# Gasoline smell after hard acceleration



## Jim K (Nov 17, 2020)

Greetings to all the Indian head fans out there.
I've been trying to correct a strong gasoline smell on the deceleration after a hard, petal to the metal, acceleration. I've tried jet/rod changes, accelerator pump arm adjustments, idle screw adjustments, etc.. etc.. I *can make adjustments *and pretty much get rid of the fumes/smell, but then I've got a bad stumble on initial acceleration (from any RPM) and when I adjust out the stumble then the smell returns on deceleration. My AFR gauge reads about 13.5 at cruise, 13.0-13.5 idling and down to 11.5-12 on acceleration.
My set up is 2x4 bbl Edelbrock performer 500CFM carbs. I'm using the back carb as primary on a progressive setup. I have the choke set up on the back carb only. I'm using both sets of idle mixtures (to keep from a lean cylinder condition on the front). Ignition is set at 16 deg. advanced at idle (Ported vacuum disconnected) Eddy Performer RPM RA IV heads, exhausted through Doug's headers w/2 1/2" pipes, all wrapped around a +.030" 428. Ignition is a pertronix 3rd gen w/60K volt coil.
Cam is a custom Crower grind, mechanical roller.
I'm at about 5,000 ft elevation and have leaned out the carbs considerably and currently have the accelerator pump arms set up on the leanest hole connection (which adds to the stumble).
I've considered adding a choke to the front carb and setting them up in parallel, thinking the front mixtures are adding extra fuel while the primary carb is the only one in operation, or just junking out the Eddy's in favor of going back to Q-jets.
Anyone have any thoughts/Ideas on how to correct this smell/fumes issue and NOT be so lean as to cause a stumble?
Thanks to all.


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## GTO Rambler (May 20, 2021)

By chance do you have a PerTronix igniter? If not, my point is mute. If so, I have found that there is an issue with not getting a full 12 volts to the PerTronix due to the resistive wire that limited the voltage that the points would see. I had the same issue at acceleration. Not burning like it should and running rich.


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## PontiacJim (Dec 29, 2012)

Your spark plugs should tell you if you are running rich.

Hook your vacuum advance back up to a manifold source and try dropping the Initial to get around 19-21 advance.

What does your distributor curve look like?

What kind of engine vacuum number? Power piston springs matched to engine vacuum?

If both carbs are not hooked up together and you are using a progressive linkage, I would shut down the idle mixture screws on the front carb - not doing anything except dumping excess gas into the engine.

Plugs gapped to .035"? Maybe 1 step hotter plug?


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## BearGFR (Aug 25, 2008)

Have you checked your float levels to be sure they're not too high? You might also try fitting pieces of vacuum or fuel hose over the car bowl vents to "extend" them, in case the source of the smell is fuel sloshing out of the vents during deceleration.

Bear


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## Jim K (Nov 17, 2020)

GTO Rambler said:


> By chance do you have a PerTronix igniter? If not, my point is mute. If so, I have found that there is an issue with not getting a full 12 volts to the PerTronix due to the resistive wire that limited the voltage that the points would see. I had the same issue at acceleration. Not burning like it should and running rich.


Rambler,
thanks for your reply/input. I'm almost positive I'm running a full 12 volts to the pertronix (yes it's an igniter 3) but it's been almost 12 years since i put it in and something I'll go check again since at 64 years, not sure I can trust my memory 100%.


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## Jim K (Nov 17, 2020)

PontiacJim said:


> Your spark plugs should tell you if you are running rich.
> 
> Hook your vacuum advance back up to a manifold source and try dropping the Initial to get around 19-21 advance.
> 
> ...


Thanks Jim,
I'll experiment around with your suggestion on the vacuum connection. As for the curve, it's 32 total all in by 2800 RPM.
Vacuum at idle is 16", at 2000 RPM it's 22". Of course it briefly goes up drastically when the carb plates close.
I'll close off the front idle mixture screws and use the primary carb screws to reset the idle mixture.
Yep, plugs are at .035" gap. I haven't looked at them since I seldom have the car out in a "normal" drive, although I need to drive it far more than i do.


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## Jim K (Nov 17, 2020)

BearGFR said:


> Have you checked your float levels to be sure they're not too high? You might also try fitting pieces of vacuum or fuel hose over the car bowl vents to "extend" them, in case the source of the smell is fuel sloshing out of the vents during deceleration.
> 
> Bear


Thanks for the input Bear.. Yep, checked, double and triple checked float levels. Pressure to the carbs is regulated to 5.5 PSI since Eddy's are pressure sensitive. It'll drop to about 3-3.5 when I open up the throttle. I did find some point of contention as to "where" to measure the float top end. Some material suggested the tip end of the float, others suggest at "mid" body on the float. I found it seems to work best when I measure from the "mid" point for float height. Float drop is at factory stated settings.
I thought about the very thing you mentioned around the carb bowl vents but Eddy's vent through back through the air cleaner and there's no "venting protrusion" that I can even find.


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## Jim K (Nov 17, 2020)

PontiacJim said:


> Your spark plugs should tell you if you are running rich.
> 
> Hook your vacuum advance back up to a manifold source and try dropping the Initial to get around 19-21 advance.
> 
> ...


Woops, forgot to reply to your inquiry around the power piston springs. Yes, I believe they are. I'm using the springs 7" of vacuum. even though I have 16" at idle, the springs for 8" vacuum were on the ragged edge of too much. They would oscillate up and down at idle since my cam has a fair amount of overlap and the vacuum signal to the intake plenum/carb would vary at a rapid rate.


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## GTO Rambler (May 20, 2021)

Jim K said:


> Rambler,
> thanks for your reply/input. I'm almost positive I'm running a full 12 volts to the pertronix (yes it's an igniter 3) but it's been almost 12 years since i put it in and something I'll go check again since at 64 years, not sure I can trust my memory 100%.


Not to be redundant, but if you have a resistive wire you are not running 12 volts unless you ran a separate wire. I thought I had 12 volts until I measured 8.75 and the tech at P freaked out.
Being a 64, I'm guessing you have a ballast resistor you have to wire to the other side.


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## Jim K (Nov 17, 2020)

Okay,
Finally found some time to tinker on my 71, I do have +12V to the Pertronics.. Thought i did but couldn't be absolutely sure since it was so long ago I installed it.
Moved the vacuum advance to manifold vacuum. Checking w/timing light it shows app 18-19 advanced w/vacuum advance connected. 
closed off the front idle mixtures completely. Reset primary mixture screws a few turns richer. Idle AFR is between 14.5 and 15.5 with a few leaner spikes. (given my camshaft, it does vary a fair amount).
Cruising AFR is around 15-16 now. It started to rain so I didn't stay out on the roads long. Last thing i want is that beast on slick roads. BUT.. that familiar throw your head in the back seat torque/acceleration is better than it's been since I moved up here from the gulf coast.
Tuning on the carbs as suggested by Jim has made the exhaust note a lot crisper and sharper than it had been. I made a quick video in MP4 but haven't as of yet, figured out how or if I can attach it here.


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## integrity6987 (May 10, 2017)

When I experienced this it turned was a loose connection of the fuel line into the Qjet. Was not an active leak - more a weep. But you could smell it and see a little on a shop towel.


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