N8Miller

hey guys,
my cousin bolted on that holley avanger 670 carb that i was inquiring aobut last week. the swap went good, but the car seems slugish. he raced his buddies mustang 5.0 (that he used to put 2-3 cars on) and now he can barely keep up. I am thinking that it might have a fuel pressure problem becuase this morning, he said he came out of his house, and the car had a puddle of gas near the front tire....in the fuel pump area it was leaking from.
heres my question: should have lost that much time/power by swapping from the holly 600 w/vaccum secondaries?
Do you have any ideas why the gas leak?

IROC4LIFE

Hey

Sounds like you have lost your tune.

First off you should check what jets were in the 600holley and comapare them to the 670Street Avenger. Most carbs come from the factory jetted on the rich side for any given application. Also the 600 might have had a lighter spring in the secondaries and the 670 has the heavier black spring.

As for the fuel leak if its a mechanical pump and there is a larger amount of fuel leaking out on the ground then it is mosy likely that the pump has failed. Before you go tearing it apart make sure all connections from the hardline that comes from the tank to the carb are secure and are not leaking. Worm gear clamps will ensure no leaks, if you are using those clamps tha come with most inline filters you could have a leak and loss of fuel pressure could be the problem. This would also explain the fuel on the ground.

Hope this helps.

82z28122

iTrader: (1)

when you get the SA carb it comes with a fuel mileage spring, but you want to put the accelaration spring in, because you will notice the differance.

N8Miller

thanks for the replies guys! ok, i think that the fuel pump is shot. my cousin says it pours out the back side of the pump---where no hoses are. would you say a fuel pressure regulator/gauge is worth the money on a carbed car?
anyway, can you tell me more about the acceraltion spring? where is it located? how much are they to replace and which one to get (50cc or 30cc---saw it in summit.com ) how do you change them?
thanks guys

82z28122

iTrader: (1)

the carb kit should have came with all the springs if you bought it brand new. Yes you should buy a fuel pressure gauge, and if you have an electric fuel pump you will need a fuel pressure regulator. for the carb, you have it recomends to set the pressure at 5-7 psi.

EvilCartman

iTrader: (1)

You can't just swap a carb on and expect it to go like a bat out of hell right out of the box. Tune it! buy a jet kit and spring assortment kit and have at it.

N8Miller

All this carb stuff is new to me! i am not familiar with the springs kit---i do know about the jet kit though. We used all the springs installing it, but would that acceleration spring help still? the car is now sputtering in 3rd gear at about 4500 rpms or so. would the lack of an acceleration spring do the trick to change that? or might it be runnin too rich, like mentioned earlier?

IROC4LIFE

OK to get the best tune follow these steps

1- Set timing to desired or Spec Base timing

2- Determain what altitude you will be using the Car at.

3- Go to the speed shop you bought the carb or contact holley tech support with the Altitude, Car, and Engine Specs they will provide you with a jet size for the Front and Rear of the carb that you should start at, with your tuning.

4- Install the Recomended Jets and set idle mitxute via the 4 screws on the metering blocks

5-Install the proper vaccum secondary spring as noted in the holley insturctions, if you dont have the instructions then www.holley.com has them in the tech section.

6-Set Accelerator pump to holley spec and road test car, if you find an bog or sputter at tip in then ajust the accel pump accordingly with 1/2 turns in or out till you find the proper setting.

:Note: the holley spec is 99% of the time right on the money with accel pump setting: Refer to carb instructions

If you are new to this then you need the holley instructions PERIOD. There are also many good books out on tuning holleys for performance.

AJ_92RS

If the pump is bad, then it will leak out the wheeping hole. that's in front of the pump (at least all the ones I've seen) when you are looking at the fuel pump from the side of the car.

If it's leaking out the back, then perhaps the gasket is leaking?

But since you say that it loses power above 4500RPM, then most likely it's the fuel pump. I've had that happen on an 81 GMC 1/2 ton. I rebuilt the carb at first, but it still did it. Then changed the fuel pump and viola. The fuel bowl was running outta fuel before the pump could refill it.

Any new carb should come pretty well tuned outta the box. Unless you have a 450HP motor that you're putting that 670 on, then it should check out OK. Don't mess with it until you've replaced the pump.

AJ

TA82

I've never had a mechanical fuel pump fail on me before because I always convert to an electric fuel pump..


BUT.. a roommate of mine bought this piece of **** beat up 1978 Corvette.. and when the fuel pump failed.. he woke up in the morning with a puddle of gas.

His pump had failed.

Todd