Leaded 110 Octane

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Re: Leaded 110 Octane

Postby jOe » Tue Jul 30, 2019 11:24 am

For even more laughs, try it with 12:1 pistons
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Re: Leaded 110 Octane

Postby Lisa » Tue Jul 30, 2019 12:05 pm

jOe wrote:For even more laughs, try it with 12:1 pistons
You got it LOL
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Re: Leaded 110 Octane

Postby jOe » Tue Jul 30, 2019 12:43 pm

It hurts just thinking about it
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Re: Leaded 110 Octane

Postby panic » Tue Jul 30, 2019 2:03 pm

Assuming high octane is available, an XL with auto-advance distributor and hot cams may have better idle quality and low speed response by shortening the advance travel distance (about 30°) by about 5° and adding this to the normal 15° initial advance, so:
Old 15° + 30° = 45°
New 20° + 25° = 45°
[url="http://victorylibrary.com/BTHP.htm"]H-D Flathead Breather Timing for High Performance[/url]
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Re: Leaded 110 Octane

Postby Ferrous_Head » Tue Jul 30, 2019 3:01 pm

Leas added to gasoline reduces it's volatility. It doesn't burn as fast. It axts in a similar way to the control rods in nuclear reactors. The use graphite rods between the fissionable material to slow the fission process sufficiently to keep it from "running away" in a chain reaction. Detonation in a gasoline engine is similar. You interrupt the combustion process by introducing a stable substance that doesn't burn.
Ideally are engines would burn all of their furl at the optimum moment which is around 73-76 degrees ATDC. (This varies with the stroke). But it's impossible for this to happen. We do a "controlled burn" which, becuase it does take time, starts dome 40 odd degrees BTDC so that at the required point ( 76 ATDC) the maximum amount of pressure is produced by the combustion process.

Using higher octane fuels in an engine that doesn't require it is going to cost you performance. ie, the engine won't perform at it's optimum even if you adjust timings to suit the fuel. Pound for pound of fuel higher leaded fuels produce less BTU's.

I think you'll find the KR's all ran on standard, not "Hi-Test" fuels.
"I know only too well the evil that I propose, but my inclinations get the better of me."
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Re: Leaded 110 Octane

Postby LDB » Tue Jul 30, 2019 3:09 pm

Occasionally I hear people claim that higher octane burns so much slower than lower octane that it makes a difference in where to set the timing at a given speed and load. Also, some claim that the higher octane burns so much slower that it will make a richer mixture and cause carbon buildup and plug fouling. The truth is today's gasoline is so "clean" that any carbon buildup in an engine in proper tune is most likely oil that has come up the cylinder passed the rings and burned with the gasoline, leaving carbon deposits behind.
Actually, the difference in detonation rates between lower and higher octane is in microseconds and will not have any effect in fuel/air ratios.
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Re: Leaded 110 Octane

Postby jOe » Tue Jul 30, 2019 4:12 pm

Ferrous- I feel a need to interject a correction here. Control rods in a nuclear reactor are usually boron or cadmium ( there’s others). Graphite was used in early reactors to build up around the cores. The rods absorb the neutrons. The principle you outlined is absolutely correct- the materials were a little off.
SCRAM it when in doubt.
Hope I didn’t sound like a Bogan.
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Re: Leaded 110 Octane

Postby panic » Tue Jul 30, 2019 4:18 pm

Jerry Branch recommended regular gas for the KR in the famous June 1965 CW interview with Gordon Jennings.
The "73-76" crank position is not based solely on the stroke length, but on the ratio of connecting rod length to stroke length (usually referred to as "n"), in an XL this is 1.95:1: 7.4375" ÷ 3.8125". At this point a typical engine has its crankpin (close to) at 90° to the rod beam, giving maximum leverage.
[url="http://victorylibrary.com/BTHP.htm"]H-D Flathead Breather Timing for High Performance[/url]
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Re: Leaded 110 Octane

Postby Lisa » Tue Jul 30, 2019 6:26 pm

The higher the octane the cleaner the burn.
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Re: Leaded 110 Octane

Postby LDB » Tue Jul 30, 2019 7:56 pm

Higher octane fuel burns no cleaner. However, different brands can have their own proprietary additives that the companies can claim makes their brand run cleaner but there are no conclusive tests or studies by any unaffiliated private entities to prove it, nor even the government.
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