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Discussion Starter #1
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????
 

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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.
 

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Discussion Starter #3
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?
 

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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.
 

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Throtle shaft binding? Weak return spring?
 

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Discussion Starter #6
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?
 

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

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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.
 

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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
 

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Discussion Starter #11
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 ...
 

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

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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.
 

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Discussion Starter #15
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
 

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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.
Much of that is correct but eliminating the Jetting Factor and consider "It'll only run rich at idle if the idle mixture screws aren't properly adjusted or if the throttle plate is open too far and it's running on the transfer slot instead of the idle mixture orifices." You can have other problems associated with Vacuum leaks, incorrect or blown Power Valve or Leaking Gaskets in the Idle Circuit; other words, it's not the fault of the jetting at Idle - Thanks to JohnZ to remind me ;o)
 

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changed the spacer to a phenolic spacer from the aluminum that came with the motor
made a big difference
but all the adjustments of the floats etc should be done
 

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Discussion Starter #18
Update, both of my jets are "70s", my power valve is a 6.5 and appears to be operating properly. After completely breaking it down again and thoroughly cleaning it, I think I have substantially reduced the fuel odor.
I do have a question, everything I read says that on a stock 295hp 350 I should not have anything bigger than a 670cfm carb. Is this fuel odor condition, just "nature of the beast" with a 750? If so, would dropping the fuel level in the bowls help this condition out? I almost never run at WOT, therefore economy and low end are my priorities - should I just buy a new, smaller carb?
 

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Discussion Starter #19
UPDATE
Turns out that a new carb was the ticket. I put a 570 Street Avenger on, and all of my fuel odors went away!!!!
 
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