av gas yes or no

[fireZ]

I am wondering if 100 low-lead fuel that is meant for small aircrafts is a good idea to run in a stock 68-302 car. I have read some articles that say it is not good for the seals in a DZ carb.

[JohnZ]

100LL won't bother any seals or gaskets, but your local airport FBO probably won't let you pump it into your car; legally it has to go in an airplane or in a container. You really don't need it - a stock 302 will run fine on pump premium if it's tuned properly.

[lakeholme]

And have you priced aviation fuel???  AirNav has a feature for private pilots on fuel prices  They're suffering, too.  John's right! A tune-up would be cheaper and run just as well.  There are a couple of threads here on CRG about high octane and the consclusiion is always, "Why more than premium?"

[sd1968z28]

there is no way in the world you can get optimun performance on pump gas. 11 to compression 7000 rpm do not mix.
fine for crusing but not for full throttle blasts it just dosen't run the same!

[Chris_Pisane]

I run it. The lead is actually supposed to be good for the carb because of its lubrication qualities.

 I talked to a race fuel distributor years ago and he said just make sure  you use more of the av gas than premium gas or you are wasting your money.I also talked to a local drag racer and dealer mechanic who uses it in his drag car.He pulls  the engine apart about every 2 years and says he has seen no sort of problem whatsoever.

 I have run it in my 69 z/28 for 12 years,no carb problems.I could never get mine to stop spark knocking under a load  till I used the Av gas.I also believe the av gas wont go bad as fast as the pump gas you get nowdays.

I also  firmly believe in and use silicone brake fluid and sea foam. My 2 cents worth.

[fireZ]

Thanks for everyones thoughts on AV gas. I can buy 100 LL for about 25 cents more a gallon as compared to Sunoco 93 so I guess it is worth trying in my 68 Z .

[camaromikey]

Sea foam is the greatest stuff on the market. Its one of the few that lives up to what it says on the can.

[sam]

Let us know how you make out.  Sam

[GaryL]

there is no way in the world you can get optimun performance on pump gas. 11 to compression 7000 rpm do not mix.
fine for crusing but not for full throttle blasts it just dosen't run the same!

Sorry, you are wrong. As JohnZ says a stock 302 properly tuned runs excellent on 93 octane. This is an old tech engine. The 30-30 cam makes this whole thing possible. The dynamic compression on a stock 302 is like in the 7's.

I use silicone brake fluid also. Never tried Seafoam. What does it do?

[bertfam]

Gary,

You asked:

Never tried Seafoam. What does it do?

Apparently it stinks up the neighboorhood!! 

Click HERE.

Ed

[Flowjoe]

I'd never heard of sea foam until I read this thread over at Nasty Z/28 http://www.nastyz28.com/forum/showthread.php?t=89103&highlight=seafoam.

I have run my '69 Z on Pump premium since the motor was rebuilt  in '85 (bored .030 and running 11:1 compression on stock heads).  Until 2003 it had a single 4bbl (650 dbl pumper until '90 and the 4053 after that) and the cast iron exhaust manifolds with the "140" off road cam (what can I say..I was young and "stooopid" in '85 - bigger is better, right?)...as long as it was tuned it ran fine...compression was all blown off at idle and just off (of course that is also why it wouldn't pass smog back in the day ).  It now has a cross ram and headers with the "140" and still runs well on 91 octane pump gas.  Have dumped 100 octane racing fuel in a few times and it didn't really seem to make a difference (although the exhaust smelt better). 

[camaromikey]

I watched a guy do the same thing at the Parts store i work at. I sold him a can of sea foam and he went out and dumped straight in the carb of his 87 C1500. It caused a white out acrossed my parking lot and the street in front of my store. That not how you're suppose to use it. Its' a fuel system cleaner that boaters developed. You pour it in your gas tank or let the enigne suck it through a vaccum line. It cleans the carb or injectors, psitons, and the valves. I run a 600 cfm holley on my car and something got gummed up inside. Alls it took was a can sea foam and a tank of gas and it cleaned itself out. You can also use it as a motor flush.

[hotrod68]

104+ octane booster works great with pump premium, but don't get any on your fingers--they'll stink for 2 days! My experience has been there is no way in hell you can run a true 11:1 engine on 93 octane gas without retarding the timing so far it gets sluggish--even with a 140 cam, much less a 30-30. You might get away with it with aluminum heads and sloppy blueprinting, but a true 11:1 will rattle like Grandma's false teeth in a snowbank.

[GaryL]

104+ octane booster works great with pump premium, but don't get any on your fingers--they'll stink for 2 days! My experience has been there is no way in hell you can run a true 11:1 engine on 93 octane gas without retarding the timing so far it gets sluggish--even with a 140 cam, much less a 30-30. You might get away with it with aluminum heads and sloppy blueprinting, but a true 11:1 will rattle like Grandma's false teeth in a snowbank.

Do you own a anything with a 302 in it? I do and it is built stock and tuned as JohnZ says and it runs just fine on 93 octane. #72 primary jets, 36* total at 2800 rpm. AC45 plugs and 15* vacuum advance at idle. The factory setting was 4* initial. How far back do you think it needs to go?  And by the way the way the quench is approx .05". The factory set these engines up for smog and ran them lean and hot. I am not trying to argue but my 302 runs fine. You are correct with a more moderrn cam selection. Please go over to Team Camaro and read on the subject.

[Flowjoe]

104+ octane booster works great with pump premium, but don't get any on your fingers--they'll stink for 2 days! My experience has been there is no way in hell you can run a true 11:1 engine on 93 octane gas without retarding the timing so far it gets sluggish--even with a 140 cam, much less a 30-30. You might get away with it with aluminum heads and sloppy blueprinting, but a true 11:1 will rattle like Grandma's false teeth in a snowbank.

I used to run 104+ and the 108 octane boost products...thought I needed them.  Found out that they leave a lot of deposits on the spark plugs (just think what the rest of the combustion chamber looks like) then I  found a better carb guy and tuner...haven't run that stuff in years and the car runs great.

[hotrod68]

Hey, Gary--that was just my humble opinion. Meant no offense. 302 to 400, I've found that a small-block needs at least 10-12 degrees initial to run sharp, and you cannot run that much crank lead on 93 octane. 4 degrees is actually around where 93 won't rattle with that much compression, but you lose so much response and power it's sickening. And they need a quick advance curve--36-38 degrees total all in by 2500. I was talking about fine-tuned ultimate performance, not getting the engine to live on the crap gas we have today. Those engines were designed when you could buy 102-octane Sunoco 260 premium with real lead at the pump for 30 cents a gallon, and they were jetted fat, not lean. A DZ 780 Holley was calibrated to run rich--72 primary jets are not lean..chuckle. Try this; buy a tank of high-octane racing gas and bump your initial timing up to 10 degrees, then flog the car. I believe you'll be amazed at how much more responsive and free-revving the engine is, and how much more crisp it is. And you'll be delighted at the extra power turned loose. I may sound like a dinosaur, and I guess I am, but this is how they were tuned back in The Day, and those 302s screamed like banshees when unleashed on good gas. Just my humble input from a guy who was there. Good luck.

[lakeholme]

to run in a stock 68-302 car.

But the original question was about "stock".  And for those of us who were around back in the day, "stock" seems to mean something different today as well...

[GaryL]

Stock to me for a DZ engine is 11:1, 30-30 cam. Yes it is overbored .030". Original 186 heads with no porting, polishing or hard seats, original intake, points distributor. Stock primary jets were #68. The factory set these engines up to run lean and hot for smog to run the AIR system. I have #72 primary jets, 36* at 2800 rpm and full vacuum advance. These changes are only good tuning, still considered stock and what many 302 owners do to their engines. I will repeat it runs strong and good. Gas is gas. The only difference is octane rating. Higher octane does not produce more power by itself. You could not use a modern fast ramp cam with 11:1 and get away with this.

JohnZ knows his stuff!

[Jerry@CHP]

Have used Av gas since the 1970s.  It's good stuff and I still use it in my own personal cars. I even used it in my stock eliminator race car until NHRA banned it in favor of using fuels that they now accept.  Car ran the same ETs with Av gas and the high dollar VP and Sunoco fuels.

I add about five galllons and then fill the tank.  Also works great if you car is going to sit. 

I have found that the over the counter additives eat away at the carb parts.  They are not user friendly to the internals of your carb.  I have many customers who are living proof of this issue.

Jerry

[JohnZ]

I have found that the over the counter additives eat away at the carb parts.  They are not user friendly to the internals of your carb.  I have many customers who are living proof of this issue.

Jerry

Very true - the "octane boosters" like 104+ are LOADED with alcohol, which eats the plating off the inside of the float bowls and metering blocks, then its affinity for mositure goes to work on the now-unprotected surfaces and corrodes them. A friend of mine who has rebuilt Holleys and Q-Jets for decades has seen this for many years on carbs that have been run with 104+.

[bertfam]

Okay, so if 104+ shouldn't be used (or any other octane booster for that matter), what do you guys recommend for people that don't have access to avgas???

Ed

[jdv69z]

Would this be true as well for fuel additives/octane boosters from manufacturers of racing gasoline products? Eg VP or Klotz, etc.?

Jimmy V.

[GaryL]

Okay, so if 104+ shouldn't be used (or any other octane booster for that matter), what do you guys recommend for people that don't have access to avgas???

Ed

How about this.  http://www.hi-flow.com/HPOP5.htm

[Jerry@CHP]

Find the closest small mom and pop airport to you.  Buy three or four of the Jegs five gallon fuel jugs and go there, fill them up as needed.  Four jugs will last you for four tanks of gas.  That way you're not running back and fourth every week.  I have six of the Jegs jugs.

Jerry

[fireZ]

Sounds good to me I can buy it at the local airport without any trouble.

[sd1968z28]

listen to jerry guys, good gas make these cars scream!!!!!! i run my car 5 gallons of race gas per fill and it works!!!

[fireZ]

I went and bought 5 gallons of 100LL AV gas this morning and boy did the car run better. I thought it was good on pump gas but now it is a different animal. Thanks Jerry

[GaryL]

Now I am thinking I will try it.

[Pacecarjeff]

Okay, so if 104+ shouldn't be used (or any other octane booster for that matter), what do you guys recommend for people that don't have access to avgas???

Ed

I use 110 leaded racing fuel. half and half 110 --- 93
It is available from the Sunoco station down by the everglades boat stations
$5.75 a gallon. pump straight into you tank.

Don't run straight 100LL AV gas in your car-- the burn rate is wrong -it must be mixed

[sam]

How about buying 5 gallons of VP Racing gas from the  Farm and Home Center and mixing it with 93 octane to fill your tank up. Its about $5.00 a gallon. As good or not as good as the AV gas?  Sam

[Pacecarjeff]

Use the VP fuel whenever you can.
They make a very nice product -
 but pretty expensive  $7.95 last I looked. 
We are very lucky with all the race boats here in Florida.
110 is easy to get.
AV gas is not really good for your car.

[GaryL]

I went and bought 5 gallons of 100LL AV gas this morning and boy did the car run better. I thought it was good on pump gas but now it is a different animal. Thanks Jerry

Did you make any tuning changes?

What is VP fuel. Why is AV gas not good?

[Jerry@CHP]

Jeff,

The burn rate is fine.  We have checked this for many years on the dyno monitoring the EGT temps on the exhaust headers.  There are absolutely no issues with running the Av gas, I ran it straight in the race car for many years.  No issues with the valve seat areas either.  It's cheaper, about $350 a gallon now and it does get the job done for less $$$.  I have been using this in my cars for over 30+ years.  All of the additives are NG IMO.

Jerry

[Pacecarjeff]

AV gas was fine as long as it is mixed.
For a long time that was all we could get here - Did not like the way the cars ran if more than 50% AV was used.
Just heard some crazy stories about guys who ran pure AV. So I mostly stayed away. 

i LOVE the 110 leaded racing fuel
That alway perks everything up nicely.

FYI  --- VP is a fuel company - I think you can even mail order from them???
They sell all different grades of High test fuels - leaded and unleaded - fine product, but expensive

I used the VP 112 for a while, untill Sunoco opened up here for 2/3rds the price.
http://www.vpracingfuels.com/vp_01_fuels.html

[Chris_Pisane]

Smart man you are  FireZ,

You tried it and you liked it just as I did. I have 2 302 cars and run them on av.I mix  5 gallons of av to 4 gallons of premiunm. That is just my mixture no science involved,I was going by what the fuel guy told me, it just works for me.I agree with hotrod 68,my self I could not get spark rattle out of my green z without retarding timing so much it ran like a weak 305. Im sure you can tune like others said to fix it.But I find it easier to go to the airport with my jazz jugs, fill them, and mix as needed.

It only took me  5 gallons of av gas to  sell me on it. For those who want to pay  $8.00 a gallon feel free. I pay about around $.60 more a gallon for av gas than premium and I feel good about that.

 I hoped jerry would chime in on this one.Many years ago this same subject came up. I dont remember if it was here or Team Camaro, but Jerry brought up the fact that  lead  in the fuel was intended  for carb and valve lubrication,And how unleaded fuels didnt provide for that.He reccomended av gas.I was leary about using it myself,even after local guys told me about it until Jerry said it was cool and then I tried it,and the results were excellent.I then recommended it to another friend in town with a 302 69 Z. He has told me many times how much  his car " Woke up" after using av gas. Also where I live,I have no idea where you can by the Sunoco fuel everyone talks about.

Ive had people tell me av gas is no good,silicone brake fluid is no good,sea foam is a joke. I believe in all of them because they work for me.

Also Av gas is blue,my favorite color.

[zzmike]

There seems to be a lot of people hanging onto "octane" in this thread like it is the "be all, end all" in the world of power production. This is certainly not the case, or the extremely high octane (approx 130 points) of LPG and CNG would certainly create more power, but in real world application, everyone viewing this thread should be able to see that they do not.

Let's start with Aviation Fuel:
The octane of aviation fuel is not measured in exactly the same way as it is in automobile fuel.

The motor method of ASTM (which once stood for the American Society for Testing and Materials, but now is an internationally recognized standardization body) testing is used to determine the motor rating of aviation fuel. This differs from the R+M/2 methods used for traditional automotive gasoline.

Because of the different ways in which automotive and aviation gasoline octane is measured one must be very careful when comparing absolute numbers. 100 octane aviation fuel is not equal to 100 octane automotive gasoline, however, the lean number rating of aviation fuel will be close.

Now let's discuss Race Fuel:
The most talked about and most easily misunderstood characteristic of gasoline is its octane rating, which is a measure of how resistant gasoline is to detonation and preignition (knocking). It is measured relative to a mixture of iso-octane and n-heptane. So an 87-octane gasoline has the same knock resistance as a mixture of 87% iso-octane and 13% n-heptane.

So how do we get gas over 100 octane??  Because iso-octane is not the most knock-resistant substance available, and when other additives or substances to enhance octane are used in the refining and manufacturing process, it skews the standard that was developed back when Jesus was still a teenager. Everyone familiar with high performance engines is aware that racing fuels and aviation fuels typically have octane ratings of 110 or higher.

It can be said that fuels with higher octane ratings burn less easily, yet they remain extremely popular because they are thought of as being a more powerful fuel.  Manufacturers recommend using a fuel with a higher octane so that an engine can be run at a higher compression ratio without having problems with knock. Compression is directly related to power, so engines that require higher octane usually deliver more power.  This is usually where the misnomer of higher octane = more power stems from.  It cannot be stressed enough that the power output of an engine not only depends on compression (naturally) but also depends on the energy content of its fuel.  Where the confusion sets in is that no simple correlation between octane rating and actual power derivation (energy content) of the fuel exists. Some people believe that adding a higher octane fuel to their engine will increase its performance, but this is not the case.  Engines perform best when using fuel with the octane rating that allows for maximum power production without detonation or preignition.  Given today's advanced refining processes and additive packages, this is typically easily obtained without the gargantuan octane numbers of yore.

Just my $0.02

[GaryL]

What fuel do you use zzmike? I have my 302 tuned as JohnZ does and I use enough Octane 130 (TEL) to get 93 octane because we only have 91 octane California. I agree that today's fuel is better than years ago. The quality of modern fuel has been discussed on TC before.

[zzmike]

Funny you should ask.  I use VP C-12.  This is advertised as 108, I believe.  I have a mechanical compression ratio close to 13:1, as well as a Lunati custom grind that necessitates the need for higher octane, and then some, just to err on the side of caution.  The engine saw extensive dyno time at Nickens Brothers while paying close attention to BSFC, BMEP, EGTs, and effective compression which required a fuel notably less than the octane rating currently in the car (98, I believe is where the car made maximum power).  The extra octane points I run just to keep it safe, and the fact that the local speed shop always has it and the fuel has a stabilizer is a bonus, since I only drive the car about twice a year.

My daily driver is a 600 Rear Wheel Horsepower 4.6 liter, which has a screw style supercharger running 19 pounds of boost and it gets 100 octane unleaded.

[Jerry@CHP]

Funny VP came up here.

I use VP C-11 in the race car now.  Very expensive $$$$.  Used to use C-12 but dyno testing showed 4-5 more horsepower with C-11.  Just about everone in Stock Eliminator uses C-11 now.  Slower burn rate.  Don't have 600 hp at the rear wheels but do have 465HP in two of my Stock eliminator 302s.  No trick parts.  Stock rocker arms, .483" lift cam and no head porting or work.  Stock carb, intake.  10.80s at 122 mph in good air.  Car weights about 3250 lbs.

Jerry

[zzmike]

That's why you're the man, Jerry  .  Mine went over 500, but we backed it off a bit.  Nice to know what it'll do, but no reason to run the original block and heads on the ragged edge without reason.

P.S.  I am still looking for a set of original standard black door and interior quarter panels for a '68, just in case you happen to stumble over some.

Cheers,

Michael Parker

[hotrod68]

I ran 104+ in the '80s and early '90s and never had a problem--maybe the formula has changed since then. But when I went to the track I filled up with 50% 92 pump gas, 50% Union 76 racing gas in an 11.75:1 400 that ran mid-12s with 3:55 gears. I drove the car every day and the 104+ was a heckuva lot cheaper than racing gas. The curse of high-octane is like zzmike alluded to; it actually burns slower to arrest the flame front and stop pre-ignition and detonation. High-octane gas doesn't make more power because it burns better--it lets you make more power because you can advance the timing with higher compression for better combustion and engine response. It's a trade-off. You can take 2 identical cars on a zero-degree day and try to start them. The car with puke 87 octane will start, while the car with 108 octane leaded racing gas will likely need help with ether or kill the battery before it fires. Most people think hi-octane means hi-volatility, but it's the exact opposite. That's the dirty little secret.

[zzmike]

104+ uses MMT to better allow your gasoline’s ability to resist detonation and preignition through the use of manganese. A lot like lead, manganese releases vapors when subjected to the high heat and pressure during combustion that in turn stabilize the end gases in the combustion chamber (those in the quench area of the small block Chevy) and keeps them from being ignited by hot spots or spontaneously exploding due to intense heat created by the resultant pressure spikes in the combustion chamber at high engine loads. This is actually different than another members postulation that alcohol is the active ingredient, when in fact it is a relatively low quantity when compared to the other aromatics in 104+; but it is the manganese in the MMT that makes for controlled combustion.  It works, MMT is found in VP and Sunoco fuels, typically when the fuel is specified as containing metallic compounds other than lead.

[Jerry@CHP]

Mike,

All of these original door panels are getting so hard to find.  Good luck.  You'll have to hit every flea market and hit them hard.  Can still be found but like everything else, parts are drying up.  I wish the damn interior companies woud make them right. 

Jerry

[JohnZ]

That's like all the popular misconceptions about nitromethane - when I ran my AA/FD in the early 60's, we normally ran about 60% nitro/40% methanol (NOT the "100% nitro" the "Sunday-Sunday-Sunday!" track announcers would have the crowd believe back then). Nitro has a LOUSY octane rating, and burns very slowly - but it carries its own oxygen, and lets you run a lot richer mixture (more fuel). We ran Joe Hunt Vertex mags and 1:1 blower drives in 392 Hemi's in those days, and push-started with the mag grounded, flipping the switch on at about 20 mph; had to run 60* advance to avoid detonation through the lights, and it wouldn't start at low rpm with the mag on with that much advance. Some guys fiddled with Hydrazine as an additive, but I never touched it - you could tell the guys that did when we ran at night, as their header flames were green; they had to flush the remaining mix in the fuel system with alcohol in the shutdown area after every run, as nitro/alcohol/hydrazine became unstable, especially on a hot day. Nitro was about $900 a drum back then, and is about $1500 today.