Q-Jet rebuild, who here has done it?

[jmorgan87]

I found a tutorial on rebuilding a Q-jet, wondering if anyone that has done a q-jet rebuild would give their 2 cents if it's fairly accurate and complete?
http://www.vetteprojects.com/kstyer/quadrajet.htm

I've rebuilt motorcycle carbs on vtwins before and have a basic understanding on how a carb works.

If anyone knows of a better tutorial or in depth explanation of the process i'd love to see it. Alot of people rag on Q-jet and say they are a nightmare to rebuild, why is that? Are they actually difficult to rebuild, or just require attention to detail? I've heard about their throttle linkage or something can be loose and cause an issue, is that the type of things you run into? worn out parts that can not be replaced, and therefore regardless of the rebuild the carb will not work correctly?

I feel confident in being able to take it apart, and put it together again how it was.. but I don't know if i'd be comfortable drilling, fabing, or realize I need to unless it's obvious.

thanks for the advice!

 

[ezez]

Re: Q-Jet rebuild, who here has done it?

I followed this guys youtube videos (several parts) when I did mine.
part one rebuild

 

[Eric 3.7LX Alpha 1]

Re: Q-Jet rebuild, who here has done it?

http://forums.iboats.com/showthread.php?t=362542

Rochester Quadrajet Rebuild Video

 

[45Auto]

Re: Q-Jet rebuild, who here has done it?

They're easy to rebuild, just like any other carb.

What's wrong with it? If it's been sitting up for long and the internal passages are plugged up solid, lots of times all the dipping and carb spraying in the world can't fix them, and you can't get to the internal passages without drilling out and replacing the plugs. Not a typical rebuild operation.

If it's in pretty bad shape and still has the manifold-heat operated choke, you may be better off getting one from here - $199 with an electric choke:

http://www.nationalcarburetors.com/marine/fourbarrelrochester.aspx

I've used them several times when a Quadrajet was too far gone to rebuild, their carbs have always looked and run like new.

 

[jmorgan87]

Re: Q-Jet rebuild, who here has done it?

The boat hadn't ran in over 4 years, been sitting.

The choke was zip tied open when I got to the boat. It also currently has an unknown amount of bad gas in the tank, i'll be emptying that out this weekend. With 5 gallons of fresh gas(added to the tank of unknown bad gas) and fresh plugs, we were able to get the boat running. Yea yea, should of drained it then, look at my restore thread to see what the interior looked like prior to cleaning. Our primary goal was to hear the motor run for any type of internal issues, such as a rod or other problem.. We had to manually choke the carb with your hand, and control the throttle with the other hand. It wouldn't idle, or run full throttle this way. You could blip it full, or hold it steady about 1/2 throttle(just two barrels), and it would hold steady..while choked. After doing this for about 10 minutes, it idled for about 10 seconds before committing suicide.

Are these plugs you drill out just a matter of removing a brass plug to gain access to a needle that you can remove? or do you mean drill out and replace with a solid plug again? I've had to do the first on bike carbs, though never replaced the plug. Just removed it, the needle/seat cleaned and put the needle/seat back.

I'll watch the videos and see if I feel comfortable with it.

I wish i knew if it had 2 gallons of bad gas, and 5 of good, or 10 bad and 5 good.. unfortunately I don't know. I'm not sure if bad gas would make it behave like this or not, i'd expect it to not fire at all instead of requiring full choke and throttle to run.

 

[fat fanny]

Re: Q-Jet rebuild, who here has done it?

There is an episode on the power block (Spike) muscle car where Rick gives a very detailed explanation of a quad re-build you can log onto thier site and watch any episode. hope this helps.

 

[jmorgan87]

Re: Q-Jet rebuild, who here has done it?

My hand can't take any more manual choking! That v8 will damn near suck the skin off.

Just ordered the QJE-5.7L from national carb. The manifold choke is zip tied open, and the carb just looks rough over all. Even if I did rebuild it, i'd still have to do deal with the choke, or just leave it open and deal with cold start head aches.

After tons of carb cleaner, fresh gas etc. If you pumped it, it crank up and run off that for a few seconds die. Any gas would kill it. If you pumped it again, put your hand over the primaries it fire, blip throttle a few times and then hold it 1/4-1/2 and she'd sit there just fine. If the secondaries opened up it kill it, but you could sit with the primaries churning away for as long as you want. Even doing that for a long time, it at best would only idle for 5 seconds before dying.

Hopefully this new carb will crank up and idle great

 

[45Auto]

Re: Q-Jet rebuild, who here has done it?

The marine Quadrajets myself and a friend have purchased from National have looked brand new and ran perfectly without touching a thing. Engines idle at 600 RPM so smoothly you can't even tell they're running. Haven't even had to touch the idle air screws, just bolt it on and go.

Good Luck!