Fuel pump for my BB C4

[corvette66]

Hello all. I have a couple questions for ya. Does anyone know how many lbs psi thoes c4 in-tank pumps put out? I know that mechanical pumps are around 7.5 psi. EFI pumps are around 28-40 psi, i think. I'm still working on this Big Block C4. Now I am deciding what to do with the fuel pump situation. The pump that is on the car is to powerful for the carburetors i would assume. So I wonder if I could use the stock pump with a fuel regulator to cut down the psi. ???????

Question for a buddy of mine..... anyone know the specs on an 1985 C4 cam shaft? (duration and lift) Also would any SB-chevy cam work as a replacement? Obviously the tourque and Hp range would change, but would any performance cam work with his stock equipment?

 

[Ken]

I would imagine that you are going to build some power with this engine, so you will probably want to add an additional fuel pump to the system. I kept my stock pump in the tank, and added a Bosch racing pump downstream before the fuel rail.

Another option I've seen bandied about, was the use of either a ZR-1 in-tank fuel pump, or one from a big block Suburban. The stock pump in the Vette runs around 40-47 psi (280-325 kPa).

 

[corvette66]

....

I didn't know you could use 2 pumps like that. So the pump in your tank, is it adding a boost to the Bosch? Do you know what model Bosch it is?

Unfortunately I'm using 2 carburetors, i don't think they would work with a 40 psi pump. Seems like that would be to much.??
What I really want to do is eliminate the old pump altogether. What could I get to replace the old sending unit so i still have the fuel guage and the lines in the tank? :confused

 

[Ken]

Dano, the stock pump is actually feeding a surge tank, this ensures full suction to the Bosch pump.

My receipt for the Bosch unit only shows:

1 Fuel Pump Bosch Racing

Sorry. The pump is mounted under my surge tank, so it's kinda hard to see any numbers down there.

As for the fact that the stock pump delivers a higher pressure, you can always use an adjustable fuel pressure regulator to compensate, to an extent, but you can only cut the pump's discharge so much before you'd do it harm from overheating.

As for eliminating the pump, unless you installed fittings at the lower portion of the tank, you'd have a hard time maintaining suction pressure to lift the fuel up over the top of the tank before it begins its downhill run to the engine. Then again, that is pretty much precluded by the fact that the Corvette tank has a polyethelene liner (or bladder if you prefer); you'd not be able to properly do that modification. A fuel cell would be a better choice in that case.

The gauge wouldn't be an issue.

 

[WhalePirot]

Perhaps a pump for the '84 Crossfire, which operates at a much lower pressure is the answer.

 

[corvette66]

alsehiauthnvoir

Well I might just have to go with a fuel cell.

Fuel pump from an 84, hmmm thats good thinking PIROT. It might work, I Didn't think of that. I'll have to find out what the PSI is.

thanx for the posts

 

[taegdh]

You've got 40 to 50 psi coming from the electric fuel pump in the tank, what you may need is a fuel pressure regulator, which diverts excess fuel back to the fuel tank. There are plenty of them which are adjustable, and the line is already there from the EFI unit.With a carb what are you going to need? 15 to 20, maybe 25 under extreme performance circumstances. You don't need to blow out some of the valves in the carb with all that extra fuel pressure.

 

[corvette66]

chjdgd,gyi.du

Yeah I agree a pressure regulator could be of help. Butt what I was concerned about was that most carb pumps run on about 7.5 lbs. With the high performance carbs and BB engine, maybe it would be over 7.5. Butt even with the fuel regulator it may not cut down the PSI from the electric pump far enough. Also like Ken mentioned it could cause an overheated pump.

I'm looking at my JEG'S catelog right now. seems the out of tank fuel pumps (electric) are running about 5-20 psi and some as high as 40. They have a few regulators that adjust from 30-70 lbs, and some 3-18 lbs. A regulator might work. Maybe I should find out what psi rating is for 2 edelbrock carbs. each one is a 700 cfm. So maybe if one edelbrock 700cfm carb runs on 8 psi, I could multiply that by 2, and get 16 psi total. My pump puts out aprox. 35-40. If i can cut it down by about 20 Psi, It might work.

Man this is confusing stuff!!!! :confused

 

[WhalePirot]

I stll think that UR complicating things too much. :eyerole

If the '84 pump delivers the pressure you need and not more, why buy any aftermarket pump, in tank or out, a regulator and who knows what else? Simplest always works best.

BUT, it's your dough.