Factory Five Racing Forum banner

1 - 20 of 61 Posts

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #1
I do not know much about carburetors.

How does the outside temperature affect carburetors? Humidity?

90 plus temps with humidity?

Fuel richness?

Jason
 

·
Registered
Joined
·
175 Posts
Carbs depend on air flow to mix the correct amount of fuel to air. The temperature and humidity of the incoming air play a part in that formula. The condition of the incoming air does have an effect. Since hotter air is less dense, it will tend to draw (slightly) less fuel than colder air. Think cold air intake advantages. More humid air is denser and will therefore tend to draw more fuel.

So, to answer your question about richness, i.e. fuel mixture: Hotter air will have a leaning out effect, and humidity will also play a part, it being denser. These changes are relatively minor on a street vehicle, so the overall effect is probably not noticeable. In a race car where very ounce of power is desired, air characteristics are compensated for by jet changes depending on conditions. I hope that clarifies thing a bit for you, and as usual, I will yield to other opinions.....
 

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #5
The original tune on the carburetors was too rich. I kept flooding the engine super hard to start tons of raw fuel smell. I chalked some of that up to inexperience. I left it like that because I had professionals do the base tune and I was trying to trust them. I did not know too much about carburetors. Eventually I backed it down myself. I made it more lean it was in the winter time.

Yesterday I drove it to work and it seemed fine. Started it back up again to go to lunch and had a puff of smoke and a little back fire. By this time it was relatively warm outside not like it has been but still pretty hot. The last several days it's been really hot and humid I feel like the car wasn't running quite right.

When I went home at around 10 at night the car was perfect, it's a lot cooler almost chilly.

I thought maybe it might have had to do with temperature I guess not.

I think I'll wait to drive it anymore until the mechanic sees it and adjust the tune or maybe there might be something more wrong with it.

I pulled the plugs a couple days ago and they were fouled. I replaced all the spark plugs and it ran perfect on a test drive. Yesterday was really the first drive after that and that was only a couple miles I live really close to work. I was hoping that the plugs were foul from when it was really rich before. I'm going to pull some plugs see what they look like today.
 

·
Registered
Joined
·
175 Posts
Carbs depend on a fuel supply in the fuel bowl which acts exactly the same as a toilet tank. The fuel pump feeds the bowl, and when full, a needle and seat shut off the supply as the float rises, until more is needed, where upon the float drops, opening the needle and seat allowing more fuel to fill the bowl. As the bowl fills, the float rises and closes the supply when the bowl is full. The float adjustment is critical and a float level that is set too high will create a flooding condition because it overfills the bowl. Same as a toilet tank with an incorrect float setting...drip..drip..drip...
 

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #7
I want to drive it to work again! I absolutely fell in love with driving this thing already.

It seemed awesome last night. IDK
 

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #8 (Edited)
I posted this the other day on other thread. But this is what it sounded like right after I replaced the plugs. It's sounds great to me. Smooth.

Just backfire every once in awhile and a little puff of smoke a couple days later

 

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #9 (Edited)
Ok pulled 3 spark plugs. Not good. 1 and 3 no good especially 3. 2 was good.
I'm having a hard time posting pic. I accidentally had my camera set on too high a resolution.
1. PS rear
2. DS rear
3. PS front

Only after a couple miles.


20200724_113650.jpg
 

Attachments

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #12 (Edited)
Unfortunately Mike Post in Hampshire Illinois is on vacation and can't get to him to at least August 7th.

The other mechanic I was taking it to that did the base tune I just lost faith with other things and the amount of money that was adding up for some odd and end things. When I called them about it they said they'll just charge me an hourly rate which is $150 an hour to look at it. All that goes to the final tune which I think they wanted 650 but the hourly rate won't exceed that cost. So that's fair but there just always seems "more" with them.
 

·
Registered
Joined
·
387 Posts
Update me on your engine, hp, intake, fuel pump, regulator and carb.
I hate to see you get ripped for some basic tuning. I will try to help.
 

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #18 (Edited)
The Carter AFB knockoff Edelbrock carbs use an electric choke...you have power to it and it’s opening fully, right?

Jeff
Yes I was concerned about this awhile back.

I was told to make sure the non electric choke carb was open. And then I got a meter to verify the electronic choke was getting power. As far as I can tell it's working.

Tomorrow I will recheck this.

Thank you
 

·
Premium Member
Joined
·
1,765 Posts
Discussion Starter #19
Update me on your engine, hp, intake, fuel pump, regulator and carb.
I hate to see you get ripped for some basic tuning. I will try to help.
Custom SBF 347 based on a 1988 Ford Mustang GT HO
Aprox 425 450 to the FW

Edelbrock Dual quad carbs with Edelbrock air gap manifold as kit.

TFS 170cc twisted wedge (the pistons were designed for that)

External electric fuel pump Carter for Carbs

I do have a regulator and fuel gauge. I believe last I looked about 5 psi. But I will take a new measurement tomorrow.

Jason
 

·
FFCobra Craftsman
Joined
·
23,051 Posts
Ck the choke first thing in the AM. Don't forget to give it half throttle to 'set' the choke first and then look at it. Then drive it and pull over 5 minutes later and look again. It should be full open. See the black disc held in place by three screws?
You can loosen those screws to twist the black thing. This one has an arrow on the surface hidden by the wire to tell you which way to turn it. They refer to it as 'lean' but you can also think about it as lean = opens more quickly or rich = stays closed longer.
 
  • Like
Reactions: jhargrove
1 - 20 of 61 Posts
Top