My Fuel Mixture is Too Rich

Bill G_old · June 5, 2011 at 8:04 PM

I wonder if one of you guys could give me some advise: lot's of black soot on tail pipes. The choke opens all the way when closed. Should I reduce the fuel mixture? Which adjustment is that? Thanks guys.

Bill G.

C6ZZKGT · June 6, 2011 at 8:00 AM Official Post

Bill, Did this happen recently or has it always been this way?

-Fred-

65Rangoon_old · June 6, 2011 at 8:13 AM

Several things I'd check: Ignition timing & idle RPM set properly. With a vacuum gauge and engine at normal operating temp, optimize both needle valve adjustments for best idle and max idle vacuum.

Verify spark plugs are the correct heat range, float levels are correct, and that the primary and secondary main jets are the correct size. Also, the power valve can be faulty (even loose) or the wrong vacuum operating range, causing excessive fuel to be dumped into the engine.

Last but not least, I'd ohm check the plug wires to ensure they aren't part of the problem.

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zray · June 6, 2011 at 8:31 AM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Bill, Did this happen recently or has it always been this way?

-Fred-

exactly what I was wondering.

If this has always been that way, then re-jetting might be in order. But if the issue is recent, then there is usually an underlying problem. Could be as simple as a plugged up air filter.

Z.

cobraboy · June 6, 2011 at 11:04 AM

Since leaded fuel has disappeared it is no longer possible to get nice grey tailpipes after a run. They are always black now.

But as said, a tune up can only help.

zray · June 6, 2011 at 5:15 PM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Since leaded fuel has disappeared it is no longer possible to get nice grey tailpipes after a run. They are always black now....."

I think it also has something to do with the grade of gasoline. My daily driver (SVT Focus) runs on premium gas and has always had a black tailpipe. So does my '66 which of course is also using premium gas. My partners Focus runs on regular gas and the tailpipe on her car is new looking and without any residue.

btw, do your eyes burn from an excess gassy smell? Thats a sure sign the engine is running rich

Z.

Edited by - zrayrichter on 06/06/2011 20:26:41

Bill G_old · June 7, 2011 at 12:44 PM

Hey guys - thanks for the comments. Some feed back from me:

The black pipes have existed for couple of years.

I use Sunoco 93 octain gas.

Carb rebuilt / restored by Pony Carbs 3 yrs ago.

Kar otherwise runs like a raped ape. Starts immediately and does not die out. Thanks, guys.

Bill G.

Bill G_old · June 7, 2011 at 12:47 PM

Oh yes, one more thing. After the kar is relatively warm, it idles around 600 - 700 RPM with choke all the way in. After it is real warm and toasty, idles at 900 RPM with choke all the way in.

Sound normal?

Thanks.

zray · June 8, 2011 at 7:40 PM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Oh yes, one more thing. After the kar is relatively warm, it idles around 600 - 700 RPM with choke all the way in. After it is real warm and toasty, idles at 900 RPM with choke all the way in.

Sound normal?

Thanks.

yes

jwc66k · June 8, 2011 at 10:52 PM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Oh yes, one more thing. After the kar is relatively warm, it idles around 600 - 700 RPM with choke all the way in. After it is real warm and toasty, idles at 900 RPM with choke all the way in.

Sound normal?

Thanks.

An idle rpm of 900 as normal? Hell no! Try to get an idle speed of 550-650 rpm (the "book" says 750 rpm but I say try for lower).

Jim

zray · June 8, 2011 at 11:29 PM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Oh yes, one more thing. After the kar is relatively warm, it idles around 600 - 700 RPM with choke all the way in. After it is real warm and toasty, idles at 900 RPM with choke all the way in.

Sound normal?

Thanks.

An idle rpm of 900 as normal? Hell no! Try to get an idle speed of 550-650 rpm (the "book" says 750 rpm but I say try for lower).

Jim

may be possible with the autolite, but not so likely with a bigger Holley (715). Even with the smaller autolite, I'd surprised if many people who drive their car year-round can get an idle speed under 700 without fiddling with it every time the air temp goes up or down 10 degrees.

Still see nothing wrong with an 900 rpm idle.

Z.

MTS_old · June 9, 2011 at 7:59 AM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Oh yes, one more thing. After the kar is relatively warm, it idles around 600 - 700 RPM with choke all the way in. After it is real warm and toasty, idles at 900 RPM with choke all the way in.

Sound normal?

Thanks.

An idle rpm of 900 as normal? Hell no! Try to get an idle speed of 550-650 rpm (the "book" says 750 rpm but I say try for lower).

Jim

Would have any worry about getting enough oil to the lifters with such a low idle? I think you might be safer up around 900.

BoS_old · June 9, 2011 at 8:18 AM

My 65 Shelby with the big 715 cfm Holley 3259 and original engine

with stock HiPo cam idles fine at 750rpm. Produces 16 inches of mercury vacum at that idle.

/Bo

jwc66k · June 9, 2011 at 10:37 AM

Note I stated "try". I got mine down by "tinkering" because I wanted to. It is a goal, primarily to keep any advance from the distributor at zero. I do this on my "A" code Mustangs and on my VW Baja and sandrail.

Jim

Back to the original post, assuming it's an Autolite, check the power valve. They do go bad.

J

Edited by - jwc66k on 06/09/2011 10:40:25

Bill G_old · June 9, 2011 at 2:07 PM

Talking to John Enyart at Pony Carburetors & he says HIPO Autolite should idle at 900 RPM.

Bill G.

jwc66k · June 9, 2011 at 6:16 PM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Talking to John Enyart at Pony Carburetors & he says HIPO Autolite should idle at 900 RPM.

Bill G.

At 900 rpm, the distributor has around 6 deg advance. That's where you start getting all of your advance at idle, which is not desirable.

Jim

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