First carb rebuild....success

[CamaroAdam73]

Re: First carb rebuild....fail

Sorry for the late response it's been a busy two days, but thanks for all the help guys.

Alright, The engine is an almost all factory 79' 403. It's all rebuilt though, but too factory specification. Only modifications are an aluminum intake and headers.
new factory spec fuel pump. Fuel return line is being used, and is free of blockage, it's a new line, new sending unit, and new gas tank. All the old equipment was shot. I will still double check the return line though just in case, but I'm almost certain it's not blocked up.

Yes i blocked off the vac port for the choke so i wouldn't have a vac leak. I've also got my vac gauge hooked up, it normally holds between 16-17 inchs of vac. Also i did remove the entire choke assembly. With one of my holleys bolted up, it holds 16-70 as well but much more steady and that's because the qjets way out of tuning. So i'm pretty sure there's no vac leak.

The engines in time too. Triple checked with my light, I've got it set at 19 BTDC right now.


Yeah i made sure the float needle seat is tight and sealed, i checked the needle/seat by pressuring/ pulling air through and it seals.

The carb was rebuilt entirely, The throttle/base, mainbody, and air horn where all stripped, blasted, cleaned and cleaned again to make sure no sand remained, and then painted.
Needle/seat are new, primary rods, piston and spring are all new.
Checkball as well, and retaining screw.
In short, everything.

I'm not sure of the specifics of the kit, but it was ordered from cliffs high performance and the primary rods are not factory spec, cliff recommended a different set. I'll be able to get all of the specs of the kit tomorrow, as for the carb number off hand i only know a bit, 170 and ends in 53 i believe, know for sure tomorrow.

As for modifications, just the deleting of the choke.

 

[Bonnewagon]

Re: First carb rebuild....fail

Sounds like you did a thorough job. This must be exasperating for you. Is the float new? Plastic? How did you block the choke vacuum? I pound a tiny ball of lead from a fishing sinker into the hole on the float bowl and file it flush, then use an electric choke housing. Just capping the little plastic fitting that fits between the bowl and housing is not good enough because it relies on the housing pressing against the bowl for a seal. Let us know the rods and carb # when you get a chance. Another drastic way to really check the needle/seat, is to mount the carb minus the air horn, just the throttle body and bowl, with just the needle/seat and plastic filler block installed and fuel line hooked up. Place a heavy bar over the float fulcrum so it stays in place. Disable the ignition and have someone crank the motor and watch to see how the bowl fills. The bowl is normally vented to atmosphere, and should only fill to the level it is set at. There is no place for fuel to leak out since all fuel must rise above the rim of the bowl to exit through various passageways. As it fills, it may splash a bit, so have a fire extinguisher handy, and don't smoke. A better way is if you have an electric fuel pump handy, you can do this on a bench, away from the vehicle. Like I said, this is a drastic measure, not for the timid, and I will only do this as a last resort as it is dangerous. But I have found that even brand new needle/seats can leak. The bowl should only fill to whatever level it is set at, no matter how long the motor is cranked, as long as pump pressure is within specs. A vacuum gauge can be used to check pump pressure, note the scale at bottom of the gauge. The fuel pump has an internal regulator that shunts excess fuel back to the tank. BUT, if the pump is producing too much pressure, or the bypass is blocked, fuel will overcome the float, and cause a bit of flooding, gently not severe, that's why it's hard to troubleshoot.

 

[CamaroAdam73]

Re: First carb rebuild....fail

Alright, i've given up on this Q-jet for now. I need to get this engine tuned in so i'm using my holley 750. I've put too much time and money into that Qjet already with no prevail.

My holley also needs rebuilt I've already got the kit, It's a holley trick kit.

http://www.summitracing.com/parts/HLY-37-754/

I called holley and that's the kit they recomended.

Right now the carb leaks from the accelerator pump, and i don't think i'm getting any fuel through the carb into the engine.


Any tips before i try and rebuild this?

 

[pontiacgp]

Re: First carb rebuild....fail

what did the q jet end up doing when you tried it? Funny thing I had a holly and couldn't do anything with. I like q-jets

 

[Bonnewagon]

Re: First carb rebuild....fail

I know Q-jets, my buddy knows Holleys. We are both very sure we have the best carb ever made, and we are both pretty good at maximizing performance. Only difference is, he has to play with his endlessly, while mine is set-and-forget.

 

[pontiacgp]

Re: First carb rebuild....fail

that's one thing I didn't like about the holley...constant tinkering

 

[Oldsmoletick]

Re: First carb rebuild....fail

I hated my edelbrock, and my holley, I love being able to tune my secondaries with nothing more than a couple rod/hanger setups, screw driver, and allen wrench (not to mention no risk of spilling gas on a hot engine ). I should smack the idiot that told me to ditch the quad for the holley, or maybe I should kick my own *ss for believing him, :lol: .

 

[pontiacgp]

Re: First carb rebuild....fail

I worked in the same industry as Adam does and in that industry it's all about paying attention to detail and working with close tolerances. A q-jet should be easy for him to rebuild so I'm thinking he's just missing something...

 

[CamaroAdam73]

Re: First carb rebuild....fail

I know i'm missing something here, and it's irritated me so bad :evil: , I just can't figure out why it's leaking fuel.

The only possible thing i can think of is that the jets are damaged somehow and are allowing a constant flow of fuel into the engine. Now that i have the Q-jet off, i'm going to pickup a mini electric fuel pump and fill the carb up with the airhorn off while it's off the engine and see what happens.


For the record, i'm 110% positive that the float is correctly set, quad checked. The checkball and retainer are set, all mainbody/air horn mounting hardware are installed correctly. Primary and secondary rods seated, new primary rod hanger and piston. All new gaskets and seals.

 

[pontiacgp]

Re: First carb rebuild....fail

The most common mistake and I know you said it's checked but the float is the main source of a problem with fuel leaking. I use the brass floats for two reason, smaller than the plastic so more fuel in the bowl and they seem to work better. If it's not the float then I have seen that little wire hanger fall off and prevent the needle from stopping the flow. One thing you could try is to purposely set the float too low to see what the fuel does then.