Q jet Question

[Mark Callanan]

I had a new Magna Fuel system installed on a 69 Camaro stocker
I ran a test and tune today and the car was off as far as ET
I checked the fuel pressure and it was at 3 pounds
I brought it up to 6 pounds and the car stumbled on the launch and the 1-2 shift on the next run
I had always thought the fuel pressure for a Q JET should be at 7 pounds or so
Any thoughts on what might be causing this?
The car is very rich as you can smell the fuel all around the car when it is run

[james schaechter]

I remember in the manual with the magnafuel stuff I bought it reminds you to check the fuel pressure at an idle, not with the engine off. I also have heard several different people commment on how far off some of the fuel pressure gauges could be.

[SSGN]

Check air door tension and float level.Could also be pulling fuel into sec.


Kevin

[Dave Ribeiro]

Mark,

Has the carb been apart for any reason, jets-etc ..?
Did you have a stumble/miss with 3 lbs of fuel pressure when you first started ? Sounds like maybe float or needle is sticking and fuel is bleeding by ? Is it clean driving around in pits & on starting line....? Maybe Danny will jump in if he is around ? Top of 1-2
shift usually points to flapper valve adjustment ? I would take carb
apart and check over really good, look for dirt or something in needle & jet area and make sure things haven't fall into bowls ...
Good Luck, keep us updated & talk to Vic Santos, he's very good with Q-jets.........

[Mark Callanan]

Originally Posted by Dave Ribeiro

Mark,

Has the carb been apart for any reason, jets-etc ..?
Did you have a stumble/miss with 3 lbs of fuel pressure when you first started ? Sounds like maybe float or needle is sticking and fuel is bleeding by ? Is it clean driving around in pits & on starting line....? Maybe Danny will jump in if he is around ? Top of 1-2
shift usually points to flapper valve adjustment ? I would take carb
apart and check over really good, look for dirt or something in needle & jet area and make sure things haven't fall into bowls ...
Good Luck, keep us updated & talk to Vic Santos, he's very good with Q-jets.........

David

The car the 1st run ran fine but didnt run the number by a tenth
Thats why I checked the fuel pressure and it was at 3 pounds
So I turned it up
Running around the pits is fine the car starts up fine and runs fine

The carb has not been touched and has been perfect till now
I think it may be a bad pressure gauge

Thanks David for stepping in here to help it is kind of you

We had to turn it up alot to get it to 6 pounds and again there is alot of fuel smell
I will look for a gauge in the morning...

[Knocky]

Mark, If using the big needle and seat (I think it is 0.135") in your q-jet, try running no more than 4-5 psi max, the float bowl will stay full. Higher psi never worked well on my 455 Pontiac either.
MWNorris

[Dave Ribeiro]

Mark,

I would try another gauge, if you can't find one , turn the pressure down to 4 lbs and see how that runs & feels ? If it works , it may get you by for this weekend .... If it doesn't work, adjust in 1/2 lb increments till it get better... Could try another carb ? Also , try ; turning on the pump & look down into carb to see if it's bleeding over with too much pressure ? ........... Good Luck .........

[Mark Callanan]

Originally Posted by Dave Ribeiro

Mark,

I would try another gauge, if you can't find one , turn the pressure down to 4 lbs and see how that runs & feels ? If it works , it may get you by for this weekend .... If it doesn't work, adjust in 1/2 lb increments till it get better... Could try another carb ? Also , try ; turning on the pump & look down into carb to see if it's bleeding over with too much pressure ? ........... Good Luck .........

David

Good call the gauge was bad

[Dave Ribeiro]

Mark,

Glad you found your problem & congrats on your Win @ the Last IHRA event at NED ....