fuel questions

[texasfunk]

here lately the truck has been wasting ALOT of gas, its a 355 with an RV cam, 750 double pumper, and vortec heads, it is an 87 so it hasd the in tank fuel pumps, it has a CHEAPY mrgasket fuel pressure regulator on it, and i thought turning it down id lose performance, but gain some mileage, but it seems not to change, the truck is definately slower, but wastes about the same, the fuel pressure reg says NOT for use on Fuel injection, and for that reason has no return line, i am going to buy a fuel pressure regulator that has for a return line, and im wondering if this might help with the MPG issue? it seems like it is wasting WAY more then it should being its not a big cam, and has stock gearing and a 700r4 with overdrive, it uses abt 1/2 a tank every 120 miles, which is the distance to and from school, can anyone help? tyhanx in advance

[Pyrotechnic]

What's your fuel pressure ? You should be using a good regulator with a return line. The stock TBI pumps put out around 14-15 PSI, which needs a return line when regulating them down to the ~6 PSI that carbs usually like.

[texasfunk]

i am not sure, it has no gauge, the fuel pressure reg has numbers on it, 1-6, and its on about 3.5

[slugish]

pretty sure your carb is too big for what you have unless its really jetted down . I bet you could get a 600 cfm eldebrock or a 650 steet avenger Holley & get better mileage & not lose any power . You just need more valve lift (ie a larger cam ) for a 750 double pumper . The vortec heads help , but are not enough alone . OR more cubic inches . Get other opinions > Iam not an expert.

[shrtbx]

I think the carb is a bit big also..600 cfm is ideal for that set up or even the 650 as stated above.

[asphaltburner]

Yo! And me three!
600-650cfm is appropriate for most small blocks. They're not capable of utilizing the cfm of a larger carb without being built for race. 750cfm would be good for a BB.
FRANKENTRUCKs' fairly well beefed 350 does quite well with it's 600 Holley, as does my Camaros' nearly identical engine with it's 625cfm Carter AFB.
Todd.

[78maliburat]

Ill swap you carbs 650 eddy

[flamingbig10]

my truck won't even go 120 miles on a full tank

[shrtbx]

a half a tank per 120 miles is really not all that bad for these trucks from all that i read here and what others get with a carb. What is that like around 15 mpg?

[texasfunk]

im not too sure, i guess im just used to the bigger gas tank of my 90, and thanks for the offer, i'd be willing to trade if it were running bad, but the truck runs amazing and i have no problems whatsoever, so id rather not touch it, and out of curiousity will a better fuel pressure regulator with a return line give me a little better mpg?