Use of 110 Octane Leaded in 327

[Donald M.]

Does anyone see any disadvantage in using 110 octane leaded (Phillips 66 racing)fuel in a stock'67 327/300 (10.25:1)? I periodically ran it about 2 years ago and it was great,like bolting on 25 more horseopower! I ran about a 4:1 ratio (Unleaded premium:racing gas)and it seemed to be just right. I would not run a steady diet of this stuff, but would like to use it for an occasional "blast".

[John H.]

Re: Use of 110 Octane Leaded in 327

Don -

The key disadvantage I see is to cash flow I also have a '67 327/300, and it runs great on good old unleaded pump premium. Burning leaded vs. unleaded will reduce the service life of your spark plugs to what it was in the 60's (remember regular tune-ups/plug changes?), but you probably don't put enough miles on it annually to make a difference anyway.

[Dick W.]

Re: Use of 110 Octane Leaded in 327

What most people do not realize that leaded racing gas has a greatly reduced amount of lead compared to the racing gas of the '70's

[Duke W.]

Re: Use of 110 Octane Leaded in 327

Ditto what John said, but the other thing to consider is timing. Different year 327/300s have different total WOT timing depending on the max centrifugal and initial. With a 25 percent mix of 110 octane leaded in unleaded premium you should be able to run more total WOT timing - up to 38-40 degrees, and a more aggresive curve, which would improve low and mid range torque.

If the timing is set to operate detonation free on unleaded premium, adding racing gas will probably not make any noticeable difference, however, on unleaded premium it could be experiencing inaudible detonation that is reduceing power. Higher octane means you can run more timing across the entire rev range which should raise the entire torque curve.

The actual specified CR of the 327/300 is 10.5, but the actual is probably in the range of 10 to 10.25 for a production machined engine.

Run

[Loren L.]

I am told - and can only say that it works -

that low lead av gas has more lead in it than the old leaded premium. Whether true or not, the '60 with popups likes it just fine when mixed with equal parts unleaded supreme.

[Clem Z.]

Re: Use of 110 Octane Leaded in 327

most race fuel has .15% by volume TEL

[Clem Z.]

100 octane LL avgas

has 2 grams per gallon of TEL.

[Lenn #40977]

Re: 100 octane LL avgas

So, for us unedumacated folks what whould that be by volume. Anyone know what it was back in the 60's?

[Richard G.]

Re: Use of 110 Octane Leaded in 327

What mix would you guys recommend for an original L71, straight-up Cam2 or a mix? I try to run it on straight Cam2, like to keep the lead straight. Duke/Clem, What timing would you use, would love to hear your opinions.

[Rich G.]

Re: Use of 110 Octane Leaded in 327

Rich

My 68 L71 was owned by a pilot friend who only ran 100LL avgas in it. I have continued that except I did run 1 tank of 93 pump gas and really noticed no difference. He drove the car about 2000 miles in 2 years and I have only put about 300 miles on it, so it is a small sample. (4:11 gears give me the opportunity to purchase gas often .) I feel better if I have at least a third of a tank of 100LL but that is not very scientific. My 66 L79 also seems happier on avgas. Whenever I'm at the airport I usuall throw 5 gals in. The exhaust smells better too. I'm interested in what other responses you get.

Rich Giannotti

[Duke W.]

Re: Use of 110 Octane Leaded in 327

The actual octane requirement varies depending on timing, inlet air temp, A/F ratio, actual compression ratio (both of which will vary cylinder to cylinder), local air density, which is highly affected by altitude, and other more esoteric factors. In short it will vary day to day, hour by hour, and certainly with the seasons.

The trick is to find the combination of initial timing and centrifugal advance curve that allows any engine to operate mostly detonation free most of the time.

Ideally this can be done with available pump premiums, but if a specific engine has more octane appetite that requires severely retarded timing, then your option is to find two fuels in the proper blend that gets the job done. Or with a higher octane blend you can run a more aggressive timing map, which will increase torque in the lower to mid range because you can get the total WOT timing in sooner.

There aren't any magic formulas. It's a matter of your ear, how much cost and inconvenience you are willing to put up with, and how good you are at juggling the ignition map.

Sixties vintage fuels had more lead than today's 100LL avgas, and commercially leaded racing gasolines probably have a comparable amount. In fact leaded regulars had almost as much TEL as premiums, but the super premiums such as Chevron Custom Supreme and Sunoco 260 had the most. Old leaded premiums derived their higher octane from a higher octane base stock blend, which usually included a higher percent of aromatics that have high inherent octane. Then about the same concentration of lead was added to both to bring the RONs to 94 and 100 which would be approximately equivalent to todays PONn or 87 and 96.

Lead is usually specified as grams or cc per gallon, and I tend to get the two confused, but in some notes I have for Unocal leaded 110 says the TEL content is
3 grams/gal. Some spec sheets I have for some other locally blended racing gasolines in So Cal list lead content of 4 grams/gal.

Duke

[Dennis C.]

Re: Use of 110 Octane Leaded in 327

I (re)build the engine with 9.5 compression ratio and drive it with "premium". It works. Trying to do much more raises the gas price from about $1.80 to $5.00
It is good to get real with what your real long term intent is. I must admit, I absolutely love the exhaust smell of leaded race gas, but unless faced with a match race, will save that for a suicide run in the garage...

[Joe L.]

Re: Use of 110 Octane Leaded in 327

Don-----

Unless you run greater initial advance to take advantage of the high octane, I can't see how this gasoline could possibly produce any significantly greater power level. Even if you do run greater initial advance I wouldn't expect that the power increase would be worth the cost or inconvenience of obtaining the racing fuel.

As I've said before, running fuel with high lead content is great for octane and marginally (and arguably) easier on exhaust valve seats, but it's BAD for everything else in the engine. That includes spark plugs, carburetors, other fuel system components, exhaust systems, and more. For me, unleaded fuel is THE way to go.

[Lenn #40977]

Re: Use of 110 Octane Leaded in 327

Would this include an original engine that has never been opened (no hardened valves)?

[Clem Z.]

there is enought lead on the valve and valve seats

so there will be no problem. unless you race or run under heavy loads for a long period of time you do not need any lead in any engine to prevent valve seat erosion