Fuel Odor and Carb Gremlins - Team Camaro Tech
Engine General Engine Discussion.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 19 (permalink) Old Mar 19th, 10, 05:12 PM Thread Starter
Tech Team
 
Join Date: Aug 2009
Location: Miami, Florida
Posts: 51
Fuel Odor and Carb Gremlins

Ok, so a while back I posted about this misterious fuel smell that I had while cruising and parked in the garage afterwards. It was suggested that a spacer would fix the problem...well it turns out that I had a 3/4 inch spacer on there already???
Well I decided to rebuild the carb, Holley 750 Vac Sec #80508, the engine is a stock 68 350. I noticed that my bowl levels were very high, and my idle mixture was a bit on the rich side (2.5 turns out on each mixture screw), and that was about all that I found out-of-spec.
Now after the rebuild, there is a lot less fuel smell, but it is still around. Also, the car idles all over the place, the RPMs stick around 1500 when I put in the clutch and roll to a stoplight, etc, but if I blip the throttle it comes back to normal.
Any ideas????
blumarln is offline  
Sponsored Links
Advertisement
 
post #2 of 19 (permalink) Old Mar 21st, 10, 09:36 AM
Senior Tech
 
Join Date: May 2001
Location: Ashby,MN, USA
Posts: 8,305
Re: Fuel Odor and Carb Gremlins

any old carbureted car is going to have some gasoline smells.. that's normal. some are worse than others. the only way to fix that is to stick to late model cars with sealed fuel systems.
as for the idle mixture screws being "out of spec" at 2.5 turns out- they might have been right on for your engine. every engine is going to be different- i've had some that wanted to be 3 turns out to idle properly. the 1.5 turns out is just a recommended baseline starting point. get a vacuum gauge and see where your really wants to be- it might just help with the weird idle issues.
the choke might not be opening all the way, either, and fully disengaging the fast idle cam. adjust it a little bit to the "rich" side and see if that helps. of course, you will want to verify that the choke linkage works smoothly with no binding.

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
novaderrik is offline  
post #3 of 19 (permalink) Old Mar 25th, 10, 02:06 PM Thread Starter
Tech Team
 
Join Date: Aug 2009
Location: Miami, Florida
Posts: 51
Re: Fuel Odor and Carb Gremlins

Thanks for the input.
As to the idle mixture screws, 1.5 turns was where I had the highest vacuum, and I realize that these "old cars" are going to have odors. But there is no way that your passengers should smell so much fuel when you are cruising that they start to get nauseaous.
I have got my choke working perfectly, the linkage is smooth as silk, and the accelerator comes off of the cam just as it should.
Any other ideas about why the RPMs would be hanging up when I come off the gas? I also feel a bit of a stumble if I am cruising and then hit the gas, any thoughts?
blumarln is offline  
 
post #4 of 19 (permalink) Old Mar 25th, 10, 02:13 PM
Senior Tech
AJ
 
Join Date: Jul 2006
Location: AUSTIN TEXAS
Posts: 3,842
Re: Fuel Odor and Carb Gremlins

What kind of exhaust system are your running?
Is it dumped, does it exit like the 67-8's, or is it ran out the back and up like the '69's?

Really need more specs on the motor before diagnosing carb or ignition problems.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
ace's68 is offline  
post #5 of 19 (permalink) Old Mar 25th, 10, 05:22 PM
Gold Lifetime Member
Scott
 
scblucam's Avatar
 
Join Date: May 2005
Location: Houston, TX
Posts: 2,429
Garage
Re: Fuel Odor and Carb Gremlins

Throtle shaft binding? Weak return spring?

68 302 M20 - 85 IROC Z
The older I get the faster I was.
scblucam is offline  
post #6 of 19 (permalink) Old Mar 25th, 10, 08:21 PM Thread Starter
Tech Team
 
Join Date: Aug 2009
Location: Miami, Florida
Posts: 51
Re: Fuel Odor and Carb Gremlins

The exhaust, I am not sure about whether it is stock or not. It runs back over the rear axle and dumps between the body and the leaf spring.

The odd part about the throttle binding/return spring idea is that everything was perfect before the rebuild... as far as the RPMs returning to idle. Also the RPMs have gone from sticking at 1500 to about 11-1200 then when I blip the throttle, I almost stall.

Could this all mostly be from too big of a carb?
blumarln is offline  
post #7 of 19 (permalink) Old Mar 25th, 10, 10:54 PM
Senior Tech
AJ
 
Join Date: Jul 2006
Location: AUSTIN TEXAS
Posts: 3,842
Re: Fuel Odor and Carb Gremlins

the shaft that holds the butterflys could be bent or warped.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
ace's68 is offline  
post #8 of 19 (permalink) Old Mar 26th, 10, 02:49 AM
Senior Tech
Ron
 
Join Date: Nov 2006
Location: North Channel Lake Huron
Posts: 3,934
Re: Fuel Odor and Carb Gremlins

People have a tendency to over-torque and unevenly Torque the carb on to the intake which does Warp the Base Plate containing the Throttle Plates. Carb Gaskets have to be consistent without broken Ears where the Carb mounting Studs are located.

Ensure the Primary Throttle Stop Screw positions the Throttle Plate in the Idle Circuit that is between the 2 orifices and not in the Transfer Slot. The Secondary Throttle Plates must be Set as per the Mfgrs Specs. Secondary Vacuum Diaphragm good. Turn the Idles Screws 1 1/8 turn off Seat. Check Floats are not pin holed, filled with Gas and set at correct height. Generally the Idle Air Screws will be about 3/4 Turn off Seat for a 2 Corner Idle Holley once set up.

Disconnect and Plug the Distributor Vacuum Pod. To eliminate any possibility of Vacuum leaks, I suggest you disconnect and plug every Vacuum Source to include the Auto-Trans Modulator SX, Power Brakes and Vacuum Choke Pull off if present. Tie the Choke open and connect a Vacuum Gauge.

Start the engine by turning the Distributor. You should not have to adjust the Throttle adjustment or Idle Air Screw very much to have the Engine firing up and idling smooth - This is the INITIAL Timing for your Engine Mark it down - Every Engine is different.

Really I can't see any reason why an Idle Air Screw should be more then 3/4 to 1 1/4 Turns of Seat unless you have Vacuum Leaks,Floats to High or Sunk, Wrong Jetting, Circuit problems or possibly a faulty Power Valve or one not within range of the Engines Vacuum at idle. Generally the Power Valve should activate approx 2 to 2.5Hg lower then the Engines Vacuum at idle. If you have a Vacuum Leak the power Valve may cause the Engine to idle Rich. The Vacuum Pod on the Distributor works in the same manor to Advance Timing while the Engines Vacuum is highest when the Throttle Plates are closed or slightly open at cruise. When the throttle is blipped the Engine Vacuum Drops, the Vacuum Pod releases the Total Advance, the Mechanical Advance takes over and the Power Valve Activates.

Mght help if you re-torqued the Intake Manifold if you suspect Vacuum Problems.

Z15CAM - There was a Viper in my Rear View
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

This was my 70 1/2 Z28

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by Z15CAM; Mar 26th, 10 at 03:09 AM.
Z15CAM is offline  
post #9 of 19 (permalink) Old Mar 27th, 10, 08:32 PM
Senior Tech
Logan
 
Join Date: Jan 2008
Location: Oliver Springs, TN
Posts: 276
Re: Fuel Odor and Carb Gremlins

Sorry to but in, I kno this ant my thread, but im haveing this same problem, and i was wondering what kinda numbers are u looking for on the vaccum guage. Ive turned my screws way over these numbers and its only shows 15 on the guage when its in park, and 10 when its in drive. so what kinda vaccum are you looking for
Camaro55 is offline  
post #10 of 19 (permalink) Old Mar 30th, 10, 12:39 PM
Senior Tech
Logan
 
Join Date: Jan 2008
Location: Oliver Springs, TN
Posts: 276
Re: Fuel Odor and Carb Gremlins

Any help is appreciated
Camaro55 is offline  
post #11 of 19 (permalink) Old Mar 31st, 10, 12:08 PM Thread Starter
Tech Team
 
Join Date: Aug 2009
Location: Miami, Florida
Posts: 51
Re: Fuel Odor and Carb Gremlins

my car is a 4spd, so I have no idea about when its in park, but in neutral, when I was tweaking the idle mixture screws, the best vacuum I could get was 16inHg

I am about ready to sell this 750cfm and buy a new 600cfm to deal with ...
blumarln is offline  
post #12 of 19 (permalink) Old Mar 31st, 10, 12:19 PM
Senior Tech
Logan
 
Join Date: Jan 2008
Location: Oliver Springs, TN
Posts: 276
Re: Fuel Odor and Carb Gremlins

Well mine has a holley 650 dp and I ant got it right yet and I've had it a year
Camaro55 is offline  
post #13 of 19 (permalink) Old Mar 31st, 10, 01:09 PM
Senior Tech
Greg
 
Join Date: Jan 2004
Location: Winston Salem, NC
Posts: 1,512
Re: Fuel Odor and Carb Gremlins

Any steel braided fuel line? They are notorious for fuel smell.

69 Camaro, 3650lbs., 400ci, TH400, Coan 10" converter, 3.50 gear
D1SC, pump gas, street car, Water/Meth injection
1.302 60', 5.956 @ 116.4 Super Sniper EFI 2019
Greg O is offline  
post #14 of 19 (permalink) Old Mar 31st, 10, 06:53 PM
Gold Lifetime Member
robert
 
Join Date: May 2009
Location: gardendale alabama
Posts: 401
Re: Fuel Odor and Carb Gremlins

Not my thread either But I am so feed up with carburators and gas smell. I am considering EZ EFI . Has anyone tried EFI ?I just want the car to crank idle and not smell like gas, not really concerned about big H/P.
rherring is offline  
post #15 of 19 (permalink) Old Apr 1st, 10, 12:53 PM Thread Starter
Tech Team
 
Join Date: Aug 2009
Location: Miami, Florida
Posts: 51
Re: Fuel Odor and Carb Gremlins

No braided lines, I just can't understand why when I drive at a constant speed of say 2000 or 2500-3000 RPM it get such a strong fuel odor........................

Also, a dp is a whole different animal alltogether
blumarln is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome