Technical Embarrassing gasoline smell

I rebuilt my flathead a few years ago. Followed the guidelines, did those things the rebuild books and resources told me to do.
The setup is:
bored 1/8th over, offy heads, offy regular dual intake, two rebuilt Holley 94s, an Isky cam, Fenton headers, Pertronix Flame Thrower coil and Pertronix Ignitor ignition.
I battled constant leaks from one of the Holley's only to find some remnants of helicoil from the previous owner...grr.
That being said, the motor is in a F-1 pickup and has plenty of ummph for the truck.
My point is: the truck has a gasoline smell and I'm sick and tired of it. I would appreciate some suggestions.
I've rebuilt the carbs 4 to 5 times, but mostly that was to locate my leak (that ended up being broken helicoil in the bowl feed inlet). I am willing to rebuild them yet again.
My thoughts:
1) the engine seems to idle best at 15deg BTDC, but I'm not hung up on that number.
2) an engine rebuilder has suggested that the full charge isn't being burnt and to lock out the distributor and only work off the initial advance, but increase the initial.

I can see the understanding of advancing the initial but worry about ping and run-on.

With the larger cam and dual carbs, what is the suggestion on the initial advance?

3) go to smaller jets
4) go one number up on the power valves

any thoughts would be appreciated, because I'm getting tired of having a nice truck that no one likes to ride inside of because of the g***y exhaust.
Oh, and there is a hint of gas in the oil...grr.

Thanks.

 

Jerry, time to get that post count up...You've been lurking...

I have 94s and yes they can be g***y, you've rebuilt them 4-5 times so you really are probably on top of things...

In hot temps I've had percolating when I pull into the garage...seems to happen in very hot temps outside...

Float levels are critical and can be played with a little to make sure the gas doesn't overfill the bowl...sticking floats, leaky floats, sticking needle valves, clogged with ****...I had a fuel filter glue give hold and some of that glue made it's way to to carb, it caused starvation issues, some minute pieces got thru the needle valve into the carb but not sure it caused any issues inside...

I have noticed when I go around corners sometimes I smell more fuel for some reason...I always thought it was the float level...I played around with that a fair bit...

How about Fuel Pressure...1.5 psi...I went to a modern 1-4psi Holley regulator with an allen key adjuster that over a sometimes unpredictable Mr Gasket one that has given many headaches...

Is your tank vented?

Vacuum advance?

Mixture Screws are obviously important...

Holleys have 3 positions for the pump in the carb on the side...1, 2, and 3 or winter , summer and extreme summer...

All your ignition, timing and even fuel matter to...It's tricky really...

I am not an engine carb/guy so I was going to have everything set by a Hotrodder/retired GM mechanic but that didn't pan out this year...

Lots of 94 Threads if you do a search...Tons in fact but lets see what the others have to say...

 

My stock merc 8cm is at 24degrees always and starts and runs fine for what it's worth

 

Does it smell of raw fuel? I find that poor burn at idle/low revs due to wild cams doesn’t. It’s more a noxious chemical smell.

If it smells of raw fuel I’d look elsewhere.

If it’s bad burn you can’t really lean the mixture, the best way is to use timing; more initial and or vac advance.

 

What do your plugs look like? Got pictures of them cold before start and after shutdown, while the engine is still hot?

 

If using rubber hose use the low permeation type

 

What is in there now ?

 

Time for an oil and filter change also……..

 

You need an Air Fuel ratio gauge, upper right on my dash. My 250 always smelled of fuel, once I installed the gauge, I knew why it smelled. It doesn't take long to figure out how rich it's running, 3 or 4 miles of driving will give you a good sample of readings. I have a 250 inline six with dual Carter W-1 carburetors, they use metering rods so I was able to pick and choose rods that would solve the over rich conditions from idle up to full throttle. 95% of the smell is gone from my truck, I now get some lean exhaust smell sometimes, but nothing as bad as the fuel smell was. You will be amazed how much the A/F changes with just a little twist on the idle mixture screw. My fuel milage went from 14 to 21 on the highway, and I thought it was running good at 14.

Mine generally stays around 15 to 17:1 A/F on the highway on level ground at 65 mph, around town the gauge is always moving, but still around 15:1, idle is 15.5:1 and a littler richer with a/c on. Full throttle, 13.5:1. Fuel changes everything depending on the ethanol content.

You might also look at your fuel tank vent, mine would stink up the garage. I made a carbon can that is mounted under the bed near the tank. The tank vent line runs to the bottom of the charcoal and the outlet goes to atmosphere. With this, all vapors from tank must p*** through the charcoal, and while running, fresh air flushes the charcoal as it enters the tank. There is a filter to keep the charcoal out of the tank. This setup really cleaned the air in the garage. I still get smells from the carburetor throats as it cools off, but it dissipates as the motor cools.

 

Raw fuel vents from the locations it is stored, the gas tank and carb float bowls. Unburned or partially burned fuel vents from the exhaust. Modern fuel is less volatile than old fuel, but still vaporizes.
As mentioned old carbs tend to vent more, so making sure the float level is set properly is crucial, and keeping the carbs cool can help. Venting the tank to under the truck rather than at the cap will help too. Make sure the exhaust isn't heating the tank. As for the combustion, make sure the carbs aren't leaking extra fuel and the mix is slightly lean.

 

Is the crankcase vented with a road draft tube or a sealed PCV system? A properly working PCV system will help remove fuel vapors (blow-by) and moisture from the crankcase and reduce fuel dilution in your oil.

 

I will answer each response here:
STOGY
- you guys know too much so I'm a little intimidated and my build wasn't fully done, plus it's a truck so it really isnt a Hot Rod, more like a resto-Mod,
- had percolating but I always let the truck sit outside before pulling in for the evening. (respectfully not my concern),
- I checked the floats numerous times; I double-check each float on each rebuild, "measure twice, drive once"
- no cornering issues, which kind of makes me think the floats are good
- 1.5er on the psi. but I will double check it. ty!
- tank is vented
- it's a Pertonix Ignitor so there's no vacuum advance, I'm stuck with initial
- my fingers got raw and singed from the mixture screws...lol. 4 half turns out. she idles great.
- i thought about the enrichment slots but I always keep it in the middle position

the gas smell really is exhaust related. and I'm not sure I can explain it but the grands don't want to get in the truck and I have 8 of them. But it could be me...

 

road draft tube is in place. I wondered if I could recycle the fumes but for now, yes sir, the road draft tube is in place ( no obstructions ). know how I know?
EVERY person who looks under the hood says "What's that?" LOL. Even the Master Mechanic at the shop.

 

48s and 6.5.

It just feels big for dual carbs.
I was thinking of going to 42s with 7.5. I'm 800 ft above Sea level. The truck is more like a cruiser than a street beater. but all input accepted.

 

If I HAD 14 I would be doing cartwheels. I think it's at 8 right now. (Embarr***ed)
where are you pulling vacuum for the gauge. The offy intake only has 1 port and I have PB and a C4. so I'm not sure if the reading would be accurate, but I'm always up for an education.
I'd REALLY be interested in getting more info on your charcoal solution.
My brother has been on me to put an A/F gauge on it. hmm...okay.

 

oh clem if you only knew. I only have 400 miles of road time and about 30 running hours on the motor. So...yeah, (Embarr***ed) let's just say it just doesn't feel right, right out of the box.
Thanks Clem.

 

57...could you be more precise? are you talking fuel line?
I'm fuel line (rubber) from the tank feed point for about 18 inches, then steel line for about 8 feet, then fuel line (rubber) to the fuel pump, then rubber to the fuel regulator (1.5 psi)
does that help?

 

Do you get the odor all the time when the vehicle is parked, or does it just linger initially when parked and then go away later or the next day? I'm thinking if its always there it may be the gas tank vent, while a carb problem should gradually go away...........but thats just a guess.

 

not really, it's more the exhaust smell. i recall my dad having issues with the SB305 station wagon and it never smelled this bad.
it percolates some when I get done driving but only when it's really hot and that's like 103 out...not sure why I even try to drive it then but...i do.
I will try more initial since the electronic ignition does not take a vacuum input.
I'm a Computer Engineer so i should fix that. hmmm...perhaps.

 

no sir, it's not always there. which leads me to believe it's a burn issue, since there is a gas smell to the oil. the truck has 400 miles on it. I changed the oil just after the first 50 miles. but I will change it again.
I get it that some of the gas in the line needs to retreat, but I do not know of a good check valve solution or if I should even use on.
Thanks EK.

 

Alan, I was never good at reading plugs, given some times a lean condition can look like a rich condition (once you get it close).
I will pull one today, usually 5 is the worst, if you could call it that.
To me they'll always looked like the burn is rich. but consider my first remark.
Thanks Alan. (my middle name)

 

For percolating add 1/4” phenolic spacers under any or each carb. With todays fuel they are a must and available on the “bay” for just about any carb base or manifold.

 

Thank you WheelTramp Brian. no stumbles, any hesitation?

 

Maybe a fish pranked you and hid some gasoline in your truck...
My Grandpa had a truck that always smelled like gas. We would roll down the flatuance dampers and it would go away.

On a serious note, I remember that most of the older trucks had a gasoline odor and when I asked about it as a kid, no one could figure it out. Wasn't that before charcoal filters were used?

 

If it were only that simple. Thanks Dave.

 

dnkt...thanks Jimmy Six!!

 

I don't think your giving yourself credit...I'm no genius either, Never been a mechanic but I'm mechanically inclined. I had my carbs rebuilt by a friend who did a good job with them but after a few years issues cropped up and was chasing stuff just like you...I took the carbs off and tore them down to make sure the openings were clear...I'm never to proud to have an ace give it their magic...Many here are those aces...Much of my know how with these came from right here...

I did say I was going to have a Retired Mechanic who is also very knowledgeable Hotrodder look at my setup from timing, plugs, idle, mixture...etc. things didn't pan out this year for that meeting but I still tinkered trying to get thing running as well as I could...

If you have fuel in the oil that's sounds like it's either dumping fuel into those carbs or the plugs are so fouled that it's getting flooded in the cylinders and it's seeping into the oil...

You do say it runs good though so hmmmm, Aans suggestion of pulling All the plugs and looking at them is a really good one...My plugs were pretty fouled was'nt my biggest problem but was a peice of the puzzle...better burning does make a big difference...

Jerry, the Hamb is a place to share and learn...thanks for sharing...By the way Trucks can be Hotrods...Just my opinion though...

 

I should do this too...hope it doesn't effect my linkage movement...it already hits the distributor cap at wot...who knows maybe it'll help...

 

What’s your exhaust set up?

 

Just replace them...they may be failing...one of the cheaper things to do as well...sometimes a hotter or colder plug is an option, that's where my knowledge goes sketchy but it may be something that will make a difference...