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6/12/14 10:26pm - Original Message: 'Fuel Question'
Jasond56
Former Member
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Kenosha, WI - USA

Vette(s):
1973 Corvette Stingray Coupe VIN 1Z37J3S418986 350 L-48 Automatic T-Tops St. Louis Assembly, 18,986th car built in 1973, Paint = 976 Mille Miglia Red, Interior = 425 Dark Red Vinyl (Ox Blood)

Joined: 5/7/2014
Posts: 154
Hello! Was wondering your thoughts on best fuel for L48 with Rochester Quadrajet. Do you suggest adding boosters and other additives to ratchet up octane # of pump gasoline? When fueling, do you guys fill up, or do you fuel little to force yourself to continually add fresh gas? As always, thanks in advance!

____________________________________
"You know, we always called each other goodfellas. Like you'd say to somebody: You're gonna like this guy, he's all right. He's a goodfella. He's one of us. You understand?"




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6/12/14 10:39pm - Reply: 'Re: Fuel Question'
daveo76
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 830
A stock L48 can probably live just fine on low grade, or at worst mid grade gas.  The bigger concern is the ethanol in today's fuel - it eats rubber and causes corrosion in our tanks, lines, pumps, and especially carbs.  You can look for a station with ethanol free fuel - I just moved to a new place and the little country store right by it has super without ethanol, but it's not cheap.  There are other additives that can help with the ethanol, but I would not think you would need an octane booster.  If you ever rebuild the Q-jet, make sure you or the builder uses a quality rebuild kit that is designed for today's ethanol fuel.  

____________________________________

 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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6/13/14 1:17pm - Reply: 'Re: Fuel Question'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19449
 It depends on where the timing is set, really. I only put premium in my '74 L-48.....and it will still ping a little when hot. My timing is set to factory specs, too. I would like to add some timing to it, but it would make it ping worse.
My opinion is to buy the best fuel you can get, that it will run properly on, whether that is Regular, Mid-grade, or Premium. The L48 should be able to operate on mid grade fuel, but fuels today are NOT what they were back then. Ethanol is only part of it, but it certainly adds to the problem. Octane boosters are simply a way to get you to part with your $$$ with no real improvements. The situation is only gunna get worse, too.....Angry


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Joel Adams
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6/13/14 6:01pm - Reply: 'Re: Fuel Question'
cingraham
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Brookline, NH - USA

Vette(s):
1976 corvette L82 red interior with white seats and door panels with ceramic headers and flow master exhaust and a Crane Cam

Joined: 5/2/2014
Posts: 46
I only run 91 octane or better and if they have 93 I run that exxon or mobile  with stock carbs

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6/13/14 6:17pm - Reply: 'Re: Fuel Question'
dyoes
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Zachary, LA - USA

Vette(s):
1974 L-48 Auto. Just your basic Vette. GM crate motor w/vortec heads and intake. Crane cam. Scorpion rockers, Edelbrock carb. Lots of parts still in boxes... :(

Joined: 1/27/2013
Posts: 201
Adams' Apple said:  The situation is only gunna get worse, too.....Angry

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If Obama had his way we'd all be driving Nissan Leafs, powered by positive thinking and unicorn milk.

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6/14/14 12:26am - Reply: 'Re: Fuel Question'
F4Gary Gold Member
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 862
I run high test with no problems, and that's with 17* of timing.  If I'm not going to drive it much, I'll put some Stabil in it.

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6/14/14 1:23am - Reply: 'Re: Fuel Question'
daveo76
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 830
What about the method of using the lowest grade that doesn't cause pinging?  My car with 9.4:1 compression and about 18 degrees of static timing doesn't seem to ping at all on mid-grade.  I usually do use premium but tried a tank of mid-grade a few tanks ago and I didn't notice any pinging.  I've always understood that using a higher octane than necessary is just dropping unnecessary $ in the tank and that the actual quality of the gas doesn't really change much with grade but maybe that logic is out of date?  I've attempted to educate non-car types in the past that putting super in their plain jane car is just a waste of money - go by what the owners manual says - but I know that system doesn't really work for a 70's Corvette.  

____________________________________

 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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6/14/14 9:19am - Reply: 'Re: Fuel Question'
Jasond56
Former Member
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Kenosha, WI - USA

Vette(s):
1973 Corvette Stingray Coupe VIN 1Z37J3S418986 350 L-48 Automatic T-Tops St. Louis Assembly, 18,986th car built in 1973, Paint = 976 Mille Miglia Red, Interior = 425 Dark Red Vinyl (Ox Blood)

Joined: 5/7/2014
Posts: 154
Thank you for the replies. I just had my timing and dwell set back to factory yesterday. They were off quite a bit. Because I was really low on fuel, I went to the station and filled up with 89 (mid grade). In south east Wisco we have 87, 89 and 93. So far, she seems to be running fine, but what is this "pinging" you guys refer too? What am I looking for when deciding which gas she likes best?

____________________________________
"You know, we always called each other goodfellas. Like you'd say to somebody: You're gonna like this guy, he's all right. He's a goodfella. He's one of us. You understand?"




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6/14/14 9:43am - Reply: 'Re: Fuel Question'
Jasond56
Former Member
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Kenosha, WI - USA

Vette(s):
1973 Corvette Stingray Coupe VIN 1Z37J3S418986 350 L-48 Automatic T-Tops St. Louis Assembly, 18,986th car built in 1973, Paint = 976 Mille Miglia Red, Interior = 425 Dark Red Vinyl (Ox Blood)

Joined: 5/7/2014
Posts: 154
Here's something I forgot to mention: when the car is idling, like at a stop light, I'll occasionally get this phantom rumble from the engine. It's not missing or skipping, it's just this rumble-like feeling. Kind of comes out of nowhere. Is that the pinging you're referring to?

____________________________________
"You know, we always called each other goodfellas. Like you'd say to somebody: You're gonna like this guy, he's all right. He's a goodfella. He's one of us. You understand?"




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6/14/14 11:27am - Reply: 'Re: Fuel Question'
Adams' Apple Lifetime Member
Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19449
 If you've ever heard a diesel engine run, you've heard "ping". On a gas engine, the ping is a little less intense/loud, but it's the same noise. Ping, or pre-ignition knock is caused by high cylinder temps and pressure. Too much timing, too much mechanical compression, and low octane fuel all contribute to the problem. "Ping" is the noise the piston makes when it rocks inside the cylinder wall. There is a normal amount of piston rock due to the clearance between the piston skirt and the cylinder wall. If the cylinder temp gets too high, the piston will rock violently, and the noise is actually audible.

The "rumble" sound you hear is something different. Could just be exhaust resonance, or it could be a heat shield, or other item vibrating and causing a rattle. Hard to say without actually hearing it. Big smile

____________________________________
Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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6/14/14 12:24pm - Reply: 'Re: Fuel Question'
Jasond56
Former Member
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Kenosha, WI - USA

Vette(s):
1973 Corvette Stingray Coupe VIN 1Z37J3S418986 350 L-48 Automatic T-Tops St. Louis Assembly, 18,986th car built in 1973, Paint = 976 Mille Miglia Red, Interior = 425 Dark Red Vinyl (Ox Blood)

Joined: 5/7/2014
Posts: 154
Gotcha. When you compare it to Diesel engine, I can understand what you're referring to. I've heard it before in big rigs. What I'm experiencing is not the pinging then. It's a rumble that's more felt then heard. Just to be clear, if she was misfiring, it would be more of a backfire correct? Like a small pop?

____________________________________
"You know, we always called each other goodfellas. Like you'd say to somebody: You're gonna like this guy, he's all right. He's a goodfella. He's one of us. You understand?"




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6/14/14 1:33pm - Reply: 'Re: Fuel Question'
F4Gary Gold Member
Gold Member
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 862
daveo76 said: What about the method of using the lowest grade that doesn't cause pinging?  My car with 9.4:1 compression and about 18 degrees of static timing doesn't seem to ping at all on mid-grade.  I usually do use premium but tried a tank of mid-grade a few tanks ago and I didn't notice any pinging.  I've always understood that using a higher octane than necessary is just dropping unnecessary $ in the tank and that the actual quality of the gas doesn't really change much with grade but maybe that logic is out of date?  I've attempted to educate non-car types in the past that putting super in their plain jane car is just a waste of money - go by what the owners manual says - but I know that system doesn't really work for a 70's Corvette.  


If your car runs great on mid-grade then using high test will not benefit you.  Keep using mid-grade.


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