360 fuel starvation problem

mika01

Well got the beast turning and now I‚Äôm running into a fuel starvation problem. The dam thing is running really lean. Here‚Äôs what I‚Äôve got: 87 Jeep YJ Wrangler, 360 V8, R4B intake, 291C heads ported, Crane 272 cam, stock fuel pump & re-used the stock stainless fuel lines running from the tank. At idle its running just a little on rich side. As I give it gas on acceleration it drops down to ideal. When I really hit it, the A/F gauge goes completely in the red and sometimes totally disappears. This also happens when I‚Äôm in 4th & cruising. Further it starts to heat up really quickly due to the lean situation. My question is which of the following is the culprit: 1- fuel pump cant feed the motor? 2- stock fuel lines too small in diameter? 3- carb floats are out of whack? If anybody has run into this situation before it would be great to get some feedback. Would be nice to have some insight from you guys here before I start tearing fuel lines out & installing electric pumps. Thanks a bunch

jeepsr4ever

Fuel pump should be alright if its in good working order. check your oil to see if its dumping fuel into the block. Also check your float height.

a440plus6

I don't think it's a stuck float ie dumping fuel in block or it would not idle.....but you did not say what carb you are running. :-|

mika01

a440plus6 wrote
I don't think it's a stuck float ie dumping fuel in block or it would not idle.....but you did not say what carb you are running. :-|

Sorry its the Edelbrock 650 AVS Thunder series with the spring loaded needles. I will check the float level tomorrow.

tufcj

What gears and tire size are you running? With big tires and high gears, you could be lugging the engine to a point where it will never run at a optimal A/F ratio. Bob tufcj

shfletch

I am having problems of a different sort, but also have a 360 in mine with the same carb as you. You might want to check your jetting if your pump and floats are good. I bought mine new and what the factory puts in the carb was not what I needed. I bought their jet kit and now it is much smoother throughout the power curve. The edelbrock manual discusses the different spring tensions and how it is affected by a large cam that kills your vacume.

mika01

I have front & rear Dana44's with 4.10's and runing 35" boggers.

mika01

shfletch wrote
I am having problems of a different sort, but also have a 360 in mine with the same carb as you. You might want to check your jetting if your pump and floats are good. I bought mine new and what the factory puts in the carb was not what I needed. I bought their jet kit and now it is much smoother throughout the power curve.

The edelbrock manual discusses the different spring tensions and how it is affected by a large cam that kills your vacume.

Thanks for the info, what jets did you use?

shfletch

I don't know off the top of my head and can look it up on the sheet I have in the jet kit. I tried many different combinations. The carb tuning instructions are very helpful with jetting for the power cycle vs. the cruise cycle. I have been tuning and building my two stroke bikes for 15 years now and they are ultra sensitive to jetting. Your jetting is affected by altitude, relative humidity, temperature. These all affect air density. The four stroke engines are the same but not as sensitive, but now you throw engine modifications into the mix and it is even more complicated. I know even my jeep which I run at the dunes in the winter where temps can go into the 30's & 40's must be rejetted for the summer here in phoenix when the temp is up to 115. It will run, but it is not nearly as crisp and sharp as it could be.

KJMac

I would start by buying a good fuel pump such as a carter or holley! then I would start jetting the carb!

mika01

KJMac wrote
I would start by buying a good fuel pump such as a carter or holley! then I would start jetting the carb!

Well my idle adjustment screws were way on the lean side. Got those set just a hair on the rich side. Also the floats were off by a pretty big margin #-o . Now pulls effortellesly past 5000. :!:

ol' school power

I wouldn't put all my faith in the a/f fuel gauge either. At WOT it can go "tilt". Also are you using a heated O2 sensor or a standard single wire unit.