69 302 on pump gas?

[69Z28-RS]

... portions removed...
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.

Interesting post...

but one clarification...  I suspect the addition of any kind of oil to the fuel in a car with a catalytic converter would NOT be a good idea???

[X33RS]

Good question Gary.    If you look at the Lucas Oil fuel additive it's recommended for all makes and models, as well as diesel.  I don't recall seeing any mention on those bottles about converters.  So not sure what to think about that.  But if I had to do a sniffer test I probably wouldn't have any in the tank for that, lol.

I used to use the Lucas fuel additive for years, but at $30 a gallon and a dozen cars it got too costly.  The mix ratio of the Lucas is also very large, so you use quite a bit more of it.  One thing I also noticed with Lucas, is that there seemed to be no ill affects if you had more than the recommended dose.  It is very forgiving.

The 2 cycle oil I've been doing is basically the same deal.  But I get a gallon of it for $13 and I mix a very small portion (4 ounces will do 20 gallons)   This seems to be the ideal ratio. So a gallon of this stuff will do about 600 gallons of gas.   The drawback is that it's not as forgiving when it comes to the mix ratio.  Get too much in there and you'll notice a little bit of a smoke show out the tailpipes.  Not harmful but performance suffers.

  I mainly started doing this just for the lubricity in the fuel, to lube the upper valve train components (valve guides, seats) as well as the upper cylinder walls as fuel is washed down and combusted.  I also mix an ounce in a 5 gallon can for the lawn equipment.   The 2 cycle oil with TCW3 in it also has mild detergents and cleaning ability (much like Lucas)

I also pick up a small MPG increase while using it.  Usually on average about 1 mpg is what I see. 

[BULLITT65]

Good thread (I just finished reading it).

So I have the original 302 in my car with just under 48k miles on it. To the best of my knowledge, from all the paperwork, and in talking to the original owners family the motor has never been out of it, or had any major service work done( ex: hardened seats installed, or stainless steel valves). My car is in northern Indiana, and the Citgo has 93 pump gas (sorry don't know the ethanol %). I have run that in the car for the last almost 1000 miles (since I got the car), and never had it ping or pre-detonate. Now mind you I am only around the car a couple times a year at best, but I do use it as a driver when I am in town, so I have been in traffic with it and it sees normal street driving. While there is not any hills in indiana to really put it under a load, I do tend to do a couple of hole shots with it on the back roads and the car runs really solid. Again this is with the stock manifolds, full exhaust (even the smog pump).
So as mentioned give it a whirl on the highest octane (91-93) pump gas you have locally and see how it performs. If you need to you can always take out a little timing and run a colder plug, or go the other route with a additive. I agree with Larry (x33RS) if you can see to putting a wide band in your car, you can really dial it in. You will never want to take that gauge out of your car once you install it. It is a great feeling to look over and see it at around 13 ( i have one in my 64 C/10)
Have fun and let us know the results.

[dutch]

Have a friend who runs a 302 configured stock and he uses local airplane (on floats) gas - 100 Low Lead that is mainly for radial engine aero stuff (110 is mostly in non radial engines around here) and he seems to like it.
He said the lead content compares well to older high test fuels for combating valve seat problems and the 100 octane rating is sufficient for use in motors such as his.
Lately the going rate - this is in CDN $$ and imperial gallons and was around $1.30 a liter when our best pump high test crap is in the $1.20 range and probably tainted with varying amounts of ethanol.
Not sure how that works out for a US gallon - but its in the $5.90 range here verses $5.40 - works and is well worth it according to his experiences!
I'm betting $5.90 per any gallon is far and away enough down in the States to buy any type of special or racing fuel - so consider yourselves lucky!   

[Z28Project]

As far as pricing goes, I just bought 15 gallons of Rockett 110 leaded for $6.66/gal. to mix with premium.

I haven't tried to buy avgas for years but when I went to buy some many years ago they wouldn't sell it to me!  Maybe that would be different now.

[X33RS]

Throughout the 80's we would occasionally swing into the local airport and could pump av gas right into the cars.  A couple of local gas stations sold good 110 octane race gas, and at that time it was $4 a gallon.  I used that on occasion.  As the years went on the price increased but what became the biggest issue was that we were no longer allowed to pump directly in the cars at the airport or at the gas station.  Had to resort to filling cans and transferring to the cars.  That gets old real fast.  It also limits the distance you can drive the car.    That same 110 octane is still sold at a couple gas stations but you'll pay $8 a gallon for it now, and you still can't pump it directly in the car.   No thanks.

After all that silliness we quit building ultra high compression engines for the street.   The last one my father had was a 12:1 motor with iron heads.   He was happy to see that engine go.   With the power that can be made on pump gas now we haven't built anything but pump gas engines ever since.  Dad's latest made 760 on crappy 91 pump.   If you truly enjoy driving these cars like we do, and go the distances that we do, making them run on pump gas is a must anymore.

In the case of the DZ engines, I still built mine with 11:1 to keep it authentic, but also because I knew it would run on pump no problem.   The overlap and off seat timing of the factory cam bleeds off enough low speed cylinder pressure that it will run fine on pump at 11:1 with normal timing curves.  Matter of fact, I wouldn't run this cam in the 302 with any less compression than what is advertised, it would just be a dog, with poor throttle response and no low end at all.

[Z28Project]

Good info!  Getting ready to have DZ engine built using JE pistons, stock heads and stock cam.  The piston domes look slightly smaller than the originals so I'm going with .030 head gasket instead of .039.  I'll see how it turns out.

[deadmetalprez1952]

Doesn't the dz come stock with .010 head gaskets?

[69Z28-RS]

Chevy's engine originally used steel shim gaskets, which are generally around 0.020"...

[deadmetalprez1952]

Have any of you guys milled the heads to use a modern say .041 head gasket but still maintain the factory compression ratio?

[Z28Project]

Oh.  Well I guess I'm not gaining anything at .030. 

I remember using the steel shim gaskets back in the day.  I used to paint them with aluminum paint on both sides before assembly.

I think I like the multi-layer type gaskets better for long term seal.  Any opinions on that?

[69Z28-RS]

If your domes are smaller, your compression will be lower..

If you use a thicker head gasket, your compression will be lower.

There are websites which allow you to put your engine data, including dome volume, head gasket thickness, etc and will compute both static and dynamic compression..

I wrote a very simple spreadsheet to compute static compression ratio which allows me to change any of the variables and see the effect...

[X33RS]

Have any of you guys milled the heads to use a modern say .041 head gasket but still maintain the factory compression ratio?

This is a critical area of the engine build for many reasons.

The factory had the pistons .020 to .025" in the hole.  With the thin metal head gasket and a 64cc head, you would be lucky to see the advertised 11:1 compression ratio.   During tear down this was all checked, with pistons in the hole pretty far, heads that CC a little large because the valves had sunk, my DZ had at best 10.5:1 to 10.7:1 because the deck height was uneven and quench was terrible.  (it's why these engines come apart on day one for stock eliminator blue printing)

Since we are talking about detonation, the ideal situation is to have tight quench.  Most engine builders will shoot for a total of about .40 to .45 quench with steel rods.  The tight quench promotes combustion motion/mixture and fights off detonation, also needs less ignition lead to make power.  Lots of benefits with this.    The worst way to go about this is having the piston in the hole and a thin gasket.
   The best way is to have the piston near zero deck and adjust the quench with the gasket being used.   You can get zero deck a few different ways with rod length and piston pin height changes, but it adds to the cost with custom parts.
    On my build, knowing what we had to start, we decked the block to put the piston .005" in the hole.  But you have to find a machine shop that is willing and able to deck the block without removing your engine stamps.   With that said, I then used a .038" gasket.   .043" quench is what we came out with.   We only gave the heads a clean up mill because we didn't want to shrink the chambers much, and used the JE factory replacement style forged .030" over pistons.  We came out with exactly 11:1 as measured.

Lots of engine building tricks like this, that help make power and in this case, makes the engine a little more octane tolerant.

[BULLITT65]

Good detailed info. thanks Larry

[bcmiller]

Mixing 2 cycle oil into the gas is nothing new.  I have done it in my trucks for years.  Like an ounce per tank.  Doesn't need much.

An old racers trick is to run MMO in aviation fuel if you think it is too "dry".

93 octane pump gas with a 302 can be done, but not universally with full timing.  Usually, as many have stated, you have to back the timing off or mix in some higher octane fuel.