My car stinks!

[Zachalanche]

I have a 67 fairlane with a 289, fairly large cam, edelbrock performer heads and a 600cfm holley double pumper. When I sit at stoplights I can smell rich exhaust, when I park in my garage, the garage will stink for days, when I pass bus stops, i can only assume I leave people teary eyed and choking. I occasionaly notice the exhuast smouldering when I shut the car off.

below are the things I have verified so far:

float levels are correct
power valve is not blown (it is a 5.5)
manifold vacuum at idle is around 10" around 900 rpm.
jetting is 64 front 71 rear - 2 sizes bleow stock and I am at 4000ft elevation.
Timing - I don't have a timing light but I have set timing to run where the vacuum is the highest.
spark plug condition - sooty on the tip of the electrode, and the end of the threads, but the porcelain and ground strap are clean.
fuel leaks - none that i can find.
vacuum leaks - none
idle screws 1.5 turns out, engine begins to stumble at .5 turns out


I know this carb is supposed to run a little on the rich side anyway, but is there anything I can do to make this car a little more pleasant to be around?

[BonzoHansen]

looks like 2 different questions

at stoplights you smell exhaust: do you have full tail pipes?

parked in garage, the garage will stink for days: stinks like what for days? Raw fuel? that is an evap issue - the tank is probably vented to the air.

[Zachalanche]

full exhuast exiting rear. I could be exagerating on how long the smell lingers in the garage, but it is the same rich exhuast smell that catches up to me at the stop light, which does smell a bit like fuel.

[hifi875]

try a IImuch fuel evap canister. lots of people on here use them. I have one but its not installed yet.

[rohrt]

Had the same symptoms with my Q-jet on a 455 with a Ultradyne cam.

The Q-jet didn't like the tight 110 LSA cam. I was also getting vacuum reading around 10-11. As I understand it the vacuum is too low and the carb would need to modified to work well with my cam. I guess the carb needed more idle bypass air. I could look down the carb and see the nozzle dripping gas. I couldn't close the primaries enough to keep it running and not pull gas from the main circuit. I had very stinky exhaust too. Starting the car in the garage for just a few seconds and the whole place stunk. My plugs were sooty black with caked on oil as well.

I ended up having my heads gone through with new valves, guides and Viton seals. I also went with a roller cam on a 114 LSA. I now have a dead smooth idle, high vacuum and more hp. And of course no more stinky exhaust. I still have just a hint of nozzle drip that I should fix but not a big deal anymore.

So my suggestion and I think it will only go so far with out serious mods to the carb are.

1. Turn the idle mix screw as lean as you can before it starts to stumble
2. Try more initial advance. This usually increases the RPM and allow you to close the primaries more to lower the RPM back down and thus less vacuum pull on the main circuit.

hopefully this would at least see if your heading in the right direction.

[705.0Merc]

I have the same carb. on my car. They are on the rich side from the factory. The idle feed restrictors need to be reduced in size. I drilled and tapped mine with 6/32 brass set screws, then used micro drill bits. I went from a .031 down to a .028. You could also stick in a piece of wire instead. Check around on googgle for some pics.

[Zachalanche]

Had the same symptoms with my Q-jet on a 455 with a Ultradyne cam.

The Q-jet didn't like the tight 110 LSA cam. I was also getting vacuum reading around 10-11. As I understand it the vacuum is too low and the carb would need to modified to work well with my cam. I guess the carb needed more idle bypass air. I could look down the carb and see the nozzle dripping gas. I couldn't close the primaries enough to keep it running and not pull gas from the main circuit. I had very stinky exhaust too. Starting the car in the garage for just a few seconds and the whole place stunk. My plugs were sooty black with caked on oil as well.

I ended up having my heads gone through with new valves, guides and Viton seals. I also went with a roller cam on a 114 LSA. I now have a dead smooth idle, high vacuum and more hp. And of course no more stinky exhaust. I still have just a hint of nozzle drip that I should fix but not a big deal anymore.

So my suggestion and I think it will only go so far with out serious mods to the carb are.

1. Turn the idle mix screw as lean as you can before it starts to stumble
2. Try more initial advance. This usually increases the RPM and allow you to close the primaries more to lower the RPM back down and thus less vacuum pull on the main circuit.

hopefully this would at least see if your heading in the right direction.

I feared lack of vacuum would be a contributor. I used to have this cam in a 351, and it always had this issue too.


I have the same carb. on my car. They are on the rich side from the factory. The idle feed restrictors need to be reduced in size. I drilled and tapped mine with 6/32 brass set screws, then used micro drill bits. I went from a .031 down to a .028. You could also stick in a piece of wire instead. Check around on googgle for some pics.

I've been hesitant to start drilling parts of my carb as I have become reaally good at tuning this thing to the point that it runs like garbage. as a result, anything that can't be undone is a concern. I will, however try the wire trick. thanks for the idea.

I have most of a 600 cfm holley with vacuum secondaries in my pile of parts. would the metering block off this carb improve the situation, or would it have a negative effect on something else?

[Shaker455]

I feared lack of vacuum would be a contributor. I used to have this cam in a 351, and it always had this issue too.



I've been hesitant to start drilling parts of my carb as I have become reaally good at tuning this thing to the point that it runs like garbage. as a result, anything that can't be undone is a concern. I will, however try the wire trick. thanks for the idea.

I have most of a 600 cfm holley with vacuum secondaries in my pile of parts. would the metering block off this carb improve the situation, or would it have a negative effect on something else?

You can send the carb to me & I can inspect & live tune it.

[rustomatic]

I like the "teary eyed" part of this scenario--it makes people think I have emotions. If the motor gags at .5 turns out, a whole 'nother turn seems like a long way further; half a turn less should be happier (normally)...

Seriously, the double-pumper sounds like too much carb, unless you're perpetually in a drag race. On that note, 64 sounds tiny, unless you have 7:1 compression. With a mild 302 and 10:1 pistons, I've needed at least 68s on the primary side to get rid of pinging. My 570 Street Avenger works great with stock jetting and a 9:1 (supposedly) X302 crate motor (.300/.500 cam and 1.94 intake side + Edelbrock RPM Air Gap). This leads me back to the double-pumping stuff; it sounds like you're just dumping way too much juice down at all times...

It's two cents...

[rohrt]

One thing I would mention with my engine that had the problem. I ran that same motor in a different car but had a single plane intake, edelbrock carb and 3 tube headers and didn't have the issue. Once I went to a duel plane iron intake, q-jet and iron long branch exhaust manifolds then the raw exhaust smell showed up. I don't know if I can blame any one part but the combination and how it worked together.

Does that 600 holly have 4 idle mixture screws? A different carb is worth a shot.

[Zachalanche]

I like the "teary eyed" part of this scenario--it makes people think I have emotions. If the motor gags at .5 turns out, a whole 'nother turn seems like a long way further; half a turn less should be happier (normally)...

Seriously, the double-pumper sounds like too much carb, unless you're perpetually in a drag race. On that note, 64 sounds tiny, unless you have 7:1 compression. With a mild 302 and 10:1 pistons, I've needed at least 68s on the primary side to get rid of pinging. My 570 Street Avenger works great with stock jetting and a 9:1 (supposedly) X302 crate motor (.300/.500 cam and 1.94 intake side + Edelbrock RPM Air Gap). This leads me back to the double-pumping stuff; it sounds like you're just dumping way too much juice down at all times...

It's two cents...



One thing I would mention with my engine that had the problem. I ran that same motor in a different car but had a single plane intake, edelbrock carb and 3 tube headers and didn't have the issue. Once I went to a duel plane iron intake, q-jet and iron long branch exhaust manifolds then the raw exhaust smell showed up. I don't know if I can blame any one part but the combination and how it worked together.

Does that 600 holly have 4 idle mixture screws? A different carb is worth a shot.


both interesting points. This car has been peiced together with what I had lying around, and to be honest I think that may be the root of most of my problems. My goal is to spend as little as possible on this vehicle and see how well I can get it to perform. This should contrast nicely with my other project where I am seemingly trying to see how much money can be spent on a car. with the heads that are currently on this engine, I know the compression is relatively low. somewhere in the high 8's. not ideal, but at least I can run regular gas. the distributor is an old mallory dual points (the points have been replaced with pertronix stuff, but who knows if the the mechanical advance is even close to right for this engine). The carb only has 2 idle screws. I have tried cracking the 2ndaries a bit to help lean the mixture. The 64 main jets are only 2 sizes below stock for this carb. 600 may be a little big for this engine, but it does pull hard all the way up to 7500RPM and possibly even further If I dared to try.

so perhaps you are both on to something saying that I need to use a differnt carb. based on my $0 budget that leaves a 600 cfm vacuum secondary carb that needs a thorough cleaning and rebuild as my next option. Although I am worried that the lack of low RPM vacuum may cause issue ith the operation of the vacuum secondaries.

[Steve Chryssos]

First, I would definitely buy a timing light and know your timing. 289's need very little base timing, like 6 degrees and often have too much -- like 12 degrees. The excess timing often presents itself as an off idle stumble. For your fuel issue, I strongly recommend removing your carburetor and inspecting the idle transfer slot adjustment as set. It should appear as a square with equal width and height rather than a tall rectangle as shown in the following photo. This is the WRONG way:

https://static1.pt-content.com/images/pt/2014/03/Holley206502013JPG-1.jpg.

Adjust down until the slot is a perfect square. I can't tell you how many carburetor tuning issues are based on an incorrect transfer slot baseline.

While you have the carb upside down, look to make sure that the throttle bores are not gummed up which might lead to sticking. ..And spray some carb cleaner in the transfer slots -- even if things are relatively new.

Next, many "phantom" issues are actually caused by production errors such as material clogging up passages or unsure metering block surfaces that are causing cross passage leaks. It's a good idea to carefully remove the fuel bowls and metering blocks and inspect the metering block gasket surfaces for cross-passage leaks. Use a straight edge on the metering surfaces. A little eyeball "blueprinting" can go a long way. Cross passage leaks are indeed possible.
Steve

[Zachalanche]

Streetfytr68,
thanks for the info, I have verified the correct amount of transfer slot is showing. this pretty much makes it so that I have to adjust idle by adjusting the stop on the secondaries.
I'll check for the crosspassage leaks, and I do have a timing light now, so I will try 6* base advance as I am sure I am much higher than that.

[Zachalanche]

After many failed attempts to time this engine correctly, I pulled my distributor, and put it on the test stand at the local auto parts stor and foud that the pertronix module was only firing on 6 cylinders at idle. even at higher speeds it still had an occasional misfire.

[MonzaRacer]

Too much timing in a 289? huh????? heck I advanced my initial timing well past 12 ran like 16-18, limited centrifugal and vacuum to a point. Too short initial timing causes engine to be dog. DP carbs will drive no worse or better if the linkage and driver are working properly together. DP ONLY opens secondary when pedal is pushed.
NOW. One place many people forget is they leave throttle pressure on the accelerator pump arms. they need to have just perceptible looseness at idle foot off pedal. IE you pick up on arm as you adjust it, there needs to be just tiny amount of free play. Never ever had any issues as Holley has multiple shooter sizes. I do agree with leaning the idle restricters, been using either devcon 5 ton epoxy or jb weld and as stated lean the restricter orifice out. ALSO might need to make sure idle air bleeds are open inside carb throat.
Had 66 galaxie, put a 4 bbl from a 73 460 ford on it and NEVER had bog or fuel issues and it got pretty good mileage as when I went too 4 spd I lost speedo cable hookup.

[hifi875]

I put the IImuch evap canister and it worked. Got rid of my fuel smell. Worth the &&

[hipockets]

You must know what the initial and full advance timing is, as well as when the centrifugal curve is "all in" to properly tune a carburated engine. If you have a big cam, you need to run more initial advance, and less centrifugal advance, and a faster curve. Look here for some ideas on initial advance.
http://www.demonfuelsystems.com/Tech/DemonSelectionGuide.asp

For the street, be sure the floats are adjusted so the fuel is at the bottom of the level window. You should also check if the IFR's in the metering block are at the bottom or the top. If they are at the top, have them moved.
http://racingfuelsystems.myfunforum.org/Relocating_the_Holley_Idle_Jet_about18.html