Thread: carb headache

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Ok folks I have my first question for the board. I have a new 350 300 hp crate gm engine and a rochester q-jet, it preforms ok but for a 300 hp engine it is defently not there. I have about 16 degrees base timing no vac leaks. when i take off (ie) getting on the highway coming up to speed it seems to just not be there, it does not bog or backfire or spit it just does not seems to rev rpms up when i steadly get it gas almost like a sag, when i floor it the secondarys kick in fine but just seems to be lacking. I rebuilt the carb 3 weeks ago and made sure every little port and crevice was clean even drill out the idle screw ports to 80 thousandsth. vac advance works great and power piston is not stuck. Any suggestions? thanks for the help!

What is your fuel pressure? How old is your fuel filter?

I am not for sure of fuel pressure it is a inline filter new and clean, is there a way to check the pressure? the fuel pump is a stock one that runs off the cam . what should the pressure be?

Did you replace the sintered bronze filter where the fuel line goes into the carb?

Most carburetor needle/seat assemblies will be happy with a maximum of 6 psi at the carb inlet. Too much less than that and you can starve the motor, particularly at WOT, any more than that and you'll probably have fuel blowin' past the needle/seat when the bowl is already full, resulting in a very rich condition.

Ok so i will get a check on the pressure somehow. If the pressure was less then 6 pounds and the motor was starving wouldnt i notice it?? (ie) sputtering or cutting out? This is not the case . But I will check it out thanks

Your distributor advance springs may be too heavy,,,there was a post recently which suggested putting the lighter springs in,,in case of insufficient advance on acceleration.

I agree with the timing thot. Maybe ucould even advance it a little.

Seems like a fuel pressure problem would affect the secondary kick in also, what about the main jets,too small or dirty?

how did it run befire the swap did u have an old reamed out sloppy motor because they will scream gears and tires have alot to do w/ it are you gonna haul a load or hual butt??
sr66

What I am looking for is to why the power just isn't there, it runs smooth and sounds great. The carb has size 73 jets and i have went though out and documented everything about the carb itself. maybe it is within the timing, I am not for sure what the advanced springs are, will check it out this weekend if it would stop raining ! It should light up those tires at a take off. I have factory 3.73 gears in the rear end. The old motor (used to ) burn em up back in the day..... I do some towing (boat) and want to have it run good to ( haul butt) .