Technical Embarrassing gasoline smell

I saw where you mentioned that you have an electric fuel pump, and that it take a while to pump up. So here are some random thoughts.........no, guesses.
First there were some counterfeit pressure regulators being sold a while back and their accuracy was questionable. Don't know if they are still a problem. When you start your engine you mention that it takes a while because the fuel flows back to the tank. That really should not be happening, at least not completely which makes me su****ious of the regulator. Also, you mention 1.5 lbs of pressure which is pretty low and I wonder if the regulator is accurate at that pressure.
Something you might try before starting your engine for the first time, turn the pump on and don't start the engine. Letthe pump run a little bit and pressurize the system and stay that way......and see if you get the gasoline smell without running the engine. Also look into the carb and see if there is any fuel dribble or strong gas smell. I would do the same thing before you ever turn the pump on, just to see what it smells like after setting over night, then you can see if there is a difference when you run the pump and after you are done running the pump. What I'm looking at here is if there is a problem with the system itself and not with the carburetors per se. Might tell you something, and might tell you nothing, but doesn't cost anything to try it.

 

This post will probably get deleted but its just an fyi. If you really want a carbureted engine to be most efficient, there are simple aftermarket devices that monitor the exhaust g***es and keep a desired Air/Fuel ratio within a small window. You can set the air fuel ratio you want and the system adds air to the intake to lean out the mixture. You can jet your carb a little rich and the system adds air to get your targeted air/fuel ratio. You can operate it with a smart phone or a tablet. There is a similar system for ignition aslo. You can adjust the ignition timing from your phone or tablet and set any timing curve you want. I'm not suggesting anyone on this site do it, but the options are out there. Beats fuel injection in many ways in my opinion.

 

I have two Stromberg 97 carbs on a Tattersfield high rise manifold on my flatty and had to make my own jets to lean them out enough. They were way too rich at the beginning and everything stinked badly after running a couple miles, even fouled the plugs. Found a couple horses with the leaner jets but still I had some smell in the cabin despite long and gastight exhaust pipes ending at the rear bumper. The fit of a PCV valve into the manifold did not solve my problem so I got rid of the little filtered engine breather on top of the pump tower and replaced it with a sealed cap. Led a 1/2" ID hose down through the manifold into the crankcase and let its other end hang down below the wishbone to act as a road draft tube. The pump tower got an oil separator. Its just a tube hanging from the cap that has vertical slits for the fumes to enter, oil will never make it up that tube as it needs to crawl upwards 5" before it could exit into the 1/4" hose that enters the airfilter direct above the inlet of the front carb. Never have any oil residue in the carb nor any smell around the car or in the cabin when standing at the lights - but I can still smell the exhaust when standing behind the car. When on the move there is of course no smell at all.

 

EK, This is what i have been doing for a few months.
Guys, it’s subtle. Its not like there is a cloud following my truck around.
The kids noses are sensitive to it and i then notice it. My wife says “what smell?” So go figure.
I will heed as much input here as i can achieve.
All your input and time spent reading and typing is far beyond my ability to repay.
I will share what I find good and bad
Thank you folks for taking time. I truly appreciate it.
Today i will replace the plugs with wider gap and go with a higher heat index plug. Thank you again.

 

The gas tank is mounted in the rear between the frame rails. There is no room to extend the tail pipes, but thanks for your time and insight!! My preference would be to have tail pipes. No room at the inn.

 

Jerry, you really have a lot of help on this one!
I replied earlier, and you have got confirmation on those. You have also supplied more info about the problem and components.
So along with your own list of things (including spacers!), I'll echo the exhaust routing to the rear and add one more simple check. Remove the hood. This will allow venting the underhood and cooler carbs.
The quality of the build from the pics shows nice work, but was the firewall fully sealed engine to cabin?
Pulling the hood might prove this out. Hope it wasn't a bear to align.

 

Been following along but can't recall all the details. How do we know the fuel pressure is 1.5psi? If its via a gauge how do we know the gauge is accurate? I'm not necessarily suggesting having calibration tested but I know, from recent experience, some of the liquid filled gauges, probably manufactured you know where, can read horribly low, but once the rubber bung has been removed a few times, burping the gauge, better readings can be obtained. I understand its to do with the gauge internally pressurising, reducing or even cancelling the true reading. If you had say 7.5 showing as 1.5 you could have serious overfuelling. Just another straw to clutch at!

Chris

 

After you sort out your tune-up to help cure what seems to be a rich running condition:

***uming manual chokes, are you sure they're fully open at normal engine operating temperatures?

Airflow under a moving vehicle tends to be a mess. If at all possible route the exhaust to exit outside of the body lines. The further back the better. Pockets of turbulence under the cab and bed may be trapping exhaust and trying to force it into the cab at certain speeds. The lowered stance of your truck may or may not be making matters worse.

An older road-draft c/case venting system doesn't really do much unless the vehicle is moving down the road. A proper PCV system will do a much better job under more running and driving conditions. It should also help to increase the life of the oil and increase oil change intervals.

Plug any unused holes in the firewall and floor pan. Make sure there's seam sealer applied where needed. Are the door and window weatherstrips properly fitted and in good condition? Installing a full rubber floor mat or carpeting can help prevent exhaust and dust from finding its way back into the cab.

When you get around to cleaning up the underhood wiring, pay particular attention to where the harness p***es thru the firewall on the driver's side. Try to find a proper grommet or at least a section of rubber hose to p*** the wiring thru. Mainly to prevent the wiring from chafing, but also to seal off another air leak from under the hood.

 

That is the correct way to go. We have seen a lot of issues over the years with those round dial POS. The Holley is a one and done and looks/works a hellofa lot better. That and your car won't burn down.

 

My fuel tank is also at the back between the rails, my single pipe goes out under the frame rail around the tank. Not much heat in the pipe that far back, so tank expansion is not much concern on mine.

Fuel cannot return to the tank once the level in the float bowl goes below the needle/seat opening, very likely your are have the same problem everyone else does with fuel evaporation and fuel creep. Todays fuels evaporate much faster than it did years ago. Fuel creep is the film of fuel you see all around the gaskets and openings. No matter how tight you get them, fuel still creeps out and stinks, and it doesn't take much to stick!

 

And depending on the pressure being delivered by that pump sometimes a return line to the tank can alleviate the pressure that remains after shutting down the car.

My roadster has a large in tank pump so I installed a return style regulator in line. The only issue with that is the "carburetor" return reg can only dial down to 4 PSi. I had to install a 12-804 to get the pressure down to 2.5 PSi for my Stromberg's to be happy.

Another tip on pressure gauges, since these old carbs require so little fuel pressure it is best to use a gauge with a 0-10 PSi range so you can dial it in accurately. A gauge with a 0-100 (for example) you can't tell 5 PSi from 10 and 1 or 2 PSi won't even move the needle.

 

I smell gas in my Chevy with tank behind seat. Never thought to look there, so we smoke outside... J I C.

 

I have been using these exact ones for years without an issue.

A gasket goes underneath them, and accounts for the radius, if it is there.

A little file work could remove it, too. Just thoroughly clean afterwards.

I just swapped three 7.5's for three 2.5's on a customer's 270 Red Ram Hemi.

The eye watering sooty little ******* is now a smooth little rocket.

 

Do them Hotrod style 60s scavengers I think they call it...I really should do that with my Coupe as well, it's difficult as I like blowing the leaves and dust off the pavement and the noise of course...

 

You could put heat shrouds to eliminate heat issues...I suspect there's a way...both you and I might have a private sigh and whisper to one self...why didn't I do this sooner...

 

Thank you, it was in another Thread on Regulators and you made the case for this one...and it's shiny...

 

Update:
Thanks men. I pulled the plugs and found some rich fouling. the former gap was .028. I've increased the gap to .038, found a small leak on the rear carb and ran it to the regulator. The pressure gauge was reading 2.5, but my bad, it was set to 2.5. That answers those questions on accuracy and consistency from the measurement equipment.
Last I moved it, it was set to 1.5...so...sorry on that.

So I moved the regulator back to 1.5. it was reading between 1.5 and 1.7 or so.
After finishing putting in new headlamps and putting on the new trim rings from WVintiques. I replaced the plugs, checked for gas leaks.
Got in and it fired up first crank. it's never done that. as in never.
I stood behind the exhaust and the smell was pleasant to me. no it did not burn my eyes.
It idled great so I took it for a short drive and I felt nearly as carefree for the first time ever. I wasn't fiddling with the choke (btw...the choke was fully open the whole time). it was pleasant.

the result is there was zero gas smell. none. it was actually pleasant, but one must not linger.

So the causes I've come across so far:
- tight gap on the plugs
- likely over-pressure on the rear carb (which begs it needs a rebuild; adding that to my list)


So I'm giving the prize to:
1) 52HardTop for suggesting a larger gap
and
2) place to Stogy for the "it might still be breaking in".

On tap tomorrow, is to:
lower the idle, increase the initial advance to 20 BTDC, take a longer drive, pull the plugs check them for tint.
The exhaust was absolutely not an issue. I'm totally happy with it.

Lesson learned:
The larger cam and overbore necessitate increasing from the stock setup.
BTW...I found the receipt from Patrick's for the cam, it's a 3/4 race per the receipt...still don't have the total lift and dwell yet.

But props to 52HardTop has me going the right direction. But thanks to all who've replied. you're all great.


so far:
1) (done) check that my pressure regulator is set to 1.5psi
2) (done) change the plugs (Champion 844-1; H10C); check the tips
a) (done) set the gap to 36
3) oil change
4) a skooch more advance; 24 sounds aggressive since the idle is good but 15 doesn't feel like enough
5) check the fuel lines from the tank to the carb
6) order and had some carb spacers
7) based on 2) check the integrity of the plug wires
8) get an A/F gauge and install it
9) get a Vacuum gauge and install it

 

Great work Team Hamb... Jerry they are a work in progress so pretty optimistic report there...Lucky guy gets to drive...I'm parked for the season...

 

That's the pressure gauge I'm using...0 to 10. thank you.

 

Hey Jerry, thanks for that Major Award! I'm a humble guy and like to look for a simple solution to something that shouldn't be so complicated. I got lucky and my experience with my old Chevy inline made me say to myself, Self, why not offer that as a possibility? I'm very happy it all worked out. I don't deserve all the honors when this place is an absolute treasure trove of mechanical brainiacs and there is nothing these guys can't solve. I hope the Grandkids will now go for a ride. Our Grandaughter will have a few neat rides to choose also before we know it!

 

I have checked the oil twice since you asked, just to confirm and I do not smell gas in the oil, despite my previous ***ertion.
I have a regulator and a gauge, the regulator is set to 1.5 psi and the gauge reads just over 1.5 psi. I am replacing the gauge next week.

 

Update;
so far, tips I will do:
1) check that my pressure regulator is set to 1.5psi (DONE)

2) change the plugs (Champion 844-1); check the tips (DONE)
a) set the gap to 36 (set gap to .038)
b) after a short run around town, 2 - 3 - 5 - 8 were rich fouled
- the Offy regular intake is closed plenum; thus 2 and 5 run off the same throttle tube and 3 and 8 run off the same throttle tube, so I've backed off the idle mixture screws for those cylinders, oddly it's both the p***enger side throttle tubes that show rich fouling...hmm.)

3) oil change ( the oil was still opaque and did not smell of gas so I will wait until after the New Year to replace it)

4) a skooch more advance; 24 sounds aggressive since the idle is good but 15 doesn't feel like enough (DONE, I moved it to 21, but the throttle response isn't what it was, so I'm going to back it to 18BTDC)

5) check the fuel lines from the tank to the carb (DONE, no leaks on the lines, I did find the drain plug was seeping gas at the higher psi, but it's dry as a bone, but I'm still going to rebuild both carbs)

6) order and had some carb spacers

7) based on 2) check the integrity of the plug wires (DONE while checking the plugs)

8) get an A/F gauge and install it (my Ford guru wants to know why)

9) get a Vacuum gauge and install it (order next week)

 

Very proactive on Ole F'ee...it must feel reborn...

 

No more stinky truck. Yay.
Better gas mileage, too.

I was getting frustrated by page 2.
Had to jump to the end to see how it was going. Sooooo glad you and the guys finally figured it out.

Ok...
Good thing I stopped by.

 

yes, it has been a learning experience for sure. I looked at my 'old flathead' books and there are mentions of kicking the initial advance and leaning out the carbs, but I guess things kind of ***ume "you've done this before".
I have but not on a 2 bbl dual carb setup. I had displaced that my intake was a closed plenum, well, it's kind of a DUH moment.
I am going to drive it like this, (which is great btw... thanks to all who replied and recommended) for another month, maybe into January, see if the plugs clean up and then do a proper oil change and another once over.
So the truck is idling now between 750 and 800 rpm (which is an exciting development), idles fine in light to light traffic, and has enough oomph to outrun Karen in her Lexus to the merge lane, when I'm in the lefthand lane.
I have no issues with the truck or the tune now, but I got people that see "uh old truck" and pull out in front of me.

So my defensive driving patience is being tested.
But for the update:

1) check pressure regulator (DONE)

2) change the plugs (Champion 844-1); check the tips (DONE)
a) set the gap to 36 (set gap to .038)
b) after a short run around town, 2 - 3 - 5 - 8 were rich fouled
- the Offy regular intake is closed plenum; so I dialed 1/4 turn on all idle screws, will check burn in mid December

3) oil change; mid-December

4) a skooch more advance; (DONE, I moved it to 21, but the throttle response isn't what it was; i left it at 21btdc and with the 1/4 turn on the idle screws the response is better.)

5) check the fuel lines from the tank to the carb (DONE)

6) order and add some carb spacers ( I will get these in January; truck budget; 'Baby needs a new pair of shoes' )

7) check plug wires (DONE while checking the plugs)

8) get an A/F gauge and install it ( I'm balking since the gauge is a 'one time tune after the tune is right thing' and most of these cost 400$ plus taking the truck to the muffler shop to get a bung weld in. if things go south next late spring/early summer I will tap the savings account )

9) get a Vacuum gauge and install it (backordered because Homer didn't research correctly)



Thanks everyone!!

 

I had a similar problem, replaced the carb, no more gas smells in my garage.
Drove me nuts, as I thought it was always running rich, but was a crack somewhere in the carb.

Is a better option to just go to a car tuner or find some one nearby ( possibly a Hamb member) who can stick one up the tail pipe to read it ?

I have only skimmed through the posts, but did you change out the power valves to 3.5 or 4.5 for each individual carb ?
And I seemed to have missed the jet size, (from what most on this forum say is normally 51), did you leave them at 48 or change them ?

I am running 2 of the larger holleys on a sbc but also went one plug size hotter, from 5 to 6, with NGK plugs, (my preferred choice of plug). So far, not many miles, only a few hundred, - but running the best it has ever run.

 

Hey stinky, you get it fixed? (Sorry I just can’t help myself sometimes)

 

yes. no offense taken. my grandkids would have agreed with you.

Yes, the gas(eous) smell is remedied.

 

I was so put out when I'd found it. because I won't put helicoil in anything, that helicoil had been in there since the day I bought it. a tap never touched it when I would clean the threads and finally I found and got a fitting from Speedway and it wouldn't seat...wtheck? Found my leak issue.

Great idea!

what I found in the carbs were a 4.5 and a 5.5. I changed them out to new 5.5s.

I found my note the other day...I swapped in 45s, at the same time I put in the 5.5 PVs.

I have been an ABC guy for many years. But I chose Champions this time and these Champions H10Cs are doing great. their heat index is 10 and I have NO qualm with them. I will go to 0.040 on the next gap though. I think my coil has plenty of oomph to make that gap.