Strong gas fumes at idle

F

F.M.G.

Junior Member
I have a 1953 Merc.flathead in my truck,it has stock holley 94 with 4.5 power valve,51 jets.It has a chevy dist.set at 25 deg.total. It runs and idles great,but the gas fumes at idle are strong. Is that just the way they do being that they are just old school carbs? Anyone else have this problem? Thanks Mike
 
Tell us about your fuel pump - if running an electric you've got to keep the pressure around 1 1/2 psi or you'll overwhelm the carb.

Compared to modern cars you will smell more fumes of all sorts - just the nature of these beasts.
 
If you smell gas under the hood you should be able to see where it is. I don't think it's normal and have never just accepted such under my hood. My usual culprit has been loose fuel connections or fuel pump housing. The gasoline is escaping somewhere and needs to be found or you risk fire.
 
The fumes are out the tail pipe.I think it has the wrong spark plugs(ngk b6L). i will change the plugs and see how it does. Thanks Mike
 
Your plug selection is fine. If their covered with soot then it's running rich and could be the power valve in the carb. Are you using the original road draft tube? Is your oil fill cap plugged up?
 
NGK B6L are excellent plugs for your flathead, pull one and "read it" the center ceramic should be a light tan color, if it is blackish you are running rich, check your fuel pump pressure, float setting, and needle seat. also could be a weak coil, although it would not run very good with these conditions. maybe that smell is a little "blowby" past the rings.
 
Check the carb for telltale staining...might indicate leaks. My 94 carb leaks fuel past the ends of the throttle shaft due to wear. Also, check to ensure your exhaust connections under the car are solid. If you're getting strong exhaust fumes you might have a leak in the exhaust system.
 
Had the same problem on my '53. Found gas seeping out of carb. Pot metal had slight warp between the body and the lower butterfly portion. A little emory cloth on a flat surface took care of it. Also used gas-proof sealer on gasket upon reassembly. Good to go!

Milt K from Pa
 
You must log in or register to reply here.
Back
Top