9psi carb

[Vengeance]

I've read that the later quadrajets are built to handle 9psi and the earlier ones are built for 4.5psi. Can an earlier quadrajet be built to handle 9psi? Would one of your rebuild kits be sufficient for 9psi? Will a Wix 33041 return type fuel filter help alleviate some of the pressure?
The numbers on my carb are 17059253 0859 BZA.
I already have the 9psi fuel pump and don't want/can't afford to get the fuel pressure regulator.
Thanks.

[tayto]

I can't answer your question, but I believe it is dependant on float height. A regulator is $30, not trying to be rude but if you can't afford that I suggested you find a new hobby

[Vengeance]

After $3,500 for everything else and still needing to buy the carb rebuild kit anyway, no there is not an extra $30 to spend. Just spend the little extra $50 on the better gaskets; just spend the little extra $40 on the better fuel pump; just spend the little extra $150 on the better pistons; just spend the little extra $40 on the better timing set....no. All of the "just a little extras" is NOT just a little more. That just shows how short sighted people are. They can only see what's right in front of them.
I actually know how to plan, and refuse to spend the "little extra" if it's not necessary. That's how I can get a build done for $3,500 when the knowledgeable builders told me it would take $5,000 minimum.

[Kenth]

Your Qjet #17059253 is a "late" style M4MC carb with good leverage on the inlet needle.
9 psi should not cause any problems using 13/32" setting on float.

[Vengeance]

Thank you.

[Cliff Ruggles]

The answer is yes as mentioned.  My rebuild kit for that carb number will have the .135" high flow N/S assembly in it (solid not "windowed) and the correct nitryphyl float.  They will easily handle 9psi w/o issues. 

I use a .145" seat in my 1977 carb at 7.5 psi with a 9/32" setting and it has been flawless for decades.  I've even cranked the pressure up past 10 psi and it still works fine and never the first indication it's going to flood or give troubles.

There are many "myths" with Q-jets, one of them being that they can't handle high fuel pressure.  This comes from the early units with the short hinge pin and huge float.  Those carbs are problematic and limited in what you can run for fuel pressure.  Even so I've set thousands of those up for racing applications with .135" fuel inlet seats at 6-7 psi and never had a single issue with any of them.

One thing I will add here is that I've seen folks have issues using "high performance" mechanical fuel pumps without a return system.  The folks who make them and folks selling them will tell you they can run "dead-head" w/o issue but I've seen a LOT of problems related to doing that.

I suppose those big pumps are "pounding" on the N/S assemblies pretty hard as the fuel has to stop and start with each stroke of the pump and even being self regulated at a given pressure they can still cause flooding issues.  One has to look at the "mechanics" of that deal right to start with.  If you install a 125 GPH mechanical pump, for example, and "dead-head" it, it's trying to push a BUTT-TON of fuel into the carb without much of a relief path. 

I use and prefer bypass systems or bypass style regulators for vehicles I set up here for "high performance" use.  Experience has taught me that running anything "dead-head" in long term service is just asking for trouble, so I take that deal out of the equation right at the start........FWIW.....Cliff