Notices
C1 & C2 Corvettes General C1 Corvette & C2 Corvette Discussion, Technical Info, Performance Upgrades, Project Builds, Restorations

54 gas out the exhaust pipe

 
Old 01-22-2019, 03:14 PM
  #1  
1963GrayGray
CF Senior Member
Thread Starter
 
1963GrayGray's Avatar
 
Member Since: Feb 2003
Location: Carlisle Pa.
Posts: 438
Thanked 12 Times in 8 Posts
Default 54 gas out the exhaust pipe

I am working on a 54 that has fuel running our the LH exhaust pipe at the junction of the exhaust pipe and the
tail pipe. (near the transmission)
The car has an electric fuel pump set at 2.5 PSI and the float levels have been set properly.
The car starts and runs great, but when pulled back into the shop, gas comes out of the exhaust.
We have owned this car for 12 years and this has just started. Removed the spark plugs and turned the
engine over and saw no indication of gas coming from the combustion chamber.
I am sort of perplexed about the source of the gas coming from the exhaust.
Dave
1963GrayGray is offline  
Old 01-22-2019, 04:23 PM
  #2  
Factoid
CF Senior Member
 
Factoid's Avatar
 
Member Since: Jul 2018
Location: San Antonio, TX/Mahopac, NY
Posts: 1,824
Thanked 406 Times in 321 Posts
Default

Do you have a return line? Could the feed or return be leaking and dripping on the exhaust pipe?
Factoid is offline  
Old 01-22-2019, 04:46 PM
  #3  
cbernhardt
CF Senior Member
 
cbernhardt's Avatar
 
Member Since: Dec 1999
Location: Lexington,NC,USA
Posts: 2,997
Thanked 131 Times in 105 Posts
Default

Have you tried turning the fuel pump ON without the engine running to look for a leak?
cbernhardt is offline  
The Following User Says Thank You to cbernhardt For This Useful Post:
1963GrayGray (01-24-2019)
Old 01-22-2019, 05:55 PM
  #4  
lars
Tech Contributor
 
lars's Avatar
 
Member Since: Aug 1999
Location: At my Bar drinking and wrenching in Lafayette Colorado
Posts: 10,718
Thanks: 0
Thanked 827 Times in 428 Posts
Default

Assuming that you have verified that it really is gasoline and not water condensation that's dripping from the exhaust (water condensation could be normal), there is a way for gasoline to get into the exhaust on the 6-cylinder engine: If any one of the 3 carbs is leaking fuel past the needle/seat after shutdown, the carb will flood and drip fuel into the bottom of the intake manifold (without the fuel necessarily getting into the cylinders). If the heat riser connection between the exhaust manifold and the intake manifold is leaking, the fuel can seep into the exhaust manifold. This is a pretty unlikely scenario, since the gasoline would tend to boil off immediately upon getting into the hot exhaust manifold. There would also be a degradation in performance with a small leak through the bottom of the intake into the exhaust. If this is the case, you should be able to see fuel dripping from the main discharge nozzles on one of the carbs after shutdown. If fuel is dripping after shutdown from one of the carbs, you need to fix the carb, and then you need to fix the leak path between the intake and the exhaust manifolds.

...But it's more likely fuel-flavored water that is condensing in the low spot in the exhaust after shutdown and leaking out the joint.

Lars

Last edited by lars; 01-22-2019 at 07:38 PM.
lars is offline  
The Following User Says Thank You to lars For This Useful Post:
1963GrayGray (01-24-2019)
Old 01-22-2019, 08:30 PM
  #5  
1963GrayGray
CF Senior Member
Thread Starter
 
1963GrayGray's Avatar
 
Member Since: Feb 2003
Location: Carlisle Pa.
Posts: 438
Thanked 12 Times in 8 Posts
Default

Factoid...There is no return line.

Charles... The leak is present with the fuel pump on and the engine off or after shutdown with the pump off, but
pressure on the system.

Lars..... I think that you may have answered my question. I suspected that the gasoline may have leaked past the needle
and seat, but I couldn't see how it could get into the exhaust system. I will not be working on the car till
next week, but I will report what I see. BTW it is gasoline and not condensation.

Thanks to all.......... Dave
1963GrayGray is offline  
Old 01-22-2019, 10:29 PM
  #6  
lars
Tech Contributor
 
lars's Avatar
 
Member Since: Aug 1999
Location: At my Bar drinking and wrenching in Lafayette Colorado
Posts: 10,718
Thanks: 0
Thanked 827 Times in 428 Posts
Default

Good luck, Dave. I think it would require a crack in the bottom plenum of the intake manifold for this to happen, which is entirely possible from heat fatigue over the years. I'll be very curious to see what you find, so please post or send me an e-mail with the final results.

Lars
[email protected]

Last edited by lars; 01-22-2019 at 10:30 PM.
lars is offline  
The Following User Says Thank You to lars For This Useful Post:
1963GrayGray (01-24-2019)
Old 01-23-2019, 09:11 AM
  #7  
DansYellow66
CF Senior Member
 
DansYellow66's Avatar
 
Member Since: Jan 2003
Location: Central Arkansas
Posts: 10,574
Thanked 639 Times in 577 Posts
Default

Originally Posted by 1963GrayGray View Post
Factoid...There is no return line.

Charles... The leak is present with the fuel pump on and the engine off or after shutdown with the pump off, but
pressure on the system.

Lars..... I think that you may have answered my question. I suspected that the gasoline may have leaked past the needle
and seat, but I couldn't see how it could get into the exhaust system. I will not be working on the car till
next week, but I will report what I see. BTW it is gasoline and not condensation.

Thanks to all.......... Dave
That is sort of what happened on my Cobra replica last weekend. I thought I set the secondary floats low enough before assembly of the carbs to allow me to adjust them up higher a little after I got it running, until fuel was at the bottom of the sight plug. I didn't shoot nearly low enough and flooded the engine after it started with fuel leaking from the exhaust system. I pulled the needle and seat as a precaution but they looked good and after lowering the floats down several more turns of the adjuster it cleaned und ran OK.
DansYellow66 is offline  
Old 01-23-2019, 09:14 AM
  #8  
csherman
CF Senior Member
 
csherman's Avatar
 
Member Since: Dec 2009
Location: Plano IL
Posts: 2,550
Thanked 229 Times in 189 Posts
2018 C1 of Year Finalist
Default

Do you have a block off plate between the intake and the exhaust manifold
These carbs are noted for leaking after shut down
Fix is an updated needle
If you dont have a block of plate - and the intake is cracked - possible for fuel to run into the intake and into the manifold - BUT MAN THAT IS ALOT OF FUEL
Take a look at your fuel pump - is the diagram leaking and pouring fuel into the vacume line and into the intake......
csherman is offline  
The Following User Says Thank You to csherman For This Useful Post:
1963GrayGray (01-24-2019)
Old 01-23-2019, 04:15 PM
  #9  
1963GrayGray
CF Senior Member
Thread Starter
 
1963GrayGray's Avatar
 
Member Since: Feb 2003
Location: Carlisle Pa.
Posts: 438
Thanked 12 Times in 8 Posts
Default

Originally Posted by csherman View Post
Do you have a block off plate between the intake and the exhaust manifold
These carbs are noted for leaking after shut down
Fix is an updated needle
If you dont have a block of plate - and the intake is cracked - possible for fuel to run into the intake and into the manifold - BUT MAN THAT IS ALOT OF FUEL
Take a look at your fuel pump - is the diagram leaking and pouring fuel into the vacume line and into the intake......
I will check these items as well as Lars suggestions and report back next week. The mechanical fuel pump is bypassed and the electric
pump is regulated at 2.5 psi. What is the configuration of the updated needle?
1963GrayGray is offline  
Old 01-23-2019, 09:46 PM
  #10  
Chuck Gongloff
CF Senior Member
Support Corvetteforum!
 
Chuck Gongloff's Avatar
 
Member Since: Apr 1999
Location: Beverly Hills/Pine Ridge Florida
Posts: 10,191
Thanked 245 Times in 193 Posts
Default

Originally Posted by 1963GrayGray View Post
I will check these items as well as Lars suggestions and report back next week. The mechanical fuel pump is bypassed and the electric
pump is regulated at 2.5 psi. What is the configuration of the updated needle?
\

Three piece spring loaded needle valve with Viton tip.

Chuck Gongloff is offline  
The Following 3 Users Say Thank You to Chuck Gongloff For This Useful Post:
1963GrayGray (01-24-2019), csherman (01-24-2019), jim lockwood (01-24-2019)
Old 01-24-2019, 09:06 AM
  #11  
TR54
Junior Member
 
TR54's Avatar
 
Member Since: Feb 2018
Location: Coralville IA
Posts: 19
Thanks: 0
Thanked 4 Times in 2 Posts
Default

I am not sure, but I don’t think it is as much an “updated” needle as the correct needle. The photo is the same as the Carter sheets show from way back in the day.
TR54 is offline  
Old 01-24-2019, 09:09 AM
  #12  
TR54
Junior Member
 
TR54's Avatar
 
Member Since: Feb 2018
Location: Coralville IA
Posts: 19
Thanks: 0
Thanked 4 Times in 2 Posts
Default

Here is a good article on these carbs that Chuck wrote that I found helpful.
TR54 is offline  
The Following 3 Users Say Thank You to TR54 For This Useful Post:
1963GrayGray (01-24-2019), Chuck Gongloff (01-24-2019), csherman (01-29-2019)
Old 01-28-2019, 05:23 PM
  #13  
1963GrayGray
CF Senior Member
Thread Starter
 
1963GrayGray's Avatar
 
Member Since: Feb 2003
Location: Carlisle Pa.
Posts: 438
Thanked 12 Times in 8 Posts
Default






I got back to working on the 54 today. I removed the intake from the head and left the fuel line from the elect. pump hooked up. I turned on the pump
and saw no fuel leaking from either end of the carburetors. (very minor seepage on center carb after 5 minutes with pump on. I examined the area where
the intake bolts to the exhaust and saw no cracks at the stainless blockoff plate. Does this plate require a gasket? None was present. The heat riser
worked fine. No cracks were visible at the intake or exhaust. I can't figure out when the gas was leaking last week why the gas leaking from the LH
exhaust pipe and not the Rh pipe. Logic tells me that if the gas was leaking straight down from the intake to the exhaust, the most direct route would
be the RH pipe. Working on the car today didn't tell me a damned thing. What the heck am I missing?
Photos attached, I hope.
Dave
1963GrayGray is offline  
Old 02-11-2019, 07:51 PM
  #14  
1963GrayGray
CF Senior Member
Thread Starter
 
1963GrayGray's Avatar
 
Member Since: Feb 2003
Location: Carlisle Pa.
Posts: 438
Thanked 12 Times in 8 Posts
Default

ttt
1963GrayGray is offline  
Old 02-12-2019, 04:48 PM
  #15  
csherman
CF Senior Member
 
csherman's Avatar
 
Member Since: Dec 2009
Location: Plano IL
Posts: 2,550
Thanked 229 Times in 189 Posts
2018 C1 of Year Finalist
Default

trying to help
are you sure its fuel from the tail pipe?
just asking
They do spit alot of water and carbon crap from the pipes
At idle - does idle putter?
- back off all three idle screws and set the idle with the middle one
make sure all three blades are shut equally
mixture screws I am back them out equally and turn each one in til it "putters" and back them out til it runs smooth.
They are low compression and the idle smell is rich...
csherman is offline  
 


Thread Tools
Search this Thread
Quick Reply: 54 gas out the exhaust pipe


Sponsored Ads
Vendor Directory

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: