Stupid question time...

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Stupid question time...

Post  BigRigTech on September 11th 2014, 7:39 am

Rolling Eyes Very Happy  I was under my car last night and I noticed something new. Last year I ran a 50/50 mix of supreme and av gas. My headers were always black with soot inside. This year I'm running straight AV 100 which I'm told is leaded and my headers are spotless inside. They look like they were washed out with brake cleaner they are so clean. Is this normal? My 1050 has 96/96 jets in it since the dyno and the plugs looked ok to me when I pulled a couple at the track.
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Re: Stupid question time...

Post  Dave C. on September 11th 2014, 8:13 am

Is it faster?

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Re: Stupid question time...

Post  BigRigTech on September 11th 2014, 8:51 am

Yes,  I rebuilt the engine last winter and made several changes from last year. Basically I only reused the rods, crank and block - everything else has be changed. Went from. 10.90's in crappy air to 10.30's in the same air.
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Re: Stupid question time...

Post  gt350hr on September 11th 2014, 12:09 pm

The change in color is common. "Street" pump gas almost always leads to black tail pipes. Race gas and AV gas burn much "cleaner" at the tail pipe/collector

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Re: Stupid question time...

Post  69F100 on September 11th 2014, 12:36 pm

When the exhaust is black most of the time it means you are running rich and when the exhaust burn a light tan color mean the air to fuel ratio is pretty close on spot. But if it never changes color you are to lean and your plugs should show a lean burn look, my Dad always used the plugs and the color of the exhaust to tune all his before everything changed to fuel injected. I learn this when him and my brother raced a 69 Mach 1 Mustang and I use this way when messing with a carb engine.


Last edited by 69F100 on September 11th 2014, 12:51 pm; edited 1 time in total
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Re: Stupid question time...

Post  dfree383 on September 11th 2014, 12:46 pm

Sounds lean to me.

With the pump gas it should be a little bit black.
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Re: Stupid question time...

Post  BigRigTech on September 11th 2014, 12:57 pm

I'll take a pic tonight. I couldn't believe how clean they were compared to what I'm used too seeing in the collectors. I'm running pure AV 100 now for fuel, no mixing like last summer.
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Re: Stupid question time...

Post  gt350hr on September 11th 2014, 3:01 pm

Your collectors need to at least be light grey to tan . Out here in California , I run my daily driver fairly lean on 87 ( pure white porcelin on the plugs) yet the tail pipes are still pitch black. This happened after the lead was taken out and other CRAP was put into the gas so we can breath easier.

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Re: Stupid question time...

Post  dfree383 on September 11th 2014, 3:06 pm

You also need to watch switching between a mix and strait av gas. IMO you need to run it strait up and stop mixing and get a good tune with it.
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Re: Stupid question time...

Post  BigRigTech on September 11th 2014, 3:33 pm

I've never run this on mix. I ran last year with 10:1 compression but it has 11.4:1 now so it sees av only.
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Re: Stupid question time...

Post  kim on September 11th 2014, 5:34 pm

The higher compression will net a cleaner burn even at idle. Most sooted tail pipes are sooted at idle and post WOT shut down where the air demand is idle yet the fuel column is still flowing at WOT.

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Re: Stupid question time...

Post  BigRigTech on September 11th 2014, 10:15 pm

Like I said they are clean...LOL





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Re: Stupid question time...

Post  IDT-572 on September 12th 2014, 6:57 pm

Leaded fuel will turn the collectors white. Looks good to me!
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Re: Stupid question time...

Post  514F-1 on September 13th 2014, 12:53 pm

Looks Ok, I run 110 in mine, and my headers are a nice light grey. If they are black, its too rich. Very Happy Very Happy
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Re: Stupid question time...

Post  butterbean on September 15th 2014, 10:38 am

Down here in Florida 100 AV gas is called 100LL and its a low lead fuel, maybe you could try adding a lead additive or a octane booster and see what happens, but the burn looks pretty good now but it may be a little lean in the cooler months, JMO,
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Re: Stupid question time...

Post  maverick on September 15th 2014, 10:54 am

butterbean wrote:Down here in Florida 100 AV gas is called 100LL and its a low lead fuel, maybe you could try adding a lead additive or a octane booster and see what happens, but the burn looks pretty good now but it may be a little lean in the cooler months, JMO,

It's only a "low lead" fuel when compared to the Avgas of old. The old aircraft fuels had a ton of lead in 'em. Current "low lead" Avgas has roughly the same amount of tetraethyl lead as our old leaded pump gas.

Its other (often overlooked) benefit is that it stores very well and doesn't go bad quickly like the crap at the corner gas station. An awful lot of aircraft sit for months at a time in all kinds of weather with minimal ill effects to the fuel. Try that with your favorite auto gas. Rolling Eyes
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