Just finished my truck. Has a 4bbl 360. I put a 650 cfm edelbrock performer on it. I get absolutely horrible mileage. Is it too big for my small block? Do I need to jet it down? Any help would be nice. Cannot afford 100 bucks a week on gas. My other 360 did way better.

 

650 cfm is not excessive for a 360. What kind of terrible mileage are you talking about? Also, need to know more about the truck. What transmission? 4x4? Lifted? Big tires? Built motor or stock? Is it possible you have vacuum leaks? Those can cause terrible fuel economy.

 

50 liters of gas got me around 75-100 kms in town. the engine is stock. 727 4x4. Stock size tires. About 4 inches of lift. No vacuum leaks. Went over it with a fine tooth comb. Maybe I need to jet it down? I live in southern Alberta. So with that elevation and stuff do I need to work on it? Thanks for the quick reply.

 

that part of the problem right there. if all you did was city driving your gas mileage will suck. i get about 9mpg or worse if all i do is city driving with either of my 318's. 3.5-5mpg is definitely low. there is actually an active thread over on RCC that is talking about carbs. i think most people said that a 650cfm is about the max you want to run a on 360.
http://ramchargercentral.com/vehicle...arb/?topicseen

 

Okay, my Ramcharger got watt better mileage then this and the engine and stuff was the same. I've never run an edelbrock carb before. So since 650 is the max I should jet
It down and stuff to help with the economy. It runs really really strong, but I keep my foot out of it. I've never had that bad mileage with any truck I've owned. My Ramcharger, my singlecab short box all had 4bbl carbs and 360. should I just call the edelbrock guys and ask what should be done? Thank you much.

 

i guess you could call up edelbrock and ask. i just noticed he found a 500cfm carb and he did a small right up on it. apparently the 500cfm one works better than the 650cfm one.
http://ramchargercentral.com/technic...-cfm-the-test/

 

Something a lot of people don't realize is that a 4bbl that is tuned right for the motor will get better fuel economy than a 2bbl. This is because a 2bbl has no secondaries, so when you stomp on it it has to be able to give that big squirt of gas through the only two jets it's got. With a 4bbl you have smaller primaries for better mpg's while cruisin', with bigger secondaries for when you need the giddyup.

I have an old Carter AFB on my '72, with a 318, and I get about 11 around town and 12 on the freeway with it (with monster 39's, 4.10's, and a 4spd) . Problem is I have no idea what size the carb is. I imagine maybe 550 or 600 cfm, but I really don't know.

 

that really make me want to try that carter AFB that i have sitting in the basement. i guess a standard transmission also doesn't hurt your gas mileage.

 

My grandfather, being a carb guru, is ordering me some rods, springs, and jets just incase, and we will play with the setups. We will set the timing back to right degrees. I also have a lose u-joint. We will get that all done asap. Thanks for the info guys. I really appreciate it. I might take off the brushguard cause it's heavy as hell. That might help. I'll get my headers and exhaust done then it'll be better I think.

 

You are right, but 4x4, 10" of lift, and 39" tires sure do. But 318's have always been known to get better mpg's than 360's.


Long tubes also help with fuel economy. Make sure your exhaust isn't too big. I have 2" duals, no crossover, with 32" (i think) thrush glasspacks right before the exit.