Carb leaking
Thread Starter
Heel & Toe
Joined: Dec 2007
Posts: 18
Likes: 0
From: MidSouth
Carb leaking
My carb seems to be leaking somewhere. Fuel is gathering below the carb on both sides of the intake. I am no mechanic so this may be a waste posting it b/c I dont want to screw anything up. It is running fine though. Any suggestions?
Intermediate
Joined: Apr 2008
Posts: 49
Likes: 0
From: Austin TX
Check your oil
Check your oil for gas smell. If the carb is flooding, it is not only splashing around the manifold, it's dripping down into the engine. If you so smell gas in the oil, do not run it until you figure out the problem. Once the problem is fixed, you'll need to change the oil...
If this is the problem, you likely have a float sticking due to trash in the carb.
If this is the problem, you likely have a float sticking due to trash in the carb.
Thread Starter
Heel & Toe
Joined: Dec 2007
Posts: 18
Likes: 0
From: MidSouth
Stuck choke
So would this have something to do with the choke getting stuck sometimes? What do I need to do to see if a float is sticking?
I am no mechanic, but it seems I may be able to find some trash if that is the problem. What other suggestions ?
I am no mechanic, but it seems I may be able to find some trash if that is the problem. What other suggestions ?
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
If you have fuel gathering on the intake on either side of the carb, the problem is that you have fuel percolating out of the main discharge nozzles after engine shutdown (it has nothing to do with the choke). What happens is that fuel will bubble out of the main discharge and fall down onto the throttle plates. It then siphons out the throttle shafts and drips onto the intake. Look down your carb and see if you can see the hot fuel bubbling or dripping out of the discharge nozzles after hot shutdown - it it does, you either have a leaking needle/seat, too high of a float level, or a heat problem that is boiling the fuel in the bowl after shutdown.
Lars
Lars
Thread Starter
Heel & Toe
Joined: Dec 2007
Posts: 18
Likes: 0
From: MidSouth
gas in the oil
the oil has a gas smell to it. the fuel is gathered after driven. Not when it sits. I soak it up and then drive it a few minutes, and the fuel is there again. And it is darker with a little oil in it too.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
The oil is coming from your intake manifold bolts - the bolts in the center of the manifold go through the heads and into the lifter galley. If there is no sealant on the bolts, the engine will blow oil up the bolts and onto the intake. Remove the 4 center bolts (2 on both sides), put some sealant on them, and re-install them.
Lars
Lars
Thread Starter
Heel & Toe
Joined: Dec 2007
Posts: 18
Likes: 0
From: MidSouth
thanks
I can get fuel on my fingers when I rub on the sides and bottom of the carb. It is leaking somewhere. The oil smells like gas Lars. I thought it was my intake bolts too so I resealed all the bolts with high temp gasket seal, and tightened them back down to 25 lbs of pressure. it is mainly fuel that is gathered between the intake bolts. And it is 99% gas, with a little oil mixed in. And What is weird is sometimes it does not leak at all, and sometimes it does. I am lost.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
If you have a Q-Jet, the only place fuel can come from in that location is by siphoning out the throttle shafts as noted earlier. You have fuel dripping down onto the shaft and it's dripping off the ends of the shaft onto the manifold. This fuel dripping can also saturate the base gasket.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Intermediate
Joined: Apr 2008
Posts: 49
Likes: 0
From: Austin TX
Mine was on a quadrajet. The flooding after running one night kept going with a siphon action, and dumped 2 gallons of gas into my oil. On that carb, I pulled the carb, popped the top of it, and cleaned the float needle and anything else I could get to, reinstalled with new fuel filter and the problem was solved. My carb had been rebuilt and ran fine for a while, so I was confident trash was my problem
I changed the oil twice to get all the gas out. If you run it with gas in the oil, you can wash down a bearing and spin it, rebuild time...
Fix the carb first. I'm not familiar with Holley carbs and how easy it might be to do it yourself. It might be time for a carb rebuild by a pro.
Once that's fixed and your oil is changed, I suggest running the car only briefly to get the fresh oil everywhere, then change it again.
Add a sniff of your dipstick to regular maintenance. Cars this old may have a lot of trash in the fuel system, and it might happen again...
I changed the oil twice to get all the gas out. If you run it with gas in the oil, you can wash down a bearing and spin it, rebuild time...
Fix the carb first. I'm not familiar with Holley carbs and how easy it might be to do it yourself. It might be time for a carb rebuild by a pro.
Once that's fixed and your oil is changed, I suggest running the car only briefly to get the fresh oil everywhere, then change it again.
Add a sniff of your dipstick to regular maintenance. Cars this old may have a lot of trash in the fuel system, and it might happen again...
Instructor
Joined: May 2006
Posts: 211
Likes: 0
From: N. Tustin Ca
750 double pumper, I also have an electric fuel pump, when I went to investigate the smell I heard that the fuel pump would come on and off
without the car running. I climbed up and looked in the carb, checked the floats, nothing. Got a rebuild kit, pulled the carb, rebuilt it, installed it. I had the same problem. One time I left the key on when I got a phone call, well hours later the fuel filled up the oil pan and manifold. ???
After bench testing with a electric fuel pump I found the Leak!!
It was leaking from a seam in the main assy.
Pull it and set up a bench test. "The safer way"
Intermediate
Joined: Apr 2008
Posts: 49
Likes: 0
From: Austin TX
on mine there was visible dirt. I got the visible stuff out with a rag, and sprayed carb cleaner for the rest. Sprayed the needle surfaces, sprayed backwards from the float needle seat to blow any big debris out backwards (and keep it from clogging worse)
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Your Holley is running excess fuel through one of the following circuits: The main discharge nozzles, the power valve circuit, or the accel pump circuit. Fuel blowing through any of these will hit the throttle blades and siphon onto the manifold as well as flood down through the engine and past your rings after shutdown. You should be able to visibly see the discharge origin by looking down the carb.
Melting Slicks
Joined: Aug 2002
Posts: 3,334
Likes: 4
From: Midland TX
My Q-Jet on my 72 was doing the same thing - even if the engine had been off for days. I think there must have been something stuck in the seat that cuts off gas from entering the carb when the bowl is full (stuck float?). I think the heat in the garage would cause the gas to expand in the tank and force it into the carb.
The intake and cylinders (with intake valves open) would fill with gas. I removed the carb and spark plugs. When I rotated the engine (by hand) gas poured out of some of the cylinders.
YES, I did disconnect the battery first and I was in the open air.
The gas runs down the sides of the cylinders and into the oil pan. That's why you get gas in the oil too.
I'd try rebuilding the carb or replacing it.
The intake and cylinders (with intake valves open) would fill with gas. I removed the carb and spark plugs. When I rotated the engine (by hand) gas poured out of some of the cylinders.
YES, I did disconnect the battery first and I was in the open air.
The gas runs down the sides of the cylinders and into the oil pan. That's why you get gas in the oil too.
I'd try rebuilding the carb or replacing it.
