Running lean, suggestions

[Tigger72]

Here's the problem im trying to work on my '72. Running lean i believe. Tell me if im off and push me in a direction based on my notes below. To start, i believe my timing to be set well based on vacuum, yet the timing light says 15deg at 5700ft elevation with that dizzy setting. Ive set the idle mixture best i can and idles good. And I've done vacuum tests at the riser and also vacuum measure is fine at idle :

• Hard to start cold even in warm weather
• Runs "good" when up to temp BUT poorly till warm
• Exaust smells
• Lost power under load even when warm (this is a recent change for the discussion) but no jerking or stalling under load

What i see:
I rebuilt the carb myself and used a sonic parts cleaner to clean it with a rebuild kit. Mistakes could of been made as its my first time through it. Same jets it has always had and ran well for 50+ years at the same elivation. Adjusted the float so when parked and turned off after running, fuel level in the window is just above half. But at idle, the fuel level is well under half in the window. When parked over night, fuel level drains to low in the window. It has a new fuel filter. But the original fuel pump. No fuel leaks that I can see.

Suggestion i was given was a weak fuel pump. Or a weak hose connection causing a poor vacuum to pull fuel.

Is there another suggestion out there based on experience where I should isolate or start my search in another direction.

Thank you!

 

[Paul_A]

Will it run better with the choke partially closed?

 

[wimberosa]

I'm having hard start issues on a '79 but I've convinced myself that my igniter is weak. Consider making sure the electrical passes the FSM spec procedures.

 

[cruisermatt]

Why do you think it is running lean?
Why do you have your timing set at 15-degrees?
What is your actual idle RPM?
What is your actual vacuum measurement at idle? (“Fine” is not a measurement)

 

[samatulich]

What do the spark plugs suggest? They'll let you know a lot about your fuel mixture.
Have you tested for intake leaks? Base of the carb may not be air tight.
Backfiring at all? Lean would Backfire through the carb, rich through the exhaust.

 

[Tigger72]

Will it run better with the choke partially closed?

When warming up even on hot days, but not when idling warm. I havnt tried it under load though. Ill try that when I get it back out.

 

[Tigger72]

I'm having hard start issues on a '79 but I've convinced myself that my igniter is weak. Consider making sure the electrical passes the FSM spec procedures.

That was last summers adventure! Ha new dizzy, e points, and all else met spec. Im hoping thats all cured now!

 

[Tigger72]

Why do you think it is running lean?
Why do you have your timing set at 15-degrees?
What is your actual idle RPM?
What is your actual vacuum measurement at idle? (“Fine” is not a measurement)

I dont know for sure if its lean, but a guess based on symptoms. If im off, im game for more suggestions! Lags and weak at take off and on hills, was told the exaust smells like its running lean, and the tough cold running but runs better warm because of fuel needs.

I most recently set timing by max vacuum and backed off slightly till smooth. To see where it landed, I puth the light on it and advanced till BB was at the needle and 15deg was where it was happy. It is weird for sure and the flywheel could be off but in the history of the vehicle, its never been torn down that far to be reinstalled wrong far as we remember. Could be part of the problem wanting to run more advanced?

Idle RPM is set at 665-670. Thats as low as I can get it right now before the adjuster screw backs off the scallop after my last idle mixture adjustment. Also weird.

Vacuum measures at 16.5in at almost 6000ft elevation which i read is well in the window. True?

 

[Tigger72]

... I puth the light on it and advanced till BB was at the needle and 15deg was where it was happy... by this i mean, I advanced the light setting to see where the vacuum set landed, to be clear.

 

[Tigger72]

Let me ask a specific question to confirm or deny what I've been collecting off other threads. This is based on what I see in my float bowl window.

What i see: when parked and off, fuel level just barely above middle. When idling and raised RPM, fuel level in lower third of window.

From what I've been reading, i ask this for confirmation: When parked and off, the level in the bowl doesnt matter. When idling and running, fuel level should be in the middle (or close) of the window.

I want to confirm because this would mean while I run, and my fuel level in bowl is lower third of the glass, im lean and need to re-adjust my float. Is this true?

Or is there a port i failed to clean well enough? Or is my fuel pump on its way out?

Thanks!

 

[cruisermatt]

... I puth the light on it and advanced till BB was at the needle and 15deg was where it was happy... by this i mean, I advanced the light setting to see where the vacuum set landed, to be clear.

The BB is 7-degrees.
Typically these run best with 10-11 degrees.
So if you wanted 11 degrees you would set your timing light to 4, which you would add to the base 7.

If you actually have 15 degrees of base timing I am surprised you can get it to idle that low.

 

[65swb45]

(Edit)
What is your actual vacuum measurement at idle? (“Fine” is not a measurement)

My new sig line!

 

[65swb45]

15” of advance at your elevation is fine IMO.

And raising your float level should improve your situation.

I don’t know why people can’t get it into their heads: the FSM is a handy reference guide; it is NOT the bible. YMMV.

None of my rigs run factory settings.

 

[charliemeyer007]

I don’t know why people can’t get it into their heads: the FSM is a handy reference guide; it is NOT the bible. YMMV.

None of my rigs run factory settings.

That's the truth for sure

 

[Pighead]

and 15deg was where it was happy...

Good, that's how I found out my engine likes to be timed a bit more advanced than what the book says.

 

[cruisermatt]

My point was more to make sure the OP was actually using the timing light correctly as a lot have the misconception that the advanced setting on their light is what their timing is at, and not acounting for the 7 degrees of base timing.

 

[pb4ugo]

It's better to use the TDC mark and the adjustable timing light strobe .

 

[Tigger72]

Winning. Spent a lot of time adjusting the float, off and on with the top of the carb many times, as the spec in the manual didn't work out at all! Needed to stop WAY lower than book calls for. It holds solid just a hair above half way up the window. Gunna let that be! Runs better than it has in a long time. I also re-tuned the idol mix and tested the timing against vacuum and have increased my vacuum to 17.5 (57000 ft) and timing is now at 13 deg.

Funny thing is, I am pretty convinced my BB on the fly wheel is at 0. I can't for the life of me find a definite TDC mark, (but highlighted one that could be). But with it Idling at peak vacuum at 650 RPM with Vac Advance hose off, it likes 13 deg and at this elevation, that sound pretty good compared to adding the 7 degrees for where the BB typically is and thinking is set to 20 deg. Does anyone else have a BB at 0? Am I off somewhere?

Thanks for your help all!

 

[mattressking]

15” of advance at your elevation is fine IMO.

And raising your float level should improve your situation.

I don’t know why people can’t get it into their heads: the FSM is a handy reference guide; it is NOT the bible. YMMV.

None of my rigs run factory settings.

Factory manual is perfect for all, but those who like to tweak, then it's a great baseline. 15* is fine at 5900 but I'd be curious to see if vacuum drops quite a bit at 7* for testing purposes.

 

[Tigger72]

Factory manual is perfect for all, but those who like to tweak, then it's a great baseline. 15* is fine at 5900 but I'd be curious to see if vacuum drops quite a bit at 7* for testing purposes.

Agree! I will test a bit in my next free time. Though running WAY smother and more predictable, I am still lacking a little power. Seen mist under load at speed. For example, it's a three speed, so plenty of RPM at 60mph, and not long ago id be able to maintain 60 or at least 55 up certain hills around me. Now on those same hills Im close to needing to down shift. I did go from a 235x70 to a 31x10.5 tire, that might be it, but the tire size doesnt seem to be that different. Thoughts?