Hello, not sure if you all recall me but last time i was here i was having motor problems. The motor is no longer a problem, i had a brand new crate installed into my 72 chevelle. It has a mild cam it's a 350 small block. Like i explained before i had the car worked on before and they also installed; Brand new PS pump, water-pump, thermastat, clutch fan, radiator rotted out, exhaust dual flowmaster 40 series also my linkage was fixed, and lastly my fuel fiter. That's pretty much all i have done to my car, right now the motor uses 20 50 motor oil. I wanted to ask a few things. First, i get terrible gas mileage, i know it is a muscle car but come on.. i get like 5 miles to the gallon, i have asked around and also just put two and two together, it has to be my carb correct? The car also backfires sometimes i'm pretty sure it's due to the fact that the flap stickes sometimes.. i have a Rooster 2bbl on it now, i'm pretty certain it's the original one so i doubt it's ever been rebuilt. I'm curious what should be done next to my car.. I also am using the original differential and transmission. another thing my lights are dim at idle and when i first start the car and let it run for a few minuetes it makes a screeching sound and it isn't the smog pump that was removed long ago, i'm guessing its the alternator, i havn't replaced that yet.
I also have some holes in my floor and what sucks is heat from my motor/exhaust comes up into the car so it leaks inside and it gets really hot into my car while i'm driving. I just want to know what i should do next, i have insurance for it and i just got the oil changed, the motor has about roughly 1,000 miles on it from rebuild. I am 18 years old turning 19 in 16 days. I wanted to get some opinions on what is the logical thing to do in my case, i'm thinking the carb since i get horrific gas mileage i know i wont get too much more gas mileage but i know i am loosing power too with my current carb.. i raced a honda at a light im pretty sure it was stock and it was a sad sight i lost horribily.. i know it is because im running on 35 year old parts but that's rediculous lol.. anyway thanks for your future comments and also happy 4th of july everyone.
look forward to the replies!

get a timing light, vacuum gauge, screwdriver, and distributor wrench and start tweaking it until it runs good and gets good mileage.
figure it out like we did before the internet (yes, we had cars then..) and just start screwing around with it and see what happens.
my first car (well, the first car that made it to the road that i could actually say was mine) was a 78 Chrysler Cordoba with a 360/4 barrel engine that got roughly 5 gallons per mile. i learned a lot just keeping that POS running. i got it for free and i was 16- life was good. the fact that it took $20 in gas for a 40 mile round trip when gas was around $1 a gallon made me want to learn how things worked..
and, if you get stuck, just ask questions. we will steer you in the right direction.

1st things first - SAFETY. Exhaust fumes in the interior are bad, patch the floor holes.

Easy things first:
Make sure the choke is staying full open when the car is warmed up. If it is not, fix that or at least make it so that it is open all the time -this however will mean it might want to stall when cold. A stuck closed choke will use a lot of gas.

Is the distrobutor's vacuum advance canister hooked up to a vacuum line? This is a must for good fuel economy.

Are ALL the vacuum lines in good condition? check these and replace as needed.

The squealing may just be a loose belt, check belt tightness. Not too tight, about 3/8 - 1/2" deflection with the tip of your thumb in the middle between two pulleys.

Dim lights - this happens on older cars. If only at idle don't sweat it yet. Make sure you have at least 13V on a volt meter when driving at highway speeds, preferrably closer to 14V.

Then the timing needs to be verified, as Derrick mentioned.

G/L

I will take a picture of the motor, i am pretty sure the vacuum line is not present.. i do know that, two hoses are plugged with screws i think? and i think one hose is connected and it goes somewhere hahha.. i will take a pic so you guys can see. as far as the floorpans yeah it's gettin bad it gets super hot in the car quick, and yes i think the fumes are making me dizzy i sometimes zone out when im driving it so im pretty sure its the fumes because i have turndowns dual exhaust and they are cut off before they meet my back and my motor heat also comes into the car. i have like 2 or three small holes probabbly a bit bigger than a golf ball, how much am i looking at for them to just patch the holes? i know it varies but i just want a price that it should be around i dont want to walk into this blindly. so far thanks for the replies.

I will probably get flamed for this but I have patched floor pans temporally with pop rivets. Clean the area with a wire brush, then spray on some rustoleum. Cut some scrap sheet metal a little larger that the hole needing to be patched drill the correct size holes for the rivets and put it down. I used tub a tile sealer on the back of the patch and pop riveted it in place. Obviously the best way is to replace the entire panel since the rust will still be there unless it is cut out. The point is is that you can do all of this your self on a very tight budget, then as you can afford to fix things correctly go back and do it. As mentioned before get a timing light and set the timing. After that get a carb rebuild kit and rebuilt the carb it is not difficult. Why are you using 20w50 oil? A lighter oil will help with mileage also.

I'd dump that 2bbl , and get a edelbrock performer intake and either a NEW qjet or a ( my pick ) NEW 650 holley dp with mech secondarys . My big block got better than 5mpg just cruising. I'd get the holes patched by having someone weld some sheet metal in there. I would'nt even think about buying new pans for acouple of small holes like you described. Get your exhaust routed to exit the vehicle too. One of these times you get dizzy you'll wake up in a ditch! Lastly i would not even think about racing a riceburner in a chevelle, there are not worthy of your gas. Keep the faith, i think it's great to see you young guys rolling in a old muscle car instead of the jap junk !

I'd dump that 2bbl , and get a edelbrock performer intake and either a NEW qjet or a ( my pick ) NEW 650 holley dp with mech secondarys . My big block got better than 5mpg just cruising. I'd get the holes patched by having someone weld some sheet metal in there. I would'nt even think about buying new pans for acouple of small holes like you described. Get your exhaust routed to exit the vehicle too. One of these times you get dizzy you'll wake up in a ditch! Lastly i would not even think about racing a riceburner in a chevelle, there are not worthy of your gas. Keep the faith, i think it's great to see you young guys rolling in a old muscle car instead of the jap junk !
I'm thinking along these same lines. You may want to consider a Holley Street Avenger carb. This would boost your performance and mileage at the same time.

I have patched floor pans temporally with pop rivets. Clean the area with a wire brush, then spray on some rustoleum. Cut some scrap sheet metal a little larger that the hole needing to be patched drill the correct size holes for the rivets and put it down. I used tub a tile sealer on the back of the patch and pop riveted it in place.

Why are you using 20w50 oil? A lighter oil will help with mileage also.
1. This is a good "temporary" do-it-yourself fix that will make your car safer to drive until you can have it repaired properly.
2. I agree. 10W30 will be fine and won't rob HP.
I'd dump that 2bbl , and get a edelbrock performer intake and either a NEW qjet or a ( my pick ) NEW 650 holley dp with mech secondarys . !

Also a good Idea. A quality intake and 4bbl will get better mpg than a 2bbl.
A 4bbl has smaller primaries and will get better milage (provided you keep your foot out of it).