exact difference was a little off, but close.

 

[jeff swisher]

Every engine is different
You already knows what it does in your car..
I know what it does in my V65
I ran it in a mustang that ran 91 most of the time and it went 4 tenths quicker 351 cleveland.
There is no perfect answer when it comes to what will this cam sound like.
What air pressure does this slick need.
how much timing does a 350 need .
all combo's are very different..
Heck i built a 350 engine that wanted 41 total timing for max performance.
Guy hydrauliced it during a rain.. replaced rods crank and pistons with the same part numbers ...kept same cam and timing set and never touched the heads or intake
It now liked 38 total timing for best power...ran the same ET though...

Tune it man, tune it..
get out the jets play with timing...
I ran e15 with no tune on my 91 octane deal
lost MPG..felt a tad quicker..but it was 100+ outside..

 

[aukai]

Bump the timing 40-42 total, may help.

 

[bdr66]

Bob at what rpm are you getting full advance? If it is somewhere less than the full 36° and your vacuum advance is not pulling the full amount at cruise it could have a lean surge at cruise.

On mine it is all in by 2200, when cruising at this rpm that is 50° of advance.

Nate I have a Lunati 60103 with 1.6 rockers, Lift .522 I/.538 E. duration 268 I/276 E on 110 lobe separation.

Todd nothing was changed but the fuel. All the improvement was on the second half of the track.
Time slips before and after, I already know my reaction time sucks My memory of the exact difference was a little off, but close.
http://i80.photobucket.com/albums/j199/64elcamino/77 Nova project/timeslip.jpg

I switch between 89 and 110 all the time and there's just no way there could be that big of a difference. Something else changed on that car and you just didn't know it. Perhaps someone took out the nerf football from behind your gas pedal.

 

[rel3rd]

Bob at what rpm are you getting full advance? If it is somewhere less than the full 36° and your vacuum advance is not pulling the full amount at cruise it could have a lean surge at cruise.

On mine it is all in by 2200, when cruising at this rpm that is 50° of advance.

My full advance is in by roughly 2800. No idea where it is at 2000 since there was never really a reason to look, as it ran/runs fine at that RPM on 87 octane. Maybe I will have the distributor re-setup since the car now has 273's and not 373's...and obviously a much lower cruise RPM.

The whole basis of this thread was to hopefully get an answer as to if the 110 had CAUSED the lean surge or not...but it appears everyone is not understanding my question...

I have zero intention of tuning the car for the 110, as it is DEFINITELY NOT NEEDED and was only added for the race gas smell, and nothing else. It's diluted a good bit now, but crappy weather has prevented me from driving it to see if the surge is gone, or at least "diluted" like the fuel.

FWIW, and although it has absolutely nothing to do with this thread, one of my old cars was run on 118 octane Torco race gas with 18psi of centrifugal boost and would run 10.20's at 132 mph (28* total timing), and on the street with 93 octane unleaded, so as not to blow a head gasket or worse, I only used 16* TOTAL timing and ran 11.20's and 121mph...

 

[nastynate]

The only answer I have is it was fouling the plugs or slower and erratic combustion. Just the same as when your timing is to low. Just some thoughts.

 

[Dakenzie1]

I have zero intention of tuning the car for the 110, as it is DEFINITELY NOT NEEDED and was only added for the race gas smell, and nothing else.

If it picked the engine up that much, it is exactly what was needed.

 

[rel3rd]

The only answer I have is it was fouling the plugs or slower and erratic combustion. Just the same as when your timing is to low. Just some thoughts.

Thank you. I believe that is what was happening as well.