Fuel mix for my 69 Camaro L78

[69SSRSL78]

I recently purchased my 69 Camaro SS L78. It is awesome, I love it. It runs pretty well and I'm burning 91 octane fuel. The engine has 11:1 compression and I'm wondering if I should mix in some higher octane fuel, like 110 octane airplane fuel. Can anyone tell me if there are risks in doing this?

[Chris396]

Mine and my cousin's L78's run just fine on 93.

[Motion Camaro]

<font color="blue">If the engine is all original, you could
put in some lead additive.

If it has been rebuilt, with hardened valve seats,
a little Octane booster once in a while will be ok. </font>

http://img.photobucket.com/albums/v131/Zorg123/valvetrain/f83b376f.jpg

[WILMASBOYL78]

I have a "few" of these engines and they like good fuel. Best results are a mix of leaded high octane with best pump gas you can get. I usually mix it about 4 to 1 pump gas to the good stuff. Using the unleaded stuff straight would not be my choice. It works in a pinch but these motors were meant to run with good fuel. The better fuel will even make the engine run cooler in my experience, and certainly make more power. I'll even throw a bottle of lead additive in once in awhile just for good measure.

wilma http://www.yenko.net/ubbthreads/images/graemlins/3gears.gif

ps: stay away from the aviation fuel it has a differnt specific gravity than auto fuel and may end of doing more harm than good. I'm no engineer but this was recommended to me by a friend who is a pilot.

[ZL1mike]

imo airplane fuel doesn't have the proper additves for car engines and what I like to do is buy a drum of VP racing fuel C12 and mix it with Sunoco gold, this has the proper mixture for 38 or even 40 degrees of total timing for cold start up and even going through the gears when I get the urge and lastly the exhaust smells a lot better too. http://www.yenko.net/ubbthreads/images/graemlins/smile.gif

[WILMASBOYL78]

Forgot about the smell, that's almost the best part. Nothing like the sweet aroma of high octane fuel and burning rubber...... http://www.yenko.net/ubbthreads/images/graemlins/burnout.gif

wilma

[Chevy454]

Here's my experience with our L72, which is virtually identical to the L78...if you haven't extensively milled the block/heads and have a GOOD set of JE or CE pistons in there then you're compression is gonna be down and a load of octane will actually slow you down.

Our L72 had a stock rebuild by ourselves, and came in at a whopping 10.2:1 compression ratio when it was all said and done...I ran 91 octane (hightest we can get here in town) with occasionally a splash of 114. Our car actually picked up by only running the straight 91...especially if it wasn't just ungainly hot outside. With the low compression and high octane, we never could get enough heat in our engine...particularly in the combustion chamber, but we even had trouble getting heat into the block itself. And we weren't running in some extremely cold climate, it was Memphis in September. Anyway, I tried just straight 91, and the thing finally got some heat in the heads and picked up...you HAVE to have a certain amount of heat in your combustion chamber and block. So, if you've got a basically stock bigblock, a splash of some good stuff might not make optimal power, but it ain't gonna hurt anything...except maybe your ET...just don't go overboard with it.

[sean70ss]

I have ran many types of motors. I have found the best thing is a 80/20 mixture that way it does not break your wallet. 15 gallon tank put 10/12 of 93 and the rest 112 or 116. remember heat kills power if your good with reading plugs you can see where the fuel mixture is. i always run my motors as cool as possiable dyno proves they make more power. Sean

[Zedder]

Good timing on this thread as I am considering building a Sunday driver for taking the family out for an ice cream and am leaning towards a driver quality restored '67 Z. With this particular car, I don't want to mess with mixing fuel etc. and had considered taking the compression down from the factory 11:1 ratio. From what I've read here and on some other sites, this isn't necessary for 91 pump gas? My last Z ran on like crazy when shutting it down and would ping loudly on acceleration - that drove me nuts. Any thoughts on this? Some have said to have the distributor recurved to correct pinging on acceleration. I'd love to learn from some of your experiences...Thanks,

[ssl78]

When I ran my car at SCR7 its was running speeds of 98 and 99 mph all day.I was using 93 octane unleaded pump gas My tank was down to about 1/8 of a tank and Greg who had the orange clone copo Chevelle there had some aviation fuel, I added 5 gals and made another run and I lost 31/2 mph. The burn rate must have been way to slow so I guess more octane isnt always the case.
This brings up a point I have been wondering about I have a L78 Chevelle a L78 Camar and a L72 Camaro I have a hard time to get any one of them to spark knock set at 8 degrees with the stoick distributors. They also seem to run better at 12-14 degrees. does this new fuel even burn slower than the old leaded fuel? I even went out and bought a new timing light thinking my old one was bad. Anybody else notice this.

[Chevy454]

Hmmm...interesting, John! http://www.yenko.net/ubbthreads/images/graemlins/naughty.gif

I tend to worry more about total timing than initial...when you're driving (and especially racing) you will be at total timing for most of the time, while you'll be at initial timing only at startup and idle. You need to find where your engine runs best with the total timing...and what your initial is will depend on how your distributor is set up. If the engine runs best with 39 degrees total, but wants to kick back when you start it, then find what initial works...then you can either sacrifice your total timing or do it right and get your distributor curved. Our cars like 12-14 initial, and depending on compression ratio anywhere from 32-40 degrees total. I've found our lower compression (10:1) L72 likes around 39 degrees while our higher compression L72 (12:1) only likes around 33 degrees. The burn rate of fuels is built into them, which is why there are a gajillion types out there...but generally the race fuels have a faster burn rate, as well as a higher ignition temperature, which help alleviate detonation.

[Mr70]

To all you guys who answered in this Topic.
What Spark Plug size/Brand are you running the 1/4 with?

[Chevy454]

NGK R5671-A...I believe the heat range is "7". AC's killed our engine on the dyno, but when I plugged in the NGK's it picked it back up and cleaned up a couple cynlinders...go with either NGK's (preferance) or Autolites.

[JoeG]

I did find that the AC'S seem to keep the tune longer for street use, ----At least in my case---Just some info----

[Chevy454]

Joe: does that still hold true today, as in the last couple years or so? The reason I ask is that our engine builder as well as some of the S/SS guys I've talked to seemed to feel like the *quality* of the AC plugs has gone away the past few years, which is why they are all going to NGK or Autolites. In fact, I believe it was Moparts that told me he was at a parts vendor's tech conference somewhere and the AC rep told the crowd that the AC plugs were being made by Champion? http://www.yenko.net/ubbthreads/images/graemlins/dunno.gif On the first L72 we had on the dyno, we made right at 30 pulls with it, and it had a stumble and rough idle with a couple different sets of AC plugs...the NGK's smoothed it out and picked up the power.

[moparts]

Stay away from the "airplane fuel" if it is true airplane fuel it has alochol in it and it will destroy your rubber parts in the fuel system....not to mention it is hard on the aluminum parts too.

For street driving I agree with Sean70ss run a 20 percent or so mix of good fuel. This will help with part throttle detonation and help lube the valve system. Don't tell Rob but there is positions on the throttle other than idle and WOT. With a properly working vac. advance and low octane fuel even 9 to 1 compression engines will spark knock under the right loads.

Just a thought, spark knock, detonation, ping or what ever they call it in your area, could be listed by the surgen general as a almost silent killer of your high compression engine.

[moparts]

Yes Rob it is hard for me a true Bow Tie Guy to admit but you can make almost anything run better on something other than the AC plugs. The new platinum plugs seem to be alot better. It was the champion rep that was bragging they made ac's for them.

[JoeG]

Don't get me wrong--I used NGK'S--Fine plug--And for sure go by your Dyno read out-- I just said in my car the AC's seem to hold a " Street" tune --no rough idle/ slight stumble longer without pulling them out to clean them up--I do have a high output ignition that use to keep the Champions going back when----Didn't mean to push one plug or another--Just something that I've observed in trying different plugs---Nothing is written in stone---Didn't intend to put starch in Moparts shorts-- http://www.yenko.net/ubbthreads/images/graemlins/tongue.gif http://www.yenko.net/ubbthreads/images/graemlins/beers.gif

[Chevy454]

No problem here, Joe, I was just hoping to pick your brain! http://www.yenko.net/ubbthreads/images/graemlins/beers.gif You may be right, though, that the ignition is helping...what box/coil you running? Exactly which range of plugs do you favor?

Moparts: vacuum advance? what's that?? http://www.yenko.net/ubbthreads/images/graemlins/naughty.gif

[Mr70]

Thanks for the input all.
I thought Marlin Stated he swithced plugs when going from the street to the strip in his Deuce,with much better results. http://www.yenko.net/ubbthreads/images/graemlins/dunno.gif
Marlin you out there?

[moparts]

JoeG I tend to agree with you on the street use for the AC plugs. Especially on the lower compression engines and lower octane fuel. Lower octane burns faster and eaiser, lower compression doesn't squash out the flame.

The higher the octane fuel and the higher the compression just makes you have a better spark to set it off.

The day we run robs engine one of the first things the guy told us was he could make the engine get 5 to 10 more hp with good plugs. We thought he was full of it so went ahead with the ac's we had in it. The plug couldn't make that much difference right? Wrong, you know how Missouri is (The show me state).
When we were running robs engine on the dyno we wondered why the guy running the dyno kept asking his wife if the engine was missing. With the noise of the engine and fans running you couldn't hear anything like a miss in the dyno rooms. I went back in the building where his wife was working and bingo I could hear the miss as plane as day. So being from Missouri we run the valves, checked the carb, and made sure we had good spark. Still the same miss at about the same rpm. Finally after we were about to give up he spoke up and said some good plugs will solve your problem. So we finally said ok,,,show us. 15 min later new ngk's arrived, installed, and engine runing at 6500 rpm full load and no miss and there was about 7 more hp showing on the readout.

Got to go now...just wondering how do I get this starch out of my shorts?

[JoeG]

[ QUOTE ]
No problem here, Joe, I was just hoping to pick your brain!

Slim Pickins-----------The actor wiseguy http://www.yenko.net/ubbthreads/images/graemlins/wink.gif

Was Mallory CD unit called the Magic box--Now MSD6 /Mallory Voltmaster coil--Mallory dual/pt dist---
Heat Range---colder plug in summer and hotter plug in winter- Always carried a fresh set of Champions,back then, in the trunk----
Better to go a little cold on the range and go to a hotter range as needed--IMO --most you can do you foul the plugs--starting off with too hot a plug can cause a pre-ignition--
--
I've got AC's in now , because of starting the car up and moving it around---------OH---NGK/Autolite very good plugs http://www.yenko.net/ubbthreads/images/graemlins/grin.gif

[sean70ss]

Spark plugs are only good for about 3 dyno pulls and that is it. And dynos are way differant form real world driving. Theyu are ok for a basline but with the ever changing air it makes them hard to be reliable especially street driven cars. 14-16 degrees is good for intial timing anything over 500 inches should really be below 36 degrees timing smaller motor likes more timing. I have run 427's with 42 degrees with no problems with a mix of gas and race gas. aviation fuel was desgined to be run at extremely high altitudes it is a dry fuel not made for street or racing engines the price is attractive though but hard on motors you take a chance on burning things up espcially with nos. my LS6 car I mix the fuel 12 gallon of 93 and the rest 116 vp fuel with 36 degrees timing actually runs 10 degrees cooler and runs hard as heck. They key is no detonation if your doing a factory rebuild to the stock specs runa little race gas and have fun or you can chage the cam to bleed off some cylinder pressure etc there are so many differant ways to accomplish this. Sean

[Chevy454]

I was thinking the amount of timing is determined more by compression ratio/cylinder pressure and flame speed than by "engine size". Bore does play a small role in it, because a larger bore I would think would need MORE timing since it takes longer to burn due to the sheer distance of the big bore? But my experience only goes up to 454ci, so that might not be right?

Anyway, higher compression means higher cylinder pressure, which means a faster flame front speed, which means you need less total timing...due to compression, the charge is more dense, because there is less *space* between the molecules which allows it to burn faster. That's why/how vacuum advance works, 'cause high vacuum conditions can tolerate a crap load of timing. But, your dynamic compression comes into affect, as you mentioned some cams will bleed off pressure or even just change the timing of the cam events...tricky stuff!

Our pair of L72s are a good example compression &amp; timing. One is 10:1 the other is 12:1, yet the higher compression engine likes 5-8 degrees LESS of total timing..same parts, same ignition, in the same car. A supercharged engine is another example...the flame front is faster in the s/c engine because of the increased cylinder pressure, so less total timing is needed. Heck, the LS1 in my '98 SS only needs like 28 degrees of total timing because of the superior flame characteristics of the Gen III heads/pistons...

Zedder: something worth mentioning is that a lean condition can lead to pre-ignition and detonation...how good was the tune on that Z?

[427TJ]

I ran 100LL Avgas in my 110,000-mile stock 325-horse 396 (10.25:1) and it ran great. The mix was about 50/50. Boy did the exhaust smell good. Nope, no drain bramage either.... Uhh, I mean BRAIN DAMAGE.

Problems encountered: After several tanks of pump 92 with 5 gals of 100LL mixed in each time the engine began idling fast, like 1500 rpm, and if I backed the idle adjustment all the way out it still wouldn't come down below a 1500-ish idle. Someone told me about the detergents in (or not in--can't remember) (no brain damage) 100LL causing problems. Another tidbit from a buddy was that you need "special carb gaskets" that the Avgas won't attack. Well, I decided that Avgas was becoming more trouble than it was worth and went back to straight pump 92 and reset the timing to minimize ping under load. After a tank or two the idle became 'adjustable' again and now the car idles at 800.

One of the local Unocal 76 stations sells 101 octane unleaded at the pump for $5/gal. They also sell higher octane leaded racing gas by the gallon but you gotta' pump it into a can and then transfer it to your car.

Good luck!

[JoeG]

I've been using some of that Jack Podell lead/octane mix--car seems to like it--

[Chevy454]

You have any trouble with it turning your plugs a funny color? I tried a couple different brands of octane boosters and they turned the plugs a light orange color?

[sean70ss]

On my 706 we use 24 degrees timing on the 588 that I have in my chevelle we use 33-34 no more. The more timing you use will cause detonation. The bigger bore is actually more forgiving then the small bore less quench. Smaller motors like more timing. Lower octane will cause detonation it explodes before it hits top dead center. Higher octane has a slower burn rate which will make more power so lets say you had 11.1 427 you used 93 ocatane with 36 degress total advance it would more then likeley ping itself to death but if you had a mix of 93 and 116 and 36 degrees it would not because of the slower flame travel. I had built a 555 a few years ago i wanted a street strip deal. 12.1 compression I ran 93 octane and vp 116 50/50 it made 893 hp on the dyno with 18 degress initial and 35 degrees advanced! I figured 50hp less in the car due to air and humidity. So basically these cars are not driven that much so give them some good fuel they will be much happier and live alot longer.

[Mr70]

[ QUOTE ]
I've been using some of that Jack Podell lead/octane mix--car seems to like it--

[/ QUOTE ]
I use this too,and noticed a real diiference from before using it.I really like it. http://www.yenko.net/ubbthreads/images/graemlins/burnout.gif

[JoeG]

Yeah Rick --Car runs good-
No Rob no different colors on plugs--I think it use to be called Lead Supreme --By Stone Oil Co.----They use to sell it in metal gal. containers---It contains TETRAETHYL LEAD---Vitamins for muscle cars----

[Chevy454]

Cool...I never tried the lead stuff, just the "octane boost"...that's probably where I screwed up!

[Chevy454]

[ QUOTE ]
Higher octane has a slower burn rate which will make more power

[/ QUOTE ]
Often times that's true, but not always! Octane is not directly related to burn speed...that is controlled by the chemistry (composition) of the fuel itself. For example: Maximal (http://www.racegas.com/fuelspecs/sunocomaximal.htm) has one of the highest octane ratings of any fuel Sunoco makes (116 octane), but it's one of it's fastest burning fuels...they use it a lot in Pro Stock.

[Jeff Murphy]

I'm using the Sunoco Supreme Leaded 112. All I can get here in England -- at $19/gallon (for a 50 gal drum). http://www.yenko.net/ubbthreads/images/graemlins/eek.gif http://www.yenko.net/ubbthreads/images/graemlins/confused.gif http://www.yenko.net/ubbthreads/images/graemlins/dunno.gif

[camarojoe]

I haven't heard anyone mention Turbo-Blue racing gasoline... maybe it's not sold nationwide? http://www.yenko.net/ubbthreads/images/graemlins/dunno.gif I believe its 115 octane, and is sold "for off road use only" at a few places in my area. I don't know what its similar to thats already been mentioned... anyone else use this stuff? Was about 3.90 per gallon here this summer.

[NCGuy68]

[ QUOTE ]
[ QUOTE ]
I've been using some of that Jack Podell lead/octane mix--car seems to like it--

[/ QUOTE ]
I use this too,and noticed a real diiference from before using it.I really like it. http://www.yenko.net/ubbthreads/images/graemlins/burnout.gif

[/ QUOTE ]

Been using it for a long time in vintage cars. Mess with spark plugs, timing and carb jets all you want. Theres' no substitute for a small dose of real Tetraethyl to wake up the car.

[Zedder]

[ QUOTE ]

Zedder: something worth mentioning is that a lean condition can lead to pre-ignition and detonation...how good was the tune on that Z?

[/ QUOTE ]

I don't think so Chevy454...I couldn't tune a car to save my life, so I took it to a local Corvette guy that has a fairly good rep. He couldn't get the thing running where he wanted it and fiddled with the carb and timing for about 2 hours before getting it "the best he could". I suspect the carb and distributor needed freshening and that it was running the off-road cam - not the stock cam.

[Schonyenko2]

We run "blue". It's pretty good stuff. Not as good as VP, but better than Casy's. It will not fire in cold weather. You'll need to blend it if it's going to be below 40. Smells great.

[musclcar]

my sbc is a 70's performance build-up running 11.5:1 comp the old 140 flat tappet cam and edelbrock TM1 intake with a holley 850DP.it runs it's best with 14 inital 42 deg. total runing either 91 octane or mixed with VP C12 or socal 114 orange

[Chevy454]

I tend to prefer the purple...the blue seems to be a lot more noticable on the intake than the purple if any gets spilled on it while pulling the bowls...

[@wot]

VP fuel is synthetic and will not mix evenly with fossil based fuel. I have stopped using it in favor of Torco race fuel. My car needs a 50/50 mix to run properly with the most advance possible before detonation.

[DarrenX33]

Will using fuel or additives with lead negatively effect a motor with hardened seats?

[Schonyenko2]

Rob, gumout carb cleaner will take the blue out of the intake.

[DaJudge]

I always run Cam II Blue which is 112 octane and is leaded. I then tune the car the old fashioned way and set the timing with a vacuum gauge , set the timing to get the most advance just before detonation even the most expensive timing light won't compensate for the ravages of time on the rubber on an old balancer, and then procede to adjust the mixtures screws to maximize vacuum. Always works for me, especially when tuning cars with original or even NOS balancers they tend to slip and the timing mark becomes inaccurate.

[k92]

I run straight 100 octane turbo blue in my '70 Chevelle, w/o any problems. Original ls6 motor is gone,in place is a 396 bored .30 over, 11.5:1 compression,comp cams magnum 280 cam,stock ls6 intake/carb/exhaust manifolds,timing is 38 total,never over heats,but will ping if I try to mix the turbo blue 50/50 with 93.I dont know how some of you guys with stock high compression motors run 93 w/o any pinging unless you are really retarding the timing or your true compression is less than what it is reported to be.

[WILMASBOYL78]

There is often a wide variation in chamber volume on some of the high performance cylinder heads. It is not unusual for the actual compression to be closer to 10.25-10.50 than 11.00-1. I have "several" L78 cars and there is a differnt fuel tolerance for each one. The only way to know for sure is to pull the heads and measure CC's and dome volume and then figure the static compression ratio. It is a lot easier just to set them up to run and back into a fuel mix that works without detonation.

wilma http://www.yenko.net/ubbthreads/images/graemlins/burnout.gif

[Chevy454]

I cc'ed a set of L72 pistons, and they averaged around 29cc, where they were *supposed* to be a 34cc dome, and the head chambers cc'ed at around 112-113cc where they're supposed to be in the 107-108cc range...this netted a compression ratio of 10.2:1...

[JoeG]

Are you fellas able to get race gas locally without going to the track---S&amp;K in L.I.--seems to be the closest to where I am and you can have it del---UPS------------

[Belair62]

I have to buy 55 gallon barrels...kind of spooky driving down the road with a barrel of 112 behind your ear ...

[DaJudge]

Its even more fun taking those 55 gallon drum off the truck by yourself.

[55chevy]

[ QUOTE ]
I have to buy 55 gallon barrels...kind of spooky driving down the road with a barrel of 112 behind your ear ...

[/ QUOTE ]

Bob.. you are supposed to unload that when you get home with it.. Not drive it around all week to show it off. http://www.yenko.net/ubbthreads/images/graemlins/no.gif

[Motion Camaro]

[ QUOTE ]
Bob.. you are supposed to unload that when you get home with it.. Not drive it around all week to show it off. http://www.yenko.net/ubbthreads/images/graemlins/no.gif

[/ QUOTE ]
http://www.yenko.net/ubbthreads/images/graemlins/scholar.gif--- http://www.yenko.net/ubbthreads/images/graemlins/scholar.gif--- http://www.yenko.net/ubbthreads/images/graemlins/scholar.gif--- http://www.yenko.net/ubbthreads/images/graemlins/scholar.gif--- http://www.yenko.net/ubbthreads/images/graemlins/scholar.gif

[Pantera]

[ QUOTE ]
[ QUOTE ]
I have to buy 55 gallon barrels...kind of spooky driving down the road with a barrel of 112 behind your ear ...

[/ QUOTE ]

Bob.. you are supposed to unload that when you get home with it.. Not drive it around all week to show it off. http://www.yenko.net/ubbthreads/images/graemlins/no.gif

[/ QUOTE ]

Ed - when you pay that much for gas you want to get all you can out of it including showing it off... Right Bob? http://www.yenko.net/ubbthreads/images/graemlins/headbang.gif