69 302 on pump gas?

[cook_dw]

Wow, that's knocking a lot of timing out of it.

They will both run on the LOWER octane just have to knock the timing down to around 28 degrees total.. 

IE lower than 90..  Im not looking for performance on 87 octane.   Im not trying to write an article for Hot Rod or insert magazine here..  I pick a point where there is not noticeable knock and the plugs look decent and run it..  That being said; I try to never run that low of octane for the simple fact I did not wish to constantly adjust the timing..  Im not at the track and neither are the majority of the cars here on the forum..  Im not gonna bore everyone with useless knowledge that doesnt benefit anyone..  Its pointless and most will have glazed over eyeballs..  Original point was to the comment on the smell of the fumes and you can make it more pleasant with fragrance additives..  You can make one of these engines work on watered down 87  if you want but these engines were not meant to be done that way so why try to reinvent the wheel..  Run 90 or 87 or piss...  Get it to run on it and enjoy it..

Im out..

[deadmetalprez1952]

I have 93 octane in a few local pumps here, sounds like a lot of you guys can only get 91 for premium pump gas. Maybe I will try to run the 93 straight and see what happens. As a last resort I can always run 3 gallons of 110ll aviation fuel to a tank.

[Kelley W King]

I hear AV gas is not good. Formulated with high altitude and additives for plane engines. If you are local  to water, boat marinas usually have high octane and most are totally ethanol free, but it ain,t cheap either.

[X33RS]

Yep 91 here is as good as it gets.   I wouldn't call any of that useless information.  Anyone that calls themselves a true car enthusiast like myself will drive these things and enjoy them.  I already have garage queens and I'm sick of that.  Getting too old to just stare at these things.   My wife loves driving them and this Z was put back on the road for her to enjoy.  Since I had the opportunity to rebuild the engine, I took advantage of some tricks.
  But with that said, being who I am, I won't detune (deface) a real deal Z28 just to run cat pee in it so I applied what most good engine builders know.  I actually built this engine with the intent to run at the PS drags and followed the rules of that class.  The car is still getting a concours type restoration though.  I want the car to look correct in everyway, but it also has to run as good as it looks.  At the same time I had to run pump gas in it.  I was confident that we could run pump with 11:1 comfortably.  It's not a purpose built track car by any means and I hope I didn't come off that way, but I enjoy the hell out of the PS drags, running stock rubber, and that's the only kind of track time the car will see for a little fun.  Not enough 1st gen Z's compete in that class.  But it's still a street car first and foremost. 
I did the same recipe with my 70 Formula about 20 years ago and raced it quite a bit, but it too was primarily a fun driven street car that ran pump gas.  Back then we had 94 Sunoco.  Now it's running on 91 and complaining a bit.  That engine is currently getting some minor changes to make it happy.

I actually find the engine part of the equation just as interesting as the restorations I do and enjoy every aspect of it.  You can really squeak some power out of these things while still looking completely stock.  Fascinating stuff.   So I would tend to think that at least some of the true enthusiasts here would be interested in the same.

[bcmiller]

Engine designs have changed and a lot of us detune for street cruising.

302s had their day. Build a 10 or 11 to 1 small block 406 if you want power from off idle and want to stay small block. 572hp @ 6000 rpm is fairly easy to do. That's not the peak hp yet, just what it was run to on the dyno during break in. And it will rev to 7500 for shifts.

[X33RS]

That's cool, I like that stuff too.  My father built a 571 Pontiac that dyno'd 760 on pump gas.  He's driving that thing everywhere and loves it.  I'm currently doing a 502 BBC with AFR heads that should go over 700hp on pump gas, it will be going in my chevelle street car.

The Z was a different deal.  Running the Pure Stock drags, your stuck with what the car came with and very little wiggle room what you can do with it.  Besides, being a real Z I just couldn't bring myself to run anything but the 302 in it so a bigger engine wasn't in the cards for this car.  Even with it's limited size it still just topped 400 hp at 6700 and carried it to 7,000.  I was happy considering no porting anyplace and a stock type cam.     Given the rules though, The Z isn't the most advantageous car to start with anyway.  My firebird is a much better package for a class like this.  But it's fun either way.

[deadmetalprez1952]

The z motor I'm running is in a 55 Bell Air, it was put together in the late 60s and sat ever since 74. I don't really want to run a different motor because to me this car is a time capsule. It is untouched from the way it was built in the late 60s. I have thought about selling it and building a more street able motor bit that just wouldn't be the same...

[bcmiller]

Nothing wrong with running what you have. Just realize what you are working with and it's limitations.

[X33RS]

Yeah it's fun for what I'm doing.  Truth be told, if I really wanted to be quick in the class, and run a camaro, I'd build a clone COPO dedicated to the class and exploit all the rules, and have some fun without the collectability worries.  With the Z I'm limiting myself with what it's capable of.  I'm in the same boat with the firebird.   At the end of the day it doesn't matter too much though, they pair you with another car based on qualify time, and then run heads up best 2 out of 3.  So you never know what you're going to get.

[X33RS]

The z motor I'm running is in a 55 Bell Air, it was put together in the late 60s and sat ever since 74. I don't really want to run a different motor because to me this car is a time capsule. It is untouched from the way it was built in the late 60s. I have thought about selling it and building a more street able motor bit that just wouldn't be the same...

Understand totally.  I have a 56 Nomad, that's had a screamin' 327 since the early 70's when my father took possession (already in it so probably longer) and the car is untouched since.  I daily drove it in highschool back then and had a blast with it.  I just refreshed that motor/trans and 4.56's in it.  I have no plans to change the car from what it is/means to me.

[Bigblockbird]

There are so many factors contributing to running Pump Gas or not.
As someone said obviously timing is a huge factor but often people forget about fuel mixture.
By that I mean your Fuel air Ratio.
On my 1969 Z/28 Original 302 Double Hump heads correct factory Cam and a Winters Crossram with those two ridiculously overfueled carbs for a Street Car, I haven't once heard any detonation even under low rpm heavy load.
I do however make sure I buy 93 Octane Ethanol Free fuel.
While Ethanol can reduce spark knock it plays hell on rubber hoses mot made for an Alcohol laden fuel.
Is 10-15% Ethanol enough to be a problem. I don't know, but I will tell you this. Alcohol of any type requires a much bigger jetting and if you run an engine lean it is much more prone to pre-ignition spark knock.

[Mike S]

 Here on Long Island, all gas sold has 10% ethanol. It used to be seasonal but it is all season now. A product like Ethanol Shield will be needed.

Mike

[X33RS]

I'm probably one of the few, maybe the only one here that is daily driving their Z with it's 11:1 302 on pump gas.

I can tell you all the gas here in AZ is 10% ethanol.  I've also tested the gas with one of those cheap testers you get off ebay and found that even though it's advertised at 10% at the pump, I've found variations as high as 17%.   So each fill up can change slightly.

Ethanol requires a richer fuel mixture.   Normal stoich AFR for real gas is 14.7:1.   With 10% ethanol mixed in stoich is 14:1 so an increase in fuel consumption of .7 is required to maintain stoich.

I use a wideband to dial my cars in and tend to run them slightly rich to compensate for this.  It's the only way to tune these carbs precisely.   I also have the pleasure of dealing with major swings in altitude, living at 5,000 ft and routinely driving as high as 7,000 and down to sea level.   Fun to find a happy medium that works well everyplace.  Lots of practice knowing what works, and can't do it without that wideband. 

What I also do with my gas is mix in 1:5 ratio (1 ounce per 5 gallon of gas) of 2 cycle oil that has TCW3.  This acts as a lubricant in the fuel.  Lead used to be your lubricant but that is now gone.  But it also has cleaning properties and has cut down on carbon buildup on a couple engines I've torn down with long term use.   I'm not sure if this has any counter active affects towards the corrosion of the ethanol but I'm happy to report that after 10 years of using it in 12 different cars here I've never had any fuel related corrosion issues anyplace in the fuel systems.

[deadmetalprez1952]

Thanks for all of the input. I have been researching avgas and I'm gonna try running a premium fuel/avgas mix. The local airport has it self serve for around 4 bucks a gallon and all of the local dirt track guys buy their fuel there instead of the expensive vp fuel.

[X33RS]

Have you tried just running straight premium pump gas yet?  What octane is in your area?

I'd certainly try pump first and save your money.    We have crap 91 here and the Z is doing fine on it.