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Carb size for a 350

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mdnichols

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Morning all,

I have a 1971 Chevy C10 4x4 that I just bought running a brand new 350 mated to a 4 speed manual of coarse. When it comes to gas mileage, I know it's not gonna be like driving a Honda, but it's only getting about 9 right now. I smell gas while driving and for a while after I turn it off. The new carb is an edlebrock 4 barrell, but I'm not sure of the size of it. I'm thinking that it should be getting about 12 to 13 miles per gallon without the four wheel drive engaged, but there is something just not right.

Do ya'll know what size carb I should be running on it and how do I know what to look for to tell the size of the current one. I'm also wondering what my timing should be at 8,000 feet above sea level, gap on plugs and what not. I'm intending on yanking the 4 speed and putting in a 5 speed which should help a fair amount on the highway, but the smell of unused fuel isn't cool.

Any input is greatly appreciated. Thanks friends and keep truckin!!

-Mike
 
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Carb size

Hey Mike,
You should be able to run a 600 cfm carb if it's a stock motor. Most of the numbers are on the front drivers side of the carb or stock quads are on the rear passenger side and I believe the holleys are on the choke flap. If you call your local auto parts store they should be able to tell you what size carb to run on your truck. Timing I believe is a set degree on manufactor specs, elevation settings probably need to be done through the carb with jets and fine tuning.Hope this helps. :)
 
Mike - Also check around your fuel pump and the fuel line connections. I had a strong gas smell that was most noticeable when driving, and after doing some digging found out the fuel pump was leaking. Replaced the fuel pump and added new lines and it went away. Good luck.
 
Will check into it.

Thanks Marvs70 and Jonsride, I'll give the carb a once over and call the auto parts store too. I have not noticed any "obvious" signs of leakage, but I will get up under it once it warms up a bit/weather wise. It's been only in the low 30's around here during the day for some time now. When I bought the truck, I had to tighten up the exhaust because it had several leaks in it where everything was loose from the previous owner putting it all together, so liquid leaks aren't out of the question either. Thanks again guys and I'll post again with my findings once I check things out. Thanks friends and keep truckin!

Mike
 
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Interested

My truck is doing the very same thing. I have a 68 with a 350. I have some strong gas fumes comming out of the exhaust. I have a Edlebrock 600 on my truck. I wonder if its got something to do with the Edlebrock carbs period. I know mine does not have the electric choke.
 
Carb size

Mike, I run a 72 4whldr manual with a 750 Edelbrock Performer on a 355 w/10.5:1 compression, Comp Cams .462/.480 lift, 262/270 duration cam and some other goodies. My mileage is comparable to yours, if not worse, especially around town. The only thing that makes this truck useable is the 3.07 gearing and 33" tires. On the highway the mileage is actually bearable. I agree on the other comments regarding the gas smell. If the carb was doing it you'd see clear signs of gas staining around the base, idle problems/stalling and your pipes would be black or have a strong gas odor at the ends when running. Like to know more about your 5 speed conversion. I was going to go automatic but figured the mileage is bad enough now, why aggravate it.

Joe B.
 
same problems

Ive got a 71 with the 600 edelbrock, i get 5 miles per gallon. From what ive heard from alot of people i just need to throw away teh edelbrock cause they tend to do that. I feel your pain.
 
you all forgot to mention something...my name is jeffery [email protected] check the gas tank and line to the tank it is exposed to things...I have some cool chevys for sale also 68 4x4-72 2wd
70-2wd all must go!!call me..im in mo.417-334-0589.
 
I just put a new Edelbrock on my '69 and it runs great, I'm getting about 10 mpg with a 3 spd manual. I don't know what rear end gears I have as of yet. Truck has low oil pressurre, kind of worries me. 25-30 lbs. on the hwy.
 
I love those Edelbrock 600s. Its a trouble free carb. On my 78 Caprice i get around 20mpg & my buddy gets about 13 in his 82 C10. Both have mild 350s and run 13s @ the track.
 
Update on the Carby deal... from original poster.

Well, as far as what I've gathered, it's a 650 4 barrel electric choke Edlebrock. I know the lines aren't leaking from cracks or anything since they are all all new. The tank is in A+ condition as are the lines leading from it. There are no fuel stains around the base of the carb or anywhere else. The exhaust is perfectly clean, but the fumes will knock you out quick. In order to start, you have to pump it about 15 times, but it purrs like a kitten while running and has no hesitation what so ever.

I have not done anything at all yet to anything, but it's finally warming up around here and I'll be starting on tinkering... I was told to ditch the edlebrock, that it was more for high performance and go with a stock AC Delco??? Anyway, wanted to do a lot more research before doing anything. Going to look at possibly upgrading the whole ignition system system too for better performance. I know replacing or upgrading will exceed the cost of what I'm paying for gas now, but it's a long term investment. I think paying 3.00 per gallon is robbery. I also think that at least 12-13mgh is doable vs. 8mpg. Between going from a granny gear 4spd up to something else that'll lower the rpm's, changing the carb and upgrading the ignition system will do well. Thanks for the updated input from everyone and I'll continue to keep ya'll posted.

Mike
 
Holley makes a good carb if you plan on wheeling your truck, its called truck avenger. It has heavy duty springs valves and float in it to keep your truck from stalling on steep inclines and declines! I think they come in 650cfm and 750 cfm, both manual or electric choke
 
All you should need is a 600 cfm carb. If you have a larger one that's okay also. If it smells of gas at the tail pipes you need to purchase a jet kit from Edlebrock. It comes factory with a general set up that will let it run on anything so so. To make it perform you need to play with the jets. This will help with the gas milelage. :eek:

If you are smelling gas in the cab then check the hose for your fuel filler. Mine had a huge hole in it and when it was full it would splash out and the cab always smelled like gas. Also check all the gas lines. The rubber gas lines only last a few years and then they crack and leak.
 
Did the fuel line at the pump look good, does your set up have a gas return vaper line . How old is the line the rubber lines if they to old clamp a little to loose your gas will bleed back leak there. might not be a bad leak enough to smell or at the tank the rubber line. you check the fuel pump is it stock two small blow out hole when the seal gives out like a water pump. That all I can think about if your carb is not showing any sings of leaks.

Oh have you checked you oil to see it it smells like gas in the oil, maybe it flooding after you stop it gas is dumping down the cylinders to the crank.
 
new ignition upgrade

i got a 1971 c10 long bed pick up 2wd v8, old v8 with quadrajet, carb leaks a little but i get about 10-13 miles per gal, depending if i just drive or have a little fun on the streets :) lol.you should check your advance curve weights in your distributors and replace them if they are worn because they also can cause u more money at the pump. and less miles per gal. i did mine and notices a difference in power and the better power u got the better miles per gallon u get. also some MSD super conducter wires will help out better to give ur engine a hotter spark and burn up all that gas with some hotter spark plugs from AC Delco . u should check your compression and see if its low. better compression more power more miles per gal.
 
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i put a 600 cfm edel on a 72 k 10 with minor up grades im in utah and we had to lean it out a couple steps but it runs great
 
I'm running a newly built 350 (355 now) with the Edelbrock 600 in my '69 2WD C/10 longbed. I get ~ 8-9 in the city in the city and about 15 highway, which should improve as the engine finishes breaking in. I've had good luck with the Edelbrock on another vehicle, though it took some tweaking. As soon as the engine is well broken in, I'll adjust the jets/needles a bit to lean it down. Don't be overly intimidated by the though of tweaking the carb; the needles and jets are incredibly easy to change, and the carb's manual has a very good adusting chart for them.
 
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