Cerridius

Ok so im going to be swaping my 305 TBI with a 5speed to a 400 Carb with a 6speed. Right now the car has the stock HP around 170 im guessing and the new engine should put it to somewhere around 400HP. Now will my stock fuel pump be able to handle a Holley 750 carb with the Mallory 4309 fuel pressure regulator? Or will I end up having to drop my fuel tank and changing out the fuel pump (I would like to avoid this). Im still new at working on cars so bear with me. Also my car right now has an electric fuel pump.

face215

is that an lt1 motor your droppin in? and to answer your question, i would think it would not be able to handle the fuel demand at the top end, and ultimatly starving the motor of fuel and causing the engine to break up.

Air_Adam

Thats not an LT1, its a gen 1 engine. Stock fuel pump... iffy. I would put a Holley 110gph mechanical pump on it, and not worry about it anymore.

Cerridius

Air Adam,

Thanks and you are correct - not an LT1--
So your saying that I need to drop my fuel tank, remove my electric pump and not worry about a fuel pressure regulator and go from there with the Holley mechanical unit? Would I have to replace the electric fuel pump with some type of sender unit?

Or,,, Can I keep the electric Fuel pump and just add a fuel pressure regulator and get the same outcome? But,,,, did I also understand you to say the stock electric pump might not get it however, could it just be upgraded to a high performing electric pump with a regulator?

cuisinartvette

Use a mech pump if it will fit, one less thing to go wrong.

Whats been done to the motor?

Youll love the torque of the 400

Cerridius

Still not to clear on what I would have to do for a mechanical fuel pump because i have a electrical right now. But the engine ummm it has stock crank&pistons and standard bore, It has stock heads(#333882) redone with stock valves, light porting and it has Crane highrev springs retainers and locks also crane 1.5ratio roller rockers. The camshaft is new its a Crane#114142 Compucam.
Im wondering what my HP should be around with a Holley 750 carb and a holley street dominator intake. Oh and also it will have Hooker 2460 shorty headers with dual exhaust

pancherj

I don't think you will be anywhere near 400HP (maybe 350) with that setup. So, your stock pump with a regulator should be fine.

Cerridius

Ok so with about 350 HP I can just use the Mallory 4309 fuel regulator and I would be fine? Im cool with less than 400 HP right now anyway.

cuisinartvette

350 tops maybe even a touch less but your torque will be outstanding, youll melt tires whenever you want. Will be responsive.

WS6LOVE

If you're using the stock heads, you're not going to see over 350. Torque should still be around 400 though

Air_Adam

I *think* you can use a mechanical pump, and just draw through the electric pump in the tank instead of removing it, without causing any problems. Don't quote me on that though. Lots of 3rdgen carbureted cars came with both an electric and mechanical fuel pump on them, and they worked just fine. The electric was used, IIRC, mainly just to prime the fuel system, but the mechanical pump was what the engine used to actually run, and just drew fuel through the electric in-tank pump.

five7kid

iTrader: (14)

No, you need to keep the electric pump running. A mechanical pump may be able to suck enough fuel through a non-operating in-tank electric to idle and cruise, but certainly not 350 HP.

The '87 model year used an in-tank electric and engine-mounted mechanical fuel pumps. A stock mechanical pump with an operating in-tank electric TBI pump should be fine.

IIRC, the Holley 110 doesn't have a return. I wouldn't use in regardless of whether or not you keep or remove the in-tank electric if it doesn't. The Carter M6626, on the other hand, does have a return, and is rated at 120 gph. I used it for 5 years on my ZZ4 clone with no problems.

Air_Adam

I stand corrected on the electric pump issue. I wasn't sure about that, as my post suggested.

I had the Holley 110gph pump. Yes it doesn't have a return on it, but I never had any issues with it? Worked great right up untill I sold that small block?

Cerridius

five7kid,

So just keep the electric fuel pump and run a mechanical fuel pump to the fuel lines below the master cylinder and to the carb?

Cerridius

So from what I'm understanding I should forget about the Mallory Regulator. Keep my electric fuel pump and run a mechanical fuel pump aswell?

five7kid

iTrader: (14)

No regulator ONLY if you use a mechanical pump with a return. That was what was stock on all 3rd gen V8's with carb.

travis401

iTrader: (1)

You basically have a few options, as mentioned by everyoneso far.

1) Keep the stock pump and run a return style regulator (which may or may not be able to feed the motor on the top end).
2) Keep the stock in tank pump and use a return style mechanical pump on the block.
3) Drop the tank and use a higher flowing in tank electric pump with a return style regulator.
4) Use just a return style mechanical pump on the block, drop the tank and switch out the electric tank pick up for a carb one.
5) Drop the tank and remove the in tank electric pump, switch to a carb pick up, and then run an external in line electric pump (probably the most expensive option).

five7kid

iTrader: (14)

You don't have to switch out the pick-up if you choose one of those options. https://www.thirdgen.org/forums/carb...nk-pickup.html

(But you do have to drop the tank...)

DoWork2day

JUST GOT AN IROC WITH A 400 IN IT. Yes I'm yelling, I'm geeked! My brother knows the previous owner, and sold the dart heads to him which are on it. I understand this motor has around 1,000 miles on it. The cam is 510 lift, a single plane intake, Holley 750 carb. Headers, with y pipe.
(WHAT HORSEPOWER DO YA THINK IT MAKES? It does have great torque as Cuisinart and WS6 said. It was raining today so I didn't get a chance to really try it out. Not even legal until tomorrow)

DoWork2day

Oh, and my car still has the electric fuel pump, probably using a regulator. I just got it I don't know exactly what it is yet! Got a deal I just wanted to get it home before that guy changed his mind. Thanks Jimmy you're the best!

Cerridius

Wait, what? are you saying thanks to me? cuz my name is Jimmy lol.

Anyway. Im gonna just keep my intake electric pump and use the Mallory 4309, i asked alot of people and they said this is the best and easiest way.

DoWork2day

haha no, the guy I bought it from is Jimmy. I just got the rear suspension together, it is truly a different car. Random adjustable torque arm, Lakewood tubular LCA's, Lakewood 50/50 drag shocks, less than $2,000 in the car making over 400 HP. Thanks Jimmy indeed.

BronYrAur

iTrader: (1)

Just saw this thread looking around. You WILL absolutely need a new fuel pump. I have a 305TBI that was pushing Maybe 200hp and it was breaking up badly up top. Don't be deceived by the stock TBI pump, it will appear to be healthy because it will hold pressure just fine every time you check it; but, it will not supply the volume that you need for that motor. Read around the TBI forum, many issues track back to fuel problems from the weak stock pump.

I went with a Walbro 190 in tank pump.